ERIKS - Technical Manual - VEDAÇÃO
December 9, 2022 | Author: Anonymous | Category: N/A
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S E A L I N G
Table
of
E L E M E N T S
Contents
In t ro d u c t io n
3
11. S t o ra g e
100
1.
O O--rin g S t a n d a rd s
5
2.
O -rin g S e a lin g P rin c ip le s
6
3.
O -rin g Ap p lic a t io n s
10
4.
B a s ic E la s t o m e rs
12
102 108 110 112 114 115 117
5.
D e s ig n in g w it h R u b b e r
25
6.
C o m p o u n d S e le c t io n • S t a n d a rd c o m p o u n d s • Vu lc -O -R in g s c o m p o u n d s • S p e c ia ls • Viton ® c o m p o u n d s • Kalr Kalrez ® c o m p o u n d s • Enca psulated T Tefl eflex ex ® c o m p o u n d s
36 39 40 41 44 52 60
12. O -rin g G la n d D e s ig n In fo rm a t io n 12. A G la n d D e s ig n S t a t ic Ax ia l 12. B G la n d D e s ig n S t a t ic R a d ia l 12. C G la n d D e s ig n D o v e t a il G ro o v e s 12. D G la n d D e s ig n B o s s S e a ls 12. E G la n d D e s ig n D y n a m ic Hy d ra ulic 12. F Hy d ra ul ulic S e eaa ls w iitt h B a ck c k-up R in g s ® S ta nda rd Tefl eflex ex O-ring Sizes 12.G 12.G G land Des ign for Enca psulated Tefl eflex ex® O -ring s 12. H G la n d D e s ig n fo r P TFE O -rin g s 12.I 12.I Grafi Grafics cs for OO-rring deformati deformations ons a cc ording ording to d in 3771 Te il 5 12.J 12.J Gland Desi Design gn ffor or Kalr alrez ez ® O -rin g s 13. O -rin g As s e m b lin g C o n d it io n s
133
14. O -rin g S iz e C h a rt
140
• • • • • • • • • • • • • • • • •
68 69 70 75 76 76 77 78 79 81 82 83 84 84 84 85 86
Da ta s he e t s Wa t e r-S t e a m Fo o d - P h a rm a Va c u u m C o n t a c t w it h p la s t ic s Hig h p u rit y - FD A - U S P P e rm e a b ilit y E x p lo s iv e d e c o m p re s s io n Min e ra l o ils Fu e ls Te m p e ra t u re Ab ra s io n Oz o ne R a d ia t io n S h ie ld in g C o lo u rs Th e rm a l e x p a n s io n
121 124 125 128
14. A A. S . 568A S t a n d a rd O -rin g S iz e s 14. B Me t ric S t a n d a rd O -rin g S iz e s 14. C J IS -S iz e s
141 150 169
15. To le ra n c e s a n d S urfa c e Im p e rfe c t io n s
174
16. Vulc-O-r ulc-O-riing ® a n d O -rin g C o rd
180
17. O -rin g Ac c e s s o rie s
185
18. O -rin g Kit s 19. Q ua d ™ -rin g s 19.A 19.A Gland Design Design for Q Quad uad ™ -rin g s 19. B S t a n d a rrd d Q ua ua d ™ -rin g S iz e s 19.C 19.C For rotating otating Quad ™ -rin g a p p lic a t io n s
186 191 192 195 203
20. Tro ub le s h o o t in g
204
7.
S p e c ific a t io n s
87
21. G lo s s a ry
207
8.
Q Qu u a lific a t io n s
94
22. C o n v e rs io n Ta b le s
216
9.
T Tee s t P ro c e d u re s
95
23. Ap p ro v a ls a n d Ac kn o w le d g e m e n t s
220
10. C o n t ro l
2
99
T EC H NI C AL
D OC U ME NT AT IO N
O -R INGS
Introduction
ERIKS st arted the d ist ri ERIKS ribution bution of O-Ri O-Rings ngs in 1952. Fr From om t his his very mo de st be ginni ginning ng in Al Alkmaa kmaa r ((the the Netherl Netherland and s), ERI ERIKS KS has bec ome a wo rl rld d leade r iin n the producti production on a nd distri distributi bution on of O-Rings and elastomeric seals. ERIKS has 2000 collaborators in 50 locations worldwide. We produce and distribute seals, gaskets, rubberproducts, engineering plastics, valves and hoses. Our focus on new mark markets ets a nd new a ppl ppliica tions tions ha s c aused ERIKS ERI KS to expand in ma ny O-Ri O-Ring ng a ppli pplica tions tions fr from om s tand ard industri ndustrial al to high high tech se mi mico co nductor-appl nductor-appliica tions. tions. Our 25 25 yea r busin busines es s rel relationshi ationship p w ith DuPo nt Dow Elastomers on Viton ® and Kalrez ® seals, our 16.000 different sto ck iitems tems wo rldw ide, o ur one-da y se rvi vice ce producti production, on, our hi highly ghly qua lifi fied ed engineering engineering sta ff are only a few examples of our goa l: to be your partner for hi high gh p erf erformance ormance se als thr throughout oughout the w orl orld. d. ERIK ERI KS sea ls are manufactur manufactured ed in acc ordance w ith state of the a rt produc produc tion tion a nd q uali uality ty co ntr ntrol ol pr proc oc edures to sa tisfy tisfy the mos t dema ndin ndingg q uality uality requirements requirements of a ny iindustry. ndustry. ERIKS ERI KS inventory inventory poli policies cies insure that a wide a ss ortment of se als a nd fl flui uid d s ea ling p roducts are read ily a vail vailab ab le. As your val value-adde ue-adde d p artner artner,, ERI ERIKS KS offers the technical expertise to provi expertise provide de c ustomized s oluti olutions ons to your sea l requirements. requi rements. Be ca use of our tr tremendo emendo us technical exper experiience , s pec ial applica applica tions tions are no probl problem em for ERI ERIKS. KS. Whether your requirement is for large quantities of durable molded goods or small quantity engineered prototypes ERIKS ERI KS is your total sea l sour source ce . ERIKS offers not only a broad range of products but a broad range o f serv serviice s a s w ell. ell. When you need se al solu soluti tions ons ERIKS will be standing by to offer superior technical support, cus tomer se rv rviice, and inventor nventoriies to s atisfy your sea l rreq eq ui uirerements q ui uickl cklyy a nd p roper roperlly. The ERIKS ERIKS o rganizati rganization on is s et up to allow allow dir direct ect conta ct betwee n you and our seal special specialiists. P lea se ca ll for additi additional onal iinfor nformation mation on thes e products or any other seal requirements you may have. Responsibility The informati information on in th thiis c ata log is b as ed o n years o f ac cumulated cumulated experience in se al technology and is intended for the use o f indiv experience indiviiduals ha ving ving tec hnica hnica l experti expertise se in the fi field eld of sea l design. G land des igns a re ac cording the llate ate st developments and c an differ differ slightly slightly from from previ previous ous issues . Due to the large vari variety ety of a ppli pplica ca tions tions a nd operating parameters, the user, through his own testing and analysis, is solely respo respo nsibl nsible e for ma king king the final selecti selection on o f product and as suri suring ng tha t all perfor performanc manc e and sa fety req req ui uirements rements are met. Please contact an ERIKS representative for assistance in making your selection as required. required. The products, fea tur tures, es, s pecifi pecifica ca tions, tions, a nd des ign infor information mation iin n thi thiss c ata log are subject to c hang e by ERIKS ERIKS a t any time w ithout notice.
3
TECHNICAL
1. O-ring
DOCUMENTATION
O-RINGS
Standards
The O-r O-ring ing has bec ome the w orl orld’s d’s most popul popular ar a nd versatil versatile e s eal due to its s imple mple s hape, low spa ce requi requirerements, a nd its a vail vailab ab ility in a va st selection of sizes and compounds to meet every industri industrial al req ui uirement. rement. The ERIKS O-ri O-ring ng m a nua l is iinten nten de d as a g ui uide de to a ss ist in the selecti selection on of the bes t O-r O-rin ing g out of the co rrec rrec t rubber compound in the right applicati tion on for eng ineers, purchase rs, a nd other users of O-ri O-rings ngs . We hope tha t you find it both convenient and helpful. Thi hiss b oo k conta ins d eta iled informati tion on c oncerni oncerning ng e las tomeric tomeric co mpound s, insta lla ti tion on information, s izing tables, and groove dimensions. The dimens ion ta bles represent sta nda rds a vail vailab ab le from from ERIK ERIKS S
There a re also military military ma terial spe cifica tions tions per a " MI MIL" L" des igna ti tion on and aerospa ce ma teri terial al spec ifica fica ti tions ons pe r a " AMS" de signation. Our sta nda rd program c overs 30.0 30.000 00 sizes in a large variety of rubber com pounds for your spec ific fic p urpos urpos e. Technical data and ad vice vice are a vailab vailab le at a ny ti time. me. Many non-standa rd si sizes zes are a vailab vailab le upon req uest. P leas e c ontac t your ERI ERIKS KS repr representa esenta ti tive. ve. Our qualified staff guarantees excellent service. It’s our goal to be your partner.
inventories. Thes e O-r O-riings a re manufa ctured in ac cordance with with a vari variety ety of standa rds for each c ountr ountry: y: AS 568A B S 1 80 6 D IN 3771 S MS 1586 AFNO R 47501 J IS B 2401 IS O 3601-1
US A Eng la n d G e rm a n y S w ed en Fra n c e J a pa n Int e rn a ttiio na na l
5
SEALING
2. O-ring Sealing Principles
O-rings are bi-directional seals, circular in in shape and cross sec ti tion. on. O-ri O-rings ngs a re generall generallyy ma de o f an elas -
ERIKS O-ri ERIKS O-rings are precision sea l components ma de from a vari variety ety of elas elas tomer tomeriic compounds .
tomeric material, butamay of other mate rials s uch s P Tbe FE made or metal. Thi hiss ha ndb oo k dea ls e ntirel ntirelyy w ith elasto meri mericc O-r O-riings a nd P TFE enca psulated elasto meri mericc OO-ri rings ngs . An O-ring seals through the deformation of the seal material by installation and media pressure to close off the gap between mating components. Higher Higher system pressur pressures es ca n ca use deformation through the gap, known as extrusion, resulting in seal failure. Choosing a harder seal material or installing back-up rings to support the O-ring may alleviate this problem.
When you s pec ify adiam n O-r O-ri ingr (I.D.) need to know the inside ete (we I.D.), , the cross se ction diameter ((W W), a nd the compound (elastomer material) from which the O-ri O-ring is to b e ma de. All sea ling a ppli pplica ca tions tions fall into one of two categories - those in which the sea l or sealed sur surface face moves , and those in which the sea l is s tationary.
Media
ID
Media
w
ID= O-ring O-ring inside d ia mete r w= OO-rring c ross sec tion tion
6
ELEMENTS
TECHNICAL
DOCUMENTATION
O-RINGS
2. O-ring Sealing Principles
A sea l that do es not move, exc ept for pul pulsa sa ti tion on ca used by c ycle press press ur ure, e, is ca lled a sta ti ticc s ea l. Those s ea ls tha t are
In designing an O-ring seal, there are usually several standard cross sectional sizes a vaila vaila ble. ble. S electing electing the best cross
subjected subj ected are ned dynaa mic mi c se a ls. T Thes hesto e amovement re ffur urther ther defi defined s recipr proca oca ti ting ng ((sea sea ls e xposed to li linear near motion) and rotary (stationary seals expose d to a rota ti ting ng s haft). haft).
ti tion on oca de pends on the a ppli pplthe ica ti tion. on. In asec reciproca ecipr ti ting ng appli applica ca ti tion, on, choice is automatically narrowed because the des ign ta bles d o not include nclude a ll tthe he sta nda rd OO-rring s izes . For any g iven piston or rod diameter, rings with sma ller cr cros os s s ections tend to twist iin n the g roove w hil hilee in mo tion. This llea ea ds to lea lea kag e a nd fail failur ure. e. The sma ller cros s sec ti tions ons for ea ch insi inside de diameter are therefore omitted in the reciprocating des ign ta bles. For dyna mi micc a ppli pplica ti tions, ons, the largest c ros s s ectional si sizes zes a vailab vailab le s houl hould d b e used to iincreas ncreas e stability.
O-r O-rings ca n be succ ess ful fullly used in static as well as dynamic applications. The rubbe r O-r O-riing s hould be c ons ide red as an incompressible, viscous fluid having havi ng a very very high surf surfac ac e tens ion. Whether by mechanical pressure from the surrounding geometry or by pressure transmitted through the hydraulic fl flui uid d o r ga s, this this extremely vi visc sc ous (elastomeric) fluid is forced to flow in the gland to produce zero clearance or a positive block to the flow of the media being s ea led . The O-r O-riing a bs orbs the sta ckck-up up of toler toleranc anc es of the uni unitt a nd its memo ry maintai maintains ns a sea led c ondition. P roper sea l des ign be gins with the careful consideration of the sealing a ppli pplica ca ti tion. on. Appropri Appropriaa te ma teri teriaa l hardness , for example, is is determi determined ned b y the fri friction and pressure to w hi hich ch the sea l will will be expos ed, a s w el elll a s the cross sec ti tiona ona l dimensi dimensions ons o f the sea l. Other key facto rs inclu nclude de temperatur temperaturee rang e, ad jac ent sur surfaces, faces, a nd medi media. a. Dynamic O-rings may fail by abrasion against the cylinder or piston walls. Therefore, the conta cting surfac es sho ul uld d b e po lishe d for long s ea l lilife. Moving Movi ng O-r O-riings that pa ss over por ports ts or other s ur urfac fac e irreg rreg ul ulaa ri riti ties es whil whilee under pressure are quickly damaged.
O-riings in recipr O-r reciproc oc a ting ting a ppli pplica ca ti tions ons must be radial radial compr compress ess ed b etween the bottom of the sea l groove and the cylinde cyli nde r wa ll for pr prope ope r sea ling a ction. This his compress ion or s q ueeze ma y cause the O-ring to roll slightly in its groove under c ertai ertain n co nditi nditions ons of motion, but t he roll rolliing a ction is not neces sa ry ffor or nor normal mal operation of the seal. The s ha pe o f the groove is uni unimporta mporta nt a s long a s it resul results ts in pr proper oper sq ueeze of the O-ring. G roove d imensions a re s hown in the ta bles beg inning nning on pag e 10 105. 5. The groove d epth is mea sured incl includi uding ng the gap.
7
SEALING
2. O-ring Sealing Principles
The te nde ncy of a n O-r O-riing to retur return n to its ori original ginal sha pe when the cross sec ti tion on iis s d efl eflected ected is the ba sic rrea ea son why O-rings make excellent seals. The s q ueeze o r rate o f compres sion iiss a major consideration in O-ring seal des ign. El Elas as tomers may ta ke u up p the sta ckck-up up of toler toleranc anc es of the uni unitt a nd its memo ry mai maintain ntainss a sea led c ondition. O-rings with smaller cross secti tions ons a re squeez ed b y a higher percenta ge to overcome the rel relativ ativel elyy higher groove dimension tolerances.
O-ring deformation
P rree s s io n = 0
P rree s s io n = 8 Mp a
In sta ti ticc appli applica ca ti tions ons the recommended squeeze is usually between 15-30%. In some c a ses the ver veryy sma ll cross sec ti tions ons ca n even be sq ueezed up tto o 30%. In vac uum applica applica ti tions ons the sq ueeze ca n even be higher. higher. Sq ueezi ueezing ng more than 30% induces induces ad diti ditional onal stress which may c ontr ontriibute to ea rly se al deterioration. In dynamic applications the recommended s queeze is between 88-16% 16%;; due to fri friction ction a nd w ea r considerations, smaller cross sections may be sq ueezed as much as 20% 20%..
0-Ring Sealing Principle
Leakage (Leakage is possible due to permeability of rubber rubber and roughness of the surface) surface)
8
ELEMENTS
TECHNICAL
DOCUMENTATION
O-RINGS
2. O-ring Sealing Principles
Identifying a sealing application type S ea ling ling Appli Applica ca tion Type s
Although s ea ling a ppl ppliica ti tions ons ca n be clas sified ed inme mathod ny dif differ ferent ent w ay s. A cosifi mmon for cl clas as sifyi sif ying ng se aling aling a ppl ppliica ti tions ons is by the type of motion experience experience d b y the a ppli pplica ti tion. on. The c ommon ap pl pliica ti tion on types a re depicted in the g raphi raphicc o n the ri right. ght.
Static
Slow Rotation Fa c e
Sealing tips • P rovi ovide de deta iled sea l install nstallation ation and a ss embly instructi instructions, ons, es pec ially ally if the unit unit co ul uld d b e s ervi erviced ced by the end-user of the product. W When hen a ppropr ppropriia te o r rreq eq ui uired, red, s pec ify the use o f OE OEM M sea ling pa rts. rts. • Within thin reas reas on, the llarger arger th thee cross se ction, the more more effectiv effectivee the s ea l. • Avoi void d s ea ling a xi xiall allyy a nd radial radiallly a t the sa me time with the the s ame OO-ri ring ng ® or Qua Qua d -ring. • Don n’’ t u uss e a s e a l a s a b e a rriin g t o supportt a loa d o r center a shaft. suppor Thi hiss w ill event ua ll llyy c a use se a l fa fa ilure.
Dynamic
Ax ia l
Surface Surface speed less than 50 fpm (15 mete rs/min) rs/min)
Oscillating Slow rota tion tion with a reversal of direction
Reciprocating Linea Linea ir motion with a reversal of direction
Rotaryhigh Speed Rotation Surftha Surface acen 50 speed reater reater fpmg(15 met ers/min) ers/min)
Selecting the seal material When selecting the seal material for the application, carefully consider: • The p rima rima ry fl fluids uids wh ich the O-ri O-ring ng ® or Quad -ri -ring ng will se a l. • Other flui fluids ds to w hi hich ch the s ea l wi willl be expose d, suc h as cleani cleaning ng fl flui uids ds o r lubricants. • The s uitab ility ility of the m a terial for the application’ s temperatur temperature e extr extremes emes - hot and cold. • The presenc e of ab ras ive external contaminants. • Lubri Lubrica ca ti ting ng the sea l and ma ti ting ng components with an appropirate lubricant before assembling the unit. • Keeping the seal stationary in its groove - don ’ t let it spin with the rotating rotati ng member. • When using b ac k-up k-up ri rings ngs , increasing the g roove w idth by the maximum thi thickness o f the ba ckup ring. • With a fa ce s eal, don ’ t try to seal around a s q uare corner corner.. Corner Cornerss must have a minimum radius of 4 times the seal cross section.
9
SEALING
ELEMENTS
3. O-ring Applications
The O-r O-riing is one of the mos t popul populaa r sea l choices bec a use: 1. The O-r O-riing is co st effective iin n pur purcha cha se price price a nd the c os t to ma chine chine the s ea l groove is relatively low. 2. As a bibi-dir directional ectional sq ueeze s ea l, the O-r O-riing c a n be us ed in an e xtr xtremely emely wide variety of successful applications, both static and dynamic. 3. The O-r O-riing ma teri teriaa l a llow s for ma xi ximum mum stretc h or co mpres sion a nd is therefore q ui uite te e a sy to insta ll, g enerall enerallyy req ui uirring no s pecial tools.
Applications: Static: There a re four va ri rieties eties o f sta tic applica appli ca ti tions ons a s noted bel below: ow: 1. Axial
The O-r O-riing c ros s sec tion tion is s q ueezed axially in the groove similar to a flat ga sket. S ee fi figure gure 11-10. 10.
Fig. 1-10
Radial The O-r O-riing c ros s sec tion tion is s q ueezed radiallyy in the groove be twe en the radiall inside (ID) a nd outs ide (OD) OD).. S ee fi figure gure 1-11.
2.
Fig. 1-11
Dovetail The O-ri O-ring ng is a lso a xi xiaa lly s q ueez ed in a do vetail groove. T The he g roove de sign allows the O-ring to be retained in the face sea l dur duriing a ss embl emblyy a nd ma intena nce . Thi hiss is be nefici neficiaa l for spec ia l a ppli pplica tions tions where the O-ri O-ring ha s to be fixed fixed b y the groove e.g . a lid w hi hich ch opens regularly. See figure 1-12.
3.
Fig. 1-12 Q
FULL THREADS TO THIS HIS POINT
CHAMFER CHAM FER RELI RELIEF EF TO HEX FLA FLATS SHOULD
45° ± 5°
15° AND E
BE WITHIN THE
± 5°
ANGLE
Boss Seals The O-ri O-ring ng is us ed for sea ling s traight threa threa d tube fit fitti tings ngs in a b os s. A bos s is a cyli cylindri ndrica ca l pr proj ojection ection on a ca sting or forging. The The e nd o f tha t proj projec ec ti tion on is machined to provide a flat, smooth surfaa ce for se ali surf aling. ng. S tra tra ight thr threa ea ds used with an O-r O-riing provi provide de a better
DIA LIMITATIONS
sea l than tapered thr thread ead s used alone. See figure 1-13.
HEX HEX SHOUL SHOULD D NOT NOT EXCEED H WHEN MEAS MEAS -
4.
F
HEIGHT
E DETAIL
O Y ‘A’
.015
SQU ARENESS BETW BETWEEN THREAD AND FACE FACE OF
URED ATDIAMET ATDIAMETER
E
Fig. 1-13 10
MIN. B O S S
J
THREAD
.031 .016 RAD
RAD
MIN.
FOR THREAD HREAD
S P O T-
RUNOUT
FACE DIAMETER
K THD .
P
D
DIA.
THIS HIS DIM. AP P LIES ONLY WHEN TAP D R ILL ILL C AN AN NOTP NOTP ASS THRU ENTIRE IRE BOS S
TECHNICAL
DOCUMENTATION
O-RINGS
3. O-ring Applications
Dynamic Applications: There a re three varieti varieties es of d yna mic applications as noted below:
Piston seal
1. Reciprocating Reciproca Recipr oca ti ting ng s eals refer to s eals used in a ppli pplica ti tions ons that s lide b ac k and forth. This This mot ion iintrod ntrod uce s fri fricc tion, which creates design considerations dif differ ferent ent fr from om thos e of s tatic s eals. The O-r O-riing ma y be hous ed in a g roove (rod s ea l) in the c yli ylinder nder w all inste ad of a groove in th the e piston surf surfac ac e (piston seal) without any change in design limitations or seal performance. S ee figure 11-14. 14.
Rod seal
Fig. 1-14
2. Oscillating Osc illating a ppl ppliica ti tions ons are tho se seeing bo th rotary and recipr eciproc oc ating movem ent. A valve spindl spindle e iiss a n example of an oscillating application. S ee figure 11-15. 15.
3. Rotary Rota ry seals ref refer er to sea ls used in app lica ti tions ons tha t rota rota te. S ee fi figure gure 1-16 1-16..
Fig. 1-15
Miscellaneous Applications Miscellaneous O-rings are used in a variety of applica ti tions ons . Wiper ipers, s, buffers, and dri drive ve belt applica applica ti tions ons are just just so me of the examples. See figure 1-17.
Fig. 1-16
Fig. 1-17 a Belt
Fig. 1-17 b Crush seal application
11
S E A L I N G
4.
Basic
E L E M E N T S
Elastomers
4.1. Select the elastomer Though " elasto mer" is synonymous with " rubbe r", it iiss m ore formall formallyy a polymer that c a n be mo difi dified to a state exhibiting little plastic flow and q uick uick or nea rl rlyy c omplete recovery from an extending force, and upon immediate rel relea ea se of the stress , w ill retur eturn n to a pproxi pproxima ma tely iits ts o wn s hape . According to the definition of the Ameri merica ca n S oc iety for T Tes es ti ting ng a nd Ma terials (A (AS S TM) for the te rm " ela s tomer" it iiss es se ntial ntial that: *An elas tomer pa rt must not break when stretched ap proxi proximate mate ly 100% 100%.. *After be ing st retche d 100% 100%,, he ld for 5 minutes minutes a nd then rel relea ea sed , it it must retraa ct to w ithin 10 retr 10% % of iits ts origina origina l
Compound A co mpound is a mixtur mixturee of b as e po lymer(s) and other chemicals which form
The physics of Rubber Rubber is is c ompos ed of long chains of rando mly or oriiented molecules. T Thes hes e
a finished rubber material. More precisely, the term term ‘co mpound’ refer referss to a specific blend of ingredients tailored for particular characteristics required to optimize optimize perfor performa ma nce in some spe cifi cificc se rvi rvice ce . The ba sis of co mpound d es ign is se lec tion of the po lymer type. T To o the elas elas tomer tomer,, the compounder may a dd reinf einforci orcing ng a gents, s uch as ca rbon black, colored pigments, curing or vulcanizing agents, activators, plasticizers, a cc elera elera tors, a nti-oxi nti-oxida da nts or antiradiation a dd iditi ditives. ves. There ma y b e hundreds of such combinations.
long c hains are subject to entang lement a nd c ross -l -liinki nking. ng. The The enta nglement has a signi signifi fica ca nt impac impac t on the visc visc oelastic pr properti operties es s uch as stress relaxation. When a rubber is exposed to stress or strain energy, internal rearrangements such as rotation and extension of the polymer chains oc cur. These c hang es o cc ur as a functi function on of the energy a ppl ppliied, the durati duration on a nd ra te of appli applica ca ti tion, on, a s w el elll as the temperature at which the energy is applied. ISO 1629 identifies approximately 25 elasto meri mericc types . Thi hiss c hapte r co vers vers the va rious rious ma teri terial al types used in o-ri o-ring ma nufac nufac tur ture. e.
length within 5 minutes after release. Resistance to the media As used throughout throughout this ma nual, the term term " medi media" a" denotes the substance reta ined b y the o-r o-riing. It may b e a liq uid, uid, a ga s, or a mi mixtur xturee o f both. It can even include powders or solids as we ll. The The c hemica l effec t of the me dia on the O-r O-riing is of pri prime me importa nce . It must not alter the operational characteristics teri stics or rreduc educ e the life expec ta ncy of the o-ring. Excessive deterioration of the O-ri O-ring must b e a voided voided . It is is easy, however, to be misled on this point. A significant amount of volume shrinkage usually results in premature leakage of any O-ring seal, whether static or dynamic. On the other hand, a compound that sw el ellls excess ivel vely, y, or develops a large increase or decrease in hardness, tensile strength, or elongation, will often continue to serve we ll for a long time as a sta ti ticc sea l, in spite of undes irable tes t resul results ts on elas tomer co mpounds . T The he fi first rst step in s electi electing ng the c orr orrec ec t ma teri terial al is to se lect a n el elas as tomer tthat hat is co mpati mpati-ble with the chemical environment.
12
High
y t r e p o r P l c a i s y h P
Low Lo w
Hig h
Cross-link Density Relationship of Cross-link Denisity and Physical Properties
T E C H N I C A L
4.
Basic
D O C U M E N T A T I O N
O - R I N G S
Elastomers
Acrylonitrile butadiene, Nitr Nitrile ile or Buna N (NBR) Nitri Nitrille, che mica ll lly, y, is a co polymer of b uta diene a nd a cryloni crylonitri trille. Acryl Acrylonitr onitriile c ontent varies in commercial products from 18% to 50%. As the nitrile content increases, resistance to petroleum base oils and hydrocarbon fuels increases, but low temperature fl flexi exibil biliity d ecrea se s. Due to its excellent excellent resi resista sta nce to petrol petroleum eum products , a nd its a bil biliity to b e c ompounded for serv serviice over a tem peratur peraturee rang e of -30 -30°° F tto o + 250 250° F (-35° (-35° C to + 1 20 20° C), nitrile is the most widely used elastomer in the seal industry today. Also ma ny mili milita ry rrubb ubb er s pec ifi fica ca tions fo r fuel a nd oil resista nt O-r O-riings req uire uire nitr nitriile ba sed compounds. It shoul should d b e menti mentioned oned that to obtain good resistance to low temperature, itit is is o ften neces sa ry to sa crifi crifice ce so me hi high gh tempe ratur raturee resistanc e. Ni Nitr triile co mpounds are s uper uperiior to most elas tomers w ith rreg eg a rd to com pression set, tear, and ab ras ion resi resista sta nce. Ni Nitr triile co mpounds do not poss ess goo d resista resista nce to oz one, s unli unlight, or w ea ther. They sho uld uld not b e s tored nea r el electri ectricc mo tors or other ozone gene rati rating ng eq ui uipment. pment. T They hey s houl hould d be kept fr from om d irect s unli unlight. Howe ver, ver, thi thiss c an b e iimproved mproved thr through ough c ompounding. NBR is is the s tand ard ma teri teriaa l for hydraul hydrauliics and pneumatics. NBR resists o il-bas ed hydraulic fluids, fats, animal and vegetable oils, flame retardant liquids (HFA, HFB, HFC), grease, water, and air. S pecial llow ow -temper -temperature ature c ompounds a re a vail vailaa ble for mi mineral neral oi oill-bas ed fl flui uids ds . By hydrogena ti tion, on, c a rboxyli boxylicc a cid a dd iti tion, on, o r PV PVC C blending, blending, the nitri nitrille po lymer ca n meet a more spec ifi fied ed rang e of physica l or chemi chemica ca l requi requirrements .
The q ua lity of Ni Nitri trille-co mpo unds de pend s o n the perce nta ge of a crylonitri crylonitrile le iin n the ba se polymer polymer.. The The fol folllow ing ta ble iindicate ndicate s the cha nge of proper properti ties es a s a function function of a cryloni crylonitri trille c onte nt.
50%
% e l i r t i n o l y r c A
18%
-15° C
Low
Higher
e r u t a r e p m e t w o l t a y t i l i b i x e l F
l i o n i e g n a h c e m u l o V
t e s n o i s s e r p m o C
-55° C
High
Lower
Low
y t i l i b a e m r e P
High
13
S E A L I N G
4.
Basic
Elastomers
Hydrogenated nitrile, or highly saturated nitrile (HNBR) Hydrogenated HNBR has recently been developed to meet higher temperatures than standard NBR whil whilee retain retainiing resistanc e to petrol petroleum eum ba se d oil oils. s. Obta ined b y hydrogena ti ting ng the nitrile copolymer, HNBR fills the gap left between NBR, EPDM and FKM elastomers where high temperature conditions require high tensile strength while mainta ini ning ng e xce llent rres es ist a nce to mo tor oil oils, s, s our ga s, a mine/oil mixtu mixtures, res, o xi xidized dized fuels, and lubricating oils. HNBR HN BR is resi resista sta nt to miner mineraa l oil oil-bas ed hydraul hydrauliic flui fluids ds , a nima nima l and veg eta ble fats, diesel fuel, ozone, sour gas, dilute acids and bases. HNBR also resists new bio-oils (biolog biolog ica l oil oils) s).. HN HNBR BR is suitable for high high d ynamic load s a nd ha s a go od a bras ion res ista nce. HNBR iiss s ui uitab tab le for temper temperaa tur tures es from from -3 -30 0° C t o + 1 50 50° C (-20° (-20° F t o + 3 02 02° F).
Carboxylated nitrile (XNBR) Carboxylated The ca rboxyl group iiss a dd ed to s ignifi gnifica ntly ntly iimprove mprove the ab rasion rres es ista nce o f NBR NBR whilee reta ini whil ning ng excell excellent ent o il and so lvent resistanc e. XN XNBR BR co mpounds provi provide de hi high gh tensilee s tr tensil trength ength a nd g ood physica l proper properti ties es a t hi high gh tempe ratur ratures es . XNBR iiss s ui uita ta ble ffor or temperat ures fr from om -30 -30°° C to + 150 150° C (-20° (-20° F to to + 30 302 2° F).
Nitrile/PVC resin blends (NBR/PVC) P VC resi resins ns a re blende blende d w ith ni nitr triile po lymers to provi provide de increas ed res ista nce to ozone a nd a bras ion. T The he P VC also provi provides des a signifi significa ca nt iimprovement mprovement iin n so lvent res ista nce, ye t ma intains simi simillar chemica l and physica l proper properti ties es , co mmonl mmonlyy noted am ong ni nitr triile elas tomers. T The he a dd iti tion on o f the P VC resins resins a lso provide provide a grea ter pi pigme gme nt-ca nt-ca rr rryi ying ng c ap ac ity which a llow better retenti retention on of pa ste l and bright bright c olor olors. s.
Ethylene Propylene, and Ethylene Propylene Diene rubber (EPM, EPDM) Ethylene Ethyl ene p ropylene ru rubbe bbe r is is a n elas tomer prepared from from e thyl thylene ene a nd propyl propylene ene monomers (ethyl ethylene ene propylene copo lymer) and at times times with an a mount of a thir third monomer (ethylene propylene terpolymers). Ethylene propylene rubber has a temperature rang rang e of -50 -50°° C t o + 1 20 20° /150 /150°° C (-60° (-60° F to to + 25 250 0° /300 /300°° F), F), d epend ing on the curing system. It has a great a cce ptance in the sea ling w orld orld b eca use of it itss excel excelllent rresistance esistance to heat, w ater and stea m, alkali alkali,, mi milld a cidic cidic and oxygenated solv solvents, ents, ozone, a nd sunlight. T These hese c ompound s a lso w ithsta nd the affect of brake fl flui uids ds a nd S kydrol kydrol™ ™ a nd other phosphate ester-based hydraulic fluids. EPDM compounds are not recommended for gasoline, petroleum oil and grease, and hydrocarbon environments. Spec ial E EPDM PDM compounds have go od resi resista sta nce to stea m. • EPDM Sulphur cured: inexpensive material for normal use, maximum temperature of + 12 120 0° C (+ 25 250 0° F). • EPDM Peroxide cured: for hot water, vapor, alcohols, ketones, engine coolants, orga ni nicc a nd in inorga orga ni nicc a cids a nd ba ses . Not rres es ista nt to mi mineral neral oil oils. s. For maximum tempera tempera tur tures es o f + 150 150°° C (+ (+ 30 300 0° F).
14
E L E M E N T S
T E C H N I C A L
4.
Basic
D O C U M E N T A T I O N
O - R I N G S
Elastomers
Neoprene rubber Polychloroprene (CR) Neoprene rubbers are homopolymers of chloroprene (chlorobutadiene) and were among the earliest synthetic rubbers used to produce seals. CR has good aging cha rac ter teriistics in ozone a nd w ea ther env enviironment ronments, s, a long w ith ab ras ion a nd fl flex ex crac ki king ng resistanc e. C R is is not effecti effective ve iin n a romati romaticc and oxygena ted solvent envi envirronments. Neoprene ca n be c ompounded for ser servi vice ce temperatur temperatures es of -4 -40 0° C to + 11 110 0° C (-40°° F to (-40 to + 23 230 0° F). Most elastomers are either resistant to deterioration from exposure to petroleum based lubricants or oxygen. Neoprene is unusual in having limited resistance to both. Thi his, s, c ombined with a broad temperature temperature range a nd mod erate co st, a cc ounts for its de sira sira bili bility in ma ny s ea l appli applica ca ti tions ons for refri refrige ge rants like Fr Freon eon ® and ammonia. CR is resistant to refrigerants, ammonia, Freon® Freon ® ( R12, R13, R21, R22, R113, R114, R115, R134A), silicone oils, water, ozone, vegetable oils, alcohols, and low-pressure oxygen. CR ha s a very very llow ow resista nce to miner mineral al oi oills.
Silicone rubber (VMQ). Sil Siliicones are a group of elastome ric materials materials ma de from from s ilicone, oxygen, hyd rogen, and ca rbon. Extr Extreme eme temperatur temperaturee rang e a nd low temperatur temperaturee flexi flexibi billity a re cha rac ter ter-istics of sil siliicone compo unds. As a group, sil siliicones have poor tensile tensile s trength, trength, tea r resistance, and abrasion resistance. Special compounds have been developed with exceptional heat and compression set resistance. High strength compounds have also b een ma de, b ut thei theirr str strength ength do es not compa re to c onventi onventional onal rrubber. ubber. Sil Siliicones poss ess excell excellent ent resi resista sta nce to extreme temperatures temperatures -50 -50° C to + 232 232° C (-58°° F to (-58 to + 45 450 0° F). F). S ome s pecial compounds resist even higher temper temperatures. atures. Retention of prope prope rti rties es o f si sillico ne a t high high temp erature is s uperi uperior or to most othe r elas tic materials. Sil Siliicone c ompounds are ver veryy clean and are used in many food a nd medica l a ppli pplica ti tions ons b eca use they do not impart odo r or taste. S ilicone c ompounds are not rreco eco mmended for dynamic O-ring sealing applications due to relatively low tear strength a nd high c oeffici oefficient ent o f fri friction. Silicone is resistant to hot ozone, UV radiation, engine oils,toanimal and veg eta ble ble fats andair, oil oils, s, a nd brake flui fluids ds . V VMQ MQ a lsoand hastransmission low resista nce mineral oils. Silicone can be compounded to be electrically resistant, conductive, or flame retardant. Many s ilico ne co mpound s ha ve a highe highe r than normal mold shri shrinkag nkag e. T Therefore herefore pr prooduc ti tion on mo lds for sil siliico ne prod ucts a re often d iffer fferent ent tha n molds for ni nitri trille.
15
S E A L I N G
4.
Basic
E L E M E N T S
Elastomers
Fluorosilicone (FVMQ) Fl Fluorosil uorosiliico ne c omb ines the g ood highhigh- a nd low-tempe ratur raturee properties properties of s ilico ne with lilimi mited ted fuel a nd o il res res ista nce. Fluorosil Fluorosiliico nes provi provide de a much w ide r operational temperature rang e tha n Fl Fluoroca uoroca rbon rubbers. P rima rima ry uses of fl fluorosil uorosiliico ne O-ri O-rings ngs are in in fu fuel el systems at temper temperatures atures up to + 177 177° C ((++ 350 350° F) a nd in a ppl ppliica ti tions ons whe re the dry-heat resista nce of sil siliico ne O-r O-riings a re req req uired. uired. Fl Fluorosil uorosiliico ne O-r O-riings ma y a lso be e xpos ed to petroleum bas ed oil oilss a nd/ nd/or or hydrocarbon fuels. In some fuels and oils; however, the high temperature limit in the fluid list is more conservative because fluid temperatures approaching 200° 200 ° C (390° (390° F) ma y deg rade the flui fluid, d, prod ucing a cids which a ttac k fl fluorosil uorosiliico ne O-r O-riings . For llow ow temperature a ppli pplica ca tions tions , fluorosil fluorosiliico ne O-r O-riings se a l a t temperatures a s low a s -73 -73°° C (-100°° F). (-100 Due to rela rela ti tivel velyy low tea r strength, hi high gh fri friction ction a nd li limi mited ted a bras ion resista nce of these materials, they are generally recommended for static applications only. Fluorosilicones with high tear strength are also available. Some of these compounds exhibit improved resistance to compression set. Many fluorosilicone compounds have a hi highe ghe r than normal shri shrinkage nkage rate s o prod uction mol molds ds for fflluorosil uorosiliico ne produc ts are often different from molds for nitrile.
Polyurethane rubber (AU, EU) Polyurethane Polyurethanes (Polyester-urethane AU), (Polyether-urethane EU) exhibit outstanding mecha ni nica ca l a nd phys ica l proper properti ties es in compa riso n with other ela ela sto mers. Urethanes provide outstanding resistance to abrasion and tear and have the highest available tensilee s tr tensil trength ength a mong a ll elasto mers w hil hile provi providing ding go od elonga ti tion on c harac teri terissti tics cs . Ether ba s ed uretha nes ((EU) EU) a re dir direc ec ted to w a rd llow ow te mpera ture flexibi flexibillity ap pl pliica ti tions ons . T The he es ter ba sed ur uretha etha nes (AU) provide provide improved a bras ion, hea t, a nd oil sw ell res ista nce. Over a tempe ratur raturee rang e o f -4 -40 0° C t o + 82° C (-40° (-40° F to to + 18 180 0° F) F),, resistanc e to petroleum ba sed oil oils, hydroca rbon fuel fuels, s, o xygen, ozone a nd w ea ther theriing is g ood. However, polyurethanes quickly deteriorate when exposed to acids, ketones and chloriinate d hyd roca rbons. C ertai chlor ertain n types of polyesterpolyester-ur urethane ethane s (AU) are a lso se nsiti tive ve to wa ter and humi humidity. dity. Po lyetheryether-ur uretha etha nes (EU) offer better resistanc e to wa ter and humidity. T hea rl inh inherent erent s a nd on resista polyur polyuretha etha ne ck ((EU) EU) is pa rti ti-cula cul rly y de sir siraa toughnes ble iin n hydraul hydrauli ic as bras yste ims w here nce high highof press ur ures es , sho loa loasea ds ,lswide metal tolerances, or abrasive contamination is anticipated.
Fluorocarbon rubber (FKM) Fl Fluoroca uoroca rbon el elaa sto mers ha ve grow n to ma jor iimportanc mportanc e in th thee s ea l industry. Due to iits ts w ide rang e of chem ica l co mpa ti tibil biliity, temperature rraa nge, low c ompress ion set, and excell excellent ent a ging cha racteri racteristics, stics, fluoroca fluoroca rbon rrubber ubber iiss the mos t signi signifi fica ca nt singlee e las tomer de veloped singl veloped in recent history. Fl Fluoroca uoroca rbon el elaa sto mers a re highl highlyy fl fluor uoriinated ca rbonrbon-ba ba sed polymer polymerss us ed in ap pl pliica ti tions ons to resist harsh c hemi hemica ca l a nd oz one a ttac k. The w ork orkiing temp eratur eraturee range is considered to be -26° -26 ° C to + 205 205° /230 /230°° C (-15° (-15° F tto o + 400 400° /440 /440°° F) F).. B ut for short working periods it will take even higher temperatures. Special compounds having improved chemical resistance are also available with new types alwa ys b ein eingg d evel eveloped oped . G enerall enerallyy sp ea king, king, w ith increas increas ing fl fluori uorine ne content, resistance to chemical attack is improved while low temperature characteristics a re d imini minished shed . There There are, how ever, spec ia lty grad e fluor fluoroc oc a rbons that c a n provide high fluorine content with low temperature properties.
16
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T E C H N I C A L
4.
Basic
D O C U M E N T A T I O N
O - R I N G S
Elastomers
Fl Fluoroca uoroca rbon O-r O-riings should be co nsidered for use in air aircraft, craft, a utomobil utomobilee a nd o ther mechanical devices requiring maximum resistance to elevated temperatures and to ® , Fluorel® ma ny flui fluids ds . FKM ((FP FP M, V Viton iton® Fluorel® ) res ist mi mineral neral oil oils and grea ses , a liphatic, aroma ti ticc a nd a lso spe cial chl chlori orinated nated hydroca rbons, pe tr trol, ol, di diese ese l fuel fuels, s, s ilico ne oil oilss a nd g reas es. It is is s ui uitab tab le for hi high gh va cuum a ppl ppliica tions. tions. Many fluoroca fluoroca rbon compo unds ha ve a higher than normal mold shri shrink nkaa ge ra te, molds for fluorocarbon products are often different from molds for Nitrile.
Perfluorocarbons (FFKM) The rel relaa ti tive ve inertnes inertnes s o f fluoroc fluoroc a rbon rubbe rs iiss p rovide rovide d b y fl fluori uorine-ca ne-ca rbon bo nds on the elas tomer ba ckbone. Ge neral nerallly sp ea king, king, w ith increas increas ing fl fluori uorine ne co ntent, res ista nce to c hemi hemica ca l attac k iiss improved. W Where here fl fluor uoroc oc a rbon ru rubbe bbe rs have a fl fluouori rine ne co ntent of 63 - 68 %, %, the perfluoroca perfluoroca rbons ha ve a fluor fluoriine c onte nt of 73% 73%.. Perfluorelastomers possess excellent resistance to extreme temperatures -26° -26° C to + 2 60 60° C (-15° (-15° F to to + 50 500 0° F) F).. FFKM FFKM pe rf rfuoroelas uoroelas tome rs: (Kalrez Kalrez ® ) offers offers the be st chemical resistance of all elastomers. Some types are particularly suitable for hot water, steam and hot amines. Some resist resi st tempe ratur ratures es up to + 326 326°° C (+ 620 620° F). Many perfluoroca perfluoroca rbon comp ounds have unusua l mold shri shrink nkaa ge, production mol molds ds for perfluorocarbon products are different from molds for nitrile.
Teflon®-FEP Teflon® FEP is a cop olymer of tetrafl tetrafluorethyl uorethylene ene a nd hexa fluorpr fluorpropylene. opylene. FEP FEP has a low er melting melti ng p oint than P TFE making iitt s uita uita ble for iinj njec ec tion mouldi moulding. ng. FEP is us ed for ® enc a ps ul ulaa tion tion w ith T TEFL EFLEX EX OO-rrings. FEP FEP has a wide spec tr trum um of chemi chemica ca l compati tibil biliity a nd te mperature rrang ang e a nd e xcell xcellent ent a ging c harac teri teristics. stics. Maxi Maximum mum operati ting ng te mperatur mperaturee for FEP is + 205 205°° C ((++ 40 400 0° F) F).. A Teflon P FA enc a ps ula ula tion is a va ila ble for highe highe r tempera tures (2 (260 60°° C ).
TFE/P (Aflas® (Aflas® ) (FEPM) (FEPM) TFE/P is a co polymer of tetra fluoroethy fluoroethy lene a nd prop ylene with a fluori fluorine ne c onte nt of a pp.phosphate-esters. 54% 54%.. Thi hiss ma teri terial al is isome s unique due toit its resistamedia nce to compatibility p etrol etroleum eum products , stea m, and In respects exhibits properties similla r tto simi o ethylene propyl propylene ene a nd fl fluoroca uoroca rbon. The co mpress ion s et resista nce at high high te mperatures is infer inferiior to sta nda rd fl fluoroca uoroca rbons. S ervi ervice ce temperatures a re -5° -5° C (25° (25° F) to + 204° 204° C (+ (+ 400 400° F). F). TFE/P p rovide rovide s improved che mica l resista nce t o a wide s pec trum trum of autom otiv otivee flui fluids ds a nd a dd itives. tives. It iiss res ista nt to eng ine oil oilss o f all types , eng ine c oolants with hi high gh level of rust in inhi hibitor bitors, s, extreme press ure ure (E (EP P ) ge a r lubri ubrica ca nts, trans mi miss ss ion a nd po we r steeri steering ng fl flui uids ds , a nd a ll types of brake fl flui uids ds including DOT 3, mineral oil oil,, a nd sili silico ne o il. il. TFE/ FE/P is idea l for heat transfer medi media, a, amines, a cids a nd ba ses , a s w ell ell as hot wa ter and stea m u up p to + 17 170 0° C ((++ 340 340°° F) F)..
17
S E A L I N G
4.
Basic
E L E M E N T S
Elastomers
Polyacrylate rubber (ACM) P olyac ryl rylaa te-A te-Acryl cryliic A Acid cid Ester. These co mpounds a re des igned to w ithsta nd hea t whilee reta ini whil ning ng oil resistanc e. S pec ia lly d es igned for sul sulfur fur bea ring ring oil a ppli pplica ca ti tions ons , ACMs a re subj subjec ec ted to hea t and b ea ring ring envir environments onments . They have g ood resi resista sta nce to dry hea t, oxyg en, sunli sunlight, ght, a nd o zone b ut thei theirr low low tempera ture ture properti properties es are rel relaati tivel velyy po or and they ha ve low s we ll in in min mineral eral oi oills. S ervi ervice ce tempera tur tures es a re --20 20°° C (-5° -5° F) to 150° 150° C (300° (300° F). F). A ACM CM iiss ma inly nly used for O O-r -riings a nd s haft s ea ls to se a l hea vy oil oilss a t hi high gh tem peratures a nd in the automo tive tive iindustry ndustry for tr traa nsmiss ion a nd po we r steering applications. Epichlorohydrin (CO, ECO) Epichlor Epi chlorohyd ohyd ri rin n rubber c ompo unds are noted for thei theirr superi superior or g a s impermea bili bility a nd phys ica l properti properties es over a w ide temperature range whil whilee ma intaini ntaining ng e xcell xcellent ent resista resi sta nce to petrol petroleum eum oil oils. s. It has a sta ble cyc ling c a pa bili bility fr from om low to hi high gh temperature. Resistance to ozone, oxidation, weathering, and sunlight are other typica l ECO q uali ualiti ties es . S ervi ervice ce temperatures a re --51 51°° C to150° to150° C (-60° (-60° F to to + 300 300° F) F).. Co mpounds fr from om this polymer ca n exhi exhibit bit a c orr orros os ive nature a nd c a n be d iffi fficult cult to process in manufacturing. Vamac® Vamac Ethylene Acrylate Acrylate . Thi hiss ma teria teria l exhibits properties s imila mila r to po lya crylate b ut ca n be formul formulaa ted to exhibi exhibitt lower temperature ca pa bili bilities ties . It has exce llent resista nce to oxidation, automatic transmission, and power steering fluids. The tem pera ture service rang e is -40 -40°° C to + 150 150° C (-40° (-40° F to + 300 300° F) F).. Styrene Butadiene (SBR, Buna S) Thi hiss ma teri teriaa l iiss simi similla r to na tura tura l rrubbe ubbe r. OO-ri ring ng usa ge has bee n on d ecli ecline ne s ince the introduction of ethylene propylene. SBR still finds service in brake fluid applications, a lthough the hi high gh te mperature range is infer nferiior to tha t of e thylene thylene p ropyl ropylene ene co mpounds . S ervi ervice ce range for tthi hiss ma teri teriaa l is -50 -50°° C to + 110 110° C (-65° (-65° F to to + 22 225 5° F) F).. Butyl (IIR) Butyl has excell excellent ent resi resista sta nce to phospha te es ter fflluids uids such a s Skydrol™ Skydrol™ , but has a n inferior high temperature limit when compared to ethylene propylene. Butyl exhibits the bes t butyl rres es istahas ncebeen to gaalls pe ility aby ndethylene s ome roc ket pr propell opellents. ents. For O O-r -riing a ppli ppli-cations, butrmeab replaced propylene. The te mpe rature s ervi ervice ce rang e for thi thiss m a teria teria l is -55 -55°° C to + 105 105° C (-65° (-65° F to + 22 225 5° F) F).. Special materials ERIKS ERI KS o ffer fferss ma ny pos sibi sibillities ties in s pec ia l O O-r -riings co mpounds to impr improve ove c ertain properties like: Silicone free and Labs free Coatings - Encapsulated FEP and PFA P TFE O-rings O-rings - Interna l Lubri Lubricc a tion - Hi Higg h P urity urity - Mi Micro cro O -ring -ring s - V Vulc-O-ri ulc-O-ring ng s .
Ask for for in informa formation tion iin n our ‘High Purity Seals Handbook ’. www.eriks.com
Homologations ERIKS ERI KS offers offers ma ny c ompo unds with homo log a tions tions , like: like: KTW – FDA – WRC – NSF – DVGW.
KTW
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NSF
WRC
DVGW
ACS ACS
KIWA
T E C H N I C A L
4.
Basic
D O C U M E N T A T I O N
O - R I N G S
Elastomers
Table 3A-1
Elastomer
NBR
EPM
CR
VMQ
FVMQ
EU
FKM
FFKM
PTFE-FEP
ASTM
Nitrile
EPR
Neoprene
Silicone
Fluoro silicone
Urethane
Fluoro carbon
Perfluoro carbon
encapsulated
20 / 90
30/90
15/95
20/90
35/80
60/95
50/95
65/90
-
Temp. ra nge ° F/° C m a x.
230/110
266/130
248/120
446/230
446/230
176/80
410/210
620/326
400/205
Temp. ra nge ° F/° C m in .
-30/-35
-67/-55
-49/-45
-67/-55
-76/-60
-22/-30
5/-15
-58/504
-76/-605
G ENERA ENERAL L Ha rd n e s s (S h o re " A" )
NOTE : The The temperature range is s trongly trongly de pendent b y the s pecifi pecificc c ompound C o m p re s s io n S e t
B
C
C
A
B
E
C
B
E
We a r R e s is t a n c e
C
C
C
E
E
A
C
C
E
G a s P e rm e a b ilit y
C
C
C
E
E
B
C
C
E
NOTE : The co mpress ion s et va lue lue for Kalrez Kalrez is relative to temperature. In low temperature applications this value is reasonable, in high temperatures ®
this this va lue is is g ood to very good.
Air
E
B
C
A
B
C
B
A
+
Alc o h o l
B
A
B
B
B
U
E
A
+
Ald e hy d e s
U
B
U
C
U
U
U
Bfi
+
Alip h a tic Hy d ro c a rb o n s
C
U
E
E
A
C
A
A
+
Alka lis
B
A
C
B
B
B
C
A
+
Am in e s
B1
B1
B1
E1
B1
U
U
Bfi
+
Anim a l Fa t s
B
U
C
C
A
C
B
A
+
Aro m a t ic Hy d ro c a rb o ns
D
U
D
U
B
D
A
A
+
Es t e rs , Alky l P ho s p ha te
U
B
U
C
U
U
U
A
+
Es t e rs , Ary l P ho s p ha t e
U
A
U
C
B
U
A
A
+
(S kydrol) Es t e rs , S ilic a te
C
U
E
U
B
U
A
A
+
Et he rs
U
E
U
U
E
E
U
A
+
Ha lo g e na te d hy d ro c a rb o n s
U
U
U
U
B
E
A
A
+
In o rg a n ic Ac id s
E
C
B
B
B
U
A
A
+
Ke t o n e s
U
A
A
C
A
U
U
B
+
Min e ra l O il, h ig h a n a line fa t s
B
U
C
C
B
A
A
A
+
Min e ra l O il, lo w a n a line fa t s
B
U
U
E
B
B
A
A
+
O rg a n ic Ac id s
C
C
C
B
B
U
C
A
+
S ilic o ne O ils Ve g e ta b le O ils
A A
A2 U
A C
E B
E B
A E
A A
A A
+ +
Wa t e r / S t e a m
C
A
E
E
E
U
B ⁄
C4
+
A B C D E U
1 2 3 4 5 +
G ood S a t is fa c t o ry Fa ir D o ub t f ul P oor U n s a t is fa ct c t o ry
S e e t h e lis t " c o m p o u n d s e le c t io n fo r c h e m ic a ls a n d flu id s " E P D M/E P R m a y s h rin k D e p e n d in g o n FKM t y p e D e p e n d in g o n c o m p o u n d D e p e n d in g o n e la s t o m e r c o re in g e n e ra l " A" A" b bee c a u s e t h e e n c a p pss u la ti tio n is FE FE P
This information is intended only as a guideline. Chemical compatibility lists should be consulted. ERIKS will provide this on request. Whenever possible the fluid compatibility of the O-ring compound should be rated "A". For a static seal application a rating "B" is usually accepta ble, but it should should be tested. Where a "B" rated compound must be used, do not expect to re-use it after disassembly. It may have swollen enough that it cannot be reassembled. When a compound rated "C" is to be tried, be sure it is first tested under the full range of operating conditions. It is also particularly important to test seal compounds under service conditions when a strong acid is to be sealed at elevated temperatures because the rate rate of degradati degradation on of rubber at elevated temperatures temperatures is is many times times greater than the rate of degradation degradation at room temperature. temperature.
19
S E A L I N G
4.
Basic
E L E M E N T S
Elastomers
Chemical and Physical Tables
r e m y l o P
) a P M ( h t e g l i s n e n r e t T S
NB R
6. 927. 6 HNB R 31. 010. 0 FKM 3. 420. 7 EP 2. 124. 1 SBR 3. 424. 1 CR 3. 427. 6 IIR 13. 820. 7 VMQ, S i, 1. 4P MQ, 10. 3 P VMQ FVMQ 3. 49. 7 AC M 8. 617. 2 EA 6. 920. 7 CS M 3-15
EC O NR ; IR AU , EU
20
10-15 3. 434. 5 6. 969. 0
s a l u ) d P o ( M M % e 0 l i s 0 n e 1 a T t
- ) o r e u A r D o h s s ( S e r n e d t r a e H m
) ( % n o i t a g n o l n E
2. 0-15 20-100 100-650 1. 720. 7 1. 413. 8 0. 720. 7 2. 110. 3 0. 720. 7 0. 33. 4 6. 2
p C m e ° T e g w n o a L R
p C m e ° T e h g n g a i H R
210 t o 250 250 t o 3000 400 t o 500 220 t o 300 210 t o 250 200 t o 250 250 t o 300 400 t o 500
99 t o 121 121 to 149 200 t o 260 104 to 149 99 t o 121 93 t o 121 121 to 149 204 t o 260
90-450
50-95
100500 100700 450600 100800 300850 100900 100480 100450 200650 100700
Fa ir- -112 to G ood -90 P o o r- -30 t o 0 G ood P o o r- -35 to G ood -30 P o o r- -60 to Fa ir -40
-80 to -68 -34 t o -18 -48 to -34 -51 to --4 40
400 t o 450 250 t o 350 250 t o 350 225 t o 270
204 to 232 121 t o 177 121 to 177 107 to 132
G oodE xc .
200800 300900 250900
G ood Fa ir Exc .
-51 t o --2 26 -57 to -40 -54 to -40
225 t o 275 180 t o 220 180 t o 220
107 t o 135 82 t o 104 82 t o 104
G oodE xc . Fa irG ood Fa irG ood
30-90 30-100 15-95 30-80 20-90
30-95
10-100
P o o rG ood
-70 t o 0 -57 t o -18 -50 t o 0 -46 to -18 -50 t o 0 -46 to -18 -75 to -46 to -40 -18 -75 to -59 to -55 -48 -70 to -57 to -30 -34 -70 to -57 to -400 -40 -178 to --1 117 to -90 -68
p F m e ° T e h g g n i a H R
30-95
0. 5-0. 8 20-10 0. 234. 5
p F m e ° T e g w n o a L R
t C a ) ° g 0 n i 0 g 1 A ( F t ° a e 2 1 H 2
G ood Exc . G ood Exc . G ood Exc . P o o rExc . G ood Exc . P o o rG ood P o o rG ood G ood G ood
3. 135-80 3. 4 0. 740-90 10. 3 0. 735-95 10. 3 0. 2-10 40-100
1-10
n o i s g s n i e t r a p R m t o e C S
-60 to -15 -70 to -40 -65 to -40
G ood E xc . Exc . G oodExc . G ood G oodExc . G oodE xc . Exc .
e c n a t m s i a s e t e S R
e c n a e t s i m a s e l F R
Fa irG ood Fa irG ood P o o rG ood E xc .
P oor
Fa irG ood Fa ir G ood G oodExc . Fa irG ood
e c r n e a t h t s i a e s e W R
Fa irG ood P oor G ood E xc . G o o d - E xc . Exc . P oor E xc .
e c t n h t a g s i l s n i u e S R
e c n a t e s n i o z s e O R
P oor G ood G ood Exc . G oodExc . Exc .
Fa irG ood G oodE xc . E xc .
Fa irG ood Fa irG ood E xc .
P oor
G oodE xc . P oor
G ood Exc . Exc .
G oodE xc . E xc .
Fa irExc .
E xc .
Exc .
E xc .
P oor G oodE xc . P oor
E xc .
Fa ir
Exc .
E xc .
Exc .
E xc .
Exc .
P oor
P oor
E xc .
E xc .
P o o rFa ir P o o rG ood
P oor
E xc .
G oodExc . Exc .
G oodE xc . E xc .
G ood E xc .
E xc .
Exc .
E xc .
P o o rG ood P oor
G ood
G ood
P o o rFa ir E xc .
P oor
G oodE xc . P oor
Fa irG ood Fa irG ood P oor
P o o rG ood
G oodExc .
E xc .
T E C H N I C A L
4.
Basic
D O C U M E N T A T I O N
O - R I N G S
Elastomers
Chemical and Physical Tables
r e m y l o P
e c n n o i a t a t s i i d a s e R R
NB R
Fa irG ood HNB R Fa irG ood FKM Fa irG ood EP G oodE xc . SBR P o o rG ood CR Fa irG ood IIR P o o rG ood VMQ, S i, P o o rP MQ, G ood P VMQ FVMQ Fa irE xc . AC M P o o rG ood EA G ood
) R I A ( n e c o n i t a a z t i s i d i s x e O R G ood
e c n a t r s e i t a s e W R
Exc .
G oodE xc . Exc .
Exc .
E xc .
Exc .
E xc .
Fa ir- G o o d Exc . E xc . G o o d - Fa irExc . G ood Exc . G oodE xc . Exc . E xc .
Exc .
E xc .
Exc .
P o o rFa ir G oodE xc . G ood
Exc .
y t i l b a e m r e g P i n s a t a G R
r o d O
n o i t n e e t t n s a e T R
Fa irExc . Fa irExc . G ood Exc . Fa irG ood Fa ir
G ood
Fa irG ood G ood
Fa irG ood G ood
P o o rFa ir
G ood
P o o rG ood G ood Exc . Exc .
G ood
G ood
Fa irG ood G ood
G ood Exc .
G ood
Fa irG ood Fa irG ood Fa irG ood
G ood G ood G ood G ood
Fa irG ood Fa irG ood Fa irG ood G oodExc . Fa irG ood Fa irG ood Fa irG ood G oodExc .
CS M
P o o rG ood
Exc .
EC O
P oor
G ood
Exc .
G ood
G ood
NR , IR
Fa irG ood G oodExc .
G oodE xc . G ood
E xc .
G oodExc .
P o o rG ood
Fa irG ood G ood Exc .
G ood Exc . Exc .
Fa irG ood Fa irG ood
AU , E EU U
g t i n r a o R e c d n n u e o i l i s e b e R R
o t n o i s s e l a h t d e A M
y t i l i b a r o l o C
r o l o C e A d M o R C
Exc .
Exc .
Back
G ood
Exc .
Exc .
-
G ood
G o o d - G o o d - B ro w n Exc . Exc . G o o d - G o o d - P urp le Exc . Exc . E xc . G ood -
Fa irE xc . Fa irG ood Fa irE xc . Fa irG ood P o o rG ood G oodE xc .
g n n i o n e i t p a r m b i a V D Fa irG ood G ood Exc . Fa irG ood Fa irG ood Fa irG ood G oodExc . Exc .
g n i e k c c n a r t a C i s x e s e l F R G ood
G ood E xc . G ood G ood E xc . G ood Fa irG ood G ood Fa irG ood G o o d - Fa irExc . E xc . G ood G oodE xc . G ood- G ood Exc . P o o r- P o o rG ood G ood
E xc .
Fa ir
Re d
G ood
G ood
-
G oodExc .
Exc .
R us t
G oodExc . G ood
G ood Exc . G ood
B lue
E xc .
G ood
-
G ood
G ood
-
G oodExc . G ood
Exc .
Exc .
-
Fa irG ood P o o rFa ir Fa irG ood
P o o rG ood Fa irG ood G ood
Fa irG ood
Fa irG ood
Fa irG ood E xc .
G ood
-
G ood
G ood
G ood
P oor
-
Exc .
E xc .
G ood Exc .
-
P o o rG ood
G oodExc . Fa irG ood
Fa ir G ood
c e n a t s i s e R r a e T
P o o rE Ex xc . P o o rG ood G oodE xc . Fa irG ood
Fa irE xc . Exc . G o o d E xc . G o o d - E xc . Exc .
e c n n o a i s t s a r i e b s A R
t h g i e W m u u s c s a o V L
G ood Exc . G oodExc . G ood
G ood
G ood
E xc .
G oodExc . G ood Exc . Fa irG ood P o o rG ood
P oor
P oor
E xc .
Fa irG ood G ood Exc . G ood Exc .
G ood
Fa irG ood G ood Exc . Exc .
G ood E xc .
Fa ir E xc . E xc .
Fa irG ood Fa ir
G ood P oor G ood
21
S E A L I N G
4.
Basic
E L E M E N T S
Elastomers
Chemical and Physical Tables (Continued)
) e t u l i d ( s d i c A
) d e t a r t n s e c d n i o c c A (
c i n a g r o ) e , t d u i l c i d A (
d c ) i e t n a a t r g r n o e , c d n i c o c A (
NB R
G ood
G ood
P oor
HNB R
G ood
G ood
FKM
G ood Exc . Exc .
P o o rFa ir Fa irG ood G oodE xc . E xc .
Fa irG ood Exc .
P o o rFa ir P oor
G ood Exc . Fa irG ood
Fa irE xc . P o o rFa ir
G ood
Fa irG ood P o o rG ood Fa irG ood P o o rG ood P o o rG ood Fa irG ood Fa ir
Exc .
G ood
G ood
Fa ir
Fa ir
P o o rFair P o o rFa ir G oodE xc .
P oor
r e m y l o P
EP SBR CR IIR VMQ, S i, P MQ, P VMQ FVMQ AC M EA
G ood
CSM
Exc .
EC O
G ood
NR ; IR
Fa irExc . Fa irG ood
AU , EU
22
P o o rFa ir P o o rG ood P oor
Fa irG ood Exc . G ood G ood Exc . G ood
) 4 s C l u r o h h t o c 1 l ( A C
) 6 s e C d u r y h h t e 1 d l C A (
Fa irG ood G oodExc . Fa irExc . G oodExc . G ood
P o o rFa ir Fa irG ood P oor
Exc . G oodExc . Fa irG ood
G oodE xc . P o o rFa ir P o o rFa ir G ood G ood
) e t u l i d ( s e i l a k l A G ood G ood Fa irG ood E xc .
) d e t a r t n s e e i c l a n k l o c A ( P o o rG ood P o o rG ood P oor Exc .
Fa irG ood G ood
Fa irG ood P oor
G ood E xc . P o o rFa ir
G ood Exc . P o o rExc .
s e n i m A P oor G ood P oor
s l i o e l & b l a a t e m i n g e A V G oodE xc . G oodE xc . E xc .
; d i 5 u & l F 4 , e 3 k t a r o B D
s l i O r e t s e l D
P oor
Fa irG ood G ood
Fa ir
l y e k l t a A , h s p r e s o t s h E P P oor P oor
P o o rFa ir G oodExc . P o o rG ood Fa ir
G oodE xc . P oor
P oor
P oor
P oor
P oor
P oor
G ood
P o o rG ood P o o rFa ir
G ood-
G ood
G oodExc . G ood
P o o rF Faa ir P oor
Fa irG ood P o o rG ood P o o rG ood G ood
G ood P o o rG ood G ood
G ood
Exc .
G ood
P oor
E xc .
G ood
P oor
E xc .
P oor
P oor
Fa irExc . P oor
P oor
Fa ir
Fa ir
P oor
G ood
P oor
G oodE xc . G ood
G ood Exc . Exc .
P o o rExc . G ood
G ood Exc . Exc .
Fa irG ood P o o rFa ir
G oodExc . G oodE xc .
P oor
G ood
G ood
P oor
P oor
P oor
G oodExc .
P oor
G ood
Fa ir
P oor
P oor
Fa ir
P oor
P oor
P o o rFa ir Fa irG ood P oor
P o o rG ood P o o rFa ir P o o rFa ir
P oor
P o o rG ood Fa irE xc .
G ood
P o o rG ood P oor
P oor
Fa irG ood P oor
Fa irG ood Fa irE xc . P o o rE xc .
E xc .
G ood
Fa irG ood G oodExc . G ood
Fa ir
G ood P oor
P oor
P o o rG ood
P oor P oor
T E C H N I C A L
4.
Basic
D O C U M E N T A T I O N
O - R I N G S
Elastomers
Chemical and Physical Tables (Continued)
r e m y l o P NB R
t e a h p s o , h s P r l e t y s r E A
s r e h t E
i c t a n o m b r o r a A c , o r l d e u y F H
d e ) d d e n e t a t x n e E g , y l e x u ( F O
G oodExc . Exc . Exc .
Fa irG ood Fa irG ood Exc .
Fa irG ood G oodE xc . E xc .
d e t a s n e t g n e o l v l a o H S
s e n o t e K
s r t e u n e q v l c a o L S
& s e s s l i a O G l . e P . u L F
P oor
P oor
Fa ir
Exc .
P oor
Fa ir
Exc .
P oor
P oor
G oodExc. P o o rGood P o o rFa ir P o o rExc . P oor
P o o rFa ir P o o rFa ir Exc .
P o o rFa ir P oor
EP
E xc .
Fa ir
P oor
P oor
P oor
P o o rFa ir G oodExc. P oor
SBR
P oor
P oor
P oor
P oor
P oor
P oor
CR
poor
P o o rG ood P oor
P o o rFa ir P oor
Fa ir
P oor
IIR
P o o rFa ir E xc .
P oor
P oor
VMQ, Si,
G ood
P o o rFa ir
P oor
P oor
P oor
Fa ir
Exc ;
E xc .
Exc .
G oodE xc . P o o rG ood P o o rFa ir Fa ir
Fa irG ood Fa ir
G ood Exc . P o o rG ood P o o rG ood P oor
HNB R FKM
P MQ, P VMQ FVMQ AC M
G oodExc . P oor
P oor
c n i t a o h b p r i a l A c , o r l d e u y F H
P o o rFa ir P oor
Exc .
G oodExc . G ood Exc . Exc .
P oor
P oor
P oor
s l i O e n o c i l i S
G ood
G ood
E xc .
G ood
E xc .
P oor
G oodExc . E xc .
P oor
P oor
G ood
Exc .
P oor
P oor
P oor
G ood
P oor
P oor
G ood
G ood
G ood
E xc .
Fa irG ood P oor
P oor
P oor
P oor
G ood
Fa irExc . P oor
Fa ir
P oor
G ood
E xc .
P o o rFa ir
P oor
P oor
Exc .
G ood
G ood
Exc .
Exc .
P oor
P oor
G ood
Fa ir
P oor
Fa ir
Exc .
P oor
P oor
P oor
P oor
P oor
P oor
P oor
G ood
P oor
Fa ir
P o o rG ood G ood
G oodExc . Exc .
G ood Exc . P oor
P oor
P oor
P oor
G ood
G oodExc . G ood
G ood
G ood
P oor
Exc .
EA
P oor
CSM
Fa ir
P oor
Fa irGood
EC O
P oor
G ood
Fa ir
Exc .
P oor
Fa ir G ood P oor
Fa ir
P oor
G ood Exc . P oor
P oor
NR , IR
G oodExc . P oor
P oor
P oor
P oor
AU , EU
P oor
Fa ir
G oodExc .
P o o rFa ir
Fa irG ood
P o o rG ood
Fa irGood P oor
P oor
Fa irG ood
Fa ir
t n a a i r e n o g i r m f e m R A
E xc .
P o o rFa ir P oor
G ood
e e - i n n m - i l m l i c i u i c i u n t n l e a A e t l A a o o r m r h t t p h g i r w l e o o e i P A L P A H
Note: the chart data provides general elastomer base properties. In many design applications, special compounds are required. ERIKS, therefore, will not be responsible for the usage of this chart in any manner.
23
S E A L I N G
4.
Basic
E L E M E N T S
Elastomers
Chemical Terms, Abbreviations, and Trade Names
Chemical Term Ac ry lo nit rile B uta d ie ne Hig hly S a tura te d Nitrile C a rb o xy la te d Nitrile Fluo ro c a rb o n Eth y le ne P ro p y le n e S t y re n e B ut a d ie n e P o lyc h lo ro p re ne Is o b uty le n e Is o p re n e S ilic o n e Fluo ro s ilic o n e P o lya c ry la t e Eth y le ne Ac ry lic C hlo ro s ulfo n a te d P o ly e t h y le n e Ep ic h lo ro h y d rin Polyisoprene • N Naa tura l • S y n th e tic P o lyure t ha n e (P o ly e s te r o r P o ly e t he r) P e rfluo ro e la s to m e r
ASTM Designated Abbreviation NB R HNB R XNB R FKM, FEP M EP , EP DM, EP T, EP R SBR CR IIR VMQ , P MQ, P VMQ FVMQ AC M AEM CSM EC O/C O NR IR AU o r EU FFP M
Polymer Trade Names C h e m ig um ® , Nipol® , Krynac ® , Paracril® , P erbunan erbunan N® , Buna Buna N ® ® ® The rb a n , Zetpol Nip o l® , Krynac ® , Chemigum ® D yn e o n ® , Viton ® , Afla Afla s ® , Fluorel® No rd e l® , Roya lene ® Vistalon ® , Buna EP ® , Keltan ® Am e rip o l S y n p o l® , S B R ® , P li lioflex oflex ® , S ter tereon eon ® Ne o p re ne ® , Ba ypren ypren ® , Butac lor® B uty l® S ila s t ic ® , SILPLUS ® , Elastosil, Wacker® FS E® , Silastic ® , Sylon ® C y a n a c ryl® , HyTem HyTem p ® , Thia c ril® Va m a c ® Hy p a lo n ® G e c h ro n® , Hydrin ® S MR ® , P ale Crepe® , Smoked Sheet ® Am e rip o l S N® , Natsyn ® Ad ip re n e ® , Millathane ® , Vibratha Vibratha ne ® , Vulkolan ® , PUR Ka lre z ® , Isolast ® , Chemraz ® , S imriz imriz® , P a rofluor ofluor®
The following are registered trademarks of their respective companies: Cyancryl - American Cyanamid Co.; Ameripol CB, Ameripol SN, Ameripol Synpol - Ameripol Synpol Co.; Butaclor - distigil; Silastic - Dow Corning Corp.; Hypalon, Nordel, Vamac, Viton - Du Pont Dow Co.; Vistalon - Exxon Chemical Co.; Stereon Firestone Tire & Rubber Co.; FSE, SILPLUS - General Electric Co.; Budene, Chemigum, Natsyn, Philoflex - Goodyear Rubber Products Corp.; Herclor - Hercules Inc.; Aflas, dyneon, sylon - Dyneon Co.; Hydrin, Hy Temp, Gechron, Nipol, Zetpol - Zeon Chemicals Inc.; Krynac, Taktene, Tornac, Perbunan N, Buna EP, Baypren, Therban - Bayer Corp.; Millathane - TSE Industries, Inc.; Adiprene, Royalene, Paracril, Thiacril, Vibrathane; Uniroyal, Inc.
24
TECHNICAL
5.
Designing
DOCUMENTATION
with
O-RINGS
Rubber
In designing an O-ring seal, it is importa nt to d etermi etermine ne the O-ri O-ring c ompo und ea rly, as the co mpound selected may
Compression Set and Squeeze
have an influence on the gland design. The a ppl ppliica tion tion d etermi etermines nes the rubbe r compound, the primary factor being the flui fluid d to be s ealed. B ut the el elas as tomer must also resist extrusion when exposed to the ma xi ximum mum anti anticip cipated ated press press ure ure a nd b e c apa ble of maint maintaini aining ng go od physica l properti properties es through through the ful fulll temperatur temper aturee range expected. This his cha pter disc uss es the next cri criteri teriaa that must be considered like compression set, hardness, tensile strength, chemica l compa ti tibil biliity, thermal effects , press press ure, ure, a nd extru extrusion. sion. Data and pr prooced ures ures enab ling the d esigner tto o meet pa rti rticular rreq eq ui uirements rements o r obta in s pec ific perfor performa ma nce fr from om the se al w ill be found in this this cha pter.
deflection that the elastomer fails to recover a fter a fix fixed ed peri period od of time under a specific squeeze and temperature. Compression set is a very important sealing factor, because it is a measure of the e xpected los s of resi resilliency or "memory" "memory" of a c ompoun ompound. d. Compress ion s et is ge nerall nerallyy d etermined mined in ai airr a nd mea sured a s a perce nta ge of ori original ginal deflection. A Allthough it iiss d esir esirab ab le to ha ve a low c ompress ion set value, this is not so critical as it might appear because of actual service variables. For instance, an O-ring may continue contin ue to s ea l after taki taking ng a 100 100% % compression set, pr provi ovided ded the temperatu turre and system pr press ess ur uree remain remain stead y and no motion motion or ffor orce ce c auses a brea k in the lliine of sea l co nta ct. Also , swelling caused by contact with the service servi ce flui fluid, d, ma y co mpensa te for compr press ess ion set. The cond iti tion on mos t to be feared is the co mbin mbination ation of hi high gh c ompress ion s et a nd s hri hrinkag nkag e. T Thi hiss w ill lead to seal failure unless exceptionally high high s q ueeze iiss employed. Compression set is calculated as follows:
Compression set is the percentage of
C =
t0 - t 1 t0 - t s
x 100 %
Squeeze
Load
Compression set c
t0
t1
ts
Original
Under
After test and
O-ring W
Load
30 min. relaxation
Compression set illustration
25
SEALING
ELEMENTS
5. Designing with Rubber
Lower compression set values indicate improved remain remainiing s ea l ca pa city. Compression set values generally increase with increased temperature and time. For O-rings the minimum squeeze should be about .007 inch. (0,175mm). The rea so n iiss t ha t w ith a very lliig ht squeeze almost all elastomers quickly take 100% co mpression se t. A go od compression set resistant c ompound can be distinguished from a poor one only when the squeeze is more than .005 inch. (0,127mm) Most O-ri O-ring s ea l a ppl ppliica ti tions ons c annot tolerate the no squeeze condition, the exceptions are the floating ring designs in special pneumatic and rotary a ppli pplica ti tions. ons. The most commonl commonlyy used sta ndards for the expression of compres sion set a re A AS S TM D 395 a nd DIN 5351 53517. 7. Tab le 3A 3A-1 -1aa gives com pression s et values for standard Eriks compounds, (S q ueez e 25%) 25%)..
Note: It iiss important to notice tha t the co mpress press ion s et cha nges with with time time a nd depends on cross s ecti ection on di diameter. ameter. Thi hiss tab le s how s these dif differ ferent ent values, values, meas ur ured ed on the sa me compound.
26
Table 3A-1a Material
NB R 36624 NB R 47702 E P D M 55914 E P D M 55914 P C S ilic o ne 71477 Ne o p re ne 32906 Vit o n® b blla c k 51414 Vit o n® g re e n 51414 Vit o n® b la c k 514320 Vit o n® V b la c k/b ro w n 514075 Quad ™ -rin -rings gs in NBR/ NBR/FPM/ FPM/EPDM
Hardness
Compression set
Temp. Range
IRHD ± 5
22h/100°C, 25%, on O-ring 3.53 mm.
°C
70 90 70 70 70 70 70 70 90 75 70/90
m a x . 20% m a x . 30% m a x . 30% m a x. 25% (150 ° C ) m a x. 40% (200 ° C ) m a x . 25% m a x. 18% (200 ° C ) m a x. 19% (200 ° C ) m a x. 18% (200 ° C ) m a x. 11% (200 ° C) C) -
-30+ 120 -30+ 120 -50+ 120 -50+ 150 -60+ 220 -35+ 110 -20+ 200 -20+ 200 -20+ 200 -20+ 2 20 00 -30+ 120
°F -22+ 248 -22+ 248 -58+ 248 -58+ 302 -76+ 428 -31+ 230 -4+ 392 -4+ 392 -4+ 392 -4+ 3 39 92 22+ 248
NBR 36624 O-rings C ro s s s e c t io n m m Co mpres s ion s et 22h/100 100°° C (212 212°° F) Co mpres s ion s et 70h/100 100°° C (212 212°° F)
1 , 78 1 4, 8 2 3, 9
3, 53 12, 8 22, 7
6, 99 9, 2 16, 8
TECHNICAL
DOCUMENTATION
O-RINGS
5. Designing with Rubber
O-ring Hardness The ha rdnes s o f an O-ri O-ring ng is important for several several rea rea so ns. The so fter the ela ela sto mer, the be tter the sea l materia materia l conforms to the s urface urface s to be sea led a nd lower pr press ess ure ure is is required requir ed t o c reate a se a l. Thi Thiss is pa rticurticularly important in low pressure seals that a re not ac ti tivated vated by fl flui uid d pr press ess ur ure. e. The s ofter the elas tome r, the hi highe ghe r the co effi efficient cient o f fri friction. ction. In d yna mi micc a ppli ppli-ca ti tions ons ho wever, the ac tual rrunni unning ng a nd breakout friction values of a harder compo und w ith llow ow er coeffi coefficient cientss of friction are higher because the load required requi red to s q ueeze the ha rder ma ter teriial into the O-ring O-ring g roove is much g reate r. The s ofter the elas tome r the more ri risk sk that a t hi high gh o perati perating ng press ur uree the elas tomer of the O-ring will extrude into the cl clearance earance g ap betw een the m mati ating ng sea l surfaces. The ha rder ma teri teriaa ls offer grea ter rres es istance to flow. With an increase in temperature, elastomers first first beco me s ofter and then eventua lly ha rder as the rubber curi curing ng process contin continues ues w ith the a ppl ppliica ti tion on of heat. The ha rdness of mos t elastome rs is is indica ndica ted b y a durometer ra ti ting ng o n a ga uge ma nuf nufac ac tur tured by the S hor horee Instrument Company or equivalent. Most elastomers are measured on the Shore " A" sca le. S hor horee A hardness of 35 35°° is soft; 90° 90° is hard. Shore "D" ga uges a re recommen recommended ded wher wheree the S hore "A" ratin ratingg is greater than 90 90°° . The most common standards for measuring ha rdnes s a re A AS S TM D2240, DI DIN N 5350 53505, 5, BS 271 2719, 9, and ISO 761 7619. 9. These s tanda rds d efi efine ne a g auge readin readingg on a standa rd sa mple mple w ith a thickness thickness of 0,25 iin. n. (6 mm.) mm.).. Alwa ys use s tand ard hardnes s disc s 1.28 in. di diaa m. by 0,25 iin. n. thick (ø 32 x6 mm.), or 6 in.x 6 in.x 0.075 in. (150x150x2 mm.) sheets piled up to a
It has been a lmost imposs ible to obta in reliable and reproducible hardness rea dings dings on sea ls w ith cur curved ved surf surfac ac es and vari variable cross s ecti ections ons s uch as Orings rings . T Thi hiss problem has plag ued the industry ffor or years a nd is ac know know ledg ed in som e s ta nda rd tests . Li Like ke AS AS TM Method D 2240-00, paragraph 6.2.1 states: "A suitable hardness determination cannot be made on an uneven or rough po int of co ntac t w ith the indenindentor" . Al Also MILMIL-P P -5510B, -5510B, pa rag raph 4.4.2. 4.4. 2. sta tes : " Test spec imens for the purpos pur pos e of ba tch testing sha ll cons ist of one compression molded hardness sp ec imen 0,25 iin. n. thi thick ck a nd 1 in. diameter minimum ( 6 mm. thick and 25 mm. diame ter) ter)." ." The sp ec ifica fica ti tion on s ta tes in a note " Hardness sha ll not be de termi termined ned from from a ctual pac kings kings ." However, for spec imens tha t are too thin or provide too small an area for accurate Shore durometer readings, the Wa Wa lla ce Micro Micro Ha rdnes s Tes ter is is the most recommended method. Meas ur ureme eme nts in Mi Micro-I cro-IRHD RHD a re more a cc ur uraa te for OO-ri rings ngs . Thi Thiss me thod of mea surement is is recorded in the sta nda rds AS TM D1415 and DIN 53519. Diff Differences erences betw een IRHD IRHD a nd S hore hore " A" a re negli negligible gible on the 6 mm thi thick ck sample. Normally, durometer hardness is referred refer red to in increments of fi five ve o r ten, a s in 60 durometer, 70 durometer, 75 durometer, etc. Not as 62, 66, or 72 duromete r. This his prac tice tice is ba se d on the fact tha t hardness is g eneral enerallly called out in specifications with a tolerance of ± 5 and also on th thee inher inherent ent varianc vari anc e fr from om ba tch to ba tch of a g iven rubber compound due to slight differences in raw raw materi materials als a nd proces sing techniques and the variability encountered in reading durometers.
minimum of 0,25 in. (6 mm.) to determi mine ne d ur urometer ometer hardnes s.
27
SEALING
ELEMENTS
5. Designing with Rubber
IRHD and Shore A
Durometer Ranges Rubber-Plastics
150 140
1,78
IHRD-Micro DIN 53 519 Teil 2 No rm : 2 m m s h e e t Tim e : 30 s e c .
PHENOLICS ACRYLICS
130
Shore A DIN 53 505
PLASTICS
110
120
100
110
90
No rm Tim e
NYLON
100 POLYSTYRENE
: 6 m m s he e t : 3 s ec.
80
90
70 70
110
POLYPROPYLENE
60 50
100 50 URETHANE
90
FLUORCARBONS 30
40 80
20 30
70
ROCKWELL R
20 60 RUBBER
CAR TIRES 10
50 40
0
DUROMETER D
30 RUBBER BANDS 20 10 0
DUROMETER A
Hardness versus Temperature
) A e r o h S ( s s e n d r a H
Temp era ture ° C Temp era ture ° F
28
TECHNICAL
DOCUMENTATION
O-RINGS
5. Designing with Rubber
Tensile Strength and Elongation
Modulus
Tensil ensilee s tr trength ength is a mea surement of
Modulus, Modul us, a s us ed b y the rrubber ubber iindusndus-
the amount of force required to rupture a n el elaa st ome ri ricc s pec imen. Tens Tens ile ile strength is a fair production control measurement used to insure uniformity of the compound, and also useful as an indication of deterioration of the compound a fter fter iitt has been iin n contac t w ith a fl flui uid d for llong ong peri period od s of time. If a large reduction in the tensile strength oc curs, the lliife of a s ea l may b e rel relaa tively short. Exceptions to this rule do occur. El Elonga onga ti tion on is a n increas increas e in llength ength express expr ess ed num numer eriica lly a s a per percentag centag e of initi initiaa l lleng eng th a t the point of rupture. This prope rty pri prima ma rily rily d ete rmi rmines nes the stretch w hi hich ch c a n be toler tolerate ate d d ur uriing the insta insta llation of a se al. An ad verse cha nge in the el elonga onga ti tion on of a co mpound a fter expos ur uree to a flui fluid d is a defin definiite s ign of de grad a ti tion on of the ma teria teria l. Elonga tion, li like ke tens ile strength, is used throughout throughout the industry try a s a check on pr producti oduction on ba tches of compound. Tes ts are pe rfor formed med on d umb-bel umb-belll shaped samples on a machine pulling them apa rt axi axiall allyy at a consta nt speed of 500 mm per minute, during which the force and elongation of the sample are recorded.
try, refers refers to stress a t a prede termi termined ned elongation, usually 100%. It gives a co mpa riso riso n for go od extr extrusion usion rres es istanc e. Modulu Moduluss normal normallly incr increa ea se s with increase in hardness and is proba bly the the be st indi indica ca tor of th thee s trength trength of a compound, all other factors being equal.
) s e e r g e d (
D H R I
Log 10M (M in psi) Hardness (IRHD) versus Young’ Young s ’s Modulus (M)
S tand ards tests for Tensile ensile strength a nd El Elong ong a tion tion a re A AS S TM D412, DI DIN N 53505, 535 05, and BS 903 903,, P a rt A A3. 3.
) a P M ( s s e r t S
1= 2= 3= 4= 5= 6= 7= 8=
Spec ial ialit ityy FKM Black FFK FFKM M S tanda rd FKM FKM White FKM Ethyl Ethylene ene P ropylene Nitr Nitril ilee Fluorsil Fl uorsilicone icone Silicone Silicone
1
2
5 3
4
7
6
) I S P ( s s e r t S
8
Elong Elong a tion (%) (%) Stress versus Strain 29
SEALING
5. Designing with Rubber
Tensile Stress-Strain Tens ile s trength is the ma xi ximum mum tensile stress reached in stretching a test piece (either an O-ring or dumbbell). Elongation: the strain or ultimate elongtion elongti on iiss the a mount of stretch at the moment of brea k. Modulus: Modul us: a lso ca lled ‘ Mod.100 Mod.100’’ ; this is the stress required to produce a given elonga ti tion. on. In the the c a se of Mod 100, the mod ul ulus us w oul ould d b e the stress requi required red to elonga te the sa mpl mplee 100% 100%.. In el elaa sto mers, the s tress is not li linea nea r w ith s train. T Therefore, herefore, the mod ulus ulus is neither neither a rati ratio o nor a c onsta nt slope but rather denotes a spe cif cifiic po int on the s tr tres es s-strain cur curve. ve. Tens ile te sts a re used for cont rol rollling product q uali uality ty a nd for determi determini ning ng the effect of c hemi hemica ca l or ther therma ma l exposure on a n el elaa sto mer. In In the llatte atte r cas e, it iiss the retention retention o f these physica l pr properoperti ties, es, ra ther than the a bs olu olute te values of the tensile tensile s tr tres es s, e longa ti tion on or modulus, that is often s ignif gnifiica nt. Tear strength The tea r strength or tea r rres es ista nce is rel relativel ativelyy low for mos t co mpounds . Thi hiss te st me as ur ures es the force to pe rpetuate a ni nick ck or cut. Sea l compoun compounds ds with poor tear resistance will fail quick-
) a P M ( h t g n e r t S e l i s n e T
Hardnes s (S hore A) A)
extreme volume sw ell extreme ell can s ometimes be toler toleraa ted. Actua lly a n O-r O-riing ca n swell only until 100% gland fill and further increas increas e of volume iiss not pos sibl sible, e, regardless of how much volume swell is observed in a full immersion test. If the free state swell exceeds 50 percent; however, a radially squeeze as sembly may be almost iimposs mposs ible ble to take apart because of the friction generated. In dyna mic mic ap pli plica tions tions , volu volume me s we ll
Volume olume cha nge is the in increas creas e or dec rea se o f the the vol volume ume of an elastomer after itit has bee n in in conta ct w ith a medi medium. um. It It is is mea sured sured a s a per percentcenta ge (%). Increa Increa se by s we ll or dec reas e by shrinkage shrinkage in volu volume me is a lmos t always a ccompani ccompanied ed b y a change iin n
up to 15 or 20 percent is usually a cc epta ble, but higher valu values es a re lilikely kely to increa increa se fri friction ction and reduc e toughness a nd ab ras ion rresistance esistance to the point that us e of a pa rticul rticulaa r compound is no longer fea sibl sible. e. Volu olume me s hr hriink nkaa ge is o ften ca used by fluids which extract the plasticizers from from the c ompound. De creas e iin n vol vol-ume is is usua lly a cco mpani mpanied ed b y a n increase in hardness. Also, as swell compensa tes for compr compress ess ion set, shrinkage will intensify the compression set effect, ca usin usingg the O-ri O-ring ng to pul pulll a wa y from from s ea ling s ur urfac fac es providing provi ding a leaka ge pa th. IItt iiss a ppa rent
hardness. Volume olume s we ll is c a used by a bs orpti orption on of ga se ous o r lliiq ui uid d med ium by the Ori ring. ng. In s tatic a ppli pplica ca ti tions, ons, even
then, tha t s hr hriinkage is far more c riti ritica ca l than swell. More than 3 or 4% shrinkage can be a serious problem for dynam ic O-r O-riing sea ls.
ly under further flexing or stress, once a crack iiss s tarted. L Low ow tear stren strength gth of a compound is also indicative of poor ab ras ion rresistance esistance whi which ch ma y llead ead to early failure of an O-ring used as a dynamic sea l. Volume change change
30
ELEMENTS
TECHNICAL
DOCUMENTATION
O-RINGS
5. Designing with Rubber
Chemical Compatibility The c hemica l guide is intende d to
Elevated Elevated temper temperatur atures es and extended exposure times may create more ag gressiv gressivee conditi conditions. ons.
a ss ist the use r in in d etermi etermini ning ng the s uiuitab ility of va ri rious ous elasto mers in many different differ ent c hemica l envi environments ronments . The The ratin atings gs are ba sed on a combinati combination on of publiished literatur publ terature, e, la borato ry tests , a ctua l fi field experi experience ence , a nd infor nformed med judgments. ERIKS uses the DuPont Dow Elastomers guide.
In some c as es, s pecif pecifiic elastomer co mpounds withi within n a ma teri terial al famil familyy ma y provide provi de improved co mpa ti tibil biliity. P lea se contact the Application Engineering Department for assistance or consult the DuP ont-Dow inter internet net c hemica hemica l resista resi sta nce guide - where you ca n find find the lates t inf information. ormation.
Note: Volume swell is only one indicator of elastomer fluid compatibility and may be based on the solubility parameter alone. Flui Fluid d a ttac k on the bac kbone of the polymer polymer may s how up a s a change in physical properties such as tensilee s trength, el tensil elong ong ation at break, and hardness.
Ela Ela stome rs ca n sw ell and /or deg rade in chemica l env enviironments through through rea cti tions ons w ith the polymer polymer bac kbone a nd cross -li -link system, or by rea ctions w ith the fil filler sys tem. In the s emiconducto r industr ndustry, y, thi thiss deg rad ation can be s een in increased contamination and reduced se a l lilife.
www.dupont-dow.com/crg
Chemical Compatibility Guide Rating System Rating A B
C
U
Description
Volume Change
Comments
Lit tle o r no e ff e c t P o s ssiib le le lo ssss of physical p ro p e rtie s No ttiic ea ea b llee c ha ng e
< 10%
Ela sstto m e r m a y e xhib it s lilig ht s w wee lling aan nd /o r lo s s o f p hy s ic a l p ro p e rt ie s u un nd e r s e ve re c o nd it io ns . Ela s to to me me r m a y e xh xhib itit s w eellling in a d d iitt iio on to a cha nge in physical proper properti ties. es. Ma y b e s uita bl ble fo r s t a ti tic a pp pp lic a ttiio ns . Ela s to to m mee r e xhib iitts a no ttiic eeaa b llee c h haa n ngg e in s w el elling a nd p hy s ic a l p ro p e rt ie s .
Exc eess ssiive c ha ha ng ng e
10-20%
20-40%
> 40%
Questionable performance performance in mos t a ppli pplica ca ti tions. ons. Ela s tto o m e r no t s u uiita bl b le fo r s eerrvic e. e.
31
SEALING
5. Designing with Rubber
Attack mechanisms: mechanisms: Chemical Compatibility
In many applications special considerations should be made for contaminati tion on or vac uum perf performance ormance .
• The proces s o f chemi chemica ca l deg rada ti tion on or che mica l iinco nco mpa tibili tibility ty is very comp lex. In ge neral neral,, deg rada ti tion on of the polymer ba ckbone a nd c ros s-li s-link may oc cur by means of: • nucleophilic attack - nucleophiles are ions or molecules that can dona te electrons. Thi hiss is the ma in cros s-linki s-linking ng mecha ni nism sm . In ce rtain chemica l med ia, nucl nucleophil eophiliic a ttac k can result in increased cross-linking and embri embrittl ttlement. ement. • d ehyd rofl rofluori uorina na tion - iin n fl fluoroca uoroca rbon elastomers the attack of aliphatic amines c an resul resultt in in the formation of unsaturated bonds in the polymer b ackb one. • polar attack - swelling caused by electrostatic interactions between the dipole dipole a nd po lymer cha in
Contamination is critical in semiconducto r ffaa brica brica tion tion a nd med ica l a ppli pplica ti tions. ons. This his ma y ta ke the form of pa rt rtiicle ge nerati neration, on, extrac tab le ions or other res idua l ga s c onta mi mination. nation.
Degrada ti tion on may a lso o ccur due to interactions of the chemical environment a nd elas tomer fi filller sys tems. Thi hiss type o f degra da ti tion on ma y be c a used by oxidation of fillers, or by chemica l atta ck of c ertai ertain n fi filllers or proces s aids.
Test methods: ISO 1817 (Liquids) AS TM D471, D1460, D 3137 (L (Liquids iquids )
Nucleophilic Attack (Unsaturated) C = C
Oxidation O-
Po lar A Attac ttac k H 2O
Chemical Attack Mechanisms
Volume Swell: Swell: The mos t comm on mea sure of chemica l co mpa tibil tibility is is vo lume s we ll. The follow follow ing ing formul formulaa is us ed in reporting vol volume ume sw ell mea surements. This his takes into a cc ount dimensional changes in all three dimensions, and is more precise precise than s pec ifi ficc dimensional sion al chang e readings for most sealingapplications. Volume Swell:
VS (%) =
(Weigh t in Air-W Air-Wt.t. in Water) Wat er) final - (Wt. in Ai Airr - Wt. in Wa te r) initial (Weig ht in Ai Airr - Weight in Wate r) ini initial tial
Note: Note: The " Weight in W Waa ter" mea sureme nt is perfor per formed med by s uspending uspending a sa mpl mplee in a c onta iner of wate r and recording it's we ight. T Thi hiss takes into c onsiderati tion on that the d ensity of a s oli olid d is eq ual to it's weight in air divided by the difference of it's weight in air and it's we ight in wate r.
32
ELEMENTS
x100
TECHNICAL
5.
Designing
DOCUMENTATION
with
O-RINGS
Rubber
Thermal Effects All rubber is subjected to deterioration
This his ca n be a criti critica ca l fac fac tor at high temp erature if the g la nd is ne a rly rly fil fillled with the O-ring or at low temperature if
a t high high te mperatur mperature. e. V Volu olume me c hang e a nd c ompress ion se t are bo th iinfl nfluuenced by heat. Hardness is influenced in a c omplex w a y. T The he fi first rst effec t of hi high gh tempe ra tur turee is to so ften the compound. Thi Thiss is a physica l cha nge, a nd will reverse when the temperature drops. In hi high gh pressure a ppl ppliica ti tions ons the O-ri O-ring may beg in to flow through the clearance clearance ga p a s the temperatur temperaturee rises, due to this softening effect. With increas ing ti time me a t high temperature, chemica l cha nges oc cur. These generally cause an increase in hardness, along w ith vol volume ume and compression set cha nges. Chang es in tensi tensille strength stren gth a nd elongation are also involved. Being chemical in nature, these changes are not reversible. The cha nges induce d by low temperature are primarily physical and reversible. reversibl e. An el elaa sto mer w ill almost completely regain its original properties when wa rmed.
the squeeze is marginal. Leaking can be the resul resultt of s ea l fa fa ilure ure a t llow ow temperature ifif the sq ueeze is s ma ll. There a re certa in reac tions tions w hi hich ch in some cir circumstanc cumstanc es ca use a n OO-rring to e xert relati relativel velyy high forces a ga inst the sides of the g roove. IIff the sea l is co mpl mpletely etely confi confined ned a nd the g land is 100% fil filled, the do minating force is the force of thermal expa nsion of the ru rubbe bbe r. The g roove mus t a lwa ys b e sufficiently wide to allow for the maximum e xpa nsion o f the O-ri O-ring. ng. There have been instances instances where a sea l has ruptured a steel gland due to expansion whe n hea ted. Theref herefore ore iitt ha s to be co nsi nsidered dered that iin n no cas e a g land fil fill in in exc es s of 95% iiss a llow ed . This his should be taken into co nsiderati tion on w hen de signi signing ng O-r O-riing g rooves for a ppli pplica ti tions ons in exces s o f 30 300 0° F (150°° C). (150 C). P lea se co ntac t your ERI ERIKS KS repres repr es enta ti tive ve for a ss ista nce in groove design.
Thermal Expansion
Thermal Expansion
Coefficient of linear thermal expansion is the rati ratio o o f the cha nge in llength ength pe r ° F or ° C to the ori original ginal llength ength a t 0 0°° F o r
FKM NB R
0° C. Co effi efficient cient of volumetr volumetriic expa nsion for solids is approximately 3 times the linear coefficient. As a rough approximation, elastomers have a coefficient of thermal expansion 10times that of steel. With Fluoroelastomers a nd P erf erflluoroel uoroelas as tomers the c oeffi oefficient cient of thermal expansion is is e ven grea ter.
VMQ FFKM EP D M S t a in le s s Alum inium TEFLON KEL-F P o ly im id e
Material
Thermal Stability 200° C /392° /392° F 120° C /250° /250° F
x10-5 / °C
230° C /450 /450°° F 300° C /570° /570° F 150° C /300° /300° F 230° C /450° /450° F 280° C /540° /540° F 275° C /530° /530° F
59-79 23 16 1. 0 4 1. 3 5-8 4-7 5
16 23
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SEALING
5.
Designing
with
rubber
Selecting O-ring cross section diameter (CSD)
Table 1 - Characteri Characteristics stics of CSD choice
In g eneral, when selecting O-r O-riings , there are benefits benefits to be g ained fr from om having both smaller and larger CSD. S ome o f the benefi benefits ts a re gi given ven below for both cases. In sta ti ticc a ppl ppliica ti tions, ons, where rapid high pressure cycling is not present, it is usuallly better to choos e a larger CS D usual if poss ible. A Ass note d a bove, larger CSD O-rings are less susceptible to the problems of compression set, sw el elll, a nd incident incidental al sur surface face da mag e. Also, larger CSD O-rings are more sta bl blee and tend not to rrotate otate on a ss embly. However, if the s ea l wi willl be subjected to rapid hi high gh press ur uree cyc ling then it is is b etter to choo se a sm a ller CS D if if pos sible. T The he s ma ller sec ti tion on se als a re less susce ptibl ptiblee to decompression problems.
For dynamic a ppl ppliica ti tions ons with sur surfac fac e co ntac t speed s less tha n 2,0 2,03 3 m/s the O-ring CSD is generally not critical. There a re also s ome g ene ral rules rules relating O-ring CSD to O-ring ID as follows:
: : : :
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