Technical Presentation - Mechanical Seals

ITT Flygt Mechanical Seals • Introduction

• Basic seal technology • ITT Flygt Sealing system • Plug-In seal • Seal material • Qualification testing • Service

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Pump anatomy

Motor Heart

Hydraulics

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Static and Dynamic seals Static seals: No relative movement between sealed surfaces

Dynamic seals: Relative movement between sealed surfaces

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Shaft seals

Stuffing box

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Lip seal

Mechanical face seal basics

Sealing interface

Spring

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Seal rings

Seal rating

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Leakage

P1

P0

P1

P0

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Lubrication modes Full film lubrication Seal ring

No wear

Lubrication film

High leakage

Mixed film lubrication Low wear Low leakage

Boundary lubrication High wear No leakage

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Mechanical face seal

Sealing interface

Spring

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Seal rings

Mechanical face Seal

Torque locks

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Leakage

h

Q~h3

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Leakage Estimated daily leakage for a 50 mm seal with different lubrication film thickness

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• 0.5 μm

A couple of drops

•

1 μm

Two table spoons

•

2 μm

One glass

•

5 μm

Half a bucket

Flatness

2 light band of sodium light

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0.0006 max

Deviation from perfect flatness max 0.0006 mm =

Flygt Sealing System

Inner seal Buffer fluid Outer Seal Impeller

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Sealing system in 3085

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Flygt Sealing System- New products

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Flygt Sealing System in 3153

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Positive closing force

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Buffer fluid • Lubricates the seal faces • Cools seal rings and other components • Dilutes leakage to minimize risk of crystallization • Doubles as coolant for new drive units.

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Spin-out

Wear caused by abrasive particles trapped by boundary current 20

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Spin-out

The spin out groove directs the abrasive particles out to the pump housing 21

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Plug-In seal

45 mm Plug-in seal

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Plug-in Seal – – – – – – – –

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Only one part to fit Fast service Protected seal faces Correct mounting guaranteed Same procedure for all seals Correct and precise spring load Pre tested Cooling pump incorporated

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Plug-in Seal

Plug-In seal series

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Seal ring material  High

Hardness

 High Stiffness  Good Sliding Properties

 High Thermal Conductivity  Low Thermal Expansion

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Seal ring material WCCR Corrosion resistant tungsten carbide. Standard material in Flygt seals

RSiC Silicon carbide. Optional material. Al2O3 Aluminium Oxide. C Carbon. Almost phased out. Only for inner seals in small products. 26

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Rubber Material Flourinated rubber (Viton) (FPM)

High temperature limit and good chemical resistance. Standard in most face seals due to high temperature limit.

Nitrile (NBR) Good for most applications. Cost effective

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Other materials Metals

Stainless steel AISI 329

Plastic Only PPS . High temperature limit, strong and stable. Excellent chemical resistance.

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Qualification testing

Seal face materials and Seal designs are approved separately. Materials are tested for tribological properties.

Seal designs are tested for mechanical performance and operational performance

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Qualification testing Approval of mechanical design properties Lab rig tests •Leakage •Pressure limit •Negative pressure opening level •Duration and wear of seal components

•Power loss •Dry running capability •Media temperature limit

•Torque lock and torque transmission capability 30

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Qualification testing Approval of operational performance Field test in products •Leakage •Wear from abrasive pump media •Clogging and wind-up of fibrous media •“Snoring operation” capability •Compatibility with product

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Performance Seal life is dependent of • Leakrate • Temperature • Presence of abrasives • Clogging • Pressure • Vibrations • Dry running • rpm 32

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performance SEAL FAILURE

•High leakage •Overheating •Abrasive wear •Thermo cracking •Solid film build up •Corrosion •Incorrect mounting •Mechanical failure 33

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Service Do not remount mechanical face seals. The seal rings will wear matching grooves into each other. If the seal is re mounted after service, the grooves will not match.

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Service

Pay attention to where to apply oil and where to apply grease

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Service

Keep hands and tools clean. Microscopic particles left on the seal faces can cause leakage.

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Service

Clean shaft and check for damage that can cause the o-ring to leak 37

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Service

Lubricate stationary o-ring. Use oil if the seal ring lacks mechanical torque lock. Otherwise, use oil or grease. 38

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Service

Grease the shaft 39

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Service

Apply some DROPS of oil on the seal surface to prevent sticking 40

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Service

Place the rotating ring in place

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Service

Apply just 20 Newton of power on the tool when mounting the grip ring. 42

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Service

Check the clearance 43

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Service

Check the seal housing and shaft for defects. Grease the shaft. 44

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Service

Oil the stationary O-rings (works as a torque lock) 45

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Service

Place the Plug in seal in place, be aware of the torque lock gets in right position 46

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Service

Mount the Retaining ring, be sure that it gets in to the groove in the shaft 47

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Service

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Service

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Service

Apply grease on the retaining ring to protect it from corrosion 50

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Run-out tolerances

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Service

Seals can run dry if the pump or mixer is filled with correct amount of buffer fluid. Seals for 80mm shafts or larger should be limited to a few minutes of dry running to avoid overheating.

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Tightness check ΔPmax=0,017*Po*t/V [bar]

ΔPmax=Pressure drop Po=pressure in test object [bar] t =test time [min] V =volume of the test object [l]

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Flygt mechanical seals

– No worries

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