Quality Control Questioner
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BASIC QA/QC QUESTIONS & ANSWERS
QA/QC Questionnaires A Fundamental Handbook for Interview QA/QC & Instrumentation Inspection ABU ZARRAR QUAISI
AL‐QAMAR
2009
QA/QC Questionnaires
Instrumentation Inspection and Quality Control Questioner Q. )
What is QA/QC? QA/QC means, “Quality Assurance/Quality Control” the purpose of this (QA/QC) is to establish the sequence of requirement for the quality of material, quality of works, its inspection and records.
Q. )
What are basic responsibilities of QA/QC personals? To ensure execution of works and comply fully as per standard and approved specs.
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What are the basic required documents for a QA/QC personal?
Q. )
The basic required documents QA/QC personal are as following: ITP: to conduct the Quality check (inspection/witness/surveillance) etc. WP: standard procedure to execute the works. (Work Procedure) P&ID: as a reference to ensure that the work is as per standard drawing. MTC: To ensure that the material complies the PES standard specs. PP: To ensure that the Instruments are installed as per P&ID and PP as per convenience. IDS/ISS: To ensure that the instrument comply with the basic requirement. RFI: To conduct the inspection of completed works. (Request for Inspection) QR: To maintain the quality records of completed works etc. QCO: To issue a warning in case of little violation and observation NCR: To issue a warning in case of serious violation of standard. (Non Compliance Report) Calibration Report: To ensure parameters are function checked as per IDS. Hook Up: To ensure that the remote connection of pneumatic is done correctly. Wiring Diagrams: To ensure that the wiring is done correctly. What are QA/QC’s ITP’s and QCP? Give a brief.
ITP: This procedure informs about the kinds of quality check (surveillance, inspection, witness or hold points) means quality of work being done in proper sequences. QCP: This procedure address the activities and requirement in details
Q. )
What is NCR? Why does it need for a QA/QC personal? NCR means Non‐Compliance Report, QA/QC personal has reserve the right to issue a warning if the contractor doesn’t comply or violate with the standard procedure. Basic QA/QC Questions & Answers |Compiled & prepared by Abu Zarrar Quaisi |AL‐Qamar| 2
QA/QC Questionnaires
Q. )
What are the general work procedures (WP)? The general sequence of activities will be as follows: a) Receiving Drawing and Documents b) Reproduction of Drawings c) Issuing of Drawing to site d) New‐Issuing New Revisions e) Shredding of Drawings f) Redlining Drawings g) Transmittal of redlines to Client (As‐built) h) Restricted access to the DCO i) Work Permit prior to start the works j) Record
Q. )
What are common PPE required? Give a brief.
Q. )
What is redlining? Brief its color coding.
Q. )
Following are the common PPE for a safe and quality works‐standard procedure: Qualification : Awareness about all kinds of safety standard/codes and work procedure. Experience : Qualified for the works execution. Use (PPE) : Proper equipments and tools shall be used to avoid injuries/loss. Safety Shoes, Helmet, Glass, Gloves, Earplugs, Harness proper tools and certified equipments.
In case of any change occur to the standard approved drawing while the project is being constructed or tested the relevant drawing will be “redlined”. Following color coding shall be used for this purpose: Red : If any addition required in the drawing. Green : If any deletion is required from the drawing. Blue : if any comment is added. What are the difference between Inspection (Surveillance), witness and Hold
Inspection Witness Hold Point
: : :
point?
Work can be execute without clients inspection and it can be Inspect some part of them if it required. Work can be execute without client inspection and then it can be inspected upon the completion of work. Work can’t be executed without client inspection.
Basic QA/QC Questions & Answers |Compiled & prepared by Abu Zarrar Quaisi |AL‐Qamar| 3
QA/QC Questionnaires
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What is difference between Hazardous and NonHazardous area? Hazardous: A Hazardous location is defined as an area where a potential for fire or explosion exist due to the presence of flammable gases, liquid or vapors, combustible dusts or fibers and flying in sufficient quantities to produce a n explosion or ignitable mixture. Non‐Hazardous: An area where no risk of presence of any kinds exposition.
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What are different kinds of certification? i) Weather Proof ii) Dust Proof iii) Water Tight iv) Explosion Proof v) Flame Proof vi) Intrinsic Safety Proof
Q. )
What is ISO? Explain some of its standards? ISO means International Standard Organization; some of them are as below: ISO: 9001, ISO: 9002, ISO: 9003 etc.
Q. )
What are Zone classifications? Give a brief. Zone classification is defining the area of hazards, they are as below; Zone – 0: A zone in which explosions gas/air mixture is continuously present or present for extended periods, during normal operation. Zone – 1: A zone in which explosions gas/air mixture is likely to occur in normal operation. Zone – 2: A zone in which explosions gas/air mixture is not likely to occur in the normal operation and if it occurs, it will only exist for a short time. Zone – 10: A zone in which explosive dust atmosphere is present continuously or for extended periods of time. A zone in which there is likelihood that explosive atmosphere may occur Zone – 11: for short periods due to unsettled dust layers.
Q. )
What are the standard heights to install the instruments?
Q. ) Q.
What is Loop – Check? To ensure that the system wiring from field to control console functioning.
A standard height to install the instruments is 1‐4 meters, but it can vary less or more as per location’s convenience.
Explain tuning of controller; (a) Closed Loop Method, (b) Open Loop Method. Tuning basically involves adjustment of α+I+D parameters to achieve good control. The gain, time, constants & dead time around the loop will dictate the settings of various parameters of controllers. a) Closed Loop Method : Ultimate gain method b) Open Loop Method : process reaction curve Basic QA/QC Questions & Answers |Compiled & prepared by Abu Zarrar Quaisi |AL‐Qamar| 4
QA/QC Questionnaires
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What are area classifications? Give a brief. As per NEC and NACA, following are the hazard classification; Class I : Location in which flammable gases or vapors may be present in the atmosphere in quantities sufficient to produce explosive or ignitable mixture. Class I gases/vapors are divided into four following groups Group A: Presence of Acetylene Group B: Presence of Hydrogen, Butadiene, Ethylene Oxide etc. Group C: Presence of Ethylene, Cyclo‐Propane, Carbon‐Mono Oxide etc. Group D: Presence of Gasoline, Acetone, Butane, Propane, Alcohol, natural gas (Methane) etc. Class II : Location in which the presence of combustible dust are in the air in sufficient quantity to ignite or explode. Class II conductive/non‐conductive dust is divided into three as below: Group E: Presence of metal dusts (Aluminum, Magnesium and chemical dusts etc). Group F: Presence of black carbon, charcoal, coal or coke dusts etc. Group G: Presence of non‐conductive dust (foam, starch, combustible plastic etc). Class III : Location in which easily ignitable fibers or flying are present but are not likely to be in suspension in air in quantities sufficient to produce ignitable mixture. Division – 1 : The Hazards are present continuously or periodically under normal operation condition. Division – 2 : The Hazards are only presents during accidental or abnormal conditions.
Q. )
Why is flow measured in square root? Flow varies directly as the square root of D.P (Differential Pressure) since this flow varies as the square root of the D.P the pen does not directly indicate flow. The flow can be determined by taking the square root of the pen. Say the pen reads 50% of chart.
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What is the diameter of the transmitter nozzle? 0.030” How will you work/remove on a control valve which is in line? Inlet and outlet discharge manual valve to be
closed by the operator and tagged. The valve No. 1 to be closed first. Control valve should be in fully open condition. Valve No. 2 closed. Secondly the line has to be drained and depressurized before removing.
1
1
Figure BY PASS VALVE
Basic QA/QC Questions & Answers |Compiled & prepared by Abu Zarrar Quaisi |AL‐Qamar| 5
QA/QC Questionnaires
Q. )
What are the standard nozzles orientations for process control systems?
Figure1 GAS SERVICE
It should be 45° either Side of the pipe or vertical
Figure 2 LIQUID SERVICE
Figure 3 STEAM SERVICE
Horizontal or 45° below of either side of pipe
Horizontal or above it 45° either side of pipe
Q. )
What is different between Open Loop and Close Loop?
Q. )
What is feedforward and feedbackward control system?
Open Loop Close Loop
: :
A Loop System which operates direct without any feedback and generates the output in response to an input signal. A loop system which uses a measurement of the output signal through feedback and a companion with the desired output to generate an error signal that is applied to the actuator.
Figure 1. Feed Forward Control
Figure 2. Feed Backward
Feed‐forward control is a system in which corrective action is based on measurement of disturbance inputs into the process. Feed backward control involves the detection of the controlled variable & counter acting of changes in its value relative to setpoint by adjustment of the manipulated variable.
Q. ) Q. )
What is Logic Gate? A Digital logic circuit with one or more input voltage but only one output voltage. What does a transmitter O/P signal start from 315 or 420 m.a.? Linear and can check up weather its “live zero” or “dead zero” Basic QA/QC Questions & Answers |Compiled & prepared by Abu Zarrar Quaisi |AL‐Qamar| 6
QA/QC Questionnaires
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Why is M.A. signal preferred for signal transmission? Noise reduction and no current drop for long transmission lines.
Q. )
Explain Cascade control (To prevent outside dist.
TT TIC REMOTE POINT STEAM PT PIC SLAVE FEED WATER PV FUEL GAS Figure. Cascade control Cascade means two controllers in series, one of them is a matter of primary & the second is the secondary or slave. The O/P of the slave controller operates the final control.
Q.
Explain three element feed water control system.
)
DRUM LEVEL CONTROL
FEED WATER CONTROL
P2
STEAM CONTROL
COMPUTING RELAY
P1
P4
P3 = R(P2‐P1‐ K)+P4+K0 R = GAIN KI = Adj. Suppression R0 = Adj. Bras
P3
Figure. FEED WATER CONTROL SYSTEM
Q. )
What is Foundation Field bus system? A fully digital control system is called Foundation Field bus system.
Basic QA/QC Questions & Answers |Compiled & prepared by Abu Zarrar Quaisi |AL‐Qamar| 7
QA/QC Questionnaires
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What are meant FAT, SAT, RAT?
Q. )
What is Microprocessor Control System? Give a brief of PLC, DCS and SCADA?
FAT SAT RAT
: : :
Factory Acceptance Test Site Acceptance Test Run Acceptance Test
Computer based control system is called Microprocessor control system. The brief of PLC, DCS and SCADA are as following: PLC : Program Logic Control system PLC’s are used in practice with the aim of achieving higher degree of availability or fault tolerance. The types are as follow: Fault Tolerant: 1 out of 2 objective systems objective: Reduce the probability of losses of production by switching to a standby system. Fail Safe: 2 out of 2 system objective: Protect life, the environment and investment by safely disconnecting to a secure “off” position. DCS : Distributed Control System. SCADA : Supervisory Control And Data Acquisition.
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What are inspection points for a cable tray installation? Material check as per approved spec, size and type, trays hook‐up, proper distance structure, tray to tray i.e. power/control/signal/low voltage and high voltage, support and fixed strong not shaking.
Q. )
What are inspection points for field instruments with impulse tubing? Material inspection as per approved spec material, type and size, installation as per Hook‐up, check line route to avoid any obstruction, check tube bending and check tube support, compression fitting of ferrules and then test (Hydro‐static test) shall be done.
Q. )
What are inspection points for cable laying?
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Material inspection as per approved materials, type and size, meggering, cable routing drawing, completion of cable route (tray, conduit or trench etc) and cable numbering (tags), cable bending, use of proper tools and equipment for cable pulling. What are inspection points for Junction Box and Marshalling Cabinets? Material inspection, type size as per approved specification, installation hook‐up for frame, bracket or stands, fixed properly means shaking free, Name Plate and Tag No. What are standard methods of Ferrules addressing to and from a Junction Box? For to side only Terminal’s Address required which shall be close to terminal either side and complete information shall be off from side after or before as per left and right side.
What are standards of installing a DP Transmitter in gas service and why? Inst. (DP Transmitter) in gas service shall be above the process to avoid the malfunctioning and drain the liquid (condensate) into the process line easily. Basic QA/QC Questions & Answers |Compiled & prepared by Abu Zarrar Quaisi |AL‐Qamar| 8
QA/QC Questionnaires
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Explain why shield of signal cable is not earthed on both sides? To avoid the current noise (Resonance)
Q. )
What is RFI? When and RFI will be raised?
How do you determine the correct installation of flow orifice? The orifice data tag shall be punched in the upstream of orifice, the data (tag) side shall be in the upstream of flow direction. Request for Inspection (RFI), RFI shall be raised only when the status of the preliminary inspection satisfactory, and the works (items) or Hold or Witness Points.
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What is final RFI? When it shall be raised up? When the QA/QC department of contractor is satisfied that the work detailed in the construction RFI is completed then request submitted for inspection to the client QA/QC department.
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What are the required documents for an inspection? Following are the required documents for an inspection: : RFI (Request for Inspection) : P&ID for line inspection : PP for location : Wiring diagram for wiring details. : Data Sheet for calibration and pressure test. : Hook‐up etc. for remote tubing/air line : QR for maintaining record. : WP (Work Procedure) to check each and every step as per spec. : QCO for issuing in case of little violation. : NCR (Non Compliance Report) for issuing in case of major violation etc.
Q. )
What are the required documents for a Remote Loop folder? Following are the required documents for a Remote Loop folder: : Loop package Check list : ILD (Instrument Loop Diagrams) : Instrument Loop Acceptance record (TR/Test Record) : P&ID (Piping & Instrumentations Diagram) : ISS/IDS (Inst. Spec Sheet/Inst. Data Sheet) : Alarm List : Calibration Record (TR) : Cable Megger Report (Primary Prior to Pulling) : Cable Megger Report (Secondary after Pulling) : Pressure Test Record (TR) : MC Check Record (Remote Loop) (Green Color) : MC (Marshalling Cabinet) Punch List : Loop Check Punch List Basic QA/QC Questions & Answers |Compiled & prepared by Abu Zarrar Quaisi |AL‐Qamar| 9
QA/QC Questionnaires
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What are the required documents for a Local Loop folder? Following are the required documents for a Remote Loop folder: : Loop package check list : ILD (if not mechanical loop) : Cable Megger Report (Primary Prior to Pulling) if not mechanical loop. : Cable Megger Report (Secondary after Pulling) if not mechanical loop. : Alarm Loop (If not Mechanical Loop) : P&ID : ISS/IDS : Calibration Record (TR) : Pressure Test Record (TR) if required : MC Check Record (Local Loop) (Green Color) : MC Punch List : Visual Check Punch List/Loop Check Punch List. What are the previous levels of inspection? Explain They are as following: Level of Inspection for Material a) Level 0 : Documents requirements only, no Inspection b) Level 1 : Inspection prior to shipping c) Level 2 : Minimum requirements, pre‐inspection meetings, one or more unspecified “in progress” surveillance visits. d) Level 3 : Same as level 2, except that “in progress” surveillance inspection shall be in regular basis. e) Level 4 : Resident Inspector continuously monitors the works. Level of Inspection for construction phase: a) Hold Points (H) : The inspection activity will not proceed without the presence of Inspector. b) Witness Points (W) : Inspection activities can be proceeding after issuing RFI. : Verification of documentation (NMR) on its correctness as per c) Review (R) spec and approved drawings. d) Surveillance (S) : Inspector has right to conduct random inspection of works. e) Inspect (I)/ Perform (P)/ : Construction can be proceeding to next phase without client Test (T) inspection. What is ITP’s? What are hold and witness Points? ITP means “Inspection and Test Plan” details of work scope and required types of Inspections. Hold Point (H) is the level of inspection that client inspection must required through RFI and cannot be proceed until inspection is done by client. Witness Point (W) is the level of inspection that inspection activity can be preceded without client inspection or client is not available as per RFI timing. Basic QA/QC Questions & Answers |Compiled & prepared by Abu Zarrar Quaisi |AL‐Qamar| 10
QA/QC Questionnaires
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What is schedule Q? Schedule Q is an attachment to the contract, which is the provision of Quality Assurance and Control, Inspection and Test Plan.
Q.
Explain ratio control (Fuel to Air Ratio control of Furnace Diagram? GAS MAIN STEAM PRC FT FRC
FV
FRC
PRIMARY SECONDARY FT RR
FUEL GAS
Figure RATIO CONTROL OF FURNACE DIAGRAM
Q. )
Analogue integrator & analogue differentiator?
ANALOGUE INTEGRATOR
ANALOGUE DIFFERENTIATOR
C R R
C V OUT
AV
AV
+
Q.
∫
V out = 1/RC Vin dt
V OUT
+
V out = Rcd/dt Vin
What is absolute pressure? Absolute pressure is the total pressure present in the system? Absolute Pressure = Gauge Pressure + Atm. Pressure
Q.
What is absolute zero pressure? Absolute zero = 760 mm Hg.
Basic QA/QC Questions & Answers |Compiled & prepared by Abu Zarrar Quaisi |AL‐Qamar| 11
QA/QC Questionnaires
Q. Q. )
What is maximum vacuum? The maxmm. Vacuum =
760 mm Hg.
What is Vacuum? Any pressure blow atmospheric pressure is Vacuum. 0 Vacuums Atm. = 760 mm.
Zero Gauge
Maxm. Vacuum 760 mm Hg Zero Absolute
Q. )
Q. )
What are the primary elements for measuring pressure? The primary elements for measuring pressure are: 1. Bourdon Tube 2. Diaphragm 3. Capsule 4. Bellows 5. Pressure Spring The above are known as elastic deformation pressure elements. 1. Types of Bourdon Tubes. 1) ‘C’ Type. 2) Spiral 3) Helix 2. Diaphragm : The diaphragm is best suited for low pressure measurement 3. Capsules : Two circular diaphragm are welded together to form a pressure capsule. Material used: PHOSPHER BRONZE, NI‐SPONGE, STAINLESS STEEL 4. Bellows : Bellows is a one‐piece, collapsible, seamless metallic unit with deep folds formed from very thin walled tubing. 5. Pressure Spring : Pressure springs of helical or spiral shape are used for measuring high pressures. How will you change the action of a control valve? If the control valve is without bottom flange the actuator needs to be charged. If the bottom flange is provided, disconnect stem, separate body from bonnet. Remove the bottom flange and the plug from body. Detach the plug from the stem by removing the pin, fix the stem at the other end of the plug and fix the pin back. Turn the body upside down. Connect it back to the bonnet after inserting the plug and stem. Connect back the stem and couple it. Fix back the bottom flange. Calibrate the Valve.
Basic QA/QC Questions & Answers |Compiled & prepared by Abu Zarrar Quaisi |AL‐Qamar| 12
QA/QC Questionnaires
Q. )
What is feedback & feedforward control? Feedback control involves the detection of the controlled variable & counter acting of changes in its value relative to setpoint by adjustment of the manipulated variable. Feedforward is a system in which corrective action is based on measurement of disturbance inputs into the process.
Q. )
Explain furnace draft control. When both forced draft & induced are used together at same point in the system the pressure will be the same as that of atmosphere. Therefore the furnace pressure must be negative to prevent hot gas leakage. (0.1” H2O)
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How will you apply wttest calibration to a leveltrol? Normal Leveltrol 1. Adjust the zero to get 0% output. 2. Connect a transparent PVC tube to the Drain point as shown in Hook‐up. 3. Fill it to the centre of top flange. 4. Adjust the Sp. Gravity or the Span adjusts. 5. Fill it up to 50% to check linearity. Loss of wt. at 0% = wt. of the displacer Loss of wt. at 100% = (wt. of the displacer – volume) x σ i.e. Volume = πr2h σ = Sp. Gravity.
Q. ) Q. )
What are the limitation of leveltrol? 72”. What will happen if the displacer has fallen? If the displacer has fallen, the output will be maximum. Has a hole in it, the output will be minimum.
Q. ) Q. )
How will you check zero of a DP level transmitter? Close both isolation valves on LP leg and HP leg, equalize, check and adjust zero if necessary.
Q. ) Q. )
How many zones are there in classΙ atmospheres?
Q. )
What is meant by term “EXPLOSIONPROOF”? Equipment designed to withstand an internal explosion and to prevent the ignition of GAS/VAPOR outside the enclosure. Three (3) zone 0, zone 1, zone 2. How many groups or gases/vapors are there in ClassΙ atmosphere? Division Zone
: Four A, B, C, D : Three ΙΙC, ΙΙB, ΙΙA
What type of conduit must be used within Class Ι zone 0/1 area? Threaded Rigid Metal Conduit. Basic QA/QC Questions & Answers |Compiled & prepared by Abu Zarrar Quaisi |AL‐Qamar| 13
QA/QC Questionnaires
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How many threads must be engaged to make a joint EXPLOSIONPROOF?
Q. ) Q.
What is the distance from an EXPLOSIONPROOF enclosure must a seal be installed?
5 Full Threads NEC 501‐4 (A) (1) requires threaded connection to be made up with at least 5 threads fully engaged. 18”
NEC 501‐5 (A) (1) conduit seals shall be installed within 18” of the enclosure.
In a ClassΙ. Zone 0 areas A 2” conduit is terminated to an enclosure containing only terminals is a conduit seal is required.
)
Yes. NEC 501‐5 (A) (1) (B) entries 2” and larger into enclosures containing terminals, splices or taps sealing fittings are required.
Q. )
Why are sealing fittings installed in conduit systems?
Q. )
What is the maximum distance a sealing fitting is installed from boundary location?
Q. )
What is the minimum thickness of the compound inside a sealing fitting?
Q. )
Explain what is meant by the term “FLASH POINT” of liquid.
To minimize the passage of gases/vapors and to prevent the passage of flames into the conduit systems can also be used to drain conduit. 10 FEET boundary.
NEC 501‐5 (A) (4) and (B) (2) requires sealing within 10 Feet either side of the
The minimum thickness shall not be less than the trade size of the sealing fitting and in no case less than 5’8 inch 501‐5 (C) (3). The minimum temperature at which a liquid gives of a sufficient concentration to form an ignitable mixture.
Q. ) Q. ) Q. )
A conduit outlet box can be used as a sealing fitting when fitted with sealing cover?
Q. )
What is the minimum information required on a classified area drawing.
Yes. A GU Type fitting can be used as a sealing fitting when fitted with a sealing cover. What is the ratio of mix powder to water? 2 parts of powder to 1 part of water (WATER : must be sweet water) What is the purpose of FIBER DAM inside a sealing? To make a foundation for the compound. The fiber dam must be strong enough and tight enough to prevent the weight of the poured compound from seeping out from the conduit. 1. Differentiation between the classified and non‐classified locations. 2. Minimum AIT (Auto Ignition Temperature) of the gas/vapor. 3. Differentiation between the groups. 4. Classified areas to be shown in plan and elevation. Basic QA/QC Questions & Answers |Compiled & prepared by Abu Zarrar Quaisi |AL‐Qamar| 14
QA/QC Questionnaires
Q.
What is the maximum internal and external surface temperatures allowed in class I Zone 2 areas? 800° of the Auto Ignition Temperature of the gas/vapor in the area. See NEC: 501‐5 (A) (1); 501‐5 (A) (4)……………………………………..
Q.
Where a mixture of gases has a mixture density less than 75% of the density of air what is it classed as? Lighter than air. See SAES –B‐068, Para 5.4
Q.
The mixture of gases/vapors of different ignition temperatures. How is the ignition temperature of the gas/vapor defined? By one of three methods Lowest individual temperature of the mixture. See SAES B‐068, Para 5.3 Test of the mixture By calculation.
Q.
What is the classification of an unventilated room? ClassΙ Div. 1 Group A / Class Ι Zone 1 Group ΙΙC
Q.
Are sealing fittings required for smart transmitters in a ClassΙ Zone 2 area? No. smart transmitters have a low wattage output and usually will not reach 80% of the auto ignition temperature of the gas/vapor, also the cable is terminated within a terminal chamber which is separate from the process by a minimum of two seals. =x=x=x=x=x=x=x=x=x=x=x=x=x=x=x=x=x=x=x=x=x=x=x=x=x=x=x=x=x=x=x=x=x=x=x=x=x=x=x=x=x=
Q.
What is the maximum %age of crosssection a conduit can be filled containing three(3) or more wires? 40% as per NEC Ch. 9 Table 1.
Q.
What is PVC in cable insulation an abbreviation for? Poly Vinyl Chloride What is the purpose of drain/shield in instrumentation wires? To reduce electrostatic noise and unwanted voltage.
Q.
Per Aramco Standards, what is minimum separation between low voltage power cables and instrumentation cables in cable trays. Minimum “300 mm.”
Q.
Per NEC, what is the maxm. Distance between supports for 2inch rigid steel conduit. Horizontal : 4.9 mtrs. (16 Feet) As Per NEC Article –Table 344:30 (B) (2) Vertical : 6 mtrs.
Basic QA/QC Questions & Answers |Compiled & prepared by Abu Zarrar Quaisi |AL‐Qamar| 15
QA/QC Questionnaires
Q.
Per Saudi Aramco standard, what is the minimum size of grounding grid conductor [cable]? 70 mm2
Q.
Per NEC, what would be the size of equipment grounding copper conductor for equipment protected by overcurrent device rated 600 amperes? NEC‐ article : 250 Table‐122. 1 AWG copper(35‐50mm2) or 2/0 AWG copper –clad (70mm2)
Q.
Per NEC, what would be the size of grounding electrode copper conductor for alternating current system having largest service conductor sized 350 kcmil? 1600 AMP. Copper conductor 4/0 AWG 120mm2
Q. )
How the grounding conductor would be connected to underground grounding grid?
Q.
a) By thermite welding or brazing . b) By approved grounding compression connectors.
What do the following letters denote on electrical equipment and explain the markings? T1‐450°C Exd –Explosion Proof Glands or Flame Proof 11B – Combustible dust Acetaldehyde, Ethylene T5 ‐ 100°C Temp.
T2‐300°C T3‐200°C T4‐135°C T5‐100°C T6 ‐ 85°C
Q.
On electrical equipment being used in hazardous area you may see the letter UL or C.S.A, what do these abbreviations stand for? UL – Under Writer Laboratories C.S.A –Canadian Standard Association
Q.
A 3 phase system has phase to phase 480V AC , what is the phase to earth/neutral voltage? Show calculation. 480/√3 =277V Line current = √3 phase voltage (√3 = 1.732)
Q.
Per NEC , what are the instances where seals fittings are needed? When a conduct run is crossing hazardous boundaries below ground requires boundary seal, side, electrical equipment, junction box & conduit. Any breaking, sparking & heat producing device must be required fittings.
Q.
How to minimize the effect of breathing in conduit installation? Low point drain and breather shall be provided.
Q.
Name type of cables suitable for class 1, division 1 and division 2 locations? Class1, division 1 ,and division2 locations suitable cable is XLPE , Polyethylene , EPR , Armored cable . Basic QA/QC Questions & Answers |Compiled & prepared by Abu Zarrar Quaisi |AL‐Qamar| 16
QA/QC Questionnaires
Q.
How many degrees bend permitted in a conduit run? 360° between pull box to pull box.
Q.
Per NEC, what is the minimum number of conduit threads should be engaged at hazardous locations? Five (5) Full Threads should be engaged.
Q.
What is the color code of grounding neutral and phase conductor? Grounding ‐ Green Neutral – White Phase – Black
Q.
What is minimum temperature rating for low voltage? 90° C Dry & 75°C Wet
Q.
Name the type of tests required for testing following cables:
• • •
Medium voltage power cables – Megger test & DC High Potential test Catholic protection – Holiday test Low voltage cables – Megger test & continuity test.
1. 2. 3. 4.
Name some of the tests required for testing following equipment: Oil type transformers – Winding test and Ratio test Electrical Motors – Winding test, Resistance test, Megger test Batteries – specific gravity, voltage, current Circuit Breakers – Megger & Ductor test, primary current Trajection test
Q.
Q.
What is the NEMA rating for electrical enclosures installed in the following environments: 1. Indoor – NEMA – article – 250 2. Outdoor – 3R , 3CR4 3. Corrosive environment – 4X
Q.
Per NEC , what is the minimum working clearance in front of low voltage electrical equipment? Minimum 3 Feet (900mm)
Q.
Per S. Aramco standard , what is the ambient temperature rating for electrical equipment? 40°C
Q.
How many divisions and groups class Ι atmospheric hazards are divided into? And what are the locations covered by each division? Class Ι ‐ zone 0 – flammable gasses or vapor are present in air classΙ ‐ zone Ι ‐flammable gasses or vapor are likely to exist under normal operation condition Basic QA/QC Questions & Answers |Compiled & prepared by Abu Zarrar Quaisi |AL‐Qamar| 17
QA/QC Questionnaires
Q.
Define following for enclosures containing arching electrical device and installed in hazardous area? 1. Type – NEMA type 4x 2. Safety factor – Exia 3. Flame tight – Exid
Q.
What type of equipment is this statement describing? The energy released from this type of equipment is insufficient to cause ignition. Class Ι zone Ι location
Q.
What are the most important things to check on lighting fixture installed in a hazardous location? And where these need to be shown? To be check and confirm fixture are explosion proof it should shown in fitting name flute itself.
Q.
Per Aramco standard, what are the acceptable types of underground conduits? Threaded rigid steel hot dip galvanized and pre coated.
Q.
What is IEEE standard work clearance around high voltage transformers? Minimum – 10 feet – 3mtrs. as per NEC table – 110.31
Q.
Per Aramco standards, what is the maximum resistance value per mined for a grounding system at industrial area? 1 OHM
Q.
How many threads of rigid steel conduit must be engaged in a hazardous area? 5 threads. As per NEC – 501.4 (A) (1)
Q.
How do you determine the correct size equipment ground conductor for a 1600 amp. Overcurrent device? As per NEC – article . Table – 250 – 122 ‐ Ground Conductor for – 4/0 AWG – 120 mm2
Q.
What size junction is required if you have a 4” conduit straight in and straight out? What size for angle pulls? As per NEC – 314.28 For straight in and straight out: less than 8 times ‐ 8×4=32”inch For angle pulls : less than 6 times ‐ 6×4=24”inch
Q.
What is the maximum percent of cross section a conduit can be filled containing 3 or more conductors? 40% as per NEC chapter – 9 table – 1
Q.
What are the requirements for conductor insulation at light fixture terminations? Insulation minimum thickness 0.25mm that have insulated suitable temperature not less than 125°C
Q.
What is the maximum number of overcurrent devices allowed in a panel board? As per NEC – 408.15 42 number.
Q.
What is a “T” number as it relates to equipment in a Hazardous Area? Basic QA/QC Questions & Answers |Compiled & prepared by Abu Zarrar Quaisi |AL‐Qamar| 18
QA/QC Questionnaires
Temperature class. As per NEC table – 500.8(B)
Q.
Can you use light fixtures as a raceway? No
Q.
Where are conduit supports required for rigid steel? Horizontal : 3 mtrs vertical : 6 mtrs . As per NEC – 344.30
Q.
Where are seal fitting required? Instrument side and enclosure side in hazardous area.
Q.
What are all the sources of information used to ensure a specific
Basic QA/QC Questions & Answers |Compiled & prepared by Abu Zarrar Quaisi |AL‐Qamar| 19
QA/QC Questionnaires
Q.
What are the process variable?
Q.
In which NEC article number for the grounding, wiring, conduit & area classification?
Q.
Name at least 5 Saudi Aramco Eng’g. Standard which is commonly used for Instrumentation. Installation and inspection.
Q.
What are a closed loop control and its example?
Q.
What are the procedure of installing a Gas service, Liquid service & steam service transmitter?
Q.
What is the safety factor for impulse tubing pressure test?
Q.
What are the contents of the loop folder?
Basic QA/QC Questions & Answers |Compiled & prepared by Abu Zarrar Quaisi |AL‐Qamar| 20
QA/QC Questionnaires
CONDUIT a. What is the minimum size of conduit for instrumentation and its support distance b. A conduit outlet box shall be installed within 18 inches of the field device, and the cable to the Instrument shall be looped one or more times within this fitting. c. Flexible conduit shall be used at the instrument end of the conduit to provide isolation from vibration and protection against thermal expansion of the rigid conduit. d. Conduit above ground in severe corrosive environments shall be PVC coated min. thickness is 40 mils per NEMA RN 1. e. Conduit fittings for outdoor rigid steel conduit and liquid tight flexible metal conduit shall be cast or forged steel, cast iron or malleable iron, either hot‐dip galvanized or zinc electroplated ( no aluminum fittings or fittings accessories shall be used in outdoor installation ) f. Conduit and cable entries to field junction boxes shall be through the bottom. Top entries are allowable and provide a drain seal installed on the conduit within 18 inches away from the enclosure.
CABLE TRAY a. The maximum spacing between expansions joints shall be based on a temperature differential of 55 deg. C an expansion gap settings shall be in accordance with the recommendations of NEMA VE 2 based on the temperature of 0 deg. C and a maximum temperature of 55 deg. C. b. All fasteners used to connect and assemble the cable tray system shall be 316 SS. c. Cable tray shall be grounded as required in SAES‐P‐111. d. Cable tray fill shall comply with NEC Article 392.
ENCLOSURES a. Enclosures’ for Instrument in outdoor plant areas shall be NEMA Type 4 in accordance with NEMA ICS 6 and NEMA 250 or IEC 60529 Type IP 65.Enclousure in severe corrosive environments shall be NEMA Type 4X or IEC 60529 Type IP 66. b. The Junction Box in a class 1 Zone 2 location and d in Hazardous areas shall be a single door NEMA Type 4X or IEC 60529 Type IP 66 box. The box construction shall meet the following requirements.
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CONNECTIONS at FIELD INSTRUMENTS and JUNCTION BOX a. Connections at field instruments shall be screw type terminal blocks. Wire nuts and spring type terminals shall not be used. Instruments’ with integral terminal blocks shall be connected directly to the field cable. b. The outer jacket of shielded twisted single pair/triad cables shall be left intact up to the point of termination. Drain wires and Mylar shields on shielded cables shall be cut and insulated with heat shrink sleeve at the field instrument unless otherwise specified by the Instrument manufacturer. c. Twisted multi‐pair triad cables shall be cut to the appropriate length to minimize looping and flexing of the cable within the junction box.
COLOR CODING Power and signal wiring shall be color coded as follows: AC Supply
DC Supply
Signal Pair Signal Triad
Thermocouple
Phase Neutral Ground Positive Negative Positive Negative Positive Negative Third Wire Positive Negative
Black White Green or green with yellow tracer Red or red sleeve over any color except green Black or black sleeve over any color except green Black White Black White Red Per ANSI MC96.1 Per ANSI MC96.1
Grounding (J902)
17.1 General 17.1.1 Electrical systems must be connected to ground for the protection of personnel and equipment from fault currents (AC safety ground) and to minimize electrical interference in signal transmission circuits (Instrument circuit ground).
17.1.2 Two grounding systems are required for instrumentation systems:
a) safety ground for personal safety.
b) Instrumentation Safety Ground.
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17.2 Safety Ground 17.2.1
All exposed non‐current‐carrying metallic parts that could become energized with hazardous potentials must be reliably connected to the equipment grounding circuits. This assures that hazardous potential differences do not exist between individual instrument cases or between an instrument case and ground. Therefore, all metal equipment and enclosures within a panel or series of panels (i.e., instrument cases, hinged doors, racks, etc.) shall be bonded with bonding jumpers and connected to a safety ground bus with a minimum copper wire size of 4 mm² cross‐sectional area. Two copper conductors, 25 mm² minimum, shall be connected from the safety ground bus to a single tie point on the safety ground grid in a closed loop configuration. Safety ground connections must be made such that when a case‐grounded instrument is removed, the integrity of the rest of the safety ground system is maintained.
17.2.2
Enclosure for field instruments shall be grounded as follows: (J‐902)
17.2.2.1
Instruments Operating at greater than 50 Volts
The enclosure for Instrument devices operating at 120 V AC or 125 VDC shall be grounded per SAES‐P‐111.
Instrument Circuit Ground (J902) 17.3.1
The purpose of instrument circuit grounding is to reduce the effect of electrical interference upon the signal being transmitted. An instrument circuit ground bus shall be provided for consolidating instrument signal commons and cable shield drain wires. This ground bus shall be isolated from the safety ground system except at a single tie point as described below.
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QA/QC Questionnaires
Tubing Installation
PPPFL‐001
PIP 4.2.8.1
Interconnecting instrument piping (tubing) between the primary metering element and the measuring instrument shall be 0.5 inch AISI Series 300 stainless steel tubing minimum. Tubing wall thickness shall be 0.89 mm (0.035 inch) minimum. Applicable piping code and process requirements shall prevail.
PIP 4.2.8.2
Interconnecting piping shall be limited to a maximum length of 6 m (20 ft) for meters in control loops. Interconnecting impulse tubing between a differential flow element and a transmitter in compressor suction service shall be kept as close as possible or close coupled.
PIP 4.2.8.3
Interconnecting Seal liquid to protect flow meter impulse tubing and secondary measurement instrumentation from corrosive fluids or to provide a stable hydraulic measuring medium shall be free flowing but not volatile under normal process and external ambient conditions. Seal liquids shall not be miscible with nor react with the process fluid being measured. Seal liquids shall be selected so that their potential for contamination of the process fluid is acceptable.
PIP 4.2.8.4
(Addition) PIP PCIDP000 "Differential Pressure Installation Details" shall be used for interconnecting the flow Differential Pressure Instruments to the root valves of the differential producers.
PIP 4.6.2.c
(Addition) Purging of impulse lines shall be considered only if other methods have failed to eliminate problems of condensation, vaporization, corrosion or plugging.
34SAMSS831 Installation 8.1.1
Pressure and D/P instruments in liquid or condensable vapor service shall be self‐ venting (i.e., mounted below the process connections) with all impulse lines sloping downward approximately 1:10 minimum toward the instrument. Pressure and D/P instruments in gas service shall be self‐draining (i.e., mounted above the process connections) with all lines sloping downward approximately 1:10 minimum toward the process connection.
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QA/QC Questionnaires
8.3 Instrument Piping and Tubing The instrument piping and tubing installation shall ensure the reliable and accurate operation of the instrument(s) involved, and allow sufficient access for maintenance, calibration and testing. It shall be possible to test all alarm and shutdown initiating devices, without interfering with the process operation of the packaged unit. Instrument tubing shall be adequately supported to eliminate any vibration transmission to the instruments or excessive load to the piping connection, process line or vessel. Tubing to and from non‐indicating instruments shall have a plugged tee or equivalent test point for calibration and testing purposes. All threaded connections shall be tapered per ASME B1.20.1. All incoming and outgoing interconnection lines shall terminate in bulkhead fittings. The lines shall be marked with the tag numbers of the corresponding instruments. Bulkhead fittings shall be installed with adequate spacing to ensure that any connection can be removed without the need to remove other fittings.
9.2.2 Tubing and Fittings 9.2.2.1
Tubing
9.2.2.2
Fittings
Stainless steel tubing shall be seamless, annealed, minimum wall thickness 1.24 mm, per ASTM A269, Grade TP‐316L. Instrument air tubing shall be ¼ inch, 3/8 inch, or ½ inch OD stainless steel. Wall thickness shall be 0.75 mm or larger. 316 stainless steel compression fittings shall be either Crawford Swagelok, Parker Hannifin A‐Lok, Parker Hannifin Corp. CPI or Hoke Gyrolock. Any proposal to use fittings other than those listed above shall be reviewed by Supervisor, Instrumentation Unit, Process Instrumentation Division, and P&CSD.
Instrument Air Supply 4. Designs (J‐901) 4.1
General 4.1.1
Instrument air supply systems shall provide dry, oil‐free air to pneumatic instrumentation, valve actuators, and other services requiring instrument‐quality air.
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QA/QC Questionnaires
4.8 Instrument Air Distribution System 4.8.1 General Requirements 4.8.1.1
Piping material shall be selected in accordance with SAES‐ L‐032. The selection of alternative piping material requires the approval of the Coordinator, Mechanical and Civil Engineering Division/CSD.
4.8.1.2
All main and branch headers shall be sloped {minimum 64 mm per 30 m (2.5 inches per 100 feet)} and provided with low point drains.
4.8.1.3
All headers shall terminate with a line‐size valve, blind, or plug to facilitate cleaning and plant expansions.
4.8.1.4
Each branch header shall connect to the top of the main header through a branch‐line‐size, full‐bore isolation valve.
4.8.1.5
Where there is a general distribution system for more than one plant, the piping shall be connected in a loop to provide two directions of supply to each plant. Isolation valves shall be provided to enable isolation of each plant.
4.8.1.6
Supply takeoffs to individual instruments (a line serving up to a maximum of four devices) shall connect to the top of the branch header through a takeoff‐line‐size, full‐bore isolation valve.
4.8.1.7
4.8.1.6.1
The minimum size of supply takeoffs is ½‐inch.
4.8.1.6.2
Twenty percent (20%) spare takeoff fittings and block valves shall be installed on the branch header.
Instrument air piping shall not be pocketed (i.e., shall not contain, U‐ sections). Instrument air piping shall not be installed underground. Exception: Instrument air branch connections may be buried to cross beneath roadways or fences where there is no existing overhead rack and where the aboveground support would interfere with crane or emergency vehicle movement. Prior approval from the General Supervisor, Process Instrumentation Division, P&CSD is required. Buried branch lines shall have low point drains, stainless steel construction and external coating per SAES‐H‐002.
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QA/QC Questionnaires
4.8.2 Header and Takeoff Sizing 4.8.2.1
The pressure drop for piping between the dryer after filter outlet and the most remotely located user shall not exceed 35 kPa (5 psi) under maximum service flow rate.
4.8.2.2
For installations in which the instrument air consumers are located more than 600 m (2000 ft) from the instrument air compressor; pipe sizes should be calculated to keep pressure drops within the above limit. Below 600 m (2000 ft) instrument air header pipe size should be selected from Table 2. (J‐901)
Table 2
Number of Users 1
‐ 4
5
‐ 9
Pipe Size
½ inch ¾ inch
10 ‐ 15
1 inch
16 ‐ 80
1½ inch
81 ‐ 150 151 ‐ 300
2 inch 3 inch
5
Testing (J-901) Pressure testing of supply system and distribution system per SAES‐L‐056, using dry instrument air or inert gas is required. Hydrostatic testing of instrument air piping is not permitted.
Basic QA/QC Questions & Answers |Compiled & prepared by Abu Zarrar Quaisi |AL‐Qamar| 27
QA/QC Questionnaires
INSTRUMENTATION QUESTIONAIRE: 1. Design and Selection of Process Control & Instrumentation System should include: Suitability, Reliability, Quality, Accuracy, and Repeatability. a) True b) False c) None 2. Sour Gas can be used in lieu of Instrument Air. a) True b) False c) None 3. Accepted Field Signals are: a) 3 – 15 psi, 4 – 20 mA, Hart & any Vendor Protocol. b) 0 – 12 psi, 0 – 16 mA, 0 – 5V. c) 0 – 30 psi, 0 – 20 mA, Hart. 4. Instrument & Control system (outdoor, unsheltered) shall be rated for operation for Outdoor Temperature of: a) 10 deg. C – 35 deg. C. b) 0 deg. C – 30 deg. C c) 0 deg. C – 55 deg. C d) 10 deg. C – 55 deg. C e) 0 deg. C – 65 deg. C 5. Downstream edge of orifice shall be Square & Sharp so they will not show a Beam of Light when checked with an Orifice Edge Gauge. a) True b) False c) None 6. Orifice Bore BETA is ratio of pipe ID and pipe OD. a) True b) False c) None. 7. At what temperature is Degree Centigrade = Degree Fahrenheit a) 32 b) 0 c) –40 d) 40 8. For temperature compensation in flow measurement with orifice, Thermowell shall be located not less than 2 and no more than 30 pipe dia. downstream. a) True b) False c) None. Basic QA/QC Questions & Answers |Compiled & prepared by Abu Zarrar Quaisi |AL‐Qamar| 28
QA/QC Questionnaires
9. Vane Type Flow Switches are preferred over Differential Pressure Type. d) True e) False f) None. 10. Straightening Vanes are preferred over straight run piping in flow metering. a) True b) False c) None 11. Rangeabilility of 10:1 is major requirement in flow measurement. Which of the following method will be most appropriate: a) Orifice b) Positive Displacement c) Turbine Meter d) Variable Area 12. Flowmeter installation shall comply with: a) API RPI 551 b) API RPI 531 c) API RPI 351 d) AMSI Sec. IV 13. Reflex Level Gauge is used for Interface Level application. a) True b) False c) None 14. Transparent Level Gauges are used for: Acid, Caustic, Dirty, Dark Color liquid. a) True b) False c) None 15. Gauge Cocks shall not be provided on gauges installed in light clean Hydrocarbons. a) True b) False c) None 16. Displacement type instruments may be used for level range upto and including: a) 1800 mm b) 1830 mm c) 1500 mm d) 2200 mm 17. Differential pressure type instruments are no preferred for liquid – liquid interface measurement. a) True b) False c) None Basic QA/QC Questions & Answers |Compiled & prepared by Abu Zarrar Quaisi |AL‐Qamar| 29
QA/QC Questionnaires
18. Capacitance type level instruments shall be used in liquid that contain entrained gas. a) True b) False c) None 19. Natural frequency & Wake frequency calculation shall not be performed on each thermowell, if calculated Wake frequency is not equal to or not greater than 80% of thermowell natural frequency. a) True b) False c) None 20. Non‐grounded Thermocouples are preferred due to quick response. a) True b) False c) None 21. For grounded Thermocouples extension wire shield drain wire shall be grounded at Thermocouple head. a) True b) False c) None 22. For ungrounded Thermocouple (T/C), extension wire shield drain wire shall be grounded at receiver instrument end to the instrument circuit ground. a) True b) False c) None 23. Resistance Temperature Detector (RTD) shall be used when greater accuracy is not required. a) True b) False c) None 24. For temperature measurement requiring maximum accuracy, following shall be used: a) T/C b) RTD – 2 wire c) RTD – 3 wire d) RTD – 4 wire e) Filled System Instrument f) Bi‐Metallic Instrument 25. PSIG – Atmos. Press. = PSIA a) True b) False c) None 26. Range of Transmitter is 20 to 100. It is called: a) Elevated range b) Suppressed range c) Elevated zero range Basic QA/QC Questions & Answers |Compiled & prepared by Abu Zarrar Quaisi |AL‐Qamar| 30
QA/QC Questionnaires
27. For viscous liquid, following orifice shall be used: a) Concentric b) Segmental c) Eccentric d) Quadrant Edge 28. Which Flowmeter is used for No Pressure Loss: a) Orifice b) Magnetic flowmeter c) Rotameter d) Positive displacement meter 29. CV of Control Valve is number of Gallons of water. A control valve pass through control valve with 5 PSIG pressure drop: a) True b) False c) None 30. Shield grounding is done at both ends of cable for analog signals. a) True b) False c) None CORRECT ANSWERS: 1 (a); 2 (b); 3 (a); 4 (e); 5 (b); 6 (b); 7 (c); 8 (b); 9 (b); 10 (b); 11 (c); 12 (a); 13 (b); 14 (a); 15 (b); 16 (c); 17 (b); 18 (b); 19 (a); 20 (b); 21 (a); 22 (a); 23 (b); 24 (d); 25 (b); 26 (b); 27 (d); 28 (b); 29 (b); 30 (b). Basic QA/QC Questions & Answers |Compiled & prepared by Abu Zarrar Quaisi |AL‐Qamar| 31
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