FREQUENTLY ASKED QUESTIONS
JUST FIND YOUR ANSWERS BELOW:
WHAT IS THE ASME CODE FOLLOWED FOR DESIGN OF PIPING SYSTEMS IN PROCESS PIPING (REFINERIES & CHEMICAL INDUSTRIES)?
B 31.3
WHAT IS THE DIFFERENCE BETWEEN PIPE AND TUBE?
Pipe is identified by NB and thickness is defined by schedule whereas tube is identified by OD.
WHAT DO YOU MEAN BY FOLLOWING TYPE OF WELDING?
SMAW: shielded metal arc welding
TIG: tungsten inert gas
WHAT IS THE LONG RADIUS ELBOW?
1.5D
NORMALLY WHERE DO WE USE THE FOLLOWING?
- Eccentric reducer: pump suction to avoid cavitations, to maintain elevation (BOP) in rack.
- Concentric reducer: pump discharge, vertical pipeline etc.
CONCENTRIC REDUCER USED IN PUMP SUCTION? (Y/N) EXPLAIN
No. Air pocket may form if concentric reducer is used at pump suction, which results in cavitations, and cause damage to pump. To, avoid this problem; eccentric reducer with flat side up is used in pump suction.
WHAT DO YOU MEAN BY CAVITATIONS IN PUMP?
A pump is designed to handle liquid not vapour. Vapour forms if the pressure in the pump falls below the liquid’s vapour pressure. The vapour pressure occurs at the right of the impeller where a sharp pressure drop occurs. The impeller rapidly builds up the pressure which collapses vapour bubbles causing cavitations and damage. This is avoided by maintaining sufficient NPSH.
WHAT DO YOU MEAN BY NPSH?
NPSH: Net positive suction head. NPSH is the pressure available at the pump suction after vapour pressure subtracted.
It is calculated as: static head +surface pressure head-the vapour pressure of your product-the friction loss in the piping, fittings and valves.
WHAT IS THE ASTM CODE FOR THE FOLLOWING?
- CS pipe= A106Gr.B
- CS fitting =A234 GR.WPB
- CS flanges=A105
- AS pipe=A335Gr P1/P11
- Cast CS valves= A216 Gr. WCB
WHAT IS THE THUMB RULE TO CALCULATE CURRENT REQUIRED FOR WELDING?
Current (Amp) = [Diameter of welding rod (mm) x 40] +/- 20
WHAT IS THE ANSI CODE FOR STEEL FLANGE AND FITTINGS?
B16.5
WHAT DO YOU MEAN BY AARH (FLANGE FINISH)?
Arithmetic average roughness height.
FROM WHICH SIDE OF PIPE WILL YOU TAKE A BRANCH CONNECTION?
When fluid is gas, air or steam and cryogenic service-Topside
When fluid is liquid- Bottom side.
WHY DO WE PROVIDE DRIP LEG IN STEAM LINE?
To remove condensate when there is a rise in the pipe along the follow direction. If we do not provide the drip leg in steam line, the condensate which forms inside the pipe will result in water hammer effect causing damage to piping system.
WHY DO WE PROVIDE HIGH POINT VENT AND LOW POINT DRAIN IN PIPING?
HPV –For removing air during hydro test
LPD – For draining water after conducting hydro test.
WHAT DO YOU MEAN BY IBR AND WHICH LINE COMES UNDER IBR PURVIEW?
IBR- Indian boiler regulation act. Steam lines with conditions listed bellow comes under IBR purview Steam lines with design pressure is 3.5 kg/cm2 and above. Line size above 10’’ having design pressure 1 Kg /cm2 and above.
WHAT IS THE NORMAL UPSTREAM AND DOWNSTREAM STRAIGHT LENGTH OF ORIFICE FLOW METER?
Upstream -15D and Downstream-5D
DESCRIBE DIFFERENT TYPES OF DESTRUCTIVE AND NON-DESTRUCTIVE TESTS?
Destructive test: Bend test, tensile test, Impact test
Non Destructive test: DPT, MPT, Radiography and ultrasonic test.
HOW MUCH SHOULD BE THE PRESSURE FOR HYDRO TEST?
1.5 times of design pressure
WHICH IS THE CRITERION FOR PIPE SUPPORT?
- Ans. Load of bare pipe+ insulation
- Load of bare pipe + water fill
- Load of valves and online equipment and instrument.
- Thermal loads during operation.
- Steam out condition, if applicable.
- Wind loads for piping at higher elevation, If required.
- Forced vibration due to pulsating now.
WHAT IS THE PURPOSE OF EXPANSION BELLOWS?
Expansion bellows are used absorb axial compression or extension, lateral shear and angular torsion developed in the pipes.
WHAT IS THE ALLOWABLE STRESS RANGE FOR CS PIPES.
2070kg/cm2
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