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# Questions Related to Pipe Fittings:- Part-2

16. On which type of flanges the use of spiral wound gasket are restricted?
ASME B16.5 does not recommend the use of 150 # rating spiral wound gasket on flanges other than welding neck and lapped joint type.
17. Up to what temperature limits the low strength carbon steel bolts should not be used for flanged joints?
Flanged joints using low strength carbon steel shall not be used above 200# C or below – 28# C.
18. How the pipe fittings are classified based on end connections?
Pipe fittings are classified based on end connection as: –
A. Socket weld fittings.
B. Screwed end fittings.
C. Beveled end or butt weld fittings.
D. Spigot socket fittings.
E. Buttress end fittings.
19. Up to what temperature the carbon steel materials shall be used?
Carbon steel materials shall be used for temperature up to 425C.
20. Which material is used for temperature above 426# C?
Alloy steel materials shall be used for temperature above 426C.
21. Which type of material is used for corrosive fluid?
Stainless steel materials shall be used for corrosive fluid.
22. Which type of piping materials are used for drinking water, instrument air etc?
Galvanized steel materials shall be used for drinking water, instrument air and NI lines (LP).
23. 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 & its thickness as BWG (Brimingham Wire Gauge or 1/100 inch).
24. From which size onwards NB of pipe is equal to OD of pipe?
From the size 14” and onwards NB = OD of pipe.
1.5D (Where “D” is the diameter of the pipe.)
1D(Where “D” is the diameter of the pipe.)

27. What is the basis of using of short radius & long radius elbow?
Long radius elbow are used for small pressure drop whereas short radius elbow are used for high pressure drops. For catalyst flows vary long radius elbows are used.
28. Normally where do we use the following?
A. Eccentric reducers.
B. Concentric reducers.
A. Eccentric reducers = pump suction to avoid Cavitation, To maintain elevation (BOP) in rack.
B. Concentric reducers = pump discharge, vertical pipeline etc.
29. Concentric reducer is used in pump suction. (Yes / No). Explain.
No. Air pockets may form if concentric reducer is used at pump suction, which results in cavitation and cause damage to pump. To avoid this problem, eccentric reducer with flat side up (FSU) is used in pump suction.
30. Where the ERW spiral & longitudinal pipes are used?
Use depends upon the availability of pipes. Nothing functional difference.
31. Where the ERW & seamless pipes are used?
Above 18” ERW pipes are used. Below 18” seamless pipes are used. Seamless pipes can sustain higher temperature & pressure.