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PIPING DESIGN QUESTIONAIRE
Authors: Kumar Rudra, Rakesh Patil and Joshua Thinakaran Oil and Gas Special Projects - L&T, Mumbai - India Copyright 2002. All Rights reserved
Simple 1. What is the ASME code followed for design of piping systems in Process pipings (Refineries & Chemical Industries)? (i) B31.1 (ii) B31.3 (iii) B31.5 (iv) B31.9 Answer (III) 2. What do you mean by following items? i.)ISLB-400 ii) ISMB-600 iii) ISHB-350 iv) ISMC-300 v) ISJB-150 vi) ISLB-200 vii)ISMB-450 viii)ISWB-400 ix) ISJC-200 x) ISLC-350 xii) ISMC-250 Answer: i.Indian STD light weight beam, Web size – 400 ii.Indian STD medium weight beam, Web size – 600 iii.Indian STD ‘H’ beam, Web size – 350 iv.Indian STD medium weight channel, Web size –300 v.Indian STD junior beam, Web size – 150 vi.Indian STD light weight beam, Web size – 200 vii.Indian STD medium weight beam, Web size – 450 viii.Indian STD wide flange beam, Web size – 400 ix.Indian STD junior channel, Web size – 200 x.Indian STD light weight channel, Web size – 350 xi.Indian STD medium weight channel, Web size – 250 3. What is this item? i.ISA-100X100X12 ii) ISA-80X50X10 iii)ISLT-100X100 Answer: i.Equal angle size 100x12 THK ii.Unequal angle size 80x50x10 THK iii.Indian STD light weight tee bar size 100x100 4. What is the difference between stub in and stub on branches? Describe with sketch.
Which one is preferred?
For branching of one size lesser of run pipe, Stub On is preferred. For other branching less than one size of run pipe stub in is preferred. The Design is based on ANSI B 31.3 5. What is the difference between Pipe and Tube? Ans: Pipe is identified by NB and thickness is defined by Schedule whereas Tube is identified by OD. 6. From which size onwards NB of pipe is equal to OD of Pipe? Ans: From the size 14” and onwards NB = OD of pipe. 7. Write down the outside diameter of following pipe? i. 3 inch ii) 6 inch iii) 10 inch iv) 14 inch Answer: i. 3 inch iii) 10 inch = = 88.9mm ii)6 inch = 168.28mm 273.06mm iv) 14 inch = 355 mm(OD= Size X 25.4)
8. What is the difference between machine bolt and stud bolt? Answer: Machine bolt has a head on one side and nut on other side but stud bolt have nuts on both sides. 9. What is soluble dam? Answer: Soluble dam is a water-soluble material used for restricting the purging gas within the pipe. 10. While welding of pipe trunion to pipe/reinforcement pad you have to put a hole or leave some portion of welding why? Answer: For venting of hot gas which may get generated due to welding 11. What do you mean by following type of welding i. SMAW ii)TIG Answer: ii. SMAW = SHIELDED METAL ARC WELDING
= TUNGSTEN INTER GAS WELDING
12. Find out the elevation of marked point ‘A’
W.P EL. “A”
3 ∅ Pipe
W.P.EL –100.050 5000
Answer: Elevation of marked point ‘A’ is 100.050 13. What should be the radius of long radius elbow? Answer: 1.5D (Where “D” is the diameter of the pipe) 14. Normally where do we use the following? i. Eccentric reducers ii)Concentric reducers Answer: i. Eccentric reducers = Pump suction to avoid Cavitation, To maintain elevation (BOP) in rack. ii. Concentric reducers = Pump discharge, vertical pipeline etc. 15.Concentric reducer is used in pump suction. (Yes / No). Explain. Answer: 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. 16. What do you mean by Cavitation 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 right at the impeller inlet where a sharp pressure drop occurs. The impeller rapidly builds up the pressure which collapses vapour bubbles causing cavitation and damage . This is avoided by maintaining sufficient NPSH. (Cavitation...
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