Piping Engineering Technical Interview Questions - Part 06

Question No. 126
What is dimensional standard for plug valve?
Answer: API 599.

Question No. 127
What is pinch valve?
Answer: Similar to diaphragm valve, with sleeves of rubber or PTFE, which get squeezed to control or stop the flow, Cast iron body, for very low service pressures like isolation of hose connections, manufacture standard.

Question No. 128
What is needle valve?
Answer: Full pyramid disc, same design as globe valve, smaller sizes, sw or threaded, flow control, disc can be integral with stem, inside screw, borged or barstock body and bonnet, manufacturers standard.

Question No. 129
How to install a globe valve?
Answer: Globe valve should be installed such that the flow is from the underside of the disk, Usually flow direction is marked on the globe valve.

Question No. 130
What are globe valve port types?
Answer: Full port: More than 85% of bore size, Reducer port: One size less than the connected pipe.

Question No. 131
What are globe valve disk types?
Answer: Flat faced type for positive shutoff, loose plug type for plug renewal or needle type for finer control.

Question No. 132
What are characteristics of globe valve stem?
Answer: Always rising design, with disk nut at the lower end and handwheel at upper end.

Question No. 133
What are types of globe valve?
Answer: Angle globe valve, plug type disc globe valve, WYE-body globe valve, composite disc globe valve, double disc globe valve.

Question No. 134
What is angle globe valve?
Answer: Ends at 90 degree to save elbow, higher pressure drop.

Question No. 135
Where plug type disc globe valve is used?
Answer: For severe regulating service with gritty liquids such as boiler feedwater and for blow off service.

Question No. 136
Where WYE body globe valve is used?
Answer: In line ports with stem emerging at 45 degree, for erosive fluids due to smoother flow pattern.

Question No. 137
What is double disc globe valve?
Answer: Has two discs bearing on separate seats spaced apart, on a single shaft, for low torque, used for control valves.

Question No. 138
What are port types for gate valves?
Answer: Full port and reduced port. Default is reduced bore. Full port has to be specified in bom.

Question No. 139
How to close a gate valve?
Answer: Turn the hand-wheel in clockwise direction.

Question No. 140
What is lantern ring?
Answer: It’s a collection point to drain off any hazardous seepage or as a point where lubricant can be injected; it is in the middle of packing rings.

Question No. 141
What are types of gate valves?
Answer: Solid plane wedge, solid flexible wedge, split wedge, double disc parallels seats, double disc wedge, single disc single seat gate or slide, single disc parallel seats, plug gate valve.

Question No. 142
What are the types of bonnets?
Answer: Bolted bonnet, bellow sealed bonnet, screwed on bonnet, union bonnets, A U-bolt and clamp type bonnet, breech-lock bonnet, pressure seal bonnet.
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