Piping Engineering / Design Blog.



Posted by Antony Thomas at Wednesday, April 15, 2009

51. What is regular pattern plug valve?
Ans : Rectangular port, area almost equal to pipe bore, smooth transition
from round body to rectangular port, for minimum pressure loss.
52. What are short pattern plug valve?
Ans : Valves with face to face dimension of gate valve, as a alternative to
gate valve.
53. What are ventury pattern plug valve?
Ans : Change of section through the body throat so graded to have
ventury effect, minimum pressure loss.
54. What are inverted plug design valve?
Ans : Plug valve with taper portion up of plug. For 8” and higher size.
55. What is pressure balanced plug valve?
Ans : With holes in port top and bottom connecting two chambers on top
and bottom of plug, to reduce turning effort.
56. What are Teflon sleeved plug valve?
Ans : PTFE sleeve between plug and body of valve, low turning effort,
minimum friction, temperature limitation, anti static design possible.
57. What are permasil plug valve?
Ans : Plug valves with Teflon seat instead of sleeves, for on off
applications, can handle clean viscous and corrosive liqiuids, Graphite seat
for high temperature applications. Drip tight shut off not possible.
58. What are eccentric plug valve?
Ans : Off center plug, corrosive and abrasive service, on off action,
moves into and away from seat eliminating abrasive wear.
59. What is dimensional standard for plug valve?
Ans : API 599.
60. What is pinch valve?
Ans : Similar to diaphragm valve, with sleeves of rubber or PTFE, which
get sqeezed to control or stop the flow, Cast iron body, for very low
service pressures like isolation of hose connections, manufacture
61. What is needle valve?
Ans :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.
62. How to install a globe valve ?
Ans : 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.
63. What are globe valve port types?
Ans : Full port: More than 85% of bore size, Reducer port: One size less
than the connected pipe.
64. What are globe valve disk types?
Ans :Flat faced type for positive shutoff, loose plug type for plug renewal
or needle type for finer control.
65. What are characteristics of globe valve stem?
Ans : Always rising design, with disk nut at the lower end and handwheel
at upper end.
66. What are types of globe valve?
Ans : Angle globe valve, plug type disc globe valve, wye-body globe
valve, composite disc globe valve, double disc globe valve.
67. What is angle globe valve?
Ans : Ends at 90 degree to save elbow, higher pressure drop.
68. Where plug type disc globe valve is used?
Ans : For severe regulating service with gritty liquids such as boiler
feedwater and for blow off service.
69. Where WYE body globe valve is used ?
Ans : In line ports with stem emerging at 45 degree, for erosive fluids
due to smoother flow pattern.
70. What is double disc globe valve ?
Ans : Has two discs bearing on separate seats spaced apart, on a single
shaft, for low torque, used for control valves.
71. What are port types for gate valves?
Ans : Full port and reduced port. Default is reduced bore. Full port has to
be specified in bom.
72. How to close a gate valve ?
Ans :Turn the handwheel in clockwise direction.
73. What is lantern ring?
Ans : It’s a collection point to drain off any hazardous seepages or as a
point where lubricant can be injected, it is in the middle of packing rings.
74. What are types of gate valves?
Ans : Solid plane wedge, solid flexible wedge, split wedge, double disc
paralles seats, double disc wedge, single disc single seat gate or slide,
single disc parallel seats, plug gate valve.
75. What are the types of bonnets?
Ans : Bolted bonnet, bellow sealed bonnet, screwed on bonnet, union
bonnets, A U-bolt and clamp type bonnet, breechlock bonnet, pressure
seal bonnet.



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