As part of a complete pigging system, pig traps allow pigs to be inserted into and
removed from a pipeline which is to undergo a pigging program and which is likely to
be under pressure.
Key
a. Pressure Gauge
b. Vent
c. Pressure Relief
d. Drain
e. Pig Signaller
f. Kicker Valve (Launcher) Bypass Valve (Receiver)
g. Mainline Bypass Valve
h. Mainline Trap Valve
i. Quick Release Closure
Introduction
1 Design Parameters
2 Operating Method
3 Selection
SEE MORE DETAIL HERE
Friday, May 4, 2012
PIPING INTERVIEW QUESTIONNAIRE
PIPING INTERVIEW QUESTIONNAIRE
1. What are the steps in selection of valve?
Ans : What to handle, liquid, gas or powder, fluid nature, function,
construction material, disc type, stem type, how to operate, bonnet type,
body ends, delivery time, cost, warranty.
2. What are functions of valves?
Ans : Isolation, regulation, non-return and special purposes.
3. What are isolating valves?
Ans : Gate, ball, plug, piston, diaphragm, butterfly, pinch.
4. What are regulation valves?
Ans : Globe, needle, butterfly, diaphragm, piston, pinch.
5. What are non-return valves?
Ans : check valve,
6. What are special valves?
Ans : multi-port, flush bottom, float, foot, pressure relief, breather.
7. What materials are used for construction of valves?
Ans : Cast iron, bronze, gun metal, carbon steel, stainless steel, alloy
carbon steel, polypropylene and other plastics, special alloys.
8. What is trim?
Ans : Trim is composed of stem, seat surfaces, back seat bushing and
other small internal parts that normally contact the surface fluid.
9. Which standard specifies trim numbers for valve ?
Ans : API 600.
10. What are wetted parts of valve?
Ans : All parts that come in contact with surface fluid are called wetted
parts.
11. What is wire drawing?
Ans : This term is used to indicate the premature erosion of the valve
seat caused by excessive velocity between seat and seat disc, when valve
is not closed tightly.
12. What is straight through valve?
Ans : Valve in which the closing operation of valve is achieved by
90degrees turn of the closing element.
13. What pressure tests are carried out on valves?
Ans : Shell-hydrostatic, seat-hydrostatic, seat-pneumatic
14. What are available valve operators?
Ans : Handlever, handwheel, chain operator, gear operator, powered
operator likes electric motor, solenoid, pneumatic and hydraulic
operators, Quick acting operators for non-rotary valves (handle lift).
15. What are two types of ball valve?
Ans : Full port design and regular port design, according to type of seat,
soft seat and metal seat.
16. What are ball valve body types?
Ans : Single piece, double piece, three piece, the short pattern, long
pattern, sandwitch and flush bottom design.
17. Why ball valves are normally flanged?
Ans : Because of soft seat PTFE which can damage during welding.
18. What are butterfly valve types?
Ans : Double flange type, wafer lug type and wafer type.
19. What are types of check valve?
Ans : Lift check valves and swing check valves.
20. What are non-slam check valves?
Ans : Swing check valve, conventional check valve, wafer check valve,
tilting disc check valve, piston check valve, stop check valve, ball check
valve.
21. Where stop check valve is used ?
Ans : In stem generation by multiple boilers, where a valve is inserted
between each boiler and the main steam header. It can be optionally
closed automatically or normally.
22. Where diaphragm valves are used ?
Ans : Used for low pressure corrosive services as shut off valves.
23. What is Barstock Valve?
Ans: Any valve having a body machined from solid metal (barstock).
Usually needle or globe type.
24. What is BIBB Valve?
Ans: A small valve with turned down end, like a faucet.
25. What is Bleed Valve?
Ans: Small valve provided for drawing off liquid.
26. What is BlowDown Valve?
Ans Refers to a plug type disc globe valve used for removing sludge and
sedimentary matter from the bottom of boiler drums, vessels, driplegs
etc.
27. What is Breather Valve?
Ans: A special self acting valve installed on storage tanks etc. to release
vapor or gas on slight increase of internal pressure ( in the region of ½ to
3 ounces per square inch).
28. What is Drip Valve?
Ans: A drain valve fitted to the bottom of a driplet to permit blowdown.
29. What is Flap Valve?
Ans: A non return valve having a hinged disc or rubber or leather flap
used for low pressure lines.
30. What is Hose Valve?
Ans: A gate or globe valve having one of its ends externally threaded to
one of the hose thread standards in use in the USA. These valves are
used for vehicular and firewater connections.
31. What is Paper-Stock Valve?
Ans: A single disc single seat gate valve (Slide gate) with knife edged or
notched disc used to regulate flow of paper slurry or other fibrous slurry.
32. What is Root Valve?
Ans: A valve used to isolate a pressure element or instrument from a line
or vessel, or a valve placed at the beginning of a branch form the
header.
33. What is Slurry valve?
Ans: A knife edge valve used to control flow of non-abrasive slurries.
34. What is Spiral sock valve?
Ans: A valve used to control flow of powders by means of a twistable
fabric tube or sock.
35. What is Throttling valve?
Ans: Any valve used to closely regulate flow in the just-open position.
36. What is Vacuum breaker?
Ans: A special self-acting valve or nay valve suitable for vacuum service,
operated manually or automatically, installed to admit gas (usually
atmospheric air) into a vacuum or low-pressure space. Such valves are
installed on high points of piping or vessels to permit draining and
sometimes to prevent siphoning.
37. What is Quick acting valve ?
Ans: Any on/off valve rapidly operable, either by manual lever, spring or
by piston, solenoid or lever with heat-fusible link releasing a weight which
in falling operates the valve. Quick acting valves are desirable in lines
conveying flammable liquids. Unsuitable for water or for liquid service in
general without a cushioning device to protect piping from shock.
38. What is diverting valve ?
Ans : This valve switch flow from one main line to two different outlets.
WYE type and pneumatic control type with no moving part.
39. What is sampling valve?
Ans : Usually of needle or globe pattern, placed in branch line for the
purpose of drawing all samples of process material thru the branch.
40. What are blow off valve?
Ans : It is a variety of globe valve confirming with boiler code
requirements and specially designed for boiler blowoff service. WYE
pattern and angle type, used to remove air and other gases from boilers
etc.
41. What is relief valve?
Ans : Valve to relieve excess pressure in liquids in situations where full
flow discharge is not required, when release of small volume of liquid
would rapidly lower pressure.
42. What is safety valve?
Ans : Rapid opening(popping action) full flow valve for air and other
gases.
43. What is foot valve?
Ans : Valve used to maintain a head of water on the suction side of sump
pump, basically a lift check valve with integrated strainer.
44. What is float valve?
Ans : Used to control liquid level in tanks, operated by float, which rises
with liquid level and opens the valve to control water level. It can also
remove air from system, in which case, air flows out of system in valve
open condition, but when water reaches valve, float inside valve raises to
close the valve and stop flow of water. Used in drip legs.
45. What are flush bottom valves?
Ans : Special type of valves used to drain out the piping, reactors and
vessels, attached on pad type nozzles.
46. What are types of flush bottom valves?
Ans : Valves with discs opening into the tank and valves with disks into
the valve.
47. What are the uses of three-way valve?
Ans : Alternate connection of the two supply lines to a common delivery
vise versa, isolating one safety valve, division of flow with isolation
facility.
48. What are uses of four way valve?
Ans : Reversal of pump suction and delivery, By pass of strainer or
meter, reversal of flow through filter, heat exchanger or dryer.
49. What is metal seated lubricated plug valve?
Ans : A plug valve with no plastic material, where grease is applied to
contacting surfaces for easy operation.
50. What are three patterns of plug valve design?
Ans : Regular pattern, short pattern and ventury pattern.
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
standard.
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.
1. What are the steps in selection of valve?
Ans : What to handle, liquid, gas or powder, fluid nature, function,
construction material, disc type, stem type, how to operate, bonnet type,
body ends, delivery time, cost, warranty.
2. What are functions of valves?
Ans : Isolation, regulation, non-return and special purposes.
3. What are isolating valves?
Ans : Gate, ball, plug, piston, diaphragm, butterfly, pinch.
4. What are regulation valves?
Ans : Globe, needle, butterfly, diaphragm, piston, pinch.
5. What are non-return valves?
Ans : check valve,
6. What are special valves?
Ans : multi-port, flush bottom, float, foot, pressure relief, breather.
7. What materials are used for construction of valves?
Ans : Cast iron, bronze, gun metal, carbon steel, stainless steel, alloy
carbon steel, polypropylene and other plastics, special alloys.
8. What is trim?
Ans : Trim is composed of stem, seat surfaces, back seat bushing and
other small internal parts that normally contact the surface fluid.
9. Which standard specifies trim numbers for valve ?
Ans : API 600.
10. What are wetted parts of valve?
Ans : All parts that come in contact with surface fluid are called wetted
parts.
11. What is wire drawing?
Ans : This term is used to indicate the premature erosion of the valve
seat caused by excessive velocity between seat and seat disc, when valve
is not closed tightly.
12. What is straight through valve?
Ans : Valve in which the closing operation of valve is achieved by
90degrees turn of the closing element.
13. What pressure tests are carried out on valves?
Ans : Shell-hydrostatic, seat-hydrostatic, seat-pneumatic
14. What are available valve operators?
Ans : Handlever, handwheel, chain operator, gear operator, powered
operator likes electric motor, solenoid, pneumatic and hydraulic
operators, Quick acting operators for non-rotary valves (handle lift).
15. What are two types of ball valve?
Ans : Full port design and regular port design, according to type of seat,
soft seat and metal seat.
16. What are ball valve body types?
Ans : Single piece, double piece, three piece, the short pattern, long
pattern, sandwitch and flush bottom design.
17. Why ball valves are normally flanged?
Ans : Because of soft seat PTFE which can damage during welding.
18. What are butterfly valve types?
Ans : Double flange type, wafer lug type and wafer type.
19. What are types of check valve?
Ans : Lift check valves and swing check valves.
20. What are non-slam check valves?
Ans : Swing check valve, conventional check valve, wafer check valve,
tilting disc check valve, piston check valve, stop check valve, ball check
valve.
21. Where stop check valve is used ?
Ans : In stem generation by multiple boilers, where a valve is inserted
between each boiler and the main steam header. It can be optionally
closed automatically or normally.
22. Where diaphragm valves are used ?
Ans : Used for low pressure corrosive services as shut off valves.
23. What is Barstock Valve?
Ans: Any valve having a body machined from solid metal (barstock).
Usually needle or globe type.
24. What is BIBB Valve?
Ans: A small valve with turned down end, like a faucet.
25. What is Bleed Valve?
Ans: Small valve provided for drawing off liquid.
26. What is BlowDown Valve?
Ans Refers to a plug type disc globe valve used for removing sludge and
sedimentary matter from the bottom of boiler drums, vessels, driplegs
etc.
27. What is Breather Valve?
Ans: A special self acting valve installed on storage tanks etc. to release
vapor or gas on slight increase of internal pressure ( in the region of ½ to
3 ounces per square inch).
28. What is Drip Valve?
Ans: A drain valve fitted to the bottom of a driplet to permit blowdown.
29. What is Flap Valve?
Ans: A non return valve having a hinged disc or rubber or leather flap
used for low pressure lines.
30. What is Hose Valve?
Ans: A gate or globe valve having one of its ends externally threaded to
one of the hose thread standards in use in the USA. These valves are
used for vehicular and firewater connections.
31. What is Paper-Stock Valve?
Ans: A single disc single seat gate valve (Slide gate) with knife edged or
notched disc used to regulate flow of paper slurry or other fibrous slurry.
32. What is Root Valve?
Ans: A valve used to isolate a pressure element or instrument from a line
or vessel, or a valve placed at the beginning of a branch form the
header.
33. What is Slurry valve?
Ans: A knife edge valve used to control flow of non-abrasive slurries.
34. What is Spiral sock valve?
Ans: A valve used to control flow of powders by means of a twistable
fabric tube or sock.
35. What is Throttling valve?
Ans: Any valve used to closely regulate flow in the just-open position.
36. What is Vacuum breaker?
Ans: A special self-acting valve or nay valve suitable for vacuum service,
operated manually or automatically, installed to admit gas (usually
atmospheric air) into a vacuum or low-pressure space. Such valves are
installed on high points of piping or vessels to permit draining and
sometimes to prevent siphoning.
37. What is Quick acting valve ?
Ans: Any on/off valve rapidly operable, either by manual lever, spring or
by piston, solenoid or lever with heat-fusible link releasing a weight which
in falling operates the valve. Quick acting valves are desirable in lines
conveying flammable liquids. Unsuitable for water or for liquid service in
general without a cushioning device to protect piping from shock.
38. What is diverting valve ?
Ans : This valve switch flow from one main line to two different outlets.
WYE type and pneumatic control type with no moving part.
39. What is sampling valve?
Ans : Usually of needle or globe pattern, placed in branch line for the
purpose of drawing all samples of process material thru the branch.
40. What are blow off valve?
Ans : It is a variety of globe valve confirming with boiler code
requirements and specially designed for boiler blowoff service. WYE
pattern and angle type, used to remove air and other gases from boilers
etc.
41. What is relief valve?
Ans : Valve to relieve excess pressure in liquids in situations where full
flow discharge is not required, when release of small volume of liquid
would rapidly lower pressure.
42. What is safety valve?
Ans : Rapid opening(popping action) full flow valve for air and other
gases.
43. What is foot valve?
Ans : Valve used to maintain a head of water on the suction side of sump
pump, basically a lift check valve with integrated strainer.
44. What is float valve?
Ans : Used to control liquid level in tanks, operated by float, which rises
with liquid level and opens the valve to control water level. It can also
remove air from system, in which case, air flows out of system in valve
open condition, but when water reaches valve, float inside valve raises to
close the valve and stop flow of water. Used in drip legs.
45. What are flush bottom valves?
Ans : Special type of valves used to drain out the piping, reactors and
vessels, attached on pad type nozzles.
46. What are types of flush bottom valves?
Ans : Valves with discs opening into the tank and valves with disks into
the valve.
47. What are the uses of three-way valve?
Ans : Alternate connection of the two supply lines to a common delivery
vise versa, isolating one safety valve, division of flow with isolation
facility.
48. What are uses of four way valve?
Ans : Reversal of pump suction and delivery, By pass of strainer or
meter, reversal of flow through filter, heat exchanger or dryer.
49. What is metal seated lubricated plug valve?
Ans : A plug valve with no plastic material, where grease is applied to
contacting surfaces for easy operation.
50. What are three patterns of plug valve design?
Ans : Regular pattern, short pattern and ventury pattern.
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
standard.
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.
PIPING JOINTS
PIPING JOINTS
Joint design and selection can have a major impact on the initial installed cost, thelong-range operating and maintenance cost, and the performance of the piping
system. Factors that must be considered in the joint selection phase of the project
design include material cost, installation labor cost, degree of leakage integrity
required, periodic maintenance requirements, and specific performance requirements.
In addition, since codes do impose some limitations on joint applications,
joint selection must meet the applicable code requirements. In the paragraphs that
follow, the above-mentioned considerations will be briefly discussed for a number
of common pipe joint configurations.
Butt-welded Joints
Butt-welding is the most common method of joining piping used in large commercial,
institutional, and industrial piping systems. Material costs are low, but labor costs
are moderate to high due to the need for specialized welders and fitters. Long term
leakage integrity is extremely good, as is structural and mechanical strength.
The interior surface of a butt-welded piping system is smooth and continuous which
results in low pressure drop. The system can be assembled with internal weld
backing rings to reduce fit-up and welding costs, but backing rings create internal
crevices, which can trap corrosion products. In the case of nuclear piping systems,
these crevices can cause a concentration of radioactive solids at the joints, which
can lead to operating and maintenance problems. Backing rings can also lead to
stress concentration effects, which may promote fatigue cracks under vibratory or
other cyclic loading conditions. Butt-welded joints made up without backing rings
are more expensive to construct, but the absence of interior crevices will effectively
minimize ‘‘crud’’ buildup and will also enhance the piping system’s resistance to
fatigue failures. Most butt-welded piping installations are limited to NPS 21⁄₂ (DN
65) or larger. There is no practical upper size limit in butt-welded construction.
Butt-welding fittings and pipe system accessories are available down to NPS 1⁄₂ (DN
15). However, economic penalties associated with pipe end preparation and fit-up,
and special weld procedure qualifications normally preclude the use of butt-welded
construction in sizes NPS 2 (DN 50) and under, except for those special cases where
interior surface smoothness and the elimination of internal crevices are of paramount
importance. Smooth external surfaces give butt-welded construction high aesthetic
appeal.
Socket-welded Joints
Socket-welded construction is a good choice wherever the benefits of high leakage
integrity and great structural strength are important design considerations. Construction
costs are somewhat lower than with butt-welded joints due to the lack of
exacting fit-up requirements and elimination of special machining for butt weld end
preparation. The internal crevices left in socket-welded systems make them less
suitable for corrosive or radioactive applications where solids buildup at the joints
may cause operating or maintenance problems. Fatigue resistance is lower than
that in butt-welded construction due to the use of fillet welds and abrupt fitting
geometry, but it is still better than that of most mechanical joining methods. Aesthetic
appeal is good.
Brazed and Soldered Joints
Brazing and soldering are most often used to join copper and copper-alloy piping
systems, although brazing of steel and aluminum pipe and tubing is possible. Brazing
and soldering both involve the addition of molten filler metal to a close-fitting
annular joint. The molten metal is drawn into the joint by capillary action and
solidifies to fuse the parts together. The parent metal does not melt in brazed or
soldered construction. The advantages of these joining methods are high leakage
integrity and installation productivity. Brazed and soldered joints can be made up
with a minimum of internal deposits. Pipe and tubing used for brazed and soldered
construction can be purchased with the interior surfaces cleaned and the ends
capped, making this joining method popular for medical gases and high-purity
pneumatic control installations.
Soldered joints are normally limited to near-ambient temperature systems and
domestic water supply. Brazed joints can be used at moderately elevated temperatures.
Most brazed and soldered installations are constructed using light-wall tubing;
consequently the mechanical strength of these systems is low.
Threaded or Screwed Joints
Threaded or screwed piping is commonly used in low-cost, noncritical applications
such as domestic water, fire protection, and industrial cooling water systems. Installation
productivity is moderately high, and specialized installation skill requirements
are not extensive. Leakage integrity is good for low-pressure, low-temperature
installations where vibration is not encountered. Rapid temperature changes may
lead to leaks due to differential thermal expansion between the pipe and fittings.
Vibration can result in fatigue failures of screwed pipe joints due to the high stress
intensification effects caused by the sharp notches at the base of the threads. Screwed
fittings are normally made of cast gray or malleable iron, cast brass or bronze, or
forged alloy and carbon steel. Screwed construction is commonly used with galvanized
pipe and fittings for domestic water and drainage applications. While certain
types of screwed fittings are available in up to NPS 12 (DN300), economic considerations
normally limit industrial applications to NPS 3 (DN 80). Screwed piping
systems are useful where disassembly and reassembly are necessary to accommodate
maintenance needs or process changes. Threaded or screwed joints must be used
within the limitations imposed by the rules and requirements of the applicable code.
Grooved Joints
The main advantages of the grooved joints are their ease of assembly, which results
in low labor cost, and generally good leakage integrity. They allow a moderate
amount of axial movement due to thermal expansion, and they can accommodate
some axial misalignment. The grooved construction prevents the joint from separating
under pressure. Among their disadvantages are the use of an elastomer seal,
which limits their high-temperature service, and their lack of resistance to torsional
loading. While typical applications involve machining the groove in standard wall
pipe, light wall pipe with rolled-in grooves may also be used. Grooved joints are
used extensively for fire protection, ambient temperature service water, and low pressure
drainage applications such as floor and equipment drain systems and roof
drainage conductors. They are a good choice where the piping system must be
disassembled and reassembled frequently for maintenance or process changes.
Flanged Joints
Flanged connections are used extensively in modern piping systems due to their
ease of assembly and disassembly; however, they are costly. Contributing to the
high cost are the material costs of the flanges themselves and the labor costs for
attaching the flanges to the pipe and then bolting the flanges to each other. Flanges
are normally attached to the pipe by threading or welding, although in some special
cases a flange-type joint known as a lap joint may be made by forging and machining
the pipe end. Flanged joints are prone to leakage in services that experience rapid
temperature fluctuations. These fluctuations cause high-temperature differentials
between the flange body and bolting, which eventually causes the bolt stress to
relax, allowing the joint to open up. Leakage is also a concern in high-temperature
installations where bolt stress relaxation due to creep is experienced. Periodic
retorquing of the bolted connections to reestablish the required seating pressure
on the gasket face can minimize these problems. Creep-damaged bolts in hightemperature
installations must be periodically replaced to reestablish the required
gasket seating pressure. Flanged joints are commonly used to join dissimilar materials,
e.g., steel pipe to cast-iron valves and in systems that require frequent maintenance
disassembly and reassembly. Flanged construction is also used extensively
in lined piping systems.
Compression Joints
Compression sleeve-type joints are used to join plain end pipe without special end
preparations. These joints require very little installation labor and as such result
in an economical overall installation. Advantages include the ability to absorb a
limited amount of thermal expansion and angular misalignment and the ability to
join dissimilar piping materials, even if their outside diameters are slightly different.
Disadvantages include the use of rubber or other elastomer seals, which limits their
high-temperature application, and the need for a separate external thrust-resisting
system at all turns and dead ends to keep the line from separating under pressure.
Compression joints are frequently used for temporary piping systems or systems
that must be dismantled frequently for maintenance. When equipped with the
proper gaskets and seals, they may be used for piping systems containing air, other
gases, water, and oil; in both aboveground and underground service. Small-diameter
compression fittings with all-metal sleeves may be used at elevated temperatures
and pressures, when permitted by the rules and requirements of the applicable
code. They are common in instrument and control tubing installations and other
applications where high seal integrity and easy assembly and disassembly are desirable
attributes.
PDMS COMMANDS: MOSTLY STRUCTRUAL
NEW STRU COPY $V1
|
COPIES STRU FROM 1 SITE TO ANOTHER
|
Q USERM
|
GIVES CREATORS NAME
|
Q PPLIN TOS START WRT/DATUM
|
GIVES TOP OF STEEL OF UB/UC
|
Q IDP @ WRT /DATUM
|
GIVES THE COORD OF A POINT
|
Q ADEG (DRAFT)
|
GIVES THE C/VIEW ANGLE (ie 90 DEG)
|
Q ANGLE (HVAC)
|
GIVES THE CE ANGLE
|
Q ATEX (DRAFT)
|
GIVES THE SLAB TEXT ATTRIBUTES
|
Q ATT
|
GIVES THE CE ATTRIBUTES
|
Q BANG
|
GIVES THE CE BETA ANGLE
|
Q BORE (PIPING)
|
GIVES THE PIPE INSIDE DIA.
|
Q BSRF (DRAFT)
|
GIVES THE ATTACHED DRG/SHT (DRWG LEVL)
|
Q BTEX (DRAFT)
|
GIVES THE TEXT/GLAB ATTRIBUTES
|
Q CHEI (DRAFT)
|
GIVES THE CHARACTER HEIGHT
|
Q CLL (PIPING)
|
GIVES THE PIPE BRANCH LENGTH
|
Q COL 4 (ETC)
|
GIVES THE ATTRIBUTED COLOUR (YELLOW)
|
Q COL ACT
|
GIVES THE CURRENT ACTIVE COLOUR
|
Q COL AIDS
|
GIVES THE CURRENT AID LINE COLOUR
|
Q COL CE
|
GIVES THE CURRENT ATTRIBUTED COLOUR
|
Q COL VIS
|
GIVES THE CURRENT VISIBLE COLOUR
|
Q CREF
|
GIVES THE CONNECTION REFERENCE
|
Q CUTL
|
GIVES THE CE CUT LENGTH
|
Q DDNAME (DRAFT)
|
GIVES THE DIMENSION OWNERS NAME
|
Q DER LEN
|
GIVES THE CE EXACT LENGTH
|
Q DESC
|
GIVES THE CE DESCRIPTION
|
Q DESP
|
GIVES THE CE PARAMETERS
|
Q DIR (DRAFT)
|
GIVES THE C/VIEW ANGLE (ie N)
|
Q DISPLAY
|
GIVES THE TOLERANCE & REPRES LEVELS
|
Q DMTXT (DRAFT)
|
GIVES THE DIM TEXT ATTRIBUTES
|
Q DNST
|
GIVES THE CE DENSITY
|
Q DPOS (DRAFT)
|
GIVES THE LDIM POSITION ON SHEET
|
Q DRNE
|
GIVES THE END CUT-PLANE DIRECTION
|
Q DRNS
|
GIVES THE START CUT-PLANE DIRECTION
|
Q DTER (DRAFT)
|
GIVES THE LAYER/LDIM TERM'TR DEFAULT
|
Q E
|
GIVES THE CE EAST CO-ORDINATE
|
Q ELEM
|
GIVES THE CE ELEMENT NAME
|
Q FPT (DRAFT)
|
GIVES THE STRA FROM POINT CO-ORDS
|
Q FRAD
|
GIVES THE PLOO/PAVE RADIU ie 100mm
GIVES THE NEXTR/VERT RADIUS ie 100mm |
Q FUNC
|
GIVES THE CE FUNCTION
|
Q GCOF
|
GIVES THE CE GROSS C OF G
|
Q GTYP
|
GIVES THE GENERIC TYPE i.e. OD, HP, TG
|
Q GWEI
|
GIVES THE CE GROSS WEIGHT
|
Q H (PIPE SUPPT)
|
GIVES THE CE HANDER HEAD CO-ORDS
|
Q HEI
|
GIVES THE CE (PLOO LVL) PLT THK
|
Q HPOS (PIPING)
|
GIVES THE CE PIPE HEAD CO-ORDINATES
|
Q HT (PIPE SUPT)
|
GIVES THE CE HANDER TAIL CO-ORDS
|
Q IDP @ WRT /*
|
GIVES THE CE P POINT CO-ORDINATES
|
Q IDPL @
|
GIVES THE PLINE NAME USING CURSOR
|
Q INREF
|
GIVES THE CE IN REFERENCE
|
Q ISPEC (PIPING)
|
GIVES THE CE (PIPE) INSULATION
|
Q ITLE
|
GIVES LENGTH OF IMPLIED TUBE
|
Q JLIN
|
GIVES THE CE JOINT LINE
|
Q JUSL
|
GIVES THE CE JUSTIFICATION LINE
|
Q LASTMOD
|
GIVES THE DAT STRU WAS LAST MODIFIED
|
Q LEN (DRAFT)
|
GIVES THE STRA LENGTH
|
Q LEV
|
GIVES THE CE LEVEL (OBSTRUCTION ETC)
|
Q LHEI (DRAFT)
|
GIVES THE TEST LETTER HEIGHT
|
Q LIST
|
GIVES THE CE FITTINGS (NEG EXTR. ETC)
|
Q LOCK
|
GIVES THE LOCK STATUS
|
Q LSHAPE (DRAFT)
|
GIVES THE LABEL LEADER LINE STATUS
|
Q MATREF
|
GIVES THE CE MATERIAL REF
|
Q MCOUNT
|
GIVES THE NOS OF SUB MEMBERS IN CE
|
Q MCOUNT SCTN
|
GIVES THE NOS OF SCTN MEMBERS IN CE
|
Q MDB
|
GIVES THE PROJECT DATABASE
|
Q MEM
|
GIVES THE CE MEMBERS
|
Q MEML
|
GIVES THE CE MEMBER LINE
|
Q MIDP
|
GIVES THE CE MIDPOINT CO-ORDINATES
|
Q MPT (DRAFT)
|
GIVES THE STRA MID POINT CO-ORDS
|
Q MTLE
|
GIVES LENGTH OF MATERIAL TUBE
|
Q MTLL
|
GIVES CL LENGTH OF MATERIAL TUBE
|
Q MTO
|
GIVES THE CE MTO STATUS
|
Q NAM
|
GIVES THE CE NAME
|
Q NCOF
|
GIVES THE CE NET C OF G
|
Q NSRF
|
GIVES THE CE NET SURFACE
|
Q NVOL
|
GIVES THE CE NET VOLUME
|
Q NWEI
|
GIVES THE CE NET WEIGHT
|
Q OBS
|
GIVES THE CE OBSTRUCTION LEVEL
|
Q ORI
|
GIVES THE CE ORIENTATION (SLOPE)
|
Q OSRF
|
GIVES THE SHEET OVERLAY (VIEW ONLY)
|
Q OWN
|
GIVES THE CE OWNER
|
Q PA (PIPING)
|
GIVES TE C ARRIVE CO-ORDINATES
|
Q PARA
|
GIVES THE CE PARAMETERS ie SERIAL SIZES
|
Q PH (PIPING)
|
GIVES THE CE PIPE HEAD ATTRIBUTES
|
Q PH BORE (PIPING)
|
GIVES THE CE (PIPE HEAD) BORE
|
Q PH OD (PIPING)
|
GIVES THE CE (PIPE HEAD) DIAMETER
|
Q PI WRT/* (PIPING)
|
GIVES THE CE (PIPE SUPPORT) LOCATION
|
Q PKEY (DRAFT)
|
GIVES THE DIM PLINE STATUS (ie TCTF)
|
Q PL WRT/* (PIPING)
|
GIVES THE CE HVAC LEAVE CO-ORDINATES
|
Q PLNA
|
GIVES THE PLINE NAMES
|
Q PLTXT (DRAFT)
|
GIVES THE PROJ TEST ATTRIBUTES
|
Q POS
|
GIVES THE CE CO-ORDINATES (START)
|
Q POS FITT
|
GIVES THE C/FITT CO-ORDINATES (START)
|
Q POS IDPL @
|
GIVES THE PLINE CO-ORD AT CE START
|
Q POS IN $V1
|
GIVES THE CE DISTANCE TO VAR. $V1
|
Q POS PIN1 WRT/*
|
GIVES THE CE CO-ORDINATES OF PIN 1
|
Q POS PLRF (DRAFT)
|
GIVES TE CURRENT VSEC CO-ORDS
|
Q POS POPLI NA PROP 0.5
|
GIVES THE CENTRE CO-ORDINATE POSITIONS OF THE PLINE (PPLI) AT (0.5X DER LEN) ON THE N/A
|
Q POS PPL1 BOS WRT/*
|
GIVES THE BOS PLINE CO-ORDINATES
|
Q POS WRT TO ID@
|
GIVES THE DIST FROM CE TO START OF IDENTIFIED MEMBER
|
Q POS1 WRT/*
|
GIVES THE CE CO-ORDINATES OF PIN 1
|
Q POSE
|
GIVES THE CE END CO-ORDINATES
|
Q POSPPLI NA PROP 0.5
|
GIVES THE CENTRE CO-ORDINATE POSITIONS OF THE PLINE (PPLI) AT (0.5X DER LEN) ON THE N/A
|
Q POSS
|
GIVES THE CE START CO-ORDINATES
|
Q POSS POSE
|
GIVES THE CE BOTH END CO-ORDINATES
|
Q POST FITT
|
GIVES THE C/FITT CO-ORDINATES (START)
|
Q POST IN $V1
|
GIVES THE CE DISTANCE TO VAR.$V1
|
Q POST PLRF (DRAFT)
|
GIVES THE CURRENT VSEC CO-ORDS
|
Q PRLS
|
GIVES THE DESP NAME TYPES
|
Q PT (PIPING)
|
GIVES THE CE (PIPE TAIL) ATTRIBUTES
|
Q PT OD (PIPING)
|
GIVES THE CE (PIPE TAIL) DIAMETER
|
Q PURP
|
GIVES THE STRU PURPOSE ATTRIBUTE
|
Q RAD (HVAC)
|
GIVES THE CE RADIUS
|
Q RCOD (DRAFT)
|
GIVES THE VIEW ORIENTATION
|
Q REF
|
GIVES THE CE PDMS REFERENCE NO
|
Q REPRES
|
GIVES THE CE REPRESENTATION STATUS
|
Q RRSF (DRAFT)
|
GIVES THE CURRENT VIEW RULE SETTINGS
|
Q SIZE (DRAFT)
|
GIVES THE VIEW O/ALL DIMENSIONS
|
Q SJUS
|
GIVES THE PLOO JUSTIFICATION ie UTOP, DCEN, DBOT
|
Q SNAP (DRAFT)
|
GIVES THE SNAP SETTING (ON/OFF)
|
Q SPRE
|
GIVES THE CE SPECIFICATION REFERENCE
|
Q STEXT
|
GIVES THE ATT PENETRATION IDENT
|
Q TCTL OR (Q CUTL)
|
GIVES THE CE CUT LENGTH
|
Q THMRF (DRAFT)
|
GIVES THE CE (SYMBOL) NAME
|
Q THPOS (DRAFT)
|
GIVES THE C/VIEW MATCHLINE CO-ORDS
|
Q TPOS (PIPING)
|
GIVES THE CE PIPE TAIL CO-ORDS
|
Q TPT (DRAFT)
|
GIVES THE STRA TAIL POINT CO-ORDS
|
Q TULE
|
GIVES THE BRANCH TUBE LENGTH
|
Q TYPE
|
GIVES THE CE TYPE ie SCTN, PANE
|
Q USER
|
GIVES THE CE USER DATABASE
|
Q USERMOD
|
GIVES THE LAST USER LOGIN ID (STRU)
|
Q VLIMITS (DRAFT)
|
GIVES THE VIEW LIMITS
|
Q VOL CE
|
GIVES THE CE VOLUME
|
Q: DTYPE
|
GIVES THE FRMW STYLE TYPE (ie STLS)
|
Q: STATUS
|
GIVES THE CE STRU STATUS ie 'AFC'
|
Q:SWCODE
|
GIVES THE CE WEIGHT CODE
|
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