A full description of a valve-type requires the engineer to specify additional information, as summarized in Work Aid 1. The 04- SAMSS-series provides additional design requirements for specific valve-types. These include:
• References to appropriate industry standards and other Saudi Aramco requirements.
• Modifications to industry standards to make a valve suitable for Saudi Aramco applications.
• Specific design, materials, testing, inspection, marking, and shipping requirements that are appropriate for Saudi Aramco applications. These typically go beyond what is already
specified in an industry standard, make selections where options are available, or provide coverage where none is available and Saudi Aramco does not wish to accept the valve manufacturer's standard design.
The following summarizes the SAMSS's that relate to valves: • 04-SAMSS-001 - Gate Valves.
• 04-SAMSS-002 - Globe Valves.
• 04-SAMSS-003 - Additional Requirements for Low- Temperature Valves.
• 04-SAMSS-005 - Check Valves, Swing-Type.
• 04-SAMSS-035 - General Requirements for Valves.
• 04-SAMSS-041 - Expanding Plug Valve.
• 04-SAMSS-042 - 4-Way Diverter Valve.
• 04-SAMSS-048 - Valve Inspection and Testing Requirements.
• 04-SAMSS-049 - Inspection and Testing Requirements for API 6A 10,000 psi Valves.
• 04-SAMSS-050 - Gate Valves, Through-Conduit-Type, API 6D.
• 04-SAMSS-051 - Ball Valves, API 6D. • 04-SAMSS-052 - Ball Valves, API 6A.
Note that several of the valve-types that are included in the listed SAMSS's were not discussed. These are beyond the scope of this course. It should also be noted that 04-SAMSS- 003 applies to all valves with a minimum design temperature between 0°C and -46°C (32°F and -50°F) regardless of type and 04-SAMSS-035 and 04-SAMSS-048 applies to all valve types. Thus, they should also be included in the valve purchase order.
Since the requirements of 04-SAMSS-035 apply to all valves, several items contained within it are highlighted below:
• The valve vendor must submit detailed drawings for Saudi Aramco review and approval.
• For drains, vents, and other body fittings:
• Threaded and socket-welded connections are limited to a maximum
of 38 mm (1 1/2 in.) NPS.
− The minimum body rating is to be Class 800 per API 602. • Buried double-block and bleed valves are to have their vent
and drain connections, and any supplied sealant injection fittings, extended aboveground in accordance with specified requirements.
• Material requirements are specified for carbon steel butt- welding end valves, hard facing material, austenitic stainless steel valves, and bonnet or packing gland bolting.
• Plating requirements are specified. • Bolting requirements are specified.
• Valve operator and actuator requirements are specified. • Quality assurance, painting and coating, preparation for
shipment, and marking requirements are specified. The 04-SAMSS-series of valve specifications generally reference industry valve standards to use as base design documents where such standards exist for particular valve- types. There are also industry standards for valve-types for which there are no 04-SAMSS specifications. Table 1 summarizes the currently available industry standards for valves, and the general extent of their coverage.
It should again be noted that Saudi Aramco has computerized the SAMSS’s requirements, as discussed in MEX 101.02. Therefore, once a particular valve-type has been selected, a complete purchase description can be obtained, along with acceptable vendors and a Saudi Aramco stock number.
Table 1. Information on Valve Sizes, Ratings and Standards VALVE TYPE BODY MATERIAL APPLICABLE VALVE STANDARD & SIZE (6) SIZE (1) AVAIL, in. RECOM SIZE LIMIT RATING AVAILABLE
Gate Steel API 600,1-24 1-24 ≥2 150-2500
Gate Steel API 602,1/4 -4 1/4-2 <2 800 (BODY)
Gate CRA (4) API 603,1/2-12 1/2 12 150
Gate, Soft-Seat Steel API 600,1 -24 3-24 ≥2 150-2500 Gate, Soft-Seat CRA (4) API 603,1/2-12 (2) 150 (3)
Gate, Venturi Steel 2-24 150-600
Gate, Venturi CRA (4) 150
Gate, Venturi Soft-Seat
Steel 2-24 150-600 (3)
Globe, Type Steel 2-8 150-2500
Ball, Soft-Seat Steel API 608,1/2-12 TO 20 150-600 (3)
Ball, Soft-Seat CRA API 608,1/2-12 (2) 300 (3)
Plug,
Nonlubricated
Steel API 599,1-24 1-18 150-2500
Plug, Lubricated Steel API 599,1-24 1-24 150-2500 Plug, Soft-Seat Steel API 599,1-24 2-36 150-600 (3) Butterfly, Rubber-
Lined
Steel 3-24 150 (3)
Butterfly, Rubber-
Lined Cast Iron AWWA C504, 3-72 3-72 25,75,150 (3)
Butterfly, Soft- Seat Steel 3-72 150-600 (3) Butterfly, Soft- Seat CRA 3-72 150-600 (3) Globe Steel TO 24 150-2500 Globe CRA 1/2-12 150-600
Swing Check Steel ALL 150-2500
Table 1. Information on Valve Sizes, Ratings and Standards (continued)
Ball Check Steel 3/4-3 <2 TO 600
Ball Check CRA 1/4-2 <2 TO 600
Dual-Plate Wafer
Check Steel API 594, 2-48 (5) (5)
Dual-Plate Wafer
Check, Soft-Seat Steel API 594, 2-48 (5) (5)
CRA = Corrosion-Resistant Alloy: Type 304, 316, or 347 stainless steel, or Alloy 20 NOTES:
(1) Varies significantly depending on material and rating. Listed size represents maximum regularly manufactured by one or more vendors for Class 150 and 300 carbon steel. Larger sizes always available on special order basis.
(2) Depends on which alloy. Up to six inch size is generally available in all alloys.
(3) Rating limited by pressure/temperature limits of soft-seat material. Refer to manufacturer's standard.
(4) Note that the pressure ratings shown in the API 603 standard are less than those in ASME/ANSI B16.5 for
Class 150. Also, the API 603 ratings are only for valves. (5) Valves in sizes: 2 in. through 12 in. available in all ratings.
14 in. through 24 in. available through Class 900 rating. 20 in. through 48 in. available through Class 300 rating.
(6) ASME/ANSI B16.34 wall thickness’ can be specified for steel or CRA valves with CA <1/8 in. When another standard also applies, both can be referenced, e.g. Class 300 nickel alloy gate valve per API 600 except wall thickness per ASME/ANSI B16.34
Sample Problem 1: Part A.
The following situation and design information is used to illustrate the valve selection process. The problem is divided into two parts.
Figure 13 shows a new pump piping system being installed at the Ras Tanura refinery. The letters “A” through “E” indicates general locations for valves. The 250 mm (10 in.) diameter pump P-101 suction line comes from T-100, and the 200 mm (8 in.) diameter discharge line goes to D-200. There is a 100 mm (4 in.) diameter diversion line coming off the discharge line that takes a portion of the flow to E-300. The following additional design conditions apply to this system:
• The pipe material is carbon steel with a 1.5 mm (1/16 in.) corrosion allowance. No special material requirements are specified with regard to low-temperature properties.
• All the pipe connections are flanged.
• The design temperature is 149°C (300°F) for both the suction and the discharge systems.
• The design pressure is 1,379 kPa (200 psig) for the suction system and 2,413 kPa (350 psig) for the discharge system. • The fluid involved is a dangerous hydrocarbon.
A
C
B
D
E
Pump P-101 From T-100 1379 kPa (200 psig) 149°C (300°F) 250mm (10") Ø Suction 100mm (4") Ø 200mm (8") Ø Discharge 2413 kPa (350 psig) 149°C (300°F)Solution: Part A
Identifying the job function required for each of the valves indicated in the system is the first step in selecting the appropriate valve-type for a particular application.
a. It will be necessary to take the pump out of service for periodic maintenance while the rest of the unit remains in operation. The valves at locations "A" and "B" must be used for this purpose. What valve function will they perform?
The valve at location "A" must completely isolate the pump from the fluid flow conditions upstream. The valve at location "B" must completely isolate the pump from the fluid flow conditions downstream. Isolating the pump from fluid flow is necessary to safely remove the pump from the system for maintenance. Therefore, these valves serve to block flow. Permitting on stream
equipment maintenance is one of the primary reasons for using a valve to block flow.
b. Pump internals are designed to turn in the direction of normal flow through the pump. They may be damaged if forced to turn backwards during upset conditions
downstream of the pump. Such conditions could cause the flow to reverse its normal direction. The valve at location "C" must prevent damage to the pump internals if an upset condition occurs. What valve function will it perform?
The valve at location "C" must prevent flow reversal back through the pump. This is a typical valve function
required in all pump and compressor discharge systems to prevent damage to the machinery.
c. Most of the pump discharge flow is to go to D-200, with the rest going to E-300 through the 100 mm (4 in.) diameter diversion line. The amount of flow going to E- 300 depends on the operational needs of the unit. It can vary from zero up to the maximum flow capacity of the 100 mm (4 in.) line. The valve at location "D" controls this flow rate. What function does it perform?
Since this valve is being used to control flow down stream of the pump, it is being used to throttle flow.
d. Another valve is in the diversion line at location "E." There are situations when it is necessary to completely isolate the system, in the vicinity of E-300, from the P-101/D-200 system. This need arises when a different fluid is being used in the E-300 system, and it is
necessary to prevent mixing of the two fluids. The valve at location "E" serves this purpose. What function does the valve perform?
This is another example of a valve being used to block
flow. In this case, equipment is not being taken out of
service with the piping being opened to the atmosphere. Instead, a piping system is being divided to perform two separate functions with different fluids. The valve is being used to block the mixing of the two fluids.
Sample Problem 1: Part B
This problem will now be continued to select appropriate valve- types for the valves at locations "A" through "E." Use Work Aid 1 and the information previously discussed to help solve this problem. The following additional information is provided to aid in this selection process:
• The change in service that requires the block valve at location "E" will sometimes occur very quickly. Thus,
separation between the two systems must be accomplished as quickly as possible. In addition, shutoff must be bubble- tight so that the two fluids do not mix.
• The throttling valve at location "D" does not need to have any tight shutoff capability, because the valve at "E" serves that function.
• The block valves at "A" and "B" do not require bubble-tight shutoff or especially quick functioning.
• The maintenance staff at the refinery is very small. Every effort is made to use low-maintenance equipment when available.
• The total pump piping system consists of two pumps in parallel, P-101A and P-101B. Only one of the two pumps is in operation at any one time, thus providing a spare to permit maintenance on the other.
Solution: Part B
Locations "A" and "B"
Referring to Work Aid 1, most of the possible block valve-types can be eliminated from consideration.
• All of the soft-seat and quarter-turn valves can be immediately eliminated because these locations do not require those features.
• The through-conduit gate valve is eliminated because this is not a pipeline service.
• The globe valve is eliminated because no throttling is required.
• The nonlubricated plug valve is eliminated because it should be considered for inherently safe services only.
With the above elimination’s, the selection has been narrowed down to a wedge-gate and a lubricated plug valve. Since a lubricated plug valve requires more maintenance to function properly (i.e., periodic addition of lubricant), a wedge-gate valve should be used.
Location "C"
Referring to Work Aid 1, both lift and ball check valves can be eliminated because they are typically available only in sizes of up to 50 mm (2 in.) in diameter. This leaves the swing check and dual-plate wafer check valves to choose from.
SAES-L-008 requires using a non-slam type check valve at the discharge of pumps or compressors that are in a parallel flow arrangement. Because of the spare pump arrangement, this is a parallel flow situation. This eliminates the dual-plate wafer check valve because of its spring-assisted closure. Therefore, a swing check valve should be used.
Location "D"
Referring to Work Aid 1, the rubber-lined butterfly valve may be eliminated because this is not a water service. That leaves either the soft-seat or metal-seat butterfly valves, or the globe valve as likely candidates.
The soft-seat butterfly valve can be eliminated since bubble- tight shutoff is not a requirement. Therefore, the metal-seat butterfly valve and the globe valve are the only potential candidates. At this point, the choice between the two valves must be based on cost and pressure drop considerations. Further information regarding the flow characteristics of the two valves, pressure drop limitations in the system, and valve cost is required to make the final selection. This information can be obtained from process engineers and the valve vendors. The metal-seated, wafer-type butterfly valve will probably have the lower cost and pressure drop, and will probably be the ultimate choice.
Location "E"
Referring to Work Aid 1, because of the requirements for quick, bubble-tight shutoff, only the quarter-turn valves can be
considered for this location.
• The rubber-lined butterfly valve is eliminated because it is not water service.
• The nonlubricated plug valve is eliminated because tight shutoff is not possible with this valve type.
• The lubricated plug valve is eliminated because of maintenance considerations.
These eliminations limit the choice to the soft-seat ball, soft-seat plug, or soft-seat butterfly valves. However, the choice cannot be narrowed to a single selection without additional information. Factors including relative cost, standardization, and availability must be considered before making the final selection.
Once the particular valve-type is selected, choices among available components and design details must be made as
appropriate. Further discussion of this aspect of valve selection is beyond the scope of this course. Participants are referred to the earlier discussions covering valve components, and the checklist contained in Work Aid 1, for additional guidance.
Determining the Required Valve Class and Associated MAOP
After a valve is selected, the rating class and MAOP must be determined. A valve is not completely specified until its class is also specified. The rating class must be supplied to the vendor. As discussed with flanges and fittings in MEX 101.04,
pressure/temperature-rating tables will be used to determine valve class. However, in the case of valves, ASME/ANSI B16.34, Valves - Flanged, Threaded, and Welding End, will be used.
This section will discuss the selection of the appropriate pressure/temperature rating class for valves.
Class is based on pressure, temperature, and material, and is determined in accordance with pressure/temperature rating tables, the material group, and design temperature and
pressure. The approach is analogous to that used for flanges and flanged fittings, discussed in MEX 101.04. Selecting class sets all the detailed dimensions for valves within the scope of ASME/ANSI B16.34. The objective is to select the lowest class appropriate for the design conditions.
ASME/ANSI B16.34 applies to new valve construction and covers pressure/temperature ratings, dimensions, tolerances, material, nondestructive examination requirements, testing, and marking for cast, forged, and fabricated flanged, threaded, and welding-end, and wafer or flangeless valves of steel, nickel-base alloys, and other alloys.
• ASME/ANSI B16.34 contains eight designated classes: 150, 300, 400, 600, 900, 1500, 2500, and 4500.
• As the number of the class increases, the strength of the valve increases. Therefore, higher valve classes can withstand higher pressure/temperature combinations. • As the number of the class increases, the cost of the valve
also increases because more material is being used to make the higher class stronger. Therefore, there is an economic incentive to use the lowest class that will meet the design requirements.
• Each of the valve material groups has a table in ASME/ANSI B16.34 that provides the ratings for that group. Figure 14 is a list of material specifications, and Table 2 is for Group 1.1 materials. Note that all pressure classes are in the one table.
Source: ASME/ANSI B16.34 - 1990. With Permission from the American Society of Mechanical Engineers.
Table 2. Standard Class Ratings for Group 1.1 Materials
A 105(a) A 515 70(a) A 675 70 A 672 B70(a)
A 215 WCB(a) A 516 70(a) A 696 gr. 0 A 675 C70(a)
A 240 LF2 (d) A 527 CI.1(d)
NOTES:
(a) Permissible, but not recommended for prolonged usage above about 800°F. (d) Not to be used over 650°F.
Table 3. Special Class, Working Pressure by Classes, psi
Temperature °F 150 300 400 600 900 1500 2500 4500 -20 to 100 285 740 990 1,480 2,220 3,705 6,170 11,110 200 260 675 900 1,350 2,025 3,375 5,625 10,120 300 230 655 875 1,315 1,970 3,280 5,470 9,845 400 200 635 845 1,270 1,900 3,170 5,280 9,505 500 170 600 800 1,200 1,795 2,995 4,990 8,980 600 140 550 730 1,095 1,640 2,735 4,560 8,210 650 125 535 715 1,075 1,610 2,685 4,475 8,055 700 110 535 710 1,065 1,600 2,665 4,440 7,990 750 95 505 670 1,010 1,510 2,510 4,200 7,560 800 80 410 550 825 1,235 2,060 3,430 6,170 850 65 270 355 535 805 1,340 2,230 4,010 900 50 170 230 345 515 860 1,430 2,570 950 35 105 140 205 310 515 860 1,545 1000 20 50 70 105 155 260 430 770
Table 3. Special Class, Working Pressure by Classes, psi (continued) Temperature °F 150 300 400 600 900 1500 2500 4500 -20 to 100 290 750 1,000 1,500 2,250 3,750 6,250 11,250 200 290 750 1,000 1,500 2,250 3,750 6,250 11,250 300 290 750 1,000 1,500 2,250 3,750 6,250 11,250 400 290 750 1,000 1,500 2,250 3,750 6,250 11,250 500 290 750 1,000 1,500 2,250 3,750 6,250 11,250 600 275 715 950 1,425 2,140 3,565 5,940 10,690 650 270 700 935 1,400 2,100 3,495 5,825 10,485 700 265 695 925 1,390 2,080 3,470 5,780 10,405 750 240 630 840 1,260 1,890 3,150 5,250 9,450 800 200 515 685 1,030 1,545 2,570 4,285 7,715 850 130 335 445 670 1,005 1,670 2,785 5,015 900 85 215 285 430 645 1,070 1,785 3,215 950 50 130 170 260 385 645 1,070 1,930 1000 25 65 85 130 195 320 535 965
Source: ASME/ANSI B16.34 - 1990. With Permission from the American Society of Mechanical Engineers.
Pressure/Temperature Ratings
Flanged-end valves are rated as Standard Class. Threaded or welding-end valves may be rated as a special class, permitting higher pressure than a Standard Class if additional inspection is made.
Class 4500 applies only to welding-end valves.
Figure 15 illustrates how temperature typically affects valve pressure limits for a given class, and how the use of soft-seat material reduces the permitted design pressure as temperature increases. Note that the actual pressure reduction with
temperature depends on the particular soft-seat material and valve seat design details.
Figure 15. Typical Pressure/Temperature Limits for Gate and Ball Valves
The procedure that is used to select the appropriate valve class is summarized in Work Aid 2A.
IDENTIFYING VALVE INSPECTION AND TESTING REQUIREMENTS
All valves require a certain degree of inspection and testing before installation and during operation. This is true for both new and reconditioned valves. The engineer generally does not actually perform or witness the tests. He must specify the mandatory tests for vendors to execute. This section reviews the types of inspection and test procedures that are utilized, where they are specified, and when they should be applied. Requirements for valve inspection and testing are covered in Saudi Aramco Materials System Specification 04-SAMSS-048,
Valve Inspection and Testing Requirements. 04-SAMSS-048
references which industry standards apply, plus additional Saudi Aramco requirements.
Several different inspections and testing methods are normally applied to valves. The selection of a particular method is
governed by valve material, rating, service conditions, and other considerations. Inspection methods vary from the quick and simple visual inspection of a valve casting and components to more sophisticated radiographic examinations. Test methods may include hydrostatic and/or pneumatic testing of the assembled valve and seats. Impact tests may be required based on the temperature conditions, material, and body thickness.
Material testing ensures that materials that are used in the valve meet material specifications with respect to chemistry, strength, and hardness. Pressure testing ensures the integrity of the valve body and valve seat tightness when closed.
Minimum Inspection Requirements for New Valves
04-SAMSS-048 requires that, as a minimum, each valve be tested, examined, and qualified per the industry standard
referenced in the purchase order and the applicable 04-SAMSS valve specification. Supplementary requirements are contained within 04-SAMSS-048. API 598, Valve Inspection and Testing, is the basic document used for inspection and testing of gate-, globe-, plug-, ball-, check-, and butterfly-type valves. The following highlight requirements that are contained in API 598 and 04-SAMSS-048, plus additional inspection guidelines. Work Aid 2A summarizes overall valve inspection and testing requirements based on 04-SAMSS-048 and API 598.
The minimum inspection required by API 598 is an examination of the valve casting and components. This examination
includes a check of all the valve features listed on the purchase order such as size, rating (and wall thickness), end connections material, etc. In addition, when a valve model number has been included in the purchase order, all dimensions should be
checked against those shown in the vendor's catalog.
Surface Examination
A visual check of the valve body casting is required to ensure conformance with the minimum casting quality specified by MSS SP-55, Quality Standard for Steel Castings for Valves, Flanges