Basis of Design Validations

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Pressure, temperature, and number of cycles are the critical factors determin­ing the performance of the valve and the durability of its seat performance. API 6D QSL in addition to the mechanical cycles, calls for the extended duration of the seat and shell tests depending upon QSL lev­els. It also increases the stringency lev­els of NDE, including visual testing (VT), magnetic-particle testing (MT), penetrant testing (PT), and radiographic testing (RT).

EN Annexure A has gone a step ahead and even defined the material of the tested valves, and defines qualifica­tions accordingly.

All of these standards recommend test­ing in both water and gas. The gas can be air, nitrogen, methane, or other gases or mixtures of gases. Though dry air is allowed as test media, ISO gives a warning on self-ignition risk when test­ing the valve above 5Mpa (50 bar). API 6D QSL level gas testing media shall be nitrogen only.

Scaling

ISO and API 6D Annexure F de­fine almost equivalent scaling factors. On pressure classes in general, a test of any pressure class shall qualify any valves having an equal or lower pres­sure class, but 6D Annex F and ISO differentiate class 600 and below, and 900 and above.

1. API6D Annexure F

• 1/2&#; &#; 2&#; &#; Any one size
• 3&#; to 24&#; &#; Three sizes smaller and two sizes higher
• 24&#; Above &#; One size smaller and two sizes larger
• ASME Class 600 validates Class 600, Class 300, and Class 150.
• ASME Class 900 validates only Class 900.
• ASME Class validates Class and Class 900.
• ASME Class validates only Class

2. ISO

• 1/2&#; &#; 2&#; &#; Any one size
• 2&#; to 24&#; &#; Three sizes smaller and two sizes higher
• 30&#; &#; 80&#; &#; One size smaller and two sizes larger

Class 600 and below is one range and class 900 and above is another range &#; in these ranges, any tested valve quali­fies itself and its lower pressure class.

3. EN

Testing any one valve in the following size range will qualify the respective size range:

• &#; 6&#;
• 8&#; to 18&#;
• 20 to 28&#;
• Greater than 30&#;

A test of any pressure class shall qualify any valves having an equal or lower pressure class. This covers all steel shell materials having mechanical properties equal to or superior to those of the test valve. The valve manufacturer shall request the independent accepted body, usually once annually, to check the continuous manufacture and testing of valves, for which a type mark was granted.

Valve Standard Specifications: API, ANSI, ASME, BS

Valve Standard Specifications: API, ANSI, ASME, BS

Design Standard:

API 600 Steel Valves &#; Flanged & Buttwelding End

API 600 is the main gate valve speci&#;cation. Valve design and construction criteria are speci&#;ed, as well as materials and trim designations.Anappendix covers information pertaining to pressure seal valves. ISO Standard is essentially the same as API 600, re-produced in the ISOformat.

API 6D Speci&#;cation for Pipeline Valves &#; Gate, Plug, Ball and Check Valves

Speci&#;cation for pipeline valves (gate, ball, plug, and check valves) API 6D is the primary standard for valves used in main line pipeline service, including gate, ball, plug and check valves.Occasionally re&#;nery and petrochemical purchasers will reference the more stringent testing requirements of API 6D,602, 609 or BS , is speci&#;ed upstream. Similarly ball valves manufactured to API 608 may be speci&#;ed as tested to API 6D.

API 602 Compact Steel Gate Valves &#; Flanged, Threaded, Welding and Extended-Body Ends

API 602 is for 100 NB (4&#;) & smaller forged steel gates valve speci&#;cation. Valve design and construction criteria are speci&#;ed, as well as materials and trim designations. This standard includes requirements forbellows seal gate valves. In 150, 300 and 600 class API 602 requires a heavier wall than ANSI B16.34

API 603 Cast, Corrosion &#; Resistant, Flanged-End Gate Valves

API 603 covers light walled gate valves in sizes NPS 15mm to 600mm (1/2&#; through 24&#;), in classes 150,300&600.These valves are used in applications where a thicker API 600 casting is not needed. However, the wall thickness normally conforms to ANSI B16.34 wall.

API 608  Steel Ball Valves &#; Flanged and ButtweldingEnds

Typically used for &#;oating ball valves, API 608 is the purchase speci&#;cation for class 150, 300, 600 and 800 class steel ball valves. Valves design and construction criteria are detailed. Trunnion mounted pipeline ball valves are manufactured to API 6D but API 608 is also allowable up to 500NB(20&#;).

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API 609 Butter&#;y Valves &#; Lug-Type and Wafer-Type

API 609 is a speci&#;cation for butter&#;y valves with lug-type and wafer-type con&#;gurations designed for installation between ANSI B16 &#;anges, 150 to class.

ASME/ANSI B16.34 Steel Valves &#; Flanged & Buttwelding Ends

ASME B16.34 is the standard in which steel valve pressure/temperature ratings are speci&#;ed. It also offers additional valve speci&#;cation data including non-destructive examination procedures for upgrading valves for special class service. Gate valves manufactured under B16.34 wall thickness minimums may not meet the minimum wall thickness required of API 600 (cast steel valves) & API 602 (forged valves) for class 150, 300 and 600.

Face-to-Face Dimensions Standard:

ASME/ANSI B16.10 Face-to-Face Dimensions of Ferrous Valves

ASME B16.10 speci&#;es the face-to-face dimensions of all &#;anged and buttweld end valves. Screwed and socket weld end valve face-to-face dimensions are not included in this standard.

End Dimensions Standard:

ASME B16.5 Pipe flanges and flanged fittings

NPS 1/2 through NPS 24 Metric/Inch Standard

ASME B16.47

Large Diameter Steel Flanges

NPS 26 Through NPS 60

ASME B16.25 Butt Welding Ends

ASME B16.11 Forged Fittings, Socket Welding, and Threaded

Test Standard:

API 598 Valve Inspection & Testing

API 598 covers the testing and inspection requirements for check, gate, globe, ball, plug & butter&#;y valves. Steel valve pressure ratings in ASME/ANSI B16.34 are required to determine API 598 test pressure for steel valves.

BS EN  Industrial Valve- Testing of Metallic Valves

Part 1 Pressure tests, test procedures and acceptance of creteria-mandatory reuirement

ISO  Valve Test Standard

Incorporates an adoption of API 6D test standard. Leakage rate A is speci&#;ed for soft seated valves and plug valves (zero leakage*). Also includes standards for gate, globe and check valves.

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