Valve Testing API 598

[valveman52]

Why do valves with the same pressure class get tested at slightly different pressures because the body material is different? (API 598)

F316 and A105N for example

 

[JLSeagull]

Which tests?

Looking at table 3, for check valves, other test pressures, note that the pressure references b below the table that includes 110% of the maximum allowable pressure at 100 degree F for steel, alloys and stainless. Type 316 stainless steel is rated for less pressure in each Class rating that A105.

 

[ballvalveguy]

Hi Valvman52,

Different metals have different strengths. Castings are the same thickness. Therefore a casting made of A105 for example would be able to hold a higher pressure than one made of 316. Most people are unaware of that because the majority of valve manufacturers only make castings out of a few metals. The manufacturers test to API 598 using the pressures for the lowest strength metal that they produce.

 

[hsbcn]

On the topic of tensile strength:

For the very technical minded:

http://www.engineersedge.com/strength_of_materials.htm

For less technical:

http://en.wikipedia.org/wiki/Tensile_strength

Heather's focus: Alloy Valves Duplex Valves Super Duplex Valves Monel Valves Inconel Valves [link titanium-valves.com]Titanium Valves[/url] & 6 Moly Valves

 

[fangl40]

Check out ASME 16.34, which specifies the pressures.

 

[JChanMe]

fangl40 is right, the ASME B16.34 specifies Pressure-Temperature ratings. The test pressure for shell test is 1.5 times of max allowable working pressure under room temp which is -29 to 38C. Different material group has slightly different working pressure even under different temperature.

James Chan

 

[ballvalveguy]

Contact Yarmouth and speak to Matt (207) 829-5359. He actually does testing and can certify valves. He will be able to answer all your questions.

 

[reverman]

Test pressures are based off the 100°F rating of the valve material and pressure class. The shell test is 1.5 times the rated pressure and the closure (seat) test is 1.1 times the rated pressure (except for most gate valves which have the low pressure closure test which is 60-100 psi no matter what material or pressure class).

For example:

Class 150 A105 has a 100° rating of 285 psi so:

Shell: 450 psi (you round up to the next 25 psi increment)
Closure: 325 psi

Class 150 F316 has a 100° rating of 275 psi so:

Shell: 425 psi
Closure: 325 psi