API 6A Product Temperature Elevation - Lower Temperature Level 2

[Dinu Stan]

Hi Everyone,

I am looking for your help to evaluate the 6A chokes with lower temperature.

API 6A temperature standards are defined the lowest temperature which go no further than -60°C (-76°F).
here i have a problem with a project which is having -101°C as minimum temperature for chokes that has to be made as per API 6A.

Whilst API 6A Appendix G specifies the elevated process temperature in the maximum level(higher temperature)only for designing a valve, since there is no mention of the process for use at lower temperatures below -60°C.

at this stage how can i comply the API 6A?
Is there any other experimental method or calculation to obtaining design by considering the lower level temperature?

Looking for some guidance for this query...

Thanks...

Dinu...

There are no secrets to success. It is the result of preparation, hard work, and learning from failure.

 

[jmec87]

Note that the scope of API 6A is "wellhead and tree equipment for use in the petroleum and natural gas industries." Consider as well that API 6A (21st Edition) Table 2 states that "Minimum temperature is the lowest ambient temperature to which the equipment can be subjected." Is this choke being used on a wellhead or tree with -101°C ambient temperature? It seems likely that the minimum temperature requirement is wrong or that the choke is outside the scope of API 6A.

However, if you do insist on making the choke to API 6A with a -101°C lower temperature rating, the only specific requirement from API 6A is charpy testing the material at or below -101° per 6.3.2.3.2.

API 6A 4.3.2 requires accounting for the effects of temperature on material strength for temperatures above 121°C but does not require anything similar for low temperatures, likely because steel strength usually decreases at high temperatures and does not decrease at low temperatures. Your stress calculations don't have to change for low temperature.

API 6A 4.2 has a general requirement that the equipment shall be designed to perform (contain pressure, function, not blow up, etc.) while in the design temperature range, so you can't just ignore it. You likely want to "consider the effects of differential thermal expansion from temperature changes and temperature gradients which the equipment can experience in service" (this was a requirement in API 6A 20th Edition 4.2.2.2 but is no longer a requirement in API 6A 21st Edition). It is up to the designer to determine if any additional considerations for low temperature are required.

 

[Dinu Stan]

Thank You jmec87...

In the project datasheet, mentioned min. temp is for operating/process temperature.
i hope now i can proceed for design based on the material strength (Charpy Impact test will do based on the statement from API 6A section 6.3.2.3.2 para 3) by qualifying the selected material at lower temperature...

also i will have a look on the design consideration for the temperature ratings as per the previous edition for the safer side.

Thanks for your support...

Dinu...

There are no secrets to success. It is the result of preparation, hard work, and learning from failure.