Extneded bonnet vs Normal Bonnet for minus 30 deg C

[Weko]

We are currently handling a project for CNG that are cooled down until minus 30 deg C. The valves would use LTCS material.

We would like to have suggestion regarding the bonnet type. Is minus 30 deg C, can use normal bonnet or shall use extended bonnet?

I am thinking of using extended bonnet because of (1) If the valve is not extended bonnet type, there will be a possibility of icing (because of humidity or rain) on the valve stem that will harden the operability. (2) The “extended bonnet” is needed so the insulation can fully covers valve.

But my supervisor insisted of using normal bonnet, since the client does not specify (infact there is no piping class from the client).

 

[uaepiping]

Extended bonnets may not be required for small bore lines up to -50 deg C.

 

[gerhardl]

How to protect against cold have to be decided by the end-user, based on the actual application (and surroundings) for the single valve.

An extended bonnet could be one of several possible precautions, but not necessarily the best, and referring to uaepiping, not required.