Minimum rating of a level gauge connecting to a pressure vessel 1

[BesantVarghees]

I am preparing a datasheet for Pressure Vessel (TEG Contactor). My client's (end user) spec says, Level gauges connecting to a pressure vessel shall be minimum ASME 300#, even though the vessel nozzle can withstand 150#. Can someone clarify why this requirement is demanded by the client. Please do ask if the provided information is not enough for a perfect answer. Thank you

 

[SnTMan]

Besant123, sometimes clients like more than the bare minimum. For example some clients require nozzles <= 2 NPS to be LWN. You could always ask them.

Regards,

Mike



The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[Jboggs]

I always love these "why did somebody else say what they said?" type questions. I understand not wanting to ask a dumb question, but regardless of what you learn here your client is the only one who really knows why that spec is there. It could be because someone just copied an old spec without really asking themselves that question! They might appreciate you pointing this out to them. Maybe not. It might be because they have a higher level spec that requires it. Whatever it is, it is their reason, and you would learn something by asking them. Not us. End of rant. Sorry.

 

[moltenmetal]

You may discover that there is nothing behind this at all- it is a rule made by the ancients, kept in the holy Specification scriptures but for reasons now long since lost- or that someone in your client's team has good reasons for this requirement that they know very well and can explain to you. You won't find this out from us, though. Ask them.

 

[1gibson]

Once upon a time, someone accidentally broke a 150# level gauge by tapping on it with a wrench, so now the spec requires 300# minimum.

 

[racookpe1978]

If all gages in the plant use 300# fittings, it is easier/cheaper/fewer replacement parts need to be provided and stored.

If all gages use the same gasket, bolts, glass, and fixtures, you don't have to worry about any one gage in the plant being "fixed" with a lower-rated part during an outage.

 

[stewbaby]

As a end user / client, we also specify minimum 1-1/2" 300# nozzle / flange. For the reasons Racookpe1978, Sntman, and 1gibson mentioned. Helps with spares, for most all sizes (not all of course) you get at least 8 bolts in the flange (stronger), and nozzle is beefer (so when some stands on it, snags it with scaffolding or other it holds up better. We even carry this over to our atmospheric storage tank so we avoid threads, beef up the nozzle, and keep spares more common.

 

[moltenmetal]

Most places use 2" and don't require the 300#, for all the reasons stewbaby mentioned and one more: nozzle corrosion allowance on carbon steel equipment. It's tough to get adequate corrosion allowance on nozzles less than 2".

Perfectly suitable standard for tanks, columns etc. 24" in diameter and larger. Totally dumb standard to apply to anything smaller than 24" though, and we see people try to enforce it on smaller stuff.

 

[BesantVarghees]

Thank you so much, SnTMan, Jboggs, moltenmetal, 1gibson, racookpe1978, stewbaby.. And that clears my doubt.