Ball valve vs DBB for drain on Bridle 1

[Woody99]

We have a level bridle (DN80) with some instruments coming off the side of a vessel. There is no drain valve and thus it's really time consuming in order to pump water back up the bridle to calibrate the instruments during shut down.

The MAOP is 300# and a tradesman suggested we use a DBB in order to provide positive isolation and then allow for a connection point for a hose to pump water back up. This will save tons of money and time over the long term however i'm not really quite sure why he would choose a DBB for this.

I'm going to suggest a reduced bore ball valve of either DN20, 40 or 50 in size to connect into the bridle through a reducing tee. These are all part of the piping spec which im not legally allowed to share.

As an undergrad i just wanted to get a second opinion on my selection or would I have to provide more information? I'm just aiming for something that is most likely the cheapest option which will provide the same result for calibration.


Thanks in advance

 

[LittleInch]

A sketch or drawing would help make sense of this as I can't work it out rom the description.

What does 300# mean? 300 psi or class 300 - both use# randomly.

DBB means Double block and bleed. A DB valve simply blocks flow from both directions.

This implies a single valve?

Your isolation philosophy should advise what type of isolation you need.

A standpipe arrangement typically looks like this: What does yours look like?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.