Instrument ball valves

[jeanfrancois3869]

Hi,

I readed in Norsok standard I-104: Fiscal measurment systems for hydrocarbon gas, a sentence which I don't understand about instrument ball valves. I quote:"For fiscal measurement applications, ball valve manifold block or an assembly of ball valves shall be applied(3/5-valve)". What does 3/5-valve mean? Is it a type of valve?

 

[JLSeagull]

A three-valve manifold is used on a pressure differential transmitter that has two impulse lines. Two valves are block valves for the impulse lines and the third is an equalizing connection to zero the instrument. This is the most common dp instrument valve arrangement.

A five-valve manifold has those same three valves and drain valves to blow down the impulse lines or drain the transmitter. These are more common in steam.

 

[moltenmetal]

...but these multi-valve manifold assemblies for differential pressure instruments usually contain needle rather than ball valves.