NRV Testing

What's an "NRV"?

NRV is a non return valve or a check valve.

What is the meaning of the question ? What are you looking by the "Advantages/ disdvantage" ?

As far as API is concerned, if you are in hydraulic business (or petroleum industry) - you can consider it to be ultimate. As far as API 6D is concerned (and API 598 too) you can be rest assured that it will meet almost all the requirements as far as the performance is concerned and additionally it freezes most of the dimensions ensuring interchangeability.

I dont have the API 598 at the moment at hand, however as far as API 6D is ceoncerned, I have some experience. And As I remember, it is OK but I had some past problems (with 2" Wafer type NRVs) and those problems are not addressed in this standard ie even with valves according to 6D these problems can recur.

a) There used to be a soft seal (rubber) below the valve (as per Fig 10 of 6D) which used to dislocate itself during the normal flow and as a result the check valve operation was not very reliable. In fact in a few cases, it just moved out of the valve and reached the inline filter (fortunately there was one after the valve)

b) The pressure / flow required to open the valve was high due to the spring and as a result the restriction and the drop was variable.

c) In a spring loaded valve (lower NB but high pressure), the spring holding mechanism used to shift due to pressure fluctuations (the pump was a piston type) and the spring pressure used to some times reduce and in a few cases flow was jammed as the washer holding the spring blocked the inlet/outlet ports.

This and a few other aspects are not covered in the API and we have gone for our own design and a few supplementary tests to ensure the problems are not passsed on to our customers. Since most of these are after a sufficiently long operation and were not indicated during our test bench operation of the system.