3 replies to this topic

[Saqib]

Hi,

 

We have to install a new relief valve on a steam drum. At the rated capacity of proposed valve, inlet line losses were high (5.5% of set pressure). Because of that different vendor proposed a pilot operated relief valve complying with ASME section I. Now the problem is that the connecting nozzle size on the boiler drum is 2.5 inch and the valve inlet size is 4 inch. I have checked the inlet line losses with an expander and the result is around 7% of set pressure. As it is a pilot operated valve, this should not be an issue we will just make sure that the capacity of the valve will be fine with the high inlet losses. But I understand that code doesnot allow a reducer to be installed on the inlet line of the PSV. But while this is a remote sensing pilot operated PSV, are we allowed to do that?

 

Would appreciated if someone could share his experience on similar situation.

 

Kind regards,

Saqib

[fallah]

Saqib,

 

Per API 520 Part II, the vessel nozzle is normally being considered as a part of PSV inlet line; then smaller vessel nozzle than PSV inlet size isn't in compliance with API 520...

[Zauberberg]

You may get away if the nozzle X-area is not smaller than the PSV orifice X-area, and there are no issues with fouling/blocking or pressure drop. Search the site, there is a lot of discussions on the subject.

[breizh]

Consider this presentation on top of information given by other members.

 

Breizh.