Installation of Nozzle upstream of PSV

[Vibanalyzer]

Dear ALL

We have a tank with VCM service, there are VCM vapors having PVC powder at the top of the tanks. PSV installed at one of the outlet line of the tank having set pressure of 16 kg/cm2. Operating pressure of the tank is 10 kg/cm2.

PVC powder in the VCM vapors got deposits in the pipe and inside the PSV (PSV found choked). Our process engineer recommend to install diameter 1" nozzle having pressure of 10 kg/cm2 inside the line targeting towards the PSV so that flushing of the PSV carried out during operation and there will no deposit of PVC powder in the line and PSV.

My question is that can we install an nozzle having pressure of 10 kg/cm2 upstream of the PSV, as this will impart high velocity towards seat and disc of the PSV which can have effects on PSV functioning (set pressure) and probability erosion effect as well. Can we install nozzle upstream of PSV (distance between nozzle and PSV bottom is approximately 10"). Please refer any code reference if it is not possible to install PSV downstream of spraying nozzle.

Appreciate your reply please.

Regards,

Sami

 

[e43u8]

Sami,

It's not uncommon using a small size line handling the steam or a cleaning medium such as gasoline which is connected to the inlet line of a PSV on dirty services such as a polymer containing fluid and would flush the PSV upstream to prevent accumulation of solid polymer there. Obviously the detail of connection and applied spray nozzle should be such that there would be no negative effect on PSV function to do the job properly...

 

[Vibanalyzer]

Dear e43u8

Indeed thankful for your reply, as you rightly pointed out that small diameter piping normally installed upstream to flush the line and PSV. However, I think the jet of nozzle normally installed in downward direction not directing hitting the PSV bottom.

Above configuration is already available in our line, however some of the VCM vapors having PVC powder still passing and chocking the line and PSV above that nozzle point (area becomes the dead end). To rectify above, our process engineer suggested to install one more nozzle in the same line but facing upward direction which will directly targeting towards the PSV. I have concern that direct impingement to PSV may have erosion effect and probably also affect proper functioning of the PSV (e.g pop pressure due to even forces on the spring of the PSV).

Is above installation acceptable as per code or not, stream directly hitting PSV.

Appreciate your reply.

Regards,

Sami

 

[Latexman]

I don't think there is a Code issue here, but I recommend you start a new thread in the Safety Relief Valve forum with a link to this thread requesting Code compliance confirmation.

You can inspect the PSV more frequently after installation of the nozzle to detect erosion or other effects. If detrimental effects are seen, the nozzle can be removed or reduced somehow. If no detrimental effects, the frequency can be extended to more reasonable time frames.

Good luck,
Latexman

Technically, the glass is always full - 1/2 air and 1/2 water.

 

[e43u8]

Sami,

There is no code or standard for such requirement hence relevant detail and configuration. In some engineering practices and books there are some recommendations to do so but without any detail; you can find attached one page of the book titled "Pressure Safety Design Practices for Refinery and Chemical Operations" refers having continuous purge of clean fluid below the PSV has been applied in dirty services.

I think, the nozzle of relieving the clean fluid can be (or even has to be) oriented toward the PSV if we expect to prevent deposit formation at PSV inlet, provided that the relevant flow rate hence the velocity of the clean fluid would be kept within a range in which there is no concern of erosion or severe impingement on PSV disc...

 

[Vibanalyzer]

Dear e43u8

Indeed thankful for your reply and reference that you have provided.

Regards,

Sami