5 replies to this topic

[aju_1807]

Hi,

The balanced bellows type relief valve is normally provided with 1/2" size port which is normally open to atmosphere (must be kept open for proper functionality of relief valve). As per our project philosophy, we need to route the port vent to safe location with hard piped connection. However, as our service is non sour and does not contain toxic gases in any significant amount,we insisted client to accept the open connection instead of piped connection.

Now, client has reverted saying that you demonstrate that the routing to the atmosphere with hard piped connection is safe. That means we need to perform teh dispersion analysis for the leakgae flow rate. We have raised query to RV vendor to provide this flow rate to perform the dispersion study. I am very sure that vendor can not provide this details.

Any suggestion \ feedback on this will be highly appreciated.

Regards,

AJ

[djack77494]

AJ,
You do not understand the principles behind this type of PSV. I suggest you find and review commonly available literature on balanced bellows safety valves. There is nothing to disperse. The bellows is completely sealed EXCEPT for the vent connection to atmosphere. So there would only be air within the bellows assembly unless you have a failure.

[fallah]

Hi,

The balanced bellows type relief valve is normally provided with 1/2" size port which is normally open to atmosphere (must be kept open for proper functionality of relief valve). As per our project philosophy, we need to route the port vent to safe location with hard piped connection. However, as our service is non sour and does not contain toxic gases in any significant amount,we insisted client to accept the open connection instead of piped connection.

Now, client has reverted saying that you demonstrate that the routing to the atmosphere with hard piped connection is safe. That means we need to perform teh dispersion analysis for the leakgae flow rate. We have raised query to RV vendor to provide this flow rate to perform the dispersion study. I am very sure that vendor can not provide this details.

Any suggestion \ feedback on this will be highly appreciated.

Regards,

AJ

You should modify your project philosophy via an agreement with your client.Almost all balanced bellows PSV'S have bonnet type VENTED to atmosphere.

It is because that any pressure variation within bellows can affect the pressure balance already exists outside of bellows on the valve disk.

Edited by fallah, 16 July 2010 - 01:58 PM.

[Lowflo]

AJ,

The client is concerned about the exposure risk in the event that the bellows cracks. That's a legitimate concern, and one that's being elevated to a higher profile throught-out industry.

The valve supplier has no way to provide a flowrate because it all depends on the severity of the bellows failure. A complete circumfrential failure will yield one flowrate while a pin-hole causes another. So, this is a risk decision that the owner must make. If it's a highly hazardous material, then we need to be more on the conservative side when calculating this leak rate through a failed bellows. In your case, a 1/8 inch pin-hole is a reasonable assumption. Just do a simple orifice calculation using an assumed hole-size, and propose that leak rate to the client. If they agree, then run a dispersion model with that flowrate passing through the bonnet hole.

[aju_1807]

AJ,
You do not understand the principles behind this type of PSV. I suggest you find and review commonly available literature on balanced bellows safety valves. There is nothing to disperse. The bellows is completely sealed EXCEPT for the vent connection to atmosphere. So there would only be air within the bellows assembly unless you have a failure.

I understand the principle of operation for balanced bellows valve and there is a reasoning for asking this query that is why I have addresssed it in this forum.

Regards,

Ajay Sharma

[djack77494]

I understand the principle of operation for balanced bellows valve and there is a reasoning for asking this query that is why I have addresssed it in this forum.

Ajay, there is no need to take offense. If you understand how the device works, then that is great. Since you know that there is ordinarily nothing to disperse, then I trust that the answer provided by Lowflo adequately addresses your issue. Would be nice to mention that.

Edited by djack77494, 20 July 2010 - 03:39 PM.