3 replies to this topic

[rs20170808@gmail.com]

I have a closed drain vessel which has two vertical submerged pumps for emptying the vessel. The vessel has in breathing and out breathing by fuel gas to maintain pressure. During pump out is there a chance of pulling in vacuum in the vessel if the inbrathing and out breathing is not working?? Should vessel be designed for full vacuum? Should there be a low low pressure trip on the pump?

Thnks

[jayari]

During pump out, if enough material is removed that the internal pressure is less than the external pressure, then the vessel will experience vacuum conditions. If the inbreathing device or path is not functioning, a vessel not designed for vacuum pressure can experience catastrophic failure when exposed to vacuum conditions.

 

It is good practice to specify for full vacuum on new vessels if there is any mode where a vessel can experience vacuum conditions. If this is an existing tank that is now being used in a new way, then vacuum protection (inbreathing ability) must be adequately sized and proper safeguarding and maintenance of this vacuum relief must also be in place. A trip for the pump on low pressure is a safeguard you mat use, but I would not rely on it as the primary method of preventing vacuum conditions.

 

Edit: Possible retrofit with support rings may be possible, but I do not have experience with that.

Edited by jayari, 15 November 2019 - 02:05 PM.

[katmar]

Depending on the size and shape of the tank it could be very expensive to design for full vacuum.  Before you do this look at the risks, and cheaper alternatives.  If the vessel fails, what happens?  Does it contain hot, toxic or flammable material?  Are there containment walls (bunds) in place to contain any spillage?  What would it cost to install double the vacuum relief devices? - probably less than building for full vacuum.  Etc, etc

[breizh]

Hi ,

If nozzle are available , you may install a rupture disk to protect the tank .

Good luck

Breizh