Overflow for Pressure Vessel?

[keschnipp]

Is there any way to protect the supply into a pressure vessel from back up? (Similar to an overflow pipe on an atmospheric tank)

We had an incident a week or so ago where a solvent got into our hot DI water (240 F) system and contaminated our final product. Needless to say, our upper management expects us to have a solution in place and this was one idea. I just don't know if it is feasible or not. Thanks for the help.

 

[unclesyd]

Not knowing the physical layout of your system I would look at these type valves as first step.
There have check valves that can be quickly inserted in a set of flanges.
The problem comes in when you block of a flow you generally build pressure a some point that has to be relieved, bypassed, or a pressure switch to shut off a pump or valve.

There are some other possibilities in using an isolation system, but this is much more expensive and can get complex rather quickly.

http://www.checkall.com/index.htm

 

[keschnipp]

I've already talked with a vendor about the checkall valve and are leaning that way to replace the existing checks (that failed).

Flow is going other places further back in the line and line pressure is controlled by VFD's on the feed pumps, so blockage of flow shouldn't cause critical overpressurization.

As far as expense, this incident has caused about a million dollar loss, so I think we could justify expense, I just don't care for complex safety systems (as our operators tend to bypass them somehow).

 

[unclesyd]

You should be able to determine the process conditions that allows this to happen and set your controls around this. If you could do a Hazop type analysis of the system this should eliminate most of the control points to work around.
We used another way around your type problem by putting a break tank to take any problems with backflow into the water system. A set of pumps charged the system from the break tank into the process. We use this where the process wouldn't allow a physical disconnect, easiest way, of the water line at the water entry point.

If you can find a control point a simple ON/OFF valve with the proper type reset would help.

http://www.lesliecontrols.com/Products/Laurence.htm