Pumps in Benzene Servive

[techv]

Friends,

We have quite a few pumps in toxic service containing benzene from 1-10% in the fluid. Though we have no special requirements except limiting VOC emissions, Supllier is expressing concerns with their seals design with this service. Pls advise as to what should be the seal designs for these pumps in benzene handling.

Tech

 

[GL431]

Benzene is carcinogenic service, no? Or is toxic and carcinogenic one and the same? Is the concern of the pump/seal supplier actual fugitive emmissions or the seal actually dissolving in the aromatic liquid? I seem to remember that on a benzene project (17 years ago in Germany) that we used hermetically sealed pumps. There were actual legal limits set for benzene emmisions. I cannot quote now what those were/are.

 

[DedalusEnviro]

1) What's the other 90-99% of the fluid?

2) What material are the seals you're using now comprised of? We're talking an elastomer, right?

According to the information I have on pure benzene, Buna-N is classed as "conditionally resistant" and Viton as "resistant." EPDM, EPT, and neoprene are "not recommended."



Dave Wichern

http://www.dedalusenviro.com

Science is a business of empiricism.

 

[epoisses]

I think the best practice for pumps in high bz containing services is sealless (canned -- mag drive is another option but we had many problems with those).

 

[tesser]

Benzene is considered as extremely carcinogenic. I think the latest TLV value is 0.5 ppm.

Usually on Benzene duties a dual pressurised seal is recommended if a mechanical seal is required. If elastomeric (rubber) O-ring materials are needed, then Fluorocarbon (Viton) is limited to relatively low temperatures (I wouldn't consider Buna-N). The only other rubber material with sufficient resistance is perfluoroelastomer which would go to higher temperatures.

 

[MJCronin]

tech,

Our company had a chemical client that required new 100% benzene pumps. They required Crane canned pumps with pump flow monitors.

Many of our clients do not like the double mechanical seals and, instead prefer to used canned pumps. Canned pumps, of course, have thier own start-up shut-down issues.....

Epoisses, specifically, what problems have you had with the mag-drives ? Who made these pumps and what service were they in ?

Regards

_mjc