Prevent steam ingress to a vented vessel

[invent11]

Hi, i am in concepetual design for a project and would like to know if the folloiwng scenario is feasible:
Consider that there are 2 vessels V1& V2 that connected by a pipe and V1 supplies steam to V2 @ constant pressure P1. V2 has vent line to atm. equipped w/ a valve. Given the size of vent line is large enough, P2 pressure in V2 will be less than P1 and steam from V1 is vented. Now If one throttles the valve so that still there would be some venting can back pressure in V2 is established so that there would be no steam engress from V1? or in other words P2>P1.

 

[rutherford703]

The picture is not clearly stated. However, for gas system, potential engergy can normally be ignored. Gas can only flow from high pressure to low pressure. If steam is supplied from V1 to V2, it is impossible for P2>P1.

 

[StevenHPerry]

Assuming there is more to the system than just what you have let on...

If V2 has some other source of mass or energy to it, yes you could backflow into V1.

Also, you're assuming that P2 and P1 are always greater than P_atm. What if V1 is shut in and steam condenses?

Least likely, if the vent valve is rapidly closed a pressure transient could temporarily make P2>P1 (steam hammer).

If backflow or external pressure creates problems, a check valve and vacuum breaker could be cheap insurance from the innumerable "what if" scenarios of operating a system.

- Steve Perry

http://www.linkedin.com/in/stevenhperry

This post is designed to provide accurate and authoritative information in regard to the subject matter covered. It is offered with the understanding that the author is not engaged in rendering engineering or other professional service. If you need help, get help, and PAY FOR IT.

 

[racookpe1978]

Doesn't matter what the two pressures or temperatures are in the two sized tanks.

For safety purposes (for access for inspection, repair, isolation, removal or whatever) you CANNOT tag out or approve EITHER tank for maintenance unless the steam is isolated (locked out, tagged out, physically isolated) completely.

A "vented tank" with steam coming in from any un-isolated source is NOT SAFE for LOTO purposes.