Anaerobic Digester Vacuum relief valve
Anaerobic Digester Vacuum relief valve
(OP)
Hi There ;
I have a question about the vacuum relief valve on digester .
from one side any pressure reduction inside the tank increases the possibility of vacuum and the vacuum relief valve prevents it but from the other side the mixture of air with gas inside the digester is explosive .
please let me know your point of view for this issue.
KR
Sam
I have a question about the vacuum relief valve on digester .
from one side any pressure reduction inside the tank increases the possibility of vacuum and the vacuum relief valve prevents it but from the other side the mixture of air with gas inside the digester is explosive .
please let me know your point of view for this issue.
KR
Sam
RE: Anaerobic Digester Vacuum relief valve
Pressure/Vacuum Valve & Flame Arrester combination unit
RE: Anaerobic Digester Vacuum relief valve
RE: Anaerobic Digester Vacuum relief valve
The digester gas is an explosion hazard whether diluted or not. Because of the explosion hazard, no open flames are allowed near a digester. Also, equipment located in the electrical classification zone around the digester are required by the NEC to be rated explosion-proof.
RE: Anaerobic Digester Vacuum relief valve
Well neither operation is ideal, but as bimr rightly states adding air into a digestor should be a non standard operation. However if you have no vacuum relief valve it is likely that the digestor would implode and collapse / buckle. The ability of large vertical cylindrical tanks to withstand any appreciable vacuum level is very low ( inches of water) before they collapse.
In relative terms a tank has a thinner wall than a coke can or maybe even a large plastic bottle. you can collapse those with just a small in breath.
Better a potential explosive mixture inside where there are no ignition sources than a collapsed tank.
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RE: Anaerobic Digester Vacuum relief valve
RE: Anaerobic Digester Vacuum relief valve
RE: Anaerobic Digester Vacuum relief valve
RE: Anaerobic Digester Vacuum relief valve
RE: Anaerobic Digester Vacuum relief valve
There are a LOT of square inches.
Is the roof concrete?
What if a pump goes haywire and throws several PSI of vacuum on the system?
Keith Cress
kcress - http://www.flaminsystems.com
RE: Anaerobic Digester Vacuum relief valve
"The second concern, would be that the vacuum relief valve could fail which could cause a vacuum in the digester and the roof could collapse."
To prevent vacuum conditions from occurring, the digested sludge should be withdrawn slowly and raw sludge, sewage, digester gas (if gas storage is
available), or water should be pumped into the digester at the same or higher rate than the digested sludge is being removed.
Study Link
RE: Anaerobic Digester Vacuum relief valve
You need to look at the design limits of your concrete digestor.
A perfect concrete sphere might be able to withstand a large vacuum load, but if this is a standard vertical tank like structure with a cone roof, then it won't.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Anaerobic Digester Vacuum relief valve
Risk Statement - Insurance Company Statement
RE: Anaerobic Digester Vacuum relief valve
Additional precautionary measures one could implement would be
a) Install a control N2 (or inert gas) line feed to this tank to keep tank pressure within the vacuum pressure limits. Setting for this regulator would be few inches of water higher than the VRV that admits air into the tank.
b)Add a low pressure alarm at CCR.
c)Have the digestor electrically grounded to prevent static buildup. Arrange to have this grounding tested every year.