Calculation of Hold Time for Novec

[sider]

Novec when released has an effect in confined spaces in terms of overpressure and underpressure which is resolved with pressure relief dampers (which open on certain pressure in both negative and positive directions and relieve the space from structural damage.

I have a question how would you approach the calculation of hold time in case that pressure relief damper is designed as a standard damper, which at the moment of dumping of Novec will be opened, after which will start to close. Since the damper takes time to close (90 s I would say) how would you calculate retention time in this case. In the case of pressure relief damper is installed, hold time is calculated using openings in construction which are defined by the fan door test. But for this case, I am not sure of the right approach.

To me, you cant just calculate the hold time taking into account openings that are known from the fan door test, since damper opening in the first 90 s will vary and there would be additional leakage of Novec through that area which has to be added to the fan door test area?
The usual pressure relief damper cant be installed since it doesn't have the standard required by AHJ.

 

[stookeyfpe]

Does the pressure increase warrant a damper? In all of the clean agent systems I've reviewed, the pressures were very low, even in small enclosures.

 

[sider]

What do you mean that pressure is low? During discharge?

From what I know, and which is an industry-standard, please correct me if I am wrong, but there is a need for discharge relief venting during Novec and similar gasses releases. There are calculations based on tests that are now used to predict these pressure. I believe those calculations were introduced by FIA(

https://www.fia.uk.com/static/uploaded/fab220fa-3bd8-4410-82d584549e0e2877.pdf)