API2000 vent capacity calculation
API2000 vent capacity calculation
(OP)
Hi
I would welcome any insight into how to calculate the capacity of a manway used for emergency relief.
Situation - I was originally asked to calculate counterbalances for vents to be added to existing tanks - hinging and couterbalancing of the manway, (requested by UK HSE). They have now been asked to show some sort of calculation for suitable sizing.
Looking through API 2000 I can calulate the required capcity for outbreathing & fire but am unable to understand how to calculate capacity of my manway.
I assume use of equation 3, (multiplied by 0.5) but what specific heats are used ?, those at inlet to and outlet from manway ? and what value Z ?
vent presure is 7.5 mBar and I doubt the client can easily supply temperatures and molecular weights.
I asume if 'k' = 1 then SCFH = 278000P1.A
Any pointers appreciated, thanks
I would welcome any insight into how to calculate the capacity of a manway used for emergency relief.
Situation - I was originally asked to calculate counterbalances for vents to be added to existing tanks - hinging and couterbalancing of the manway, (requested by UK HSE). They have now been asked to show some sort of calculation for suitable sizing.
Looking through API 2000 I can calulate the required capcity for outbreathing & fire but am unable to understand how to calculate capacity of my manway.
I assume use of equation 3, (multiplied by 0.5) but what specific heats are used ?, those at inlet to and outlet from manway ? and what value Z ?
vent presure is 7.5 mBar and I doubt the client can easily supply temperatures and molecular weights.
I asume if 'k' = 1 then SCFH = 278000P1.A
Any pointers appreciated, thanks





RE: API2000 vent capacity calculation
just a thought, SShep
RE: API2000 vent capacity calculation
ak
RE: API2000 vent capacity calculation
If you can somehow retrofit certified lids then this would obviously be your best bet.
RE: API2000 vent capacity calculation
The end user is stuck with whats there for at least a year until next shutdown
ak
RE: API2000 vent capacity calculation
Steve Braune
Tank Industry Consultants
www.tankindustry.com
RE: API2000 vent capacity calculation
RE: API2000 vent capacity calculation
Also noticed that equation 3 does not make sense
because k > 1 , P2^(2/k) always less than P2^(k+(1/k)) and hence SCFH value incalculable (root of -ve No.)
Is this a misprint? should it be (P2/P1) raised to power ?
The use of (P2/P1)^ gives flow rate in line with groth model 2400A when manway given coefficient of dischrge = 0.5
clarification much appreciated
ak
RE: API2000 vent capacity calculation
In my version, it's not particularly clear, but it appears that the equation inside the square brackets is:
(P2/P1)^(2/k) - (P2/P1)^((k+1)/k)
Note that it looks like the second exponential is (k+1)/k, not k+(1/k) as in your post.
Since P2>P1, this is negative if k<1, positive if k>1. This is then multiplied by k/((k-1)MTZ), which then means that it is always positive, prior to taking the square root.
Note that this equation doesn't work if k=1!
RE: API2000 vent capacity calculation
I suspected must be the case but did not think of (K+1)/k
It makes a large difference. So much so that at their low set pressure of 7.5mbar all the existing openings are too small
maybe they will have to investigate other options
ak
RE: API2000 vent capacity calculation