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Great work snickster! As you say the point for the "of air" is that the basis for the relief rate is based on air through a nozzle. This depends on composition for an ideal gas so I need to use equation D.35 to convert. I saw someone suggest Grahams law, which also makes sense to me now.

Thanks for responding. Why do they state "of air" for all the rates in API2000 if it is a perfect gas, reasonable assumption at tank conditions, then stating Nm3/h makes the MW irrelevant?

For API 2000 the relief rates are defined as Nm3/h of air. When looking at for example thermal inbreathing - My tank is blanketed with fuel gas with a PCV that will open up at 0.1 barg to let fuel gas in. Once I have the required flow rate in Nm3/h of air how to work out fuel gas consumption...

To Heaviside1925: People change minds! No, it is simply pressure control based on an upstream separator; the Separator is fed from multiple wells/choke valves. Precise control is not necessary. Control is required across the entire range. Again, precise control is not necessary, just need to...

Hi, We are in a position where we are about to install a pressure control valve but new requirements have come in for a much lower turndown so the intention is to install a small control valve in parallel to provide the turndown. There needs to be controllability all the way from the normal...

Thanks both. For clarity I am taking max pump pressure as suction vessel psv set point plus pump dead head. 1504 - I was really concerned with the implication that to avoid a high pressure trip you need to set the design pressure of the system at max presume/0.7. Little inch - 7.2.2.2. I’ve...

Hi all, API 14c states that a high pressure trip on the pump (others) discharge is not required if the “Maximum discharge pressure does not exceed 70pc of the maximum allowable working pressure of the discharge piping”. It also states a psv on the discharge is not required if “Maximum...

Hi, Can anyone point to a reference which details how to design a finger type slug catcher

Thanks! That’s an extensive list, I’ll see what I can get my hands on

Hi all, Is there a good reference document or article that discusses the location of ESD valves? E.g. ESD valves are located on the liquid outlet of vessels presumably to isolate the liquid inventory in case of a leak. Also, they will be at fire area boundaries to prevent flammable materials...

Ok thanks all.

Hello all, General advice for defining a control valve DP at design flow is 0.7 bar or 30% of total system DP, whichever is higher. For low pressure gas systems the minimum of 0.7 bar can be unachievable as it is not available. Can any one point me to guidance for defining this for low pressure...

Thanks for the reply Latexman. I think you might have misunderstood me regards your first extract, I am talking about the PAHH on the upstream vessel. The analogy would be that if I was doing a gas blow by calculation I would take the upstream pressure as the PAHH (max operating pressure), not...

Hello all, When considering use of API 521 Section 4.2.2 – use of admin controls. If I have a high pressure vessel feeding a lower pressure heat exchanger with locked open isolation valves then for the closed outlet case if the upstream vessel has a PAHH set at less than 1.3 x design pressure...

Thanks Casflo. Yes, I think that is a good point. The 0.7 bar min is probably based on not having too big a control valve but in this case due to the choking it doesn't matter since it does not affect the control valve Cv until you get to a very low DP, in this case ~0.1 bar. Making my...

Hi Latexman, I don't think that would work for me. The LCV is controlling the level in the upstream vessel and there's only a few mins holdup at peak flow. The upstream vessel is filled from elsewhere with a flow that ramps up over time (10 hrs) and then stops. This is repeated a couple of...

Hi there, A problem I've come across a few times and had a few different opinions so I thought I would asked here... Typical rule of thumb for allowable control valve pressure drop is 30% of the total frictional losses or a minimum of 0.7 bar. How critical is the minimum value... I have a...

Thanks don1980 - your PSV knowledge is extensive! For anyone interested in 4126 part 3 there is the following applicable to safety valves in combination with bursting discs. "Calculate the total inlet pressure drop (difference of stagnation pressures, i.e. non-recoverable losses) using the...

Ok thanks all.

Hi, I have just got some vendor quotes back and looking at reviewing the inlet/outlet line sizing based on the chosen vendor. The project is in Europe with vessels to EN 13445. One vendor states an actual Kd and orifice area and then apply a de-rating factor of 0.9 to calculate the rated...