I had to design a fixed roof API 650 produced water skim tank. There was a requirement to blanket it with fuel gas to prevent air ingress. I would like to know what is the normal practice used to design the fuel gas lines and the regulator. i.e whether to size for the thermal inbreathing requirement only OR to consider the total of thermal + tank outflow requirements for inbreathing? The thermal breathing requirement alone was approx 300 sm3/hr. The tank had a continuous inflow and out flow of about 1250 m3/hr which leads to approx. 1250 sm3/hr of gas requirement considering outflow only; if the inflow stops.

Should we design the fuel gas for 300 sm3/hr only considering the fact that this will be a regular phenomenon?
Can the stoppage of inflow with outflow on maybe regarded as an emergency supposed to happen once in a while?

Can anyone explain the normal design practice and the logic involved?

Regards
Benoy

It is required that you follow API 2000, period. That's really all that is necessary to say about this.

Read the other posts in this Forum. They and the recommended website will give you more insight.

If you have any more specific questions after reading these sources, do not hesitate to post them.

Benoy, Phil is correct.

Also, you must consider all modes of potential failure, and their consequences and design accordingly.

There are some articles on my website if you are interested.