Free Surface of Lube Oil Reservoir as per API 614 1

[Henrique Orlandini]

Hello,

I'm designing a lube oil reservoir as per API 614 guidelines, but one characteristic is puzzling me. In API 614, 1.3.6.2.6 says that "[...] free surface of oil in the reservoir shall be a minimum of 60 cm² for each liter per minute of normal flow".

I tried checking another literature and other references, but I found very little about this specific requirement.

What would be specifically this "free surface of oil" that is very much dependent on lube oil flow?

I apologize if this question isn't fitting for this forum.

Thanks in advance.

 

[MJCronin]

Both the "rundown level" and "free surface" area should be used in configuring an API-614 compliant lube oil tank and system.

It is my understanding that the "free surface area" requirement is in API-614 in order to liberate dissolved/entrained air from the lube oil

Rundown Level Defines the highest level that the oil may reach in the reservoir. This happens typically after shutdown, and after all oil from drain lines and overhead oil-containing vessels have emptied back to the reservoir. Minimum of one inch of freeboard (airspace) mustbe provided.

Free Surface Area -API 614 requires a minimum free surface area based on normal oil flow. This requirement will determine the configuration and proportions of the LO tank. reservoir. As the design oil flows increases, and thus tank size increases, rectangular tanks becomes unattractive, due to structural requirements for bottom and side stiffening requirements. The designer must consider either horizontal or vertical cylindrical reservoirs. Based on the free surface requirements in the API standard, as well as plant layout and space limitations, an optimum configuration can be chosen.

MJCronin
Sr. Process Engineer

 

[Henrique Orlandini]

Thank you very much!