3 replies to this topic

[vinod]

Hi ALL

Do all low pressure tanks require an overfill protection line or can i protect the tank by preventing the overfilling by giving a high high level switch (highly reliable)?

Thanks and regards

Vinod

[Art Montemayor]

Vinod:

A storage tank overfill is a hazard scenario - especially if the fluids involved are hazardous: toxic, flammable, explosive, corrosive, etc.

The scenario gets more complex when the tanks are being filled by transfer pumps with a designed TDH that exceeds the Maximum Allowable Pressure (MAWP) of the tank. All low pressure, API-type, storage tanks are designed to take a very relatively small MAWP (15 psig is the highest I've used) and, as such, will fail structurally is taken beyond the MAWP. You don't want to go there.

That is the over-riding reason for having overfill protection. You are free to use whatever protection you decide - even NO PROTECTION. That is up to you, your company, your local safety authorities, your insurance company, and your government. We can't tell you what you must do and can't do. All I can do is ask you to use your professional engineering ethics and good intentions for the sake of society. It is up to you (& your company) to decide if you want to take that stance or not. Depending on the fluids & process involved and the location, I would never design or operate a storage tank without 100% + safety controls on potential overfilling. That means I would have redundant safety controls to prevent any potential overfill scenario.

If you are a professional engineer you know better than to expect a specific answer to your query when you haven't even told us the fluids, pressures, temperatures, sizes, locations, processes, and scope of work involved. Therefore, you will appreciate that I can't comment any further. If you furnish COMPLETE basic data, scope of work, and drawings then we can furnish more specific comments or recommendations.

[fallah]

Hi ALL

Do all low pressure tanks require an overfill protection line or can i protect the tank by preventing the overfilling by giving a high high level switch (highly reliable)?

Thanks and regards

Vinod

Both should be applied:
Firstly HHLS activated relevant alarm...
And then,in the case of HHLS malfunction liquid would be relieved through overflow line...

[JoeWong]

Vinod,
Latest API STD 521 has ADDED a section related to OVERFILL (read more here).