Low pressure PSV selection

[Chonwe]

Hello everyone, can you help me with this question?

Is there a PSV for low-pressure and small flow requirements? I need a PSV to be set to 20 mbar with a flow based on API 2000 of 1.3 Nm3/h of air. As you can infer, it's for the ventilation of a small tank. For your information, the tank is designed to handle 0.5 bar, but the discharge requirements force the pressure not to be above 20 mbar. I have seen pressure valves that handle this pressure, but are very expensive. Also, always I found that are oversized for my requirements.
Is there a better way to handle this problem?

Thanks!

 

[Latexman]

Conservation vents from Protectoseal, Groth, Shand & Jurs, and Oceco. You can Google more.

Good Luck,
Latexman

 

[LittleInch]

Google "tank breather valves"

What's "very expensive"?

What is expensive is if you destroy your tank....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[shvet]

Any valve cost is 1/1000 of a tank cost. How is it able to be expensive?

Small does not mean cheap. Note that cost of a valve is not linear of its capacity/weight/dimensions. Cost of item itself takes only portion of total price and for many products production cost is negligible comparing to cost of marketing, delivery and certification.

 

[Chonwe]

You are correct. I was used to PSVs set at 2 to 6 bar. The cost of those is approximately 1/10th of the price of this 21 mbar PSV, which is why I'm concerned (For obvious reasons, the mechanics of these PSVs are different). The only thing that makes me doubt is that these low-pressure PSVs are commonly used in larger storage tanks (in my plant, they are used for tanks ranging from 100 up to 1000 m3). My current requirement is for a 3 m3 tank, so the cost of the PSV relative to the tank is quite high.
Thank you all!

 

[LittleInch]

Simple weight based valves should be relatively cheap?

Is there any reason it's not free vented?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[shvet]

Pricing is not always fair or obvious. Have you made sure 10x price of this PSV is fair? As per my experience such situation is common - atypical equipment/details are surprizingly extremely expensiveand one shall pay $100 for 10 ordinary PSVs and $100 for 1 rare PSV even those are identical. This is why we had specialized vendors for such items.

Where is this tank located?

Why PSV? Why not a liquid seal or hinged hatch or weak seam or similar?

 

[LittleInch]

At that flow rate 20mbar = 200m H20

Try a simple liquid seal?

Also 1.3 Nm3/hr and you need 0.5 bar to make it go away?

Why?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.