How to hydrotest the tank designed to storage liquid SG=1.5

[SJEC]

I am working on the design of a tank in according with API 650 to storage some chemical with SG = 1.5.

I just doubt how can I hydrotest it?
Can I use some other liquid such as salt water etc?
I doubt the corrosion problem caused by salt water.

Thanks

 

[JStephen]

Just hydrotest with water like normal. It's not feasible to stress the shell above the product stress level as in a petroleum tank, so you don't try.

 

[SJEC]

thanks JStephen.

The SG of product inside the tank is about 1.5.
It is for petroleum plant, however it is not used to storage petroleum product.

Do you have another ideas?

 

[JoeTank]

I suggest that you increase the level of RT and MT in recognition that hydrotest will not produce high stress levels.

Joe Tank

 

[JStephen]

That is not an uncommon situation, typical with acid, caustic, fertilizer, molasses, sulfur, etc. And normally, the tanks are just hydrotested like normal.

A similar situation occurs when you add corrosion allowance. The hydrotest will stress the as-built shell higher than a light petroleum product will, but likely still won't reach the design stresses due to the extra material.

If the contents were especially hazardous, you could increase RT as Joe suggested. If it was a very small tank, you could actually overfill and/or pressurize the tank. You could add 50% extra shell height as freeboard, and then operate at 2/3 the shell height, but I've not seen this actually done in practice. The problem then is that somebody somewhere is likely to fill the tank up beyond the 2/3 point anyway, so you may be creating a hazard rather than reducing it.

 

[mecharya]

Also consider this: Since here the operating weight is more than the hydrotest weight, for checking tank settlement it is better to increase the freeboard.
And for hazard situation, an overflow nozzle might solve the problem.