Recent content by lizking

1. API 520 is now titled a "Standard." (Eighth Ed.) 2. Keep in mind that if your discharge dP meets your overpressure at values above 10%, it may not meet it at 10%. All the cases have to be checked. (has to do with the RV capacity being directly proportional to relieving pressure; but dP is...

(Heat input) x (specific heat) / (mass of fluid) will give you temperature rise per time. You have your "allowable" temperature rise from the API formula. Now determine if the resulting time is sufficient enough for you to take mitigating action.

1. You may take credit for the protection (insulation that meets certain criteria) with an appropriate factor per API 521. 2. If you can assume that the fluid is being heated somewhat uniformly, then yes you can look at how long the fluid would have to be heated to get to the design pressure of...

JohnGP is correct. This clause is not referring to vacuum conditions.

You may look into risk-based inspection methodologies. See API 580 & 581. Companies sell software to utilize the techniques.

Latexman is correct: it depends on the disk type. I would also add that there are "fail-safe" designs that actually will burst at lower that the specified burst pressure with "backward" flow. This type is used if you're worried about someone installing it backwards.

Remember the bellows is protecting against built-up backpressure as well. If that valve opens, how will the additional backpressure affect the capacity? I would say, after a "short" time period, you're in "conventional" mode. I know, I know.... how short is short?

Look into an API "risk based inspection" (RBI) methodology.

That's what the transient analysis would tell you. Frequently, as you state, a PRV will not act fast enough. Also, the analysis will determine a required location of the relief device. Sometimes it must be right on the vessel (as opposed to the in/out piping).

Depends largely on fluids. Gas on tubeside (high pressure side)and liquid on shellside with more than a 1000 psi differential warrants a transient analysis.

Thanks, Morten. In my opinion, you could interpret the "1.1 PS restriction does not apply" two ways: 1. Take the overpressure higher, say to 21% like ASME; or, 2. Don't allow any overpressure (0%). However, I've seen blanket statements that ALL overpressure scenarios are to be restricted by...

Does anyone know what the allowable overpressure is for the fire case per the European Pressure Equipment Directive (PED)? Their "Guideline 5/2" is clear as mud. Is it 0%, 10% or something greater than 10%?

I believe it's because a fire case is such a rare circumstance and even rarer that the RV discharges. Thus ASME allows 10% over the 10% = 21%.

maybe the tank was designed to Section VIII !!

For conventional RVs, a constant (stress CONSTANT) superimposed backpressure is subtracted from the set pressure to obtain "spring setting" or CDTP (cold differential test pressure). Built-up backpressure is NOT included. Note: caps used for emphasis.