I guess, OP has more issues with the flow range that goes outside the operating envelope of a constant speed drive pump than the back pressure control and he is finding a solution with a VFD to cover the wide flow range (specially on the lower side).
Keep it simple. The backpressure set point of 10 psi will not have enough energy to provide for the friction loss of 12 psi in the downstream piping. In this situation, there will be no flow at the receiving tank. To get the flow, either increase the set point or reduce the piping length. By...
It is all about stress. You need to convert the test pressure to stress. Use Barlow's equation. Make sure that stress does not exceed YS. Typically, companies keep it limited to 0.9YS at test temperature.
It's a bit of mind puzzling in the beginning. You need to learn the relationship between...
when you say, "upon review" and make a statement that it 'doesn't meet B31.4 code', you much have studied the stress report in detail. Don't you have the stress model or is your statement based on the report only?
Typically, the Code wants that the piping system should be taken as a whole when...
OP,
If the main line gas flow is unidirectional ( which I assume is yes, DIB is the best option). The first MOV XX3 is a welded valve, which is good for gas service. It has a better joint strength than a flanged valve, specially after the S-bend (U/G to A/G). The second manual valve is obviously...
The intent of the restriction orifice (RO) is to have a controlled flow to the atm tank. Put the RO downstream of the block valve.
Yes, the block valve will see a DP of 700 psig when you open it. Once, the flow starts, there will be pressure drop across the RO that will stabilize the line pressure.
Look at TGS4 response on 11 April. His is a first hand knowledge on what he did to an over-pressure event. It requires a FFS, not a theoretical stress analysis.
There is no Fire Load Case given in ASME BPVC Code. Usually, after a fire event, you/your company has to initiate a FFS. Essentially, it will be assessment of mechanical properties of components subject to heat exposure and re-rating/replacement if required.
You need to call an expert third...
I agree with LittleInch. It's a lot of valve and they are expensive.
The PID is for a Receiver Station. One HV/MOV, DIB (a DIB provides double isolation from one end, ie. upstream as apposed to single isolation for DBB) would have sufficed.
Welded/Flanged construction is not an issue as many gas...
OP,
Both H2 and H2S are highly flammable and explosive gases. In addition H2S is highly toxic. You need to be extremely careful to take the refurbishment work.
LEL/LFL for both H2S and H2 is 4% in air at room temp.
Limiting Oxygen Concentration (LOC) for H2 is also 4%. H2S has no LOC...
1. For gravity drain, the pipe size and the flow rates are matched to the available energy. The available energy is the elevation difference (termed head) between the supply and delivery points.
For maximum natural flow, the available energy equals the friction loss in the pipe.
You can choose a...
Wait a minute. How a stress analysis or hydrotest will tell that YS is exceeded or not exceeded? And wasn't the piping protected for overpressure? By Code, it should be.
In the context of overpressure, I would assume that the system had exceeded the design pressure. If you are talking of...
Remember, the calculated stress ratio is the greatest of the three stress criteria given in ASME B31.3 Fig. 323.2.2B.
The 3rd criteria is essentially the equivalent Primary and Secondary load criteria in PV design. For displacement loads, you should include thermal, restraint movement and...
Hi Dan,
The key to find your answer is follow Appendix O and determine Sbsel following Joint Component Approach O-4.2.
Integrity of a flange joint is dependent on integrity of all the assembly components - the flange, gasket and bolt. Para O-4.2 is a stress check for all the components both at...
PED 2014-68-EU is for stationary pressure equipment.
PED had recognized and accepted ASME B31.3 - process piping code indirectly through two supporting documents:
ISO 15649: Petroleum and Natural Gas Industries - Piping.
EEMUA Publication No. 202: Guide to the use of ISO 15649.
These...
The Code will not tell you if you can tie-in to a flanged connection or not. Many Owners will have their own specification not allowing flanged connections to a flare header - the reason being - to avoid ingress of air/oxygen to form a combustible mixture with the vented/flared gas. Of course...
Dan,
The key to keeping the appropriate bolt preload at both ambient (installation) and operating condition (500C) is to determine the bolt stress (Sbsel) is as per Appendix-O. O-4.2 will take you through all the checks at both ambient and operating conditions for the flange assembly - bolt...
You should revisit your design. The top part of 310S you said will be operating at creep (650-675C) and 100,000 hrs. (say 12 operating years ). One of the things designers overlook is the design life when taking stress values from BPVC Sec II Part D. For vessel that predominantly operates in the...
That's the direction I would go in absence of any dimensions not found in a standard (example ASME B16.47) acceptable to the construction Code - qualify by Sec VIII Div1 Appendix 2.
You should treat B31.8 831.4.2(c) and 831.4.2(j)(3) separately for understanding. Whereas 831.4.2(c) talks about a complete encirclement reinforcement type that we encounter in daily life, 831.4.2(j)(3) talks about hot tapping/plugging fittings, where the reinforcing sleeve is pressurised and is...
