Working Pressure over Design Presure

It had been discussed here.

can you just simply give me a formula how to calculate working pressure into design pressure, i think my question is clear.....

thank you,

argeef1

Well put...Amen

I'm assuming you were so suppressed by deadline time as you replied not being so mannered. In link I gave in post#1 there had been suggested rule to multiply working pressure on 1.5 in order to get design one.

Abdel Halim Galala gave more detailed answer based on ASME code.

Greater coefficient is better to get more reliable instrument in terms of its life span,but it might cause worse sensitivity. It's up to you which coefficient is suited your particular needs. You're the designer at all.

regards,

caramba.

Hey,Guest I did not read a Thank You in any of your reply's.I think it was very gracious of this forumn to give you any info after your email.Kudo's to the answers and a slap on your wrist for your attitude,Thank you would be sufficent!

To Everyone,

So sorry for my very impolite attitude on this section, i have to say this because i feel very unprofessional for what i have commented to "CARAMBA" and others was affected too..........and to thank you all for the reply i have read.......the reason of being so rude is because i can't find the formula for this undergound piping design pressure, the running fluid will be jet fuel (JP-8), but thanks again for everybody for giving me such good idea.

A member,

argeef1

Make sure you are well advised on the problems of electrostatic charge build up on the inner surfaces of pipelines carrying light hydrocarbon fuels where proper grounding is not in place.

This may appear to be a bit of a side issue; but I believe it is relevant to your project.

Ed Weldon

I can't say for all but I didn't mind at all as I do agree that referred link was not exactly for pipe design problem but gauge choosing one. Although as you noticed the approaches coincide practically. Plus I really felt you're under a work pressure right now :). It's just working situation. Peace.

The discussion in Caramba's link makes a number of interesting points. Another consideration receiving scant mention are those conditions where a pump or compressor in the system contributing to the total pressure may produce a higher pressure than at the design point. Some examples are:

1. Accidental restriction or closure of the pipe discharge.

2. Unexpected specific gravity or viscosity increase in the process fluid.

3. Unexpected speed increase in the pump or compressor prime mover due to factors such as AC frequency variations in electric power, poor frequency control in motor generator set, governor failure in engines or turbines, control failure in variable frequency AC drives.

4. Overpressure in normal operation or failure modes of pressure relief valves.

5. Failure of liquid level control in storage tanks/reservoirs.

6. Human operator error.

Other factors in liquid systems are the presence of water hammer as well as system instability due to the system curve crossing the pump performance head/capacity curve in two places. This latter condition comes about where high static head, low friction head and a high specific speed centrifugal pump are combined.

The extent to which these higher pressures contribute to the working pressure in the calculation will necessarily depend on the probability of their occurance especially together in the same time frame.

Ed Weldon

Congratulations !

You are really the "Master of Codes". It is not a joke but a sign of appreciation of your knowledge and professional answers.

I am glad for your intervention because it supports what I wrote in my previous comment.

Thank you nick name,

But you have rated "Good Answer" (score 3), where I have rated only (score 1)... just joking.

As in real life technical quality is not always estimated at its real value.

Dear all,

Good discussion.

I understood this post was created in Mechanical engineering forum. Let see how a process engineer looks at the following terms :

• Maximum Allowable Working Pressure (MAWP)
• Design Pressure (P_D)
• Maximum Allowable Operating Pressure (MAOP)
• Maximium Operating Pressure (MOP)
• Normal Operating Pressure (P_O)

Let's start from bottom to top.

Normal Operating Pressure (P_O) - System pressure as expected to be operated at during normal operation throughout the design life of the system. For example, a system with normal operatiing pressure 100 psig, the pressure gauge should be able to measure 100 psig.

Maximum Operating Pressure (MOP) - Maximum system pressure as expected during normal operation, may occur in some process transient period or different campaigns and it built into the design to cater for any uncertainties due to start-up, fouled, decayed, etc. It provides some level of flexibility for a proper operation of the system throughout the entire life of the system.

Maximum Allowable Operating Pressure (MAOP) - Maximum system pressure that can be allowed to ensure a proper operation of an a device.

Design Pressure (P_D) - A pressure choosen / specified (normally choosen by process engineer) to have certain margin (i.e. 10%) above the MOP. It is a maximum pressure in the system that are :

- NOT expected during normal operation

- May only occur during emergency situation as as fire, loss of utilities, valve failure, any abnormal operation corresponding to a short duration, mal-operation, etc

Design pressure becomes MINIMUM pressure that can be hold by any components within the system without mechanical failure. It is used to define the minimum MAWP of components within the system. For example, design pressure is used to calculate minimum vessel wall thickness.

Maximum Allowable Working Pressure (MAWP) - A maximum gauge pressure permissible by a equipment / device (at coincident temperature specified for that pressure) and is governed by code.

In many cases...

P_O <= MOP < MAOP < P_D <= MAWP

Good answer.

I have really problem with termins which your are using in practice.

I worked before with Russian and European standarts (NDT) and procedures.

There are another terminology in Russian documents.

Can you give Links for standarts numbers (ASME, ASNT, API...) where I can find this temins?

Thanks in advance.

Sir, can you explain me what are operating pressure, max allowable operating pressure, maximum allowable workable pressure,mas design pressure, hydrotest pressure & mill test pressure & relationship between these. If shut off head is 76kg/cm2 of pump of LPG pipeline then what should be MAOP and MDP in this case as per ASME 31.4 with reference to ASME 31.4 If i am correct then operating pressure can be ascertained by 10% surge on pipeline resistance and elevation consideration downstream of pumping station to receipt terminal.operation pr=72% of pr corresponding to SMYS. design pressure =80% of pressure corresponding to SMYS. hydrotest pr= 90% of pressure corresponding to SMYS.Are these relationship is correct , Please guide me.

The working pressure states the maximum pressure that you may safely use this piping. The burst (design) pressure is normally not made available to discourage those who would exceed the safe (working) pressure. Age, corrosion and fanny fatigue gradually reduce the burst pressure as well. Then there is liquid vs gas. A compressible fluid in a 20 inch diameter pipe at pressure of 215 psig could bring new meaning to the word burst. Hope those cranky guys don't get you down.

<...Working Pressure...> is always equal or less than the <...Design Pressure...>, as the former is related to equipment condition, which varies with time. That's why periodic inspection reports are essential to maintain burst/collapse indemnity insurance cover on the equipment. There is no need to calculate <...Working Pressure...>, as that will appear on the periodic inspection report.

If in doubt, consult a qualified Insurance Inspector.