Sizing Piping or Linepipe 1

[stonetech]

when we design piping or pipeline, when to use design pressure, when to use maximum operating pressure? when we size the thickness, what to use? what 's the difference between piping design and pipeline design?
what's the difference between design pressure and MOP?
As for pipeline tie-in, can I tie in a pipeline with MOP of 9930kPa to a pipeline with MOP 7580kPa? The former line is from a well head with shut in pressure of 6000kPa?
Any reply is appreciated.

 

[BigInch]

Pipeline is a very very very long pipe. It may also be definded by regulatory definition. If it crosses public property, it will probably be a pipeline. Check your code to see if your installation falls within one definition or the other.

Design pressure is the maximum pressure needed to deliver your product during the worst case scenario, plus hydraulic surge pressure, plus safety increase to cover calculation inaccuracies and operational flexibility. It is the pressure that you (or your engineers) will use to "design" the pipe or pipeline.

Theoretically, maximum operating pressure should equal design pressure, but there is a subtile, but legally binding difference. Maximum Allowed Operating Pressure is the (Hydrostatic) Test Pressure divided by the Test Factor. Choose your TEST PRESSURE to yield an MAOP greater than or equal to your DESIGN PRESSURE when using the appropriate test factor. The TEST FACTOR is set by your design code, area classification and/or possibly some other applicable regulation and is typically equal to somewhere in a range between 1.25 and 1.5. See your code for the proper factor. On a pipeline, the test factor may vary from pump or compressor station, line pipe, road crossing, fabricated assembly, uninhabited area, densely inhabited area, etc. all being different.

Choose your wall thickness such that it will reach your design pressure AND allow you to reach your needed test pressure, all such that the resulting MAOP will be >= Design Pressure.

You can tie-in a higher MAOP line to a lower MAOP line. The tie-in must have a Pressure Safety Valve (PSV) and an Emergency Shut Down (ESD) block valve, with those set to never allow pressure greater than the MAOP of the lower pressure pipeline to pass from the high pressure line to the lower pressure line.

With that arrangement, you could operate your high pressure line with high pressure from the well near its inlet, then flow product with the associated pressure loss, to your tie-in point and hopefully reach the lower pressure pipeline close to the MAOP of the lower pressure pipeline. If you reach the tie-in with too much pressure, a pressure control valve may be needed to regulate the HP pipeline discharge into the LP pipeline.

Chances are that you may need all the above at the tie-in in this order.

Hi pressure pipeline outlet to tie-in.
Emergency Shut Down Valve,
Shut when pressure rises higher than Lo Press PL MAOP.
Discharge Pressure Control Valve,
set to Lo Press PL's MAOP
Pressure Safety Valve,
Set to Lo Press Pipeline's MAOP.
block valve to positively close the tie-in and all
connection between the two lines,
Outlet into the Low Pressure Line.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[stonetech]

Thank you so much, BigInch

 

[BigInch]

You can also see my web page "Blog" topic, "Designing a Pipeline".

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com