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[Shailes1982]

Dear All,

 

Refer attached sketch of my system

We intend to do blowdown calculations for the 16" NGL Pipeline ( 2.2 km) through a 3" globe valve. Initially pipeline is 100% liquid filled.

Please note that depressurization/blowdown line tap off connection is located at the bottom of pipeline at the start of 2.2 km pipeline.

We r performing this calculations via Hysis dyanmic depressurisation utilty calculations. However I have following quiries:

1. Can we model this system using "Hysys Depressurization Utility" by considering pipeline as a horizontal vessel with height equal to pipeline length.

2. As blowdown line tap off connection is from bottom of pipe we are expecting some liquid flow at the start of blowdown which will flash through blowdown valve and results in two phase flow . However, dynamic utility predicts 100 % vapor if we select vapor flow equation (under valve parameter) and 100% liquid for liquid flow equations. Please suggest which flow equation we should select under Valve parameter

 

 

Also, Dyanmic depressurisation utilty gives consistent results when for Cv 93 ( 3" globe valve) ( step size 0.05 second)  However, if we reduce the Cv value to 4 ( 3/4" globe valve and step size upto 0.001), some inconsistentency results is taking place, We have tried this system with step size of 0.001second.

Please share your experience related with the same.

 

Please refer to the attached snap shot of the Model Developed for the 16" NGL Pipeline Blowdown system.

 

Intent of the Blowdown operation is to depressurize the 16" NGL 2.2 km long Pipeline (PIPE-100) from upstream of the Pipeline; i.e., manual depressurization of the Pipeline by closing the upstream and downstream valve "XV" and "VLV-100".

 

Please guide us step by step procedure for performing dynamic analysis of the above system.

 

Is the developed model approach correct - i.e., is it possible to have reverse flow through PIPE-100 in the Blowdown scenario?

 

Please guide

 Hysys Pipeline sketch.docx   96.75KB   126 downloads

 sketch.pdf   135.54KB   153 downloads