In piping systems sudden changes in flow cause pressure unbalanced forces between elbows, valves, tees, reducers, and other inline components. These forces damage the piping system when it is not properly designed to accommodate them.
The main advantage of using PASS/START-PROF + PASS/HYDROSYSTEM is that 3D piping model can be easily converted between these software packages both ways.
3D piping model from
PASS/START-PROF can be converted into 3D piping model in PASS/HYDROSYSTEM, then generate 3D water hammer loads for all nodes at certain moments of time (not only just in one node!) and pass it directly into stress analysis software PASS/START-PROF automatically (not manually!).
PASS Suite START-PROF + HYDROSYSTEM allows us to model it very easy, just in several clicks, and help to find a way to reduce water hammer damage of the piping system. Let’s study how to perform stress analysis of the piping system from water hammer loads.
The simple piping system created in PASS/START-PROF software is shown on below screenshot:
After saving the PASS/START-PROF file, we can open it using PASS/HYDROSYSTEM software.
Set pressure 0.15 MPa at node 1, and 0.16 MPa at node 11
Choose water steam library
Define the period of surge analysis 2.5 sec, data output stem 0.01 sec, and dynamic load factor DLF=2.0.
Select Valve in node 12 and in the “Waterhammer” tab set that valve is immediately closed.
Run Isothermal Flow analysis
Run water hammer analysis
After that export unbalanced pressure forces into (.ctpf) file. Also HYSROSYSTEM allows to export data into (.frc) file that can be opened by CAESAR II.
(.ctpf) file contains forces multiplied by DLF factor for all nodes in piping models at several most dangerous moments of time. The most dangerous moments of time is found automatically by HYROSYSTEM software.
This is the (.ctpf) file structure
This means, that PASS/HYDROSYSTEM generates unbalanced pressure loads for all nodes in the piping system at a certain moment of time.
Now open PASS/START-PROF, open Operation Mode Editor and import waterhammer forces into first operating mode.
Eight additional force-based load cases are imported from the file
You can check the force values at any node properties
Now run piping stress analysis and see results
Deformed Shape at any moment of time
Stress table at any moment or time
And maximum stresses from all load cases (static and all moments of time during waterhammer)
The same table can be checked for displacements, support loads, flange leakage, expansion joint deformations, etc.
Watch the following video with detailed analysis process described above:
Some more ready references for you…
Alex Matveev is one of the authors of pipe stress analysis codes GOST 32388-2013 Process Piping, and GOST 55596-2013 District Heating Networks. He is also one of the developers of PASS/Start-Prof software, which is developed since 1965 and used in 95% of process, power, district heating, gas and oil transportation design companies in Russia and CIS countries; it is a standard de facto in that region