Print this pagePipe Damage
Surge pressures commonly cause the highest and lowest pressures that will ever occur in a pipe and hence are the dominant design case and most frequent cause of damage and failure. Typical damage could include:
- Cracked or ruptured pipe
- Weld failures
- Joint failures
- Leaks
- Gasket failures
- Excessive pipe movement
Controlling the surge pressures is one method of reducing system design and test pressures.
In simple terms, there are probably four dominant failure mechanisms caused by surges:
- Excess pressure
- Vacuum collapse
- Fatigue
- Excess bending moments and stress due to movement
One company believes that surge pressures cause over 50% of all leaks!
We see pipe movement especially in process plants and pump stations and this often causes failure. Commonly this is due to rapidly applied forces from surge pressures causing out-of-balance forces that are not suitably supported. The rate of rise of pressure is important in these situations and hence can be exacerbated by vapour problems, NRV and air valve slam.
The output from our surge program is used to quantify the forces that will occur and hence allows pipe designers to specify correct pipe supports.
The surge pressures are the normal design case for all thrust blocks and so these cannot be designed until the surge pressures have been calculated.
Controlling surge pressures can often be a commercially useful way of reducing the costs of pipe supports, thrust blocks and can reduce the test pressure of many systems.
This is useful at design stage, but can be even more beneficial when existing systems are being altered and upgraded and details of original thrust blocks are not known.
