The importance of field pressure testing a Pipeline

The internal field pressure test is done on completed pipeline installations over the completed pipeline or in operational test sections.  The test pressure load should furnish experimental proof of operational safety and not intended to qualify the pressure resistance of components, but rather the joint quality.  The pressure capabilities for components are quantified in the appropriate manufacturing standards.  Usually the pressure test is done with either water or gas (with air or nitrogen). The following comparison shows differences between water and air as a test medium. Water is an incompressible medium which means setting, for example, a 1m PVDF pipe D160 under pressure of 3 bar, results in an energy of 1 Joule. In contrast air is a compressible medium with the same pipe at 3 bar pressure, creates an energy of 5,000 Joules. If there were a failure during the pressure test, the water filled pipe may fly 0.2m high, the air field pipe 110m.  And this with a pressure test of only 3 bar. Thermoplastic materials, including PE and PB, demonstrate a ductile fracture behavior, which means that brittle fracture most likely cannot occur.  Nevertheless, safety precautions must be taken into consideration during the internal pressure test. Georg Fischer literature provides the test pressure for water of 1.5 bar x PN, or 1.3 x PN.  Gas air mixtures of PN maximum 10 bar and compressed air of maximum pressure 1.1 x PN.  It is also recommended to refer to the SDR and pipe wall temperature when calculating the test pressure. The internal pressure test involves both a pre test and main test.  The pre test serves to...

Why does water hammering exist?

The phenomenon of water hammer is generally poorly understood in the water industry. In the home, water hammer may occur when a fast closing solenoid valve such as those found in dishwashers, washing machines, toilets, or fast closing single lever kitchen taps, shuts off water flow too quickly. The result may be heard as a loud bang, repetitive banging (as the shock wave travels back and forth in the plumbing system), or as some shuddering.   Another cause of water hammer may be due to high water pressure on the cold water mains pipe that enters your property. This can be solved by installing a pressure reducing valve or a pressure limiting valve. Loose pipes or insufficiently clipped pipes are another cause as they can rattle inside walls and can often be difficult to access in order to fix.   Noisy pipes and noisy plumbing can sound bad enough through the day but may sound 100 times louder at night when most of the population is in bed sleeping.   Water hammer can cause pipes to burst if a weakness exists in your internal pipe work, however this occurs infrequently (a weakness can often occur if your pipes are corroded or if they have weak joints). Water hammer can also cause pipes to move if they are not well secured – resulting in fatigue cracks or friction holes.   The single most effective thing to do to reduce water hammer is to install the correct pipe in the first place. Polybutylene is ideal for all domestic hot and cold water system as it will absorb and compress sound rather...