Digital Hydrostatic Testing
WHAT IS HYDROSTATIC TESTING?
Traditionally speaking, a hydrostatic test, also known as a “hydro test” or “pressure integrity test” is a leak test performed to test the integrity of a pipe, storage tank, pressure vessel, control components or connections (welded, fused or mechanical) of a vessel that will facilitate or store pressure while in service. These tests can be performed on anything from a section of pipe, to the flanges on a valve, or even on the valve itself prior to being put into service. The purpose of these tests is to provide traceable and verifiable pressure data which is then used to monitor and, in some cases, improve safety on new and/or existing pressure systems. Hydrostatics tests are performed at every phase during the life of the vessel, from its point of fabrication, before installation, after installation and then routinely thereafter while in active service.
COMMON APPLICATIONS IN WHICH PRESSURE TESTS ARE REQUIRED
- Installation and maintenance of transmission and distribution pipelines
- Installation of fire water systems (plants, refineries or other)
- Residential gas service installations
- City gate monitoring of incoming pressure
- Installation of new piping systems (oil, gas, water, sewer)
- Fabrication of pipe or storage tanks/vessels
- Sprinkler systems
- Pigging, hot tapping or stopple work
- HDPE pipe replacement
WHY IS IDENTIFYING LEAKAGE IMPORTANT?
Identifying potential leaks is of the upmost importance to ensure the safety and integrity of a pressure vessel or pipeline before and during service. Leakages of any kind can lead to catastrophic incidents involving environmental chemical hazards, injury and in some cases death. These critical tests document the initial integrity of the pressure vessel. Results are then reviewed and signed off on by a third -inspector, clearing the unit under test for service. Hydrostatic tests are also performed regularly once a vessel is put into service as part of The Mega Rule (2020), a federally mandated standard designed to ensure that the integrity of the system does not deteriorate over time. Deterioration caused by rust, corrosion, vibration, tectonic plate movement, overpressure, or other environmental factors can lead to weaknesses in the vessel or vessel’s connections which can cause system failure and injury if not properly monitored and maintained.
HOW ARE HYDROSTATIC TESTS PERFORMED?
There are several different applications for performing hydrostatic tests, however traditionally speaking, these tests are performed by isolating the vessel under test, sealing it off completely, and pressurizing it with water (hydrostatic integrity test) or air/nitrogen (pneumatic integrity test) to 1.5x the rated operating pressure of the vessel. Once pressurized to the appropriate rating as defined by standards and codes laid out by DOT, ANSI, ASME and the state governing bodies, it must maintain that pressure for a predetermined period of time as defined by the applicable standard in use without any significant loss of pressure. The duration of the test as well as the allowable pressure fluctuations can vary greatly by application and are defined within the test operator’s procedures in accordance with the standard being used. Testing requirements such as pressure and duration can also vary depending on the vessel’s material, size, length and environmental factors so it’s important to consult the regulatory guidelines for your application prior to performing any pressure test to ensure compliance. While the vessel is under test, the pressure/temperature can be monitored by using traditional mechanical equipment such as a chart recorder; however, digital hydrostatic testing equipment:
- Reduces equipment and annual maintenance costs
- Increases efficiency without sacrificing stringent requirements needed for third party approval
- Increases reliability and integrity of test results
- Improves documentation retention and traceability
- Simplifies the delivery and storage of test reports via electronic transmission
- Is more robust and easier to transport
- Can record multiple variables simultaneously
WHAT DETERMINES IF A TEST PASSES OR FAILS?
Typically, a hydrotest is considered passable as long as the pressure does not exceed or dip below a set of predetermined pressure ratings, or MAOPs (Min/Max Allowable Operating Pressures). As mentioned above, these MAOPs can vary across different applications, however they serve as a base “threshold” for a pressure test to ensure that the piece of material under test can actually sustain its pressure without interference from outside factors. In other words, the pipe or vessel must hold a stable pressure without an outside operator adding to or removing pressure from the system while on test. As long as the pressure stays within its allowable threshold during the entire duration of the test, it passes. Any consistent and prolonged steady drop in pressure below the minimum allowable threshold defined by the standard in use indicates leakage in the system resulting in a failed test.
There are a couple of instances where pressure manipulation during a test is acceptable and this is why charting temperature along with pressure is so critical. Per Boyle’s Law, pressure and temperature trend together with a constant volume. As temperature rises in an enclosed vessel, so does pressure. Conversely, if temperature decreases, pressure will drop (much like we see with our tire pressures during the first cold snap of the year). Thus, an operator is allowed to “bleed off” or remove pressure from his system during test to prevent overpressure only if the temperature is causing the pressure to rise. The pressure must then stabilize with the temperature and continue trending between the MAOPs. On the opposite end of the spectrum, an operator is allowed a certain number of “strokes” to add pressure to his system in the event that temperature caused a decrease. These strokes are not allowed on every test and must adhere to the approved testing procedure in place.
MECHANICAL vs DIGITAL TESTING METHODS
A mechanical hydrostatic test typically requires five standard pieces of test equipment whereas a digital hydrostatic test may only require one to produce traceable results. This switch alone can lead to very fast return on investment (ROI) in asset maintenance costs alone.
|MECHANICAL HYDROSTATIC TEST EQUIPMENT||DIGITAL HYDROSTATIC TEST EQUIPMENT|
|– Pressure/Temperature Chart Recorder
– Paper Charts & Chart Pens
– Deadweight Tester
– Pressure Relief Valve (optional)
– Hydrostatic Test Pump (optional)
– Ashcroft Analog Pressure Gauge
|– Vaetrix DCR Digital Chart Recorder
– Pressure Relief Valve (optional)
– Hydrostatic Test Pump (optional)
Our Vaetrix division manufactures several products designed to fit all types of hydrostatic and pneumatic pressure testing needs. Get a quote to purchase or rent hydrostatic testing equipment today! Email: [email protected].
We supply hydrostatic and pneumatic pressure testing equipment to all sectors of the oil & gas industry including, but not limited to, pipeline operators, pipeline contractors, fabrication shops, mechanical & maintenance contractors, gas distribution contractors, utility contractors, municipalities and more.