Pressure testing procedures are key to ensuring the integrity of a wide variety of industrial components and equipment ' including pipes, tanks, pressure vessels, fittings, and more. These tests are vital in both new component manufacturing, during routine maintenance, and quality verification of a component.
For more information, please visit SUNCENTER.
Pressure testing can be done using two different methodologies:: hydrostatic and pneumatic. Hydrostatic tests utilize water as a medium, while the latter uses gas. There are important differences between both, most notably the level of energy released at failure. Let's explore those differences and how we can keep your staff safe under both scenarios.
Hydrotest or hydrostatic testing is typically used for higher pressure components. Although water is most commonly used, other fluids such as oil or hydraulic fluid are sometimes used based on the materials under test and corrosion considerations.
On the other hand, pneumatic testing is regularly used for lower pressure components. Air is commonly used as the test medium, although another gas such as nitrogen can also be used in particular circumstances where low chemical reactivity is desired.
It is important to understand that water or oil are considered to be incompressible under the most reasonable pressures used in pressure testing. This is beneficial in that the test requires less energy to exert the required pressure than if a compressible medium is used. Less energy in means less energy out in the case of a failure.
Because pneumatic tests use a compressible gas, more energy is required to reach the required pressure. This energy is stored in the compressed gas and can be released explosively on failure. For this reason, pneumatic testing represents a significant hazard above and beyond hydrostatic testing. How much of a hazard?
An explosion of 200 ft. of 36 in. pipe containing 500 psi of pressure can create a blast wave nearly equivalent to 80 lb of TNT.
Pneumatic testing is much more dangerous than hydrostatic testing. Pneumatic testing requires higher levels of training, a pressure relief device is mandatory, and a higher safety rating of an enclosure such as TotalShield's Shielding Rooms or Machine Enclosure is needed.
Based on the higher risk associated with pneumatic pressure testing, should hydrostatic testing always be used? Well, not necessarily. Let's look at some of the considerations.
No matter which pressure testing process is used, the safety of your staff should be a top priority. Let's discuss now how to ensure safety during both pressure testing processes.
If you want to learn more about the topic, find here a complete comparison of hydrostatic and pneumatic testing.
In the case of hydrostatic pressure testing, there is a risk of injury from a high-pressure stream of liquid hitting the operator or the possible expulsion of a subcomponent such as a bolt or flange at high velocity. To prevent injury, all test components should be secured to avoid movement under pressure.
These are some hydrotest pressure safety protocols you should follow:
TotalShield manufactures a range of pressure testing blast containment products to add a final level of protection for hydrostatic testing. We can provide blast and impact-resistant Shielding Rooms for testing on larger items or smaller benchtop mounted enclosures for small components.
In either case, we work with the operator of the hydrostatic test to determine likely modes of failure and then calculate the energy associated with the ballistic impact of an ejected subcomponent.
It is critical to analyze the size and mass of every component that might be ejected and then design an enclosure with a margin of safety to contain those ballistic objects. Our engineers can also work with your team to create inlet and outlet ports in the enclosure for test fittings such as fluid hoses and drains.
As we've mentioned before, the risks associated with pneumatic testing are much greater than in a hydrostatic scenario. Like hydrostatic testing, there is the threat that an object will be ejected ballistically. There is also a risk of explosive blast. Put simply, an object under pneumatic pressure becomes a bomb, and at higher pressures, the explosive energies associated with a failure can be catastrophic.
Remember, we are adding significant amounts of energy to the system to compress the gas enough to reach the desired pressure. Upon rupture, that energy is released. This can result in an explosive event that releases a pressure wave and shrapnel and can result in grievous injury or death.
All of the safety precautions mentioned above for hydrostatic testing also apply to pneumatic testing. In addition, a pressure relief device should be considered to any pneumatic testing. These devices can take many forms: a simple plug designed to be ejected above a certain pressure, safety valves, or relief valves can be used.
The training of personnel is also vitally important in pneumatic testing. Only employees who have the required training and experience should be allowed to conduct pneumatic testing.
TotalShield's shield pneumatic pressure testing enclosures are designed with a margin of safety for both ballistic failure and stored energy release in the pneumatic testing scenario. We work with your team to determine the total pressurized volume and total mass of the Unit Under Test (UUT) to ensure that you receive an enclosure certified to keep your staff safe in the event of failure.
For a more complete guide, read our Pneumatic Pressure Testing Handbook blog series.
Both pneumatic and hydrostatic testing play a vital role in manufacturing and maintenance. When done properly, these are safe activities.
Our engineers can help you design a shielding room, shield pressure testing enclosure, or ballistic shielding blanket that will keep your people safe while doing pneumatic and hydrostatic testing.
Are you interested in learning more about pneumatic test rig? Contact us today to secure an expert consultation!
Pressured systems require testing before being newly operational or after a downtime. Non-destructive tests like Pneumatic and Hydrostatic Tests are used to validate such pressurized assemblies and components before they can be functional.
PFC regularly and efficiently performs Pneumatic and Hydrostatic tests of such pressurized systems. These tests are performed on piping and tubing assemblies, valves, gauges, gas cylinders, and other pressure vessels.
It is important to note that these tests are not performed during normal operations, and they also can monitor an already tested system. They only apply to non-operational assemblies and systems.
Hydrostatic or Hydro Testing is a process that uses liquid to pressurized an item for strength and leaks. After shutdown and repairs, a Hydrostatic test is often required to validate that the equipment is prepared to operate under desired conditions once it is returned to service.
A hydrostatic test involves filling an item (component, piping or tanks) with a liquid removing the air contained within it, and then pressurizing the system up to 1.5 times the design pressure limit of the unit. The pressure is held for a particular duration, and then the next step is visual observation. A drop in pressure indicates that there is a leak.
Also, the visual inspection is often enhanced by applying a tracer or fluorescent dye to the liquid to identify cracks and leaks effectively.
A hydrostatic test will expose leak points and notifies about internal or external structural problems with the tank (such as cracks) that might lead to leaks later on.
The 3 widely used hydrostatic testing techniques are CGA, DOT, and ISO -12. CGA is the prime preference in most cases, followed by DOT and then ISO -12.
A pneumatic test uses air, or an inert gas such as nitrogen, to pressurize the system to 110% of its original pressure limit. Then, a holding period is applied for a fixed duration, and the results are monitored to determine the safety and integrity of the system.
A pneumatic test determines the safety capabilities of a pressured system by detecting leaks, understanding maximum capacity, and testing Joint fittings.
Pneumatic tests are necessary to ensure your pressure system's safety, reliability, and leak tightness. So, when a newly installed or repaired pressure system is about to be operational again, a pneumatic test is performed to validate the systems' safety and reliability.
The test also helps understand the limits and capabilities of a pressured system, which are crucial to know before putting any piping into service.
And quite understandably, the test also helps to know that your equipment meets industry qualifications or not.
Pressure tests are mandatory for validating the integrity and safety of pressured systems. While both hydrostatic and pneumatic tests work on the same principle, hydrostatic testing is always preferred first.
Pneumatic testing poses a threat if the pressure is not efficiently controlled. While hydrostatic test uses water or a liquid, the gas in pneumatic testing can be 200 times more potent for the same volume and pressure conditions.
With such higher stored energy levels, the gas from pneumatic testing is more likely to cause damage if mishandled.
Therefore, besides being easy and more accurate, industry standards require contractors to consider hydrostatic testing before proceeding with pneumatic testing.
However, pneumatic testing becomes the only choice in certain conditions such as:
Precision Fabricating and Cleaning has nearly six decades of experience in testing various materials and pressured piping, tubing, valves, and vessels. Our facilities and experienced personnel are capable of handling Pneumatic and Hydrostatic tests up to 30,000 psi.
Our entire workforce is highly trained, understands the importance of accurate testing for safe operations, and performs tests according to CGA, ISO, ASME, ASTM, SAE, and other industry standards.
If you want to learn more, please visit our website pressure bench.