4 Advice to Choose a high pressure test unit

14 Apr.,2024

 

Pressure gauges for 40,000 psi and above are critical for numerous applications where monitoring extremely high system pressures is a required safety precaution. Such gauges must be manufactured so they can withstand the rugged conditions they will be exposed to at these extremely high pressures.

Ultra-high-pressure applications are typically found on pumping systems used to generate flow at extremely high pressures. Your pressure gauge must be able to withstand extreme pulsation and vibration. If it is not manufactured to tolerate such conditions, it can fail and cause damage to your equipment or possibly your operators.

How do you know if your pressure gauge is well-suited for ultra-high pressure?

This article will explain the requirements for a gauge to handle high stresses successfully and what you should consider when selecting a gauge for your process.

Considerations When Selecting Ultra-High-Pressure Gauges

Pressure gauges manufactured for such conditions must be assembled to exacting standards. Only gauges manufactured per ASME B40.100 or EN 837-1 should be considered. Gauges manufactured to these standards must pass fatigue and vibration testing to confirm they are suitable for use.

In addition, the long-term life cycling of the gauge can be enhanced by incorporating a throttling device within the gauge to reduce the hydraulic pressure spikes created by the pump. The design and type of throttling device should be reviewed based on the type of media and whether abrasives may be present, which can clog a throttling device.

The design and manufacture of the bourdon tube system is also an important factor. The design of the tube must be such that it can withstand very high pressures and potential overpressure of the system.

With ultra-high pressures, safety is of the utmost concern. Any pressure gauge used for these ultra-high pressures should always have a solid-front case style.

A solid-front case is designed with a solid internal wall, which has the bourdon tube located toward the rear of the case. In the event of a catastrophic event, the tube will rupture towards the rear and not the front of the case where an operator may be located (see Figure 1 below).

Figure 1: Solid Front Pressure Gauge Operation

 

The process connection is also an important safety consideration. With NPT unable to contain higher pressures, you will need a stronger, better-sealing fitting that's designed specifically for high pressure.

Depending on the level of pressure in your application, there are several types of connections to choose from. In instrumentation, the most common is the 9/16 -18 in. UNF-2B female port for ¼ in. O.D. high-pressure tubing (often designated by the brand reference “Autoclave F-250-C”).

The inlet itself is a simple female straight-thread port, distinguishable by its interior flat bottom with a counter-sunk pressure passage hole in the center (see Figures 2 and 3 below).

Common Ultra-High-Pressure Applications

There are a number of applications that require specialized instruments that are designed to handle ultra-high-pressure environments.

Water Blaster

Water blaster applications use pressurized water to clean. These pressures range from 10,000 to 40,000 psi. Typical applications are:

  • Heat exchanger cleaning

  • Pipe cleaning

  • Tank and pressure vessel cleaning

  • Tank trucks

  • Process line and reactor cleaning

  • Surface preparation and profiling

  • Refractory and rubber lining removal

  • Scales, coatings and epoxy removal

  • Vapor, polymer and resin lines cleaning

  • Paint booth cleaning

Water Jet

These applications present a unique set of challenges in measuring pressure. With high pressures of 35,000 psi and above, coupled with the presence of vibration and pulsation, these applications demand rugged pressure instrumentation.

In these applications, high-pressure water, often mixed with an abrasive, is used to cut a variety of materials such as:

  • Metal

  • Concrete

  • Stone

  • Asphalt

  • Glass

  • Plastic

Ashcroft Ultra-High-Pressure Gauges

Ashcroft offers quality options for ultra-high-pressure gauges. These gauges are specially made to withstand high-stress applications.

1379 Pressure Gauge

The 1379 pressure gauge is manufactured per ASME B40.1 specifications. The gauge has a solid-front, 6-inch dial size and aluminum case. Key features include:

  • Pressure ranges available up to 100,000 psi

  • Micrometer adjustable pointer

  • PLUS!™ Performance option dampens vibration, shock and pulsation effects

T6500 Pressure Gauge

The T6500 pressure gauge is manufactured per EN 837 specifications. The gauge has a solid-front, 100 mm dial size and is available in 304 Stainless steel (standard) or 316 Stainless steel (YW option). Key features include:

  • High pressure up to 100,000 psi (7,000 bar)

  • Solid-front, all-welded, Stainless-steel case

  • Weatherproof protection IP66

  • ATEX approval Ex II 2 GD c

  • Dry, liquid filled or PLUS!™ Performance option

We don’t like to pressure you, but we have more information.

Now that you know what factors to consider when finding a quality ultra-high-pressure gauge, you can research the solution that’s right for you to help keep your process running and your operators safe.    

For more information on pressure gauges, check out some other articles we’ve written:

Feel free to contact us today to talk with one of our experts and get all your measuring instrument questions answered.

You can also download our eBook to learn how to avoid pressure equipment failure:

Pressure tests are a non-destructive way to guarantee the integrity of equipment such as pressure vessels, pipelines, plumbing lines, gas cylinders, boilers and fuel tanks. It is required by the piping codes to confirm that a piping system is able to bear its rated pressure and it has no leaks. Pressure testing, also called hydrostatic testing, is carried out after the cooling or heating installation of any pipeline and before it is put into use.

By performing a pressure test we find a reliable method for testing all types of pipework, including the ones in district cooling or district heating systems. This type of analysis, besides guaranteeing the right functioning, will also allow us to detect if there are leaks in a specific pipe so that reparations can be made.

The most widely used code for pressure and leak test is the ASME B31 Pressure Piping Code. Among its several sections, the requirements and procedures listed in the codes below are followed by Araner:

  • ASME B31.1 Power Piping
  • ASME B31.3 Process Piping
  • ASME B31.5 Refrigeration Piping

Pressure tests may be done either with liquid, usually water (hydrostatic), or with gas, usually dry nitrogen (pneumatic).  

 

General requirements of pressure test

  1. Stress exceeding yield strength: the test pressure may be reduced to the maximum pressure that will not exceed the yield strength at test temperature.
  2. Test fluid expansion: If the test pressure is to be maintained for a period of time and the fluid in the system is subject to thermal expansion, precautions shall be taken to avoid excessive pressure.
  3. Preliminary pneumatic test: a preliminary test using air at no more than 170 kPa (25 psi) gage pressure may be made prior to hydrostatic or pneumatic testing to locate major leaks.
  4. Examination for leaks: a leak test shall be maintained for at least 10 minutes, and all joints and connections shall be examined for leaks.
  5. Heat treatment: Leak tests shall be conducted after any heat treatment has been completed.
  6. Low-test temperature: The possibility of brittle fracture shall be considered when conducting leak tests at metal temperatures near the ductile-brittle transition temperature.
  7. Personnel protection: Suitable precautions in the event of piping system rupture shall be taken to eliminate hazards to personnel in the proximity of lines being tested.
  8. Repairs or additions after leak testing: If repairs or additions are made after the leak test, the affected piping shall be retested.
  9. Test records: Records shall be made of each piping system during the testing, including:
    • Date of test
    • Identification of piping system tested
    • Test fluid
    • Test pressure
    • Certification of results by examiner 

 

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Preparation for testing

  1. Exposure of joints: all joints including welds not previously pressure tested shall be left uninsulated and exposed for examination during the test.
  2. Addition of temporary supports: piping systems designed for vapor or gas shall be provided with additional temporary supports if necessary to support the weight of the test liquid.
  3. Restraint or isolation of expansion joints: expansion joints shall be provided with temporary restraint if required for the additional pressure load under test.

Isolation of equipment and piping not subjected to pressure test: Equipment that is not to be subjected to the pressure test shall be either disconnected from the system or isolated by a blank or similar means.

Figure 1: Isolation of piping

Hydrostatic Test

  1. Test fluid: The fluid shall be water unless there is the possibility of damage due to freezing or to adverse effects of water on the piping or the process. In that case, another non-toxic liquid may be used.
  2. Provision of air vents at high points: Vents shall be provided at high points of the piping system to purge air pockets while system is filling.
  3. Pressure and procedure: The pressure limits are different for ASME B31.1 and ASME B31.3.
   

ASME B31.1 Test Power Piping

The hydrostatic test pressure at any point in the piping system shall not be less than 1.5 times the design pressure, but shall not exceed the maximum allowable test pressure of any non-isolated component, nor shall it exceed the limits of calculated stresses due to occasional loads.

ASME B31.3 Test Process Piping

The test pressure shall be not less than 1.5 times the design pressure. When the design temperature is greater than the test temperature, the minimum pressure shall be calculated by eq.  P T = 1,5P S T/S , where =allowable stress at test temperature, S=allowable stress at component design temperature, P=design gage pressure. The test pressure may be reduced to the maximum pressure that will not exceed the lower of the yield strength or 1.5 times the component ratings at test temperature. The pressure shall be continuously maintained for a minimum time of 10 minutes and may then be reduced to the design pressure and held for such time as may be necessary to conduct the examinations for leakage. Examinations for leakage shall be made of all joints and connections.

 

 

Pneumatic Test

  1. Precautions: Pneumatic testing involves the hazard of released energy stored in compressed gas. Particular care must be taken. It is recommended to be used only when piping systems are so designed that they cannot be filled with water, i.e, refrigerant systems; or when piping systems are to be used in services where traces of the testing medium cannot be tolerated.
  2. Test fluid: The gas used as test fluid, if not air, shall be nonflammable and nontoxic, such as nitrogen.
  3. Pressure and procedure: the pressure limits and methodology is different for the codes mentioned above.

ASME B3.1 Test Power Piping

The pneumatic test pressure shall not be less than 1.2 nor more than 1.5 times the design pressure of the piping system. It shall not exceed the maximum allowable test pressure of any non-isolated component. The pressure in the system shall gradually be increased to not more than 1/2 of the test pressure, after which the pressure shall be increased in steps of approximately 1/10 of the test pressure until the required test pressure is reached. The pressure shall be continuously maintained for a minimum time of 10 min. It shall then be reduced to the lower of design pressure or 100 psig [700 kPa (gage)] and held for such time as may be necessary to conduct the examination for leakage. Examination for leakage by soap bubble or equivalent method shall be made of all joints and connections.

ASME B31.3 Test Process Piping

The test pressure shall not be less than 1.1 times the design pressure and shall not exceed the lower of 1.33 times the design pressure or the pressure that would produce a nominal pressure stress or longitudinal stress in excess of 90 % of the yield stress of any component at the test temperature. The pressure shall be increased until a gage pressure, which is the lower of 0.5 times the test pressure or 170 kPa (25 psi), at which time a preliminary check shall be made. Thereafter, the pressure shall be gradually increased in steps until the pressure is reached, holding the pressure at each step until the piping strains are equalized. The pressure shall then be reduced to the design pressure before examining for leakage. During the test, a pressure relief device shall be provided, having a set pressure not higher than the test pressure plus the lower of 345 kPa (50 psi) or 10% of the test pressure.

 

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ASME B31.5 Test Refrigeration Piping

The test pressure shall be at least 1.1 and shall not exceed 1.3 times the design pressure of any component in the system. The pressure in the system shall be gradually increased to 0.5 times the test pressure, after which the pressure shall be increased in steps of approximately 1/10 of the test pressure until the required test pressure is reached. The test pressure shall be maintained for at least 10 minutes. It may then be reduced to the design pressure and conduct the examination for leakage. During the test, a pressure relief device shall be provided, having a set pressure above the test pressure, but low enough to prevent permanent deformation of any of the system components.

What are the benefits with outsourcing pressure testing?

Working with a company that specializes in heating and cooling services, maintenance and testing is often more beneficial than integrating dedicated personnel inhouse, reducing cost, time, and resources.

Other benefits of outsourcing a pressure test include:

  • Faster turnaround time
  • Increased safety for your staff
  • mproved product quality assurance
  • Decreasing repair costs
  • Minimizing risk exposure and liability claims.

 

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Why is it important to do a pressure test with asme procedure?

Pressure tests carried out according to the asme procedure allow us to guarantee the correct performance of the system and to detect that there are no leaks and that the installation is robust. 

That is why it is important to consider specialised district energy contractors such as Araner. It is essential to work with top-notch, quality-oriented professionals to ensure the safety of the plant.

ARANER, the industrial cooling engineering experts

We are experts in designing, manufacturing and installing tailor-made industrial cooling solutions with a positive economic impact. We have worked worldwide in the development of Turbine Inlet Air Cooling, District Cooling and Thermal Energy Storage. Get in touch with our experts if you are interested in any of our solutions or if you need technical advice. We will be glad to help!    

4 Advice to Choose a high pressure test unit

Pressure Test: Hydrostatic and Pneumatic Test Requirements