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1. Are Accumulators, Inc. accumulators and components interchangeable with other manufacturers' accumulators?

Yes, Accumulators, Inc. accumulators and components are typically interchangeable with accumulators supplied by other manufacturers. In some cases, standard Accumulators, Inc. parts are of newer design and may not be fully interchangeable; however, we can often provide parts for older and non-standard designs. We maintain an extensive cross-reference of our competitors' products. Contact the Accumulators, Inc. Sales Department for detailed information.

2. Do Accumulators, Inc. pressure vessels meet any type of inspection codes?

Most Accumulators, Inc. units are designed to the strict guidelines of the ASME Boiler and Pressure Vessel Code and are stamped with the "U" symbol and registered with the National Board of Boiler and Pressure Vessel Inspectors. Many other design approvals or authority reviews, such as CE, DNV, ABS, CRN, Lloyds, NR-13, AS1210, etc. are available by request at additional cost. We can also modify existing units under the National Board Inspection Code "R" stamp

3. Does Accumulators, Inc. perform recertification of accumulators?

We can perform a variety of stress tests on in-service accumulators such as hydraulic pressure testing, hydro testing, magnetic particle testing, visual inspection, and ultrasonic testing along with repair and refurbishment of substandard components. Our engineering department can prepare documentation required to meet a third party accumulator recertification standard.

4. What type of testing do Accumulators, Inc. pressure vessels receive?

Most Accumulators, Inc. pressure vessels are subject to ASME specified high-pressure hydro tests, magnetic particle tests, chemical analysis, physical analysis, hardness tests, charpy test analysis, and dimensional inspections. Other tests are available at additional cost.

5. Does Accumulators, Inc. have a quality control program?

Yes, Accumulators, Inc. has an extensive quality control program that is periodically reviewed by local, state, national and international agencies. All code designs, code quality control records, quality control manuals and procedures are open to authorized inspectors.

6. Are certifications and traceability available from Accumulators, Inc. and what is the fee?

ASME U-1A data reports are available upon request at no charge. Certifications, or material certificates appropriate to the respective code(s) are available at additional cost. Shells are traceable to the day of manufacture, bladders to the month of manufacture and other components on a case-by-case basis. All vessels are registered with the National Board of Boiler & Pressure Vessel Inspectors.

7. Are Accumulators, Inc. products covered by any warranties?

Yes, the Accumulators, Inc. product warranty is the strongest in the industry. Contact the Accumulators, Inc. Sales Department for detailed information.

8. What is the proper method of bladder storage?

To obtain the maximum storage life:

  1. Leave the bladder in the black UV bag in which it was shipped.
  2. Store in a closed box and lay flat to avoid folding. If space permits, bladders can be slightly inflated.
  3. Do not expose to light, particularly sunlight or fluorescent lighting.
  4. Avoid extreme temperatures. Optimal storage temperature is 65-70 degrees F.
  5. Avoid dirt, dust, grease, chemicals and fumes.

9. Why use dry nitrogen gas (N2)? Is it safe to use helium?

Nitrogen is a safe, inert, non-explosive gas that is readily available at reasonable costs.


Shop air has oxygen and when exposed to petroleum-based fluids or grease, can diesel (explode) under pressure. Pure oxygen is even more volatile. Other gases are expensive, corrosive or explosive.


Helium has several characteristics that can cause system failures. Gas leakage, explosive thermal expansion and a negative Joule-Thomson coefficient are all causes for major concern. Accumulators, Inc. recommends that only dry nitrogen gas be used to precharge accumulators. Please see our full study on the Usage of Helium in Hydropneumatic Accumulators (.doc) for more information.

Caution! While nitrogen is non-explosive, it is still very dangerous when pressurized

There are several grades of nitrogen gas available. For use in our accumulators, we recommend Commercial/Industrial Grade. This is the most common grade available and the most cost effective. It has been used with accumulators for over 50 years. The average purity is 99.5%. Higher grade gas is, of course, acceptable. The N2 MSDS is available from the factory at no cost.

10. What oil port threads are available?

NPT is standard for bladder accumulators while SAE is standard for piston and diaphragm accumulators. We offer many other thread types and sizes from stock or as a special order, some at additional cost. Contact the Accumulators, Inc. Sales Department for detailed information.

11a. What are the advantages of bladder accumulators over piston accumulators?

  1. Rapid response to pressure changes and work cycle.
  2. Complete separation of gas and fluid.
  3. Highly resistant to fluid contamination.
  4. Low maintenance, trouble-free operation.
  5. Readily available, low cost replacement parts.
  6. Eliminates costly down time on expensive systems due to simple repair.

11b. What are the advantages of piston accumulators versus bladder accumulators?

Piston accumulators are highly-customizable and can handle much larger volumes and higher pressures and temperatures than many bladder accumulators. Additionally, a wider tolerance for the initial precharge setting allows for a higher fluid-to-gas ratio for certain applications.

12. What is the correct pre-charge for an accumulator?

Each application has different pre-charge requirements. Our online Sizing Tool can help calculate the best accumulator precharge for your application. You can also consult the Accumulators, Inc. Service Manual for guidance or contact the Accumulators, Inc. Sales Department for further assistance.

13. How often should the pre-charge be checked while an accumulator is in service?

If the accumulator unit is on a high cycle application it should be checked at least weekly. If the unit is used for emergency standby or pressure holding, it should be checked at least once per month. For remote or difficult to access locations, electronic permanent mount pressure monitoring has many advantages. Contact the Accumulators, Inc. Sales Department for further information.

14. What is the correct way to pre-charge an accumulator?

Consult the instructions listed on the accumulator, shipped with replacement bladder kits and in the Accumulators, Inc. Product Catalog.

Generally: Use an Accumulators, Inc. C&G Assembly and a regulator to slowly pre-charge the unit to 40 psig. This is the most critical part of the pre-charge. Next, you may begin to charge your unit to the pressure required to operate appropriately.

15. What is the proper way to mount an accumulator?

The preferred orientation is vertical; however, a horizontal mounting is acceptable when lubricated properly, with a small loss of efficiency. Accumulators, Inc. recommends bolting the accumulator to a skid unit using approved mounting brackets. We manufacture several acceptable types.

16. Can Accumulators, Inc. make a special accumulator for my application?

Yes. We're experts in "Special Orders" design and manufacture. Among our clientele are Fortune 500 companies, government agencies and the U.S. military. Designs can be proprietary to the customer.

17. When should I use a safety block on my accumulator?

Accumulator safety blocks, or isolation valves, can be used in virtually any application. For absolute safety, there is no better method than the use of a safety block to isolate a charged accumulator. Because an accumulator stores a tremendous amount of power in a relatively small volume, safety blocks are always a smart option for the safety of operation personnel and maintenance technicians. Additionally, safety blocks can eliminate costly system downtime by allowing technicians to remove a single accumulator from a rack without having to shut down the entire manifold.

Our safety block has a full flow design with an integrated 90 degree ball valve, with no loss of flow or added pressure drop.  When the accumulator is isolated from the system, the ball valve is turned off, thus allowing safe discharge of the accumulator fluid either manually or with an optional solenoid dump valve.  Also built into our block is a safety relief valve for maximum system pressure setting.

18. When should I use a burst disc on my accumulator?

Bladder accumulators traditionally do not require the use of a burst disc. Our design uses a homogeneous steel shell free from welds, joints and seams, which provides a high safety factor. Additionally, our bladder accumulators are designed so the fluid port opening(s) in the shell will spread open well below the designed burst pressure, thus extruding the seals and relieving all fluid pressure. Finally, in a bladder accumulator, a rubber bladder normally separates the fluid and the gas. If an excessive high temperature situation occurs, such as a fire, the bladder will melt, thus mixing the gas with the fluid. The melted bladder, mixed with the hydraulic fluid, becomes one media, and as the mixture leaks out the fluid end, there would be no high pressure gas retained.

For those customers that insist on the use of a burst disc with our bladder accumulators, we recommend the use of our transfer barrier design. The gas end of our transfer barrier accumulator allows for additional service ports for pressure monitoring equipment such as a burst disc, pressure gauge and pressure transducer.

Piston accumulators often use burst discs for additional safety due to the fact that the gas and fluid are separated by a metal piston, the housing is not a homogeneous design, and the gas and fluid ports are not able to otherwise relieve pressure in an emergency condition. Our piston accumulators have three main sections; a shell and two end caps. During overpressurization or an abnormal operating condition, if no relief valve or burst disc is installed, the components may fail beyond their safety factor.

19. Does Accumulators, Inc. accept any major credit cards?

We accept most major credit cards.


20. How can I request a quote?

Use our RFQ tool to receive price and availability on any of our products or Contact the Accumulators, Inc. Sales Department.

21. Is Accumulators, Inc. environmentally conscious?

Our manufacturing process produces no pollution and uses only minimal electricity. In addition, we recycle cardboard, office paper, junk mail, glass, plastic and aluminum. Employees are encouraged to bring their recyclables from home as well. We pride ourselves on being Earth-friendly.

phone: 713-465-0202 - fax: 713-468-1618 - email: info@accumulators.com

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