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Accumulators & Reservoirs

Accumulators (sometimes called reservoirs) are an integral part of most pumped fluid systems. These important devices provide two primary functions:
  • Expansion volume to accommodate changes in fluid density over a wide temperature range
  • Positive fluid inlet pressure to ensure optimum performance of the system pump

PDT provides accumulators in a wide variety of configurations for use in fluid cooling systems and hydraulic power systems. Our accumulators provide maintenance free operation in harsh environments ranging from high performance military fighter aircraft to high-altitude, long duration unmanned surveillance aircraft to robotic vehicles operating on Mars. PDT designs and manufactures accumulators suitable for use with a wide variety of fluids including water/glycol, hydraulic oil, refrigerants and dielectric coolants.

PDT accumulators are offered in two basic configurations: piston and bellows. The piston accumulator has a moveable element supported by elastomeric seals. In many units, a coil spring provides the force necessary to ensure fluid pressurization over the operating range of the accumulator. In other cases, the piston is pressurized by a regulated external gas source. Piston accumulators provide many years of reliable service at an attractive price point.

For extreme environments, or in systems that have zero tolerance for leakage, a welded metal bellows is used in lieu of the piston. For this configuration, the piston is replaced by a flexible bellows capsule that has no elastomeric seals to wear out. A sealed gas charge on one side of the bellows provides the stored energy to pressurize the system fluid. Flexible metal bellows are designed for millions of operating cycles and typically last the life of the vehicle in which they are installed.

PDT is also expert in the unique requirements of the self-pressurizing or “bootstrap” accumulator. In this configuration, a high-pressure source acts on one end of dual-area piston; the other side of the piston is in contact with the low-pressure fluid. Based on the area ratio between the two sides of the piston, a pressure multiplication effect is achieved which provides fluid pressurization without the need for springs or a sealed gas charge. An additional benefit of the bootstrap configuration is that once the high-pressure source is removed, no residual pressure remains on the fluid system which enhances safety and facilitates system maintenance.

Accumulators provide an ideal location to incorporate fluid level sensing instrumentation for the cooling or hydraulic system. PDT can provide electronic fluid level sensors with scaled electrical output, visual indicators or both features in the same unit.

Accumulator design is dependent upon a few key variables:
  • Fluid selection
  • Operating and storage temperature range
  • Desired pressure output (typically driven by pump selection)
  • Total volume of system fluid
  • Level sensing requirements

PDT uses these inputs, along with information about the system and/or vehicle application, to select the optimum accumulator for each installation. As an expert in centrifugal and positive displacement pumps, PDT is well equipped to design and supply the appropriate accumulator for your pumped fluid system, even if we did not provide the pump. Contact a PDT application engineer to determine the optimum accumulator solution for your system’s needs.

Download Product Literature on Bootstrap Reservoirs

Download Product Literature on High Pressure Bootstrap Reservoirs