Livingston & Haven

United States

Diaphragm accumulators are a cost effective option for numerous functions involving energy storage, shock absorption or pulsation dampening in a hydraulic or fluid system. They are well suited for applications where smaller fluid volumes and flow rates are adequate and that require or involve: Compact designLow weightFlexible mounting positionsExtremely quick shock responseLow costLow lubricity fluids, like waterDiaphragm Accumulators have been successfully applied in both industrial and mobile applications for energy storage, maintaining pressure, leakage compensation, and vehicle hydraulic systems.HYDAC manufactures two types of diaphragm accumulators: Non-repairable (welded)Repairable (threaded)Diaphragm Materials Not all fluids are compatible with every elastomer at all temperatures, therefore, HYDAC offers the following materials: NBR (Standard Nitrile)LT-NBR (Low Temperature Nitrile)ECO 30 (Epichlorohydrin)IIR (Butyl)FPM (Fluorelastomer)others (available upon request)To determine which material is appropriate, always refer to fluid manufacturers recommendation. Corrosion Protection For use with certain aggressive or corrosive fluids, or in a corrosive enviroment, HYDAC offers protective coatings and corrosive resistant materials (i.e. stainless steel) for the parts that interface with the fluid or are exposed to the hostile enviroment. Mounting Position Diaphragm accumulators are designed to mount in any position. In systems where contamination is a problem, we recommend a vertical mount with the fluid port oriented downward. System Mounting HYDAC diaphragm accumulators are designed to be screwed directly onto the system. We also recommend the use of our mounting components, (detailed on page 84) to minimize the risk of failure due to system vibrations Some common applications of diaphragm accumulators are: Agricultural Machinery & EquipmentForestry EquipmentMachine ToolsMining Machinery & EquipmentMobile & Construction EquipmentOff-Road EquipmentFor specific examples of applications using diaphragm accumulators, please see page 89.Construction Both types of diaphragm accumulators have the same basic construction. The difference is in the shell. The welded version has a shell that is electron-beam welded, and therefore cannot be repaired. The threaded type has a shell made up of two halves (top and bottom) which are held together by a threaded locking ring.

Piston Accumulators are a cost effective option for numerous functions involving energy storage, and sometimes shock absorption in a hydraulic or fluid system. They are well suited for applications needing: High Pressure RatiosLarge Volumes of OilHigh Fluid flow ratesVolumes monitoring by way of piston position sensor or switch systemsAdvantages of Using the Low-friction Sealing System (type 2): Minimum frictionSuitable for low pressure differentialsNo start-up friction, no stick-slipLow noise, no vibrationHigh piston speeds up to 12 ftsec continuousImproved accumulator efficiencyHigh life expectancy, low maintance requirementsConstruction HYDAC piston accumulators consist of: A cylinder with a finely finished internal surfaceAn end cap on the gas side and fluid side, sealed with 0-ringsA lightweight metal pistonA variety of sealing systems are available depending on the applicationSealing Systems Precise information about the proposed operating conditions is required in order to select the most appropriate sealing system. Important criteria for this selection are: Number of actuations or cyclesPiston speedTemperature fluctuationOperating fluidCleaniness of fluidMaintenance requirementsSeal Materials The following sealing elastomers are available, depending on the operating conditions: NBR (acrylic nitrile butadiene rubber)FPM (fluoro-elastomer)PUR (polyurethane)Suitable materials are also available for low temperature applications. Fluids The following sealing materials are suitable for the fluids listed below: NBR, resistant to: Mineral Oils (HL and HLP)Non-flammable fluids from groups HFA, HFB, and HFCWater and seawater up to approx. 100CNBR, not resistant to Aromatic hydrocarbonsChlorinated hydrocarbonsAmines and ketonesHydraulic fluids from the HFD GroupsFPM, resistant to: Mineral Oils (HL and HLP)Hydraulic fluids from the HFD GroupsFuels as well as aromatic and chlorinated hydrocarbonsInorganic acids (but not all, please contact HYDAC)System Mounting HYDAC piston accumulators may operate in any position. Vertical installation is preferable with the gas side up. We recommend the use of our mounting components, which are detailed on page 84, to minimize risk of failure due to system vibrations. Effects of Seal Friction The permissible piston velocity depends on the sealing friction. Higher piston velocities are possible where there is less sealing friction. HYDAC piston accumulators with low friction piston seals allow continuous operating velocities of up to 12 ftsec with short bursts, up to 15 ftsec (see type 2 piston). Small pressure differentials between gas and oil side improve the effectiveness of HYDAC piston accumulators. To emphasize the friction effect on the pressure curve during an accumulation cycle, measurements with various sealing systems are illustrated. The measurements graphs below are a true representation of the gas and oil pressure of piston accumulators with different sealing systems. The comparison of these two measurements clearly shows the difference int he pressure differential between gas and oil side: Graph 1: p max. 125 psi Graph 2: p max. 14.5 psi The effect of the sealing friction on the working pressure is particularly striking in traditional piston designs. Abrupt piston movements (the stick-slip effect) are caused by the seal friction as shown in Graph 1. the low sealing friction of HYDAC type 2 pistons drastically reduces the stick-slip effect therefore maximizing piston responsiveness.

Diaphragm type accumulators are used for energy storage, shock and vibration absorption and leakage oil or volume compensation in hydraulic systems. They consist of a pressure-resistant tank (high-tensile steel) whose interior is split into a gas and a fluid side by an elastic diaphragm. When the operating pressure is increased, hydraulic fluid flows into the accumulator and compresses the gas until the gas pressure is identical to the fluid pressure. When the operating pressure is reduced, the gas expands again and, in this way, feeds the hydraulic system with hydraulic fluid. Nominal volume 0.075 to 3.5 litersComponent series 1X and 2XMaximum operating pressure 350 barHydraulic accumulator as per Pressure Equipment Directive 9723ECDiaphragm material for different applicationsUse e.g. as energy storage in intermittent operation systems, energy reserve for emergencies, compensation of leakage losses, shock and vibration absorption

Bladder-type accumulators are used for energy storage, shock and vibration absorption and leakage oil or volume compensation in hydraulic systems. They consist of a seamless pressure vessel (high-tensile steel) whose interior is split into a gas and fluid side by an elastic bladder. When the operating pressure is increased, hydraulic fluid flows into the accumulator and compresses the gas in the bladder until the gas pressure is identical to the fluid pressure. When the operating pressure is reduced, the gas expands again and, in this way, feeds the hydraulic system with hydraulic fluid. Nominal volume 1 50 litersComponent series 4XMaximum operating pressure 350 barHydraulic accumulator as per Pressure Equipment Directive 9723ECBladder material for different applicationsUse e.g. as energy storage in intermittent operation systems, energy reserve for emergencies, compensation of leakage losses, shock and vibration absorption