and the system pressure can be maintained withinan acceptable range for long periods of time.Accumulators also compensate for thermalexpansion and contraction of the liquid due tovariations in temperature.A liquid, flowing at a high velocity in a pipewill create a backward surge when stoppedsuddenly by the closing of a valve. This suddenstoppage causes instantaneous pressures two tothree times the operating pressure of the system.These pressures, or shocks, produce objectionalnoise and vibrations which can cause considerabledamage to piping, fittings, and components. Theincorporation of an accumulator enables suchshocks and surges to be absorbed or cushionedby the entrapped gas, thereby reducing theireffects. The accumulator also dampens pressuresurges caused by pulsating delivery from thepump.There are times when hydraulic systemsrequire large volumes of liquid for short periodsof time. This is due to either the operation of largecylinders or the necessity of operating two or morecircuits simultaneously. It is not economical toinstall a pump of such large capacity in the systemfor only intermittent usage, particularly if thereis sufficient time during the working cycle for anaccumulator to store up enough liquid to aid thepump during these peak demands.The energy stored in accumulators maybe alsoused to actuate hydraulically operated units ifnormal hydraulic system failure occurs.Four types of accumulators used in Navyhydraulic systems are as follows:1. Piston type2. Bag or bladder type3. Direct-contact gas-to-fluid type4. Diaphragm typePISTON-TYPE ACCUMULATORSPiston-type accumulators consist of acylindrical body called a barrel, closures on eachend called heads, and an internal piston. Thepiston may be fitted with a tailrod, which extendsthrough one end of the cylinder (fig. 9-5), or itmay not have a tailrod at all (fig. 9-6). In the lattercase, it is referred to as a floating piston.Hydraulic fluid is pumped into one end of thecylinder and the piston is forced toward theopposite end of the cylinder against a captiveFigure 9-6.—Floating piston-type accumulator.9-5
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business
