ADVANCED FLUID MECHANICS
48
4:2:1 DIAPHRAGM ACCUMULATOR It consists of two hollow, hemispherical metal sections bolted together at the center. One of the halves has a fitting to attach the unit to the hydraulic system and the other half is provided with an air valve for charging the unit with compressed air or nitrogen. Mounted between the two halves is a synthetic rubber diaphragm that divides the accumulator into two sections. The accumulator is initially charged with air through the air valve forces the diaphragm upward against the inner surface of the upper section of the accumulator. When the system pressure is down and when additional oil is required in the hydraulic circuit, the gas expands, the oil from the accumulator is forced into the system to make up the pressure drop in the system. A shutoff button, which is secured at the base of the diaphragm, covers the inlet of the line connection when the diaphragm is fully stretched. Because of its small weight- to volume ratio, it is used exclusively for mobile applications. The restriction is on the deflection of the diaphragm.
Fig. 4.1 Diaphragm accumulator 4:2:2 SPRING LOADED ACCUMULATOR A spring loaded accumulator is similar to the weight – loaded type except that the piston is preloaded with a spring which is the source of energy that acts against the piston, forcing the fluid into the hydraulic system. The pressure generated by this type of accumulator depends on the size and preloading of the spring. In addition, the pressure exerted on the fluid is not a constant. The spring- loaded accumulator typically delivers a relatively small volume of oil at low pressures. Thus, they tend to be heavy and large for high- pressure, large –volume systems. This type of accumulator should not be used for applications requiring high cycle rates because the spring will fatigue and lose its elasticity. The load characteristics of a spring are such that the energy storage depends on the force required to compress the spring. Uncompressed length of a spring represents zero energy storage. As a spring is compressed to the maximum installed length, a minimum pressure value of the liquid in a ram assembly is established.
FOR MORE DETAILS VISIT US ON WWW.IMTSINTITUTE.COM OR CALL ON +91-9999554621