MTS Series 111 Accumulator - Manual (Page 15)

3.3.0 Functional Description
Series 111 Accumulators can reduce fluctuations in hydraulic lines due to sudden changes in hydraulic flow
rate. They also act as a short-term energy source for high-rate tests by providing additional hydraulic flow for
short periods to meet irregular peak demands. Like a capacitor, accumulators filter out pulses in the hydraulic
fluid to provide steady hydraulic pressure.
Accumulators are like a hydraulic version of a capacitor. They are hydro-pneumatic devices located at strategic
points in a hydraulic system. They may be connected to the pressure line and to the return line.
Accumulator
Description Item
Nitrogen Side 1
Piston 2
Fluid Side 3
Hydraulic Fluid 4
Accumulators are precharged with pressure. Precharge pressure is the pressure of the compressed gas
(usually nitrogen) before hydraulic fluid is introduced.
Inserting accumulators into the hydraulic lines permits some fluid to be stored under pressure a short distance
from the servovalve and actuator. This has the effect of keeping fluid in the lines in motion and reducing the
inertia and line restriction considerations. When the servovalve opens and line pressure begins to drop, the
accumulator in the hydraulic service manifold (HSM) immediately supplies part of the fluid volume and
maintains the line pressure. Then, when the servovalve closes, the hydraulic power supply (HPS) recharges
the accumulator, causing fluid in the lines to remain in motion.
The pattern and frequency of the signal that drives the servovalve will have considerable effect on the HSM
accumulator efficiency. Square wave signals, for example, cause a greater demand than sine wave signals
or ramp signals.
Series 111 Accumulator Product Information 15
3.0 Introduction