Description Of Earthquake Simulator Hydraulic Operation

General

The system basically comprises of a power pack and several individual valve stations.

The power pack can be located up to thirty metres away from the machine and is a self contained unit.
Individual valve systems are designed to provide fluid for control of the vertical motion cylinders, horizontal motion cylinders and platform jacking cylinders which are used for the installation of the machine.

Operations (Power Pack)

This unit comprises of the reservoir, motor pump assembly, pressure and return line filtration, no load starting and pump vent valve and heat exchanger.

Referring to the schematic drawing, fluid is drawn into the pump from the 400 litre resovoir. A suction valve is fitted to allow the pump to be removed without draining down the system. A suction strainer is fitted to the pump suction to prevent ingress of particles.

The motor is currently Direct Inline Starting (DIL), but it should be in Star-Delta startup with the pump vent valve being energised on the Delta run mode. Whenever the simulator is stationary for extended length of time this valve should be de-energised.

A pressure gauge is fitted to monitor pump delivery pressure which is 76 Bar (1100psi)

Inside the power unit is a 10 micron nominal pressure filter. The status indicator can be seen from outside the panel but the panel has to be removed to replace the element.

A ball valve is fitted and must be isolated before changing the pressure filter element.

The return filter is a canister type which can be replaced only when the power unit is switched off. The check valve is fitted to hold the positive head of oil preventing it from overflowing the reservoir and cavitating the system.

An electrically operated heat exchanger is included within the system to keep the fluid temperature to 50/55 degrees celsius, fluid tempearture is sensed from the fluid temperature switch installed inside the reservoir.

Operations (Valve Stations)

Vertical Motion

The vertical motion of the simulator is achieved through 21 pairs of cylinders (displacement is 38mm) with each pair operating a floor piece. The cylinders are fitted with self aligning couplings which allow for the horizontal motion.

Each pair of cylinders are driven by a single valve which allows the cylinders to raise or lower by a set amount depending on the input signal duration.

An oriface is included to limit the speed of cylinder movement.

Any number and combinations of the vertical motion cylinders can be energised at once to a maximum of 9 pairs.

On loss of voltage signal the floor pieces will rest at their final position.

Each valve enclosure is connected at each end of the manifold to the hydraulic system to ensure minimal pressure drop and minimum return flow restriction.

Horizontal Motion

Horizontal motion of the earthquake simulator is via two cylinders (displacement is 30mm) These cylinders are driven by a proportional valve, fluid from this valve passes through a dual overcenter valve which gives a controlled deceleration eliminating shocks and sudden jerking from the platform.

The electrical control amplifier for the proportional valve has built in maximum speed control, ramp up/down adjustments.

Hose Connections

All connections are by hydraulic hoses and using JIC 37 flared fittings throughout.

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