Owner's manual

Series 322 Load Unit Introduction

Load frame The load frame is the basic structure which provides the reaction mass for the

force train. The T-slot base of the load frame is one end of the reaction mass and

the crosshead is the other end of the reaction mass. Installing a specimen and

other fixtures or components between the load unit base and the crosshead create

a force train.

The load frame and the other hydraulic components mounted to it collectively

create the load unit. The base houses the actuators, servovalves, and hydraulic

manifold. The crosshead is mounted above the base by two columns. A control

panel lets you operate the crosshead lifts, locks, and grips to assist in specimen

installation procedures.

Crosshead lifts

and locks

The crosshead can be positioned anywhere along the load frame columns. It is

moved along the column with hydraulic lifts. When the crosshead is in an

appropriate test position, it is hydraulically clamped to that position. This lets

you change the load unit to test specimens of different lengths.

Actuator manifold The 298.XX or 293.XX actuator manifold (also called a hydraulic service

manifold or HSM) acts as the hydraulic interface between the HPU and the

components mounted to the manifold (actuator, servovalves, and accumulators)

of the load unit. It contains the required hydraulic porting and piping to

accommodate the hydraulic components. The manifold can also control the

hydraulic pressure to the load unit.

Actuators The 244 Actuator can be located in the middle of the load unit base or crosshead.

It is a hydraulically powered piston that applies linear displacement of (or load

into) a specimen. It can apply equal power in tension and compression. One end

of the test specimen is installed into a fixture which is mounted to the end of the

actuator rod.

The 215 Rotary Actuator can be mounted with appropriate fixturing to the T-slot

table. The rotary actuator applies angular displacement of (or torque into) a

specimen. It can apply equal power in a cloacwise or counterclockwise direction.

Servovalves The Series 252 Servovalves regulates the direction and flow of the hydraulic

fluid to and from a hydraulic actuator. The servovalve responds to the polarity

and magnitude of the command signal generated by the controller.

Accumulators The Series 111 Accumulators suppress line-pressure fluctuations. The load unit

includes a pressure-line accumulator to provide fluid storage so a constant line

pressure can be maintained at the servovalves for maximum performance. The

return-line accumulator minimizes return-line pressure fluctuations.

Pressure control The load unit can be configured for several pressure configurations. The free

flow configuration passes the hydraulic pressure from the HPU (or hydraulic

service manifold) through the manifold to the hydraulic components. The

hydraulic pressure options include on/off control, high/low/off control, and high/

low/off control with a proportional valve to ramp the pressure transitions.

Transducers The load unit includes a force transducer and an LVDT.