205 AND 211 TRACK-TYPE EXCAVATORS Hydraulic Hammer (With Stroke Frequency Adjustment) Caterpillar

Hydraulic Hammer (with stroke frequency adjustment) - Fig WH 217

(1) Hydraulic oil reservoir

(2) Double variable displacement pump

The left hand pump supplies the left hand valve bank and through the pressure balance, the hydraulic hammer.

(3) Pressure balance

Electrohydraulic pilot controlled 3/2-way valve, acting as a flow splitter, the priority flow of which (for hammer operation) is electrically switched "ON" or "OFF". It contains a pressure relief or pressurizing valve in the priority circuit and a check valve protecting the high pressure tank integrated into the hammer against an abrupt discharge.

(4) Control valve bank, left side

(5) Quick release couplings

(6) Hydraulic hammer

(7) Electrical switch for hammer operation (on the instrument panel)

(8) Foot switch for hammer operation (in operator's compartment)

(9) Electrical switch for stroke frequency adjustment (on the instrument panel)

(10) 3/2-way valve for stroke frequency adjustment

(11) Pressure relief valve Adjustment: 180 bar (18 000 kPa)

NOTE: At maximum engine speed, the flow adjustment on the hammer is to be limited to 90 liter/min.

Boom Check Valves Fig. WH 199

NOTE: The boom check or isolating valves, as they are sometimes referenced, are actually a flow control valve in case an oil line in the lift cylinder circuit is broken while the boom is raised.

(1) Left hand valve bank

(A1) Retract boom cylinders(B1) Extend boom cylinders

(2) Right hand valve bank

(A4) Extend boom cylinders (compound circuit)

(3) Sensing device

(1) Extend boom cylinders

(3) Retract boom cylinders

(4) Boom cylinder, left with flange mounted check valve

(5) Boom cylinder, right with flange mounted check valve

(6) Shutoff valve for overload protection device (if equipped.

(7) Pressure switch for overload protection device with gauge connection

(8) Restrictor or orifice

(9) Pilot line going to check valve (see topic, Overload Protection Device)

NOTE: If equipped with a built-in check valve, Item 22 of Hydraulic Circuit Diagram WH 200, boom shutoff valve with restrictor check valve and nonreturn valve, and Item 23, a shutoff valve for emergency lowering of the boom cylinders is omitted.

Item 8, restrictor is absolutely required to make sure, in case of any rupture in the unprotected gauge line from the check valve to pressure switch, Item 7, the oil leakage and, therefore, the lowering speed, is clearly kept below the requirements of preliminary standards.