Clearwater Yarder Operator's Manual , Valve Adjustments

Clearwater Yarder Operator's Manual

Valve Adjustments

Adjusting Skyline Brake

The skyline winch brake must be adjusted so it will slip if a high load is accidentally introduced into the skyline cable. The brake should be adjusted so that it will slip when the cable load slightly exceeds the maximum line pull of 7,500 pounds.

Failure to adjust the skyline winch brake properly may result in line loads that overload the cable and may cause it to break. In addition, the excessive load may damage other components.

The following procedure can be used to adjust the skyline winch brake. Follow these steps after the skyline has been adjusted for maximum line pull and the initial brake adjustment has been made in accordance with the wheel motor instructional manual.

Secure all four guylines to adequate anchors and secure the skyline cable to an adequate tailhold. (This adjustment must be performed with all of the cable out except about one half of the first layer on the winch drum.)
With the engine at full throttle and the hydraulic oil temperature at approximately 100° F, move the skyline controller to bring the cable in.
When maximum line pull is obtained, set the brake.
Adjust the brake adjuster screw until the brake starts to slip, then turn the screw to tighten the brake by one notch.
Release the brake and repeat the procedure to make sure that the brake will hold. If it does not, tighten the brake adjuster screw in one-notch increments until it holds. (The brake adjustment is the same as those found on cars with drum brakes.)
The brake should be checked occasionally during normal operation to make sure it will not slip under heavy line load and adjusted as indicated above if necessary. This procedure must be repeated any time the brake adjustment has been changed for any reason.

Pump Actuator Linkage

If any winch drum rotates more than 2 rpm with its controller in neutral, its brake off, and no load on the cable, adjust the linkage (figure 9) between the pump actuator (SLI part PCS-600) and the pump low pressure servo control (Dynapower part 892629). Follow the procedure in the pump actuator installation and service manual.

Drag

The amount of drag for each drag circuit is adjusted initially by opening the low pressure relief valve one-half turn (figure 5). This should give a drag pressure for the mainline and haul-back of approximately 400 psi and can be checked for each system by:

Setting the brake
Setting engine at fast idle
Activating the drag mode switch
Slowly moving the manual controller to bring the line in
Observing the system high pressure gage, and adjusting the low pressure relief valve to give the desired drag pressure (400 psi)

Normally the amount of drag practical will be determined by the load it creates on the engine.

If the engine lugs down considerably when the drag is in use, reduce the drag low pressure relief valve setting slightly.

Circulation

Each circulation system contains a flow control valve (figure 10) in the shifting circuit, and a low pressure relief valve and a flow control valve in the dynamic braking circuit. These reduce the potential for damage to the hydraulic system due to hydraulic slack loads should the system accidentally be shifted from the circulation mode to normal operation while the winch drum is still turning.

Photo of a flow control valve.
Figure10—Typical flow control valve.

The initial setting for the flow control valves in the shifting circuits of the skyline, mainline, and haul back systems is approximately one complete turn open. This should provide a 1-second shifting interval for each system and can be checked by the following procedure:

With the hydraulic system at operating temperature (about 100° F). the engine at idle and the brake set:

Activate the circulation mode; at this time, the hydraulic oil can be heard flowing through the motor valve body.
Deactivate the circulation mode and measure the time that the oil is heard flowing through the motor valve body. This is the shifting interval.
Repeat the procedure and adjust the flow control valve for each system until a 1-second shifting interval is obtained.

The dynamic braking circuit was added to the main pump relief valve section and also contains a flow control valve (figure 10) that controls the amount of time the low pressure relief valve (figure 5) can relieve any high pressure surges that may develop in the system when shifting. This flow control valve should be adjusted for a 3-second dynamic braking interval, and the low pressure relief valve adjusted for a dynamic braking pressure of approximately 800 psi.

In each dynamic braking circuit the initial setting for the flow control valve is one-sixteenth of a turn open. For the low pressure relief valve the setting is approximately one-quarter turn open. Settings can be checked by the following procedures:

Dynamic braking pressure—With the hydraulic system at operating temperature, the engine at fast idle and the brake set:

Activate the circulation mode for a system.
Slowly move the respective controller to the "in" direction until no increase in the high pressure gage reading is observed. Stop movement and hold the controller in this position. This pressure is the dynamic braking pressure.
Adjust the low pressure relief valve to produce a dynamic braking pressure 800 psi, then release the manual controller.

Dynamic braking interval—With the hydraulic system at normal operating temperature, the engine at fast idle, and the brake set:

Activate the circulation mode for a system.
Set the respective controller slightly past the point that causes pressure to reach the dynamic breaking pressure of 800 psi.
Place the circulation mode switch in the "off" position and measure the time between switch off and when the system pressure starts to increase above the dynamic braking pressure. This time is the dynamic braking interval and should be approximately 3 seconds. If it is not, adjust the flow control valve and repeat the procedure.

Skyline Brake Release Interval

The skyline brake hydraulic circuit has a flow control valve that controls the brake release time, and thus the rate at which heavy skyline loads can be released and the energy absorbed by the hydraulic system. This valve regulates oil flow and allows the brake to release slowly. It should be adjusted so there is a 3-second interval between switch off and when the brake is actually released. The initial setting is approximately one-sixteenth of a turn open. To check this setting, use the following procedure:

With the hydraulic system at normal operating temperature, engine at fast idle, and the skyline brake set:

Position the skyline manual controller so the system high pressure gage reads approximately 2,500 psi.
Move the brake switch to the "off" position.
Measure the time from brake switches off until the pressure starts to drop. This is the brake release interval and should be approximately 3 seconds. If it is not, adjust the flow control valve and repeat the procedure.

If a knocking sound is heard in the skyline hydraulic system when the brake is released while the skyline is bearing a heavy load, readjust the flow control valve so that it allows a longer time interval, even if the interval has been set at 3 seconds. Failure to adjust the system properly may result in damage to components in the hydraulic system.