Use these general instructions to replace a hydraulic cylinder

Safety instructions

Follow the manufacturer's instructions on hydraulic cylinder storage, transport and lifting.

Be careful when lifting heavy loads. Make sure that lifting plates and shackles are properly used. Make sure that the lifting slings are correctly positioned at the lifting point. Make sure that the overhead crane cables pull straight up so that the part to be lifted can not swing and cause a hazardous situation.

WARNING: Crushing hazard and impact hazard. Follow the mill instructions while lifting heavy loads.

WARNING: Crushing hazard and impact hazard. Follow the working methods described in these instructions in order to avoid a crushing hazard and an impact hazard.

Hydraulic cylinder replacement

The following are general replacement instructions for hydraulic cylinders. If there are no detailed instructions in the operating and maintenance manual provided with the equipment or in the hydraulic cylinder manufacturer's instructions, follow the instructions below when replacing a hydraulic cylinder.

Preparative actions

1. Stop the equipment.

WARNING: Unexpected start-up. In order to prevent an unexpected start, the equipment must be in a safe state during maintenance and repair work. Refer to mill safety instructions for maintenance.

2. Ensure that the devices to be maintained and other devices in the maintenance area are in a safe position. If the device has safety latches, the device must be supported by the safety latches. If the device does not have safety latches, set the device into such a position from which it cannot lower or swing due to gravity.

3. If the device still can lower or swing after these measures, control the device into such a position in which the device can be locked in place with blocking or restraining devices.

4. Lower the loads that are supported by hydraulics down or onto mechanical locks so that they do not cause any pressure in the system with their weight.

WARNING: High-pressure fluid ejection hazard. Follow mill maintenance instructions on hydraulics.

5. Turn off the hydraulic pump. Close the shut-off valve in the hydraulic circuit valve cabinet before maintenance. Release the pressure from the circuit before maintenance.

6. Close the shut-off valve for compressed air supply to the valve cabinet before maintenance. Release the pressure from the circuit before maintenance.

WARNING: High-pressure gas ejection hazard. Follow mill maintenance instructions on pneumatics.

7. Disconnect the winder energy sources. Discharge the stored energy.

WARNING: Unexpected start-up. Disconnect the energy sources. Refer to the mill instructions for disconnecting equipment energy sources.

Removal of hydraulic cylinder

1. Lock the device in its place for cylinder replacement. Use lines, chain hoist, or crane to prevent the device from moving during cylinder maintenance.

2. Make sure that the cylinder to be replaced is not pressurized.

3. Measure the hydraulic cylinder assembly dimension.

4. If necessary, remove any covers that could possibly prevent the cylinder replacement.

5. Take the hydraulic cylinder into support. Use lifting equipment that is robust enough considering the lifting method and the load.

NOTE: Make sure that the part to be removed cannot swing and cause a hazardous situation.

6. Detach the hydraulic hoses or hydraulic pipes so that the hydraulic cylinder can be lifted away. Take the hydraulic pipes on support, if necessary.

7. Protect the connection holes of the hydraulic cylinder and the ends of the hydraulic pipes.

8. Dismount the hydraulic cylinder supports.

WARNING: Crushing and impact hazard. Remove the last mounting carefully. If the hydraulic cylinder is not properly supported, the hydraulic cylinder may swing.

9. Lower the cylinder carefully.

Hydraulic cylinder installation

1. Before installation check the following in the hydraulic cylinder.
- The hydraulic cylinder is intended for the place in question.
- The hydraulic cylinder connections are of the correct size and in correct places.
- The hydraulic cylinder seals are of the correct type.
- The hydraulic cylinder end damping is of the correct type.
- The hydraulic cylinder fittings are correct.

2. Clean and lubricate lightly with oil the visible part of the piston rod.

3. If the eye bearing or other parts are to be lubricated afterwards, lubricate the bearings of the fasteners.

4. Adjust the installation measure of the hydraulic cylinder to the value measured above. Lock the eye fastened to the piston rod. If you are not sure about the measure, compare the measured value to the installation measure mentioned in the hydraulic cylinder assembly drawing of the device.

NOTE: The assembly dimension of the old cylinder is usually a good basis for the installation of the new cylinder.

NOTE: If the hydraulic cylinder stroke must be pulled to the other end, remove the protective plugs of the hydraulic cylinder connection holes.

5. If the hydraulic cylinder is equipped with end dampening, adjust the end dampening of the new hydraulic cylinder to be the same as in the old hydraulic cylinder.

6. Check that the hydraulic cylinder connection holes are set in the right direction.

7. Lift the hydraulic cylinder into its place.

8. Fasten the hydraulic cylinder into its place.

9. Tighten the fasteners of the hydraulic cylinder.

10. Remove the remaining protective plugs and guards.

11. Fasten the hydraulic pipes or hydraulic hoses.

12. Remove the lifting equipment from the hydraulic cylinder, if necessary.

13. Remove the device support and restraining carefully.

WARNING: Crushing and impact hazard. Remove the last mounting carefully. If the hydraulic cylinder is not properly supported, the hydraulic cylinder may swing.

Completing actions

1. Fasten the removed guards in their places.

2. Refer to mill instructions on connecting equipment energy sources.

3. If the hydraulic cylinder is equipped with test couplings, connect the a measuring hose with a quick coupling to them and use it to bleed the cylinder. Bleed the hydraulic cylinder by controlling the device into the direction that was used for the last time. Run the hydraulic cylinder repeatedly between home and work position until the movement is smooth and there is no air in the hydraulic system.

4. Adjust the end cushion of the new hydraulic cylinder until the device does not slam at the stroke end any more. Adjustment is sufficient when both sides of the device move synchronized and without a slam to the extreme position.

5. Make sure after a few work cycles that the adjustments stay in their places.

For more information on hydraulic cylinder maintenance and training opportunities, contact your Valmet representative and check out Valmet's Paper Machine Maintenance School.