Page 13 - Troubleshooting Paper Mill Hydraulics Sample Excerpt 2

No. 3 P.M. Winder Power Supply and Rider Roll

18 Proportional Regulator

This regulator converts a 4-20 milliamp signal into a proportional air
pressure. The air pressure is applied to the No.17 valve’s pilot port.
The No.14 valve will energize when winding paper which directs oil
from the pilot port of the No.13 reducing valve to the inlet port of the
valve No.17. Once the hydraulic pressure overcomes the air
pressure, the No.17 valve will shift open. The pressure downstream
of No.13 will shift the No.13 spool allowing only enough oil through to
maintain the pressure required to hold valve No.17 in the open
position. When initially winding the paper, a higher pressure will be
directed to the cylinders permitting a higher nip force of the Rider Roll
on the core. As the paper is wound, the pressure to the cylinders will
gradually drop, which reduces the nip force exerted by the Rider Roll.
The PT1 pressure transducer converts the pressure directed to the
full piston sides of the cylinders into an electrical signal. The machine
controller is programmed to maintain a desired nip force on the roll as
the paper is wound. Once the pressure transducer indicates that the
desired pressure has been reached, the current to the no.18 coil will
be controlled to allow only enough oil through the no.13 valve to
maintain the desired pressure.

19 Air Regulator

This regulator is used to supply air pressure to the no.18 electrically
controlled regulator.

20 Pressure Reducing Relieving Valve

This valve will reduce the system pressure down in the rod sides of
the Rider Roll cylinders to the setting of the valve spring. The spool
will shift between fully open and fully closed allowing only enough oil
flow through the valve to maintain the spring setting. If the pressure
exceeds the spring setting, the valve will shift into the relieving mode.
The pressure will be ported back to the tank through the valve spool
until it drops once again to the spring setting.

Troubleshooting Papermill Hydraulics Page 43