Method in the hydraulic roll control system of a papermaking machine or the like and a multipressure hydraulic roll control system

A method for use in the hydraulic roll control system of a papermaking machine comprising the steps of:

• pumping oil with a first pump from a single reservoir to a first pressure;
• passing the oil at the first pressure through a filter and a heat exchanger and lubricating a plurality of roll bearings and a gearboxes, also supplying oil which is passed through the filter and the heat exchanger to a second pump at a regulated pressure of 20 bar to 30 bar;
• and
• raising the pressure of the oil supplied to the second pump to on the order of 80 bar by means of the pump, and supplying oil at a pressure of on the order of 80 bar, to a plurality of crown-compensated rolls.

A multipressure system for hydraulic roll control in a papermaking machine, comprising:

• an oil tank having a single compartment;
• at least one low pressure pump which draws oil from the oil tank compartment;
• a first manifold carrying oil from the at least one low pressure pump to a plurality of points of service, the points of service including a plurality of roll bearing lubrications or drive gearbox lubrications;
• at least one high pressure pump connected to receive oil from the at least one low pressure pump and to elevate the pressure of the oil received therefrom, oil being delivered from the high pressure pump to pressure-loaded zones of a hydraulic roll;
• at least one pressure regulator positioned between the at least one low pressure pump and the oil tank to regulate oil pressure supplied to the high-pressure pump to between 20 bar and 30 bar;
• and
• at least one filter and at least one cooler positioned after the at least one low pressure pump and before the at least one high pressure pump, and wherein oil from the points of service is arranged to pass back to the oil tank, wherein the multipressure system is implemented as a single low-pressure circuit and wherein oil flows directly to the points of service essentially at the line pressure of the low-pressure circuit or at a pressure level higher than that of the primary circuit by virtue of stepwise elevating the line pressure with the help of the at least one high-pressure pump.