A sensor, sensor disk, sensor measurement correction system, and method used in measuring a parameter in the refining zone. The sensor includes a spacer that spaces its sensing element from the disk. In one preferred embodiment, the spacer is made of an insulating material that insulates the sensing element from the thermal mass of the disk to prevent the thermal mass from affecting sensor measurement. The sensor includes a housing carried by the spacer that, in turn, carries the sensing element. Where the sensing element is a temperature sensing element, the housing is thermally conductive and the housing and spacer enclose the sensing element. Each sensor is disposed in the refining surface, preferably in its own separate bore in the disk and flush with or below axial refiner bar height. Signals from one or more sensors are processed by a processing device linked to a module containing calibration data that is applied to make sensor measurements more accurate. The module holds calibration data from sensors that are precalibrated before the sensor disk in which they are assembled is shipped, along with the module, to a fiber processing plant where the disk is installed in a refiner and the module connected to the processing device. In one preferred embodiment the sensor or sensors are carried by a sensor module that can be a removable segment of a refiner disk.

A pulp screen cylinder that includes screen media releasably engaged with a frame at spaced locations opposing movement of the media away from the frame during screening. A preferred frame includes a plurality of spaced engaging structures that releasably engage screen media. A preferred frame includes an arrangement of flow windows that are triangular or rhomboid. A preferred method includes producing a frame cylinder by centrifugal casting and machining flow windows using a jet cutting process. A preferred screen media has a plurality of spaced apart engaging structures that each releasably engages the frame at spaced apart locations. A preferred screen media is of wedgewire construction having engaging structure carried by a plurality of spaced wire retaining clips. A preferred clip has vee-shaped rounded slots and an arm thicker than an end wall. A preferred engaging structure includes a projection that has a lip or hook for releasable interlocking engagement.

A system (30) and method for determining stock consistency and for using consistency as a process variable to control some aspect of operation of a refiner (32) used to refine stock. The system includes at least one sensor (70 or 180) from which some refiner characteristic is obtained that is used by a processor (38) in determining consistency. The method uses the characteristic, such as temperature or pressure inside the refiner or in a refining zone (304) of the refiner, along with at least one other refiner parameter in determining consistency. A controller (274) uses the consistency determined in controlling some aspect of refiner operation. In one preferred controller, consistency is compared with a consistency setpoint and adjustments are made to try to converge consistency with the setpoint. The controller can be paused to accommodate other changes made to refiner operation and released when steady state refiner operation is achieved.

A refiner plate for a rotary disk refiner that is adjustable. The refiner plate has a portion of its refining surface that is adjustable relative to some other part. In one preferred embodiment, the refiner plate has a part of its refining surface that can be angularly adjusted relative to some other part of the refining surface. In another preferred embodiment, at least a part of its refining surface is axially displaceable to accommodate changes in the refining gap. To permit a plate to be quickly changed, guides or pistons with generally J-shaped grooves can be used to attach the plate to its mounting surface.