US 5,220,843 AGranted

In situ method of determining the thrust on valve components

AssigneePortland General Electric Company

InventorThomas A. Rak

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Abstract

Without disassembling a valve stem from a valve, the valve is decoupled from a valve actuator such that the valve stem and attached valve disc or body may shift to and from a seated position without interference by the actuator. Known loads are applied to the decoupled valve stem to cause a strain gauge output which corresponds to the known load. The strain gauge is mounted to the valve stem or other force reactive components of the valve which react by changing in dimension in response to the applied known load. The relationship of the applied load to the strain gauge output is determined to thereby calibrate the valve stem. The load is removed and the valve stem is recoupled to the valve actuator for operation. From the strain gauge output during either or both static and dynamic operation of the valve, the thrust on the valve stem is directly obtained and is used to evaluate the performance of the valve and actuator.

Claims12

Dependent claims

A method of determining the thrust exerted on the force reactive portions of a valve during movement of a valve body, the valve body being movable to and from a closed position in which the valve body is seated in an associated valve seat and closes a flow path between an inlet and an outlet to the valve, the valve body being coupled to a valve stem and moved to and from the closed position in response to a valve actuator which applied an axial valve actuating force to a portion of the valve stem which is spaced from the valve body, the method comprising the steps of:

positioning a strain gauge on a force reactive portion of the valve, the strain gauge providing an output corresponding to dimensional variations of the force reactive portion of the valve at the location of the strain gauge in response to application of the valve actuating force to the valve stem;
decoupling the valve stem from the valve actuator;
calibrating the strain gauge by applying at least one known test load to the decoupled valve stem without removing the valve stem from the valve and monitoring the output from the strain gauge in response to the known test load;
removing the test load;
recoupling the valve steam to the valve actuator;
monitoring the output from the strain gauge in response to the application of a valve actuating force by the valve actuator.

3 more elements

Dependencies are inferred from the claim text.