GB2095407A

GB2095407A - Valve status indicator

Info

Publication number: GB2095407A
Application number: GB8109130A
Authority: GB
Original assignee: Ferranti PLC
Current assignee: Ferranti International PLC
Priority date: 1981-03-24
Filing date: 1981-03-24
Publication date: 1982-09-29
Also published as: DE3209361A1; NO820949L; FR2502734A1; GB2095407B

Abstract

A valve status indicator for indicating that a gate valve is completely open (or completely closed) to permit the passage of a solid pipeline tool through it, consists of a pick up coil wound on a land formed in the valve body. The coil is positioned near a body face 13 along which an element 12, connected to the valve closure member slides so as to form part of the magnetically permeable core of the coil when the valve is nearly open (or closed). An air gap between a shoulder 12' of the element and the land 16 varies with the position of the closure member and consequential changes in the reactance of the coil, in which an alternating current flows, indicate the extent to which the valve fully opens (or closed). <IMAGE>

Description

SPECIFICATION Valve status indicator This invention relates to valve status indicators for indicating whether a valve is open or closed in response to an operating instruction and in particularto the extent to which the valve is fully opened or fully closed.

Pipeline valves, such as gate valves, are used in undersea oil pipelines and are operated remotely as isolating valves being either fully open, to present no impedance to flow, or completely closed to stop flow. Such valves may be operated to be opened hydraulically against a closing spring which provides a fail-safe system.

Valves may be held in one state for considerable periods of time and any accumulation of debris within the pipe may interfere with the operating mechanism or valve seat to such an extent that when the valve is eventually operated it does not fully open or fully close.

When a valve having a nominally open status is less than fully open problems can arise in passing servicing tools along the pipeline if any such tool becomes jammed.

It is an object of the present invention to provide a valve status indicator capable of indicating the nominal operating status of the valve and the extent of a departure from the nominal.

According to the present invention a valve status indicator comprises a pick-up coil fixed with respect to the valve body and relative to which an element, operably coupled to the valve closure member, moves, said body and said element, in at least one operative state of the valve, forming a magnetically permeable core for the coil whereby the coil reactance varies with the degree of completeness of the core by the element, and a detection circuit responsive to the reactance of the pick-up coil as a function of the completeness of the core to provide an output signal indicative of the position of the element relative to the body.

Preferably the coil is located with respect to the body such that the completeness of the core by the element is between maximum and minimum values for the valve member being completely in the associated operating state.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which: Figure I(aJ is a sectional elevation through a portion of a valve showing the pick-up coil arrangement of the present invention, Figure l {b) is a circuit diagram of the detection circuit used with the pick up coil of Figure 1(a), Figure 2 is a sectional elevation through a portion of a valve showing an alternative pick up coil arrangement, and Figure 3 is a sectional elevation through a portion of a valve showing yet another pick-up coil arrangement.

Referring to Figure 1 a valve, such as a gate valve, has a body made of high permeability ferrogmatic material such as steel, only a section 11 of which is shown. The closure member, or gate, of the valve (not shown) is driven by hydraulic or mechanical means and has an element 12 which connects the drive to the closure member and moves therewith along a face 13 of the body 11. Typically the element 12 may be cylindrical and pass down a bore in the body.

The element 12 is also of a high permeability ferrogmatic material and assumes the position shown when the closure member is 100% open, no part of the closure member intrudes into the pipe.

The element 12 is movable to the left and right of the Figure in accordance with the drive to the valve and is arranged so that shoulder 12' takes up the position 14, indicated by chain dotted lines, when the valve is about 105% open and takes up the position 15, indicated by the broken lines 14, when the valve is 95% open. Upon closing the element 12 moves further to the right.

A pick-up coil 16 is wound around a land 17 formed by cutting a recess 18 in the body 11. The land 17 and coil 16 are located at a position on the body between the element travel positions 14 and 15.

The land 17 and the remainder of the body form a U-sectioned core for the coil having pole faces at the surface 13 of the body. When the valve approaches an open state the element 12 moves to a position at which it forms an extension of the core, the air gap now being between the shoulder 12' and the land 16.

The air gap thus reduces from a maximum when the valve is 95% open to a minimum when the valve is 105% open.

The reactance of the coil 16 depends upon the reluctance of the core which is in function of the air gap in it.

Referring now to Figure 1 (b) which shows the detection circuit 20, this comprises an oscillator 21 producing sinusoidal signals to a bridge circuit 22.

Two arms of the bridge are formed by an inductor 23 and the pick up coil 16 and the other two arms by resistors 24,25. The output of the bridge is fed to a differential input amplifier 26 which provides an indicator signal to output terminal 27.

The bridge is balanced such that the reactance of the coil, varied by the air gap causes a correspondingly varying output signal from the amplifier 26.

The output may thus be calibrated so as to provide not only a signal, which by its presence indicates the valve has responded to an opening instruction, but one whose amplitude demonstrates that the valve has opened completely.

Figure 2 shows an alternative arrangement of the pick up coil in which the recess 18 and land 17 are formed part way along the face 13 of the body not at one end of it. The conductors of the coil 16 are fed by way of a duct 28 drilled in the body.

Figure 3 shows yet another arrangement of the pick-up coil, which is similar to that shown in Figure 1 (a) but in which the coil 16 is wound around a land 30 attached to the body for example by screws, and not formed from the material of the body by making a cavity. This construction permits adaptation of existing valves with little disturbance to the valve and is particularly suited to valves in which only available element shoulder 12' moves clear of the body (as shown).

The exact positioning of the pick up coil on the body is open to wide variations depending on the construction of the valve and only non-detailed parts 11,12 have been shown.

It will be appreciated that the device, or an additional device, could be used to monitor complete closure of the valve, or the taking up of any intermediate position assigned to it.

Claims

1. A valve status indicator comprising a pick-up coil fixed with respect to the valve body and relative to which an element, operably coupled to the valve closure member, moves, said body and said element, in at least one operative state of the valve, forming a magnetically permeable core for the coil whereby the coil reactance varies with the degree of completion of the core by the element, and a detection circuit responsive to the reactance of the pick-up coil as a function of the completeness of the core to provide an output signal indicative of the position of the element relative to the body.

2. A valve status indicator as claimed in claim 1 in which the coil is recessed in a cavity within a face of the body over which the element slides.

3. A valve status indicator as claimed in claim 2 in which the cavity is formed around a land of the body material forming part of the core.

4. A valve status indicator as claimed in any one of claims 1 to 3 in which the coil is located with respect to the body such that the completeness of the core by the element is between maximum and minimum values for the valve member being completely in the associated operating state.

5. A valve status indicator substantially as herein described with reference to and as shown in any one of Figures 1 to 3 of the accompanying drawings.