GB2193349A - Relief/safety valves - Google Patents

Abstract

A system is disclosed for monitoring/testing operation of the servo operation of a pneumatically assisted spring loaded relief and/or safety valve 1 without loss of supplementary valve member closure loading at 3A. This comprises shut off valves FIVA & B, 3 way cock TBB (to which a pump can be fixed), a number of pressure gauges for monitoring operation and a relay valve R35P to which the loading on upper chamber 3A is fed back to assist the biasing force acting in the closing direction of the relay. To ensure valve operation when signalled, but pilot activation fails to remove valve member supplementary loading, such pressure is fed back to the control diaphragm of the regulator supplying servo valve lift assisting pressure thus augmenting it's output pressure by a like amount. These pressures, lift inhibiting, and lift assisting, are equal and self cancelling, each applied to it's opposing actuator chamber. Valve lift assisting servo pressure is controlled by the preset spring loading of it's regulator. The pressure gauges, suitably located, demonstrate pressure changes during simulated servo cycle operations. The system also includes pilot valves 5A and 5B. <IMAGE>

Description

SPECIFICATION A means applied to fluid pressure protected systems to ensure relief and/or safety (R/S) valve preset pneumatic assistance irrespective of preset valve lift inhibiting servo or arbitrary loading bias and to monitor simulated valve servo operation without interruption of valve closing bias This invention relates to double acting pneumatic servo systems having single or dual pilot servo control, both as described under patent number GB 2077393.

Means are added to the basic diagrams in the above patent, so that during 'normal' working conditions within the protected fluid pressure system a preset valve member lift inhibiting servo pressure is fed to the R/S valve actuator upper chamber but at the same time servo pressure is excluded from the actuator lower chamber.

A feed back is taken from the upper chamber to continuously provide an equally modifying pressure output from the lower chamber servo supply regulator to augment the preset valve lift assisting pressure. These two identical opposing pressures are self cancelling when simultaneously fed into their respective actuator chambers. On pilot activation, valve member lift inhibiting loading is exhausted from the upper chamber whilst the valve lift assisting augmenting element is removed from the output of the lower chamber servo supply regulator. Thus, preset valve member lift assistance is provided, a result which also follows when unintentional pressure remains within the upper chamber due to failure of pilot activation to remove it.Also, auxiliary equipment is provided so that servo functional changes may be simulated and observed during normal working pressure conditions in the protected fluid pressure system without disturbing the R/S valve. The following diagrams illustrate the feed back method of cancelling arbitrary R/S valve closing bias and auxilliary equipment to demopstrate simulated servo assisted valve operations; From basic diagram Fig. 1, under patent number GB 20773931 Fig. 1 Servo system with single pilot control, operating single diaphragm on/off relay valves 4A and 4B, the former controlling servo pressure feed preset through regulator R2 to actuator upper chamber, the latter controlling preset servo pressure subject to feed back augmenting control from actuator upper chamber through regulator R3SP, to actuator lower chamber.

Fig. 2 Servo system with single pilot control, with controlled servo pressure fed through regulator R2 direct to actuator upper chamber, so dispensing with relay valve 4A, bypass cocks and associated pressure gauge.

Servo pressure to lower chamber is, as Fig. 1, preset through regulator R3SP, and subject to feed back augmenting control.

From basic diagram Fig. 2, under patent number GB 2077393; Fig. 3 Servo system with dual pilot control operating dual diaphragm on/off relay valves 4C and 4D, the former controlling servo pressure feed preset through regulator R2, the latter controlling preset servo pressure subject to feed back augmenting from actuator upper chamber through regulator R3SP, to actuator lower chamber.

Fig. 4 Servo system with dual pilot control, with controlled servo pressure fed through regulator R2 direct to actuator upper chamber, so dispensing with relay valve 4C, bypass cocks and associated pressure gauge. Servo pressure to lower chamber is, as Fig. 3, preset through regulator R3SP, and subject to feed back augmenting control.

Fig. 5 Sectional view of regulator R3SP on pneumatic servo supply to actuator lower chamber and common to the four servo system line diagrams.

The function of this regulator is to supply controlled servo output to the R/S valve actuator lower chamber 3B, which is at any time the sum (gauge pressures) of the designed valve lift assisting pressure and the valve lift inhibiting pressure in the actuator upper chamber 3A, and operates as follows:The service mains pneumatic supply PSS passes through the control orifice CV and the throttled pressure is transmitted by lower control diaphragm SCD/L to the control spring which is preset at PSA to provide the calculated servo pressure in the actuator lower chamber 3B for required valve lift assistance.

The upper control diaphragm SCD/U is loaded by pressure conditions within the actuator upper chamber referred back through connection SRP to equally influence the regulator output pressure.

An outlet relief valve RV is to discharge excess flow through the regulator at vent V in response to falling pressure within the actuator upper chamber.

The scrap view shows an additional load bearing upper and lower control diaphragm to lessen possible diaphragm failure between servicing.

The referred feed back pressure from the R/S valve actuator upper chamber is equally reflected in the output pressure of the regulator R3SP feeding the lower chamber. These two pressures are self cancelling when simul taneously applied to their respective cham bers. Thus the valve member lift inhibiting conditions (downward) are balanced by an equal lift assisting element (upward), the nett calculated lift assistance being controlled by the regulator preset spring adjustment.

The object of servo operation monitoring is to observe by changes in the readings of pressure gauges in the servo lines to the R/S valve actuator the response of the relay control valves to individual pilot test activation.

These servo changes are not necessarily persued ultimately to the valve actuator chambers, but certain temporary precautions taken in the servo auxiliary controls to prevent R/S valve disturbance, maintaining as far as possible, the constant closure load on the valve member during stable working conditions in the fluid pressure system. These precautions will become obvious as the monitoring processes are described.

Simulated monitoring of servo functioning will minimise the frequency of obligatory R/S valve operational tests, the very nature of which are self destroying to essential valve member sealing function.

Four consistent parametric pressure considerations in an individual servo protected fluid system such as instanced in the opening descriptive paragraphs, are: (1) valve member servo supplementary loading, (2) preset fluid relieving, (3) fluid normal working, (4) servo valve member lift assisting.

Is is to be noted that, during monitoring, she difference between (2) and (3) will present considerable lift inhibiting load to the valve member, which vanishes on actual 'in service' servo operation at the pilot/valve spring set pressure.

In the following text dual pilots are considered as norm and individual pilot activation being common to both single and dual pilot systems, the former system is covered, ignoring any references to 'alternative' pilots.

PILOT ACTIVATION MONITORING PROCE DURES: (a) At pilot/valve spring preset pressure and using external pilot sensing pressure raising means such as test pump.

ISOLATE the selected pilot from the fluid pressure system by closing stop valve FIV on the corresponding connection to the pilot sensing system.

Connect the sensing point at three way valve TP to the discharge of a suitable test pump at TP.

A small manual hydraulic pump unit rated for the duty would be adequate.

Increase the applied pressure until the pilot activates at the set point.

Observe response of the relay valves. Check relay valves involved from diagram used.

If response is satisfactory, slowly reduce the test pressure by venting it to atmosphere at valve TP until the blow down setting of the pilot is reached and the pilot closes down at a few per cent below the fluid system working pressure.

Close external ports at TP and remove test pump.

Reconnect fluid pressure system to tested pilot sensing element by opening stop valve FIV.

Check restoration of initial servo conditions.

During the quoted pilot activation, the 'alternative' pilot remains inactive due to it's set point being above the sensing pressure from the fluid pressure system.

Repeat monitoring process on 'alternative' pilot.

The foregoing means of activating the pilot(s) by means of external sensing pressure application is necessary when monitoring access to the instrument is not permitted. If, however, temporary manipulation of a pilot is permissible during monitoring, the following methods are simple and quickly effected and for which no test pump is required nor modification to the branch connections from the fluid pressure enclosure to the respective pilot sensing element connection. The isolating valves on these lines will then be for emergency use only and not for monitoring. Also three way valve TP may be dispensed with.

(b) Carefully reduce the operational setting of the selected pilot down to the actual obtaining fluid working pressure until pilot activates and relay valves, as diagram used, respond.

On satisfactory response, raising the pilot operating adjustment to the original setting will close the instrument down.

The 'alternative' pilot set at a higher operating pressure than the one under monitoring activation, remains inactive, maintaining a constant servo output to the relay valves.

Each pilot immediately after monitoring, must be restored to it's original pressure setting.

(c) This method involves activating the pilot(s) by carefully lifting the free end of the flapper a few thousandths of an inch from the face of the nozzle, so uncovering the bleed hole and exhausting the pilot output.

This does prove the pneumatic functioning of the instrument and wil serve to monitor the R/S valve simulated operation, however not using the pilot pressure sensing mechanism.

An adjustment of the pressure would not vary appreciably over long periods but should be included in the monitoring process at suitable intervals.

Manipulation of the flapper must not constrain it's mounting nor impair the pneumatic seal normally between nozzle face and corresponding face of flapper.

Again, pilot(s) must be checked before re storing to service.

PNEUMATIC SUPPLIES TO SERVO ASSISTED RELIEF AND/OR SAFETY VALVES. PRESSURE GAUGES SHOWN THUS ( ).

Supplies to pilot(s) through regulators R1 and R4, suitable for pilot instrument and relay valve operation. Servo supplies to actuator determined by R/S valve/actuator sizing and parametric pressure conditions of individual instal lations, Constant pressure preset servo supply (R2G), subject to pilot/relay valve control to actuator upper chamber 3A. Constant pressure preset or augmented servo supply (R3G), subject to pilot/relay valve control to actuator lower chamber 3B. In the following operational descriptions the compatibility of the present Fig. 3 with Fig. 2 under GB 2077393 will be apparent as equipment is identified and the nomenclature followed through.Also, the effect of self regulating compensation for arbitrary retained valve member closure loading will be seen, this device being effective, as in Fig. 4, when supplementary loading is fed continuously to the upper chamber and relay valve 4C dispensed with.

Upper and lower actuator chambers are each fitted with an identical three way valve, 3AT and 3BT respectively, remotely operated by low voltage D.C. solenoid, switched 'in' manually but cut 'out' by readily adjustable automatic delay reset TIMER. Valve internal trim consists of a common port, which, when the solenoid is inactive, connects the chamber to the relay valve. The alternative, with solenoid energised and the valve 'operated', the servo supply port is closed and the chamber is voided to atmosphere through the valve venting port. THESE VALVES ARE NOT OPER ATED UNLESS SPECIFICALLY INDICATED OTHERWISE. In emergency, with both chamber isolating/venting valves simultaneously 'operated', the R/S valve is unrestricted by the actuator and becomes conventionally self operating.Individually operated, the chamber valves can promote servo bias towards, either R/S valve member closure during simulated monitoring, or lift assistance during operational tests during fluid pressure system working pressure conditions.

DURING NORMAL WORKING PRESSURE WITHIN THE PROTECTED FLUID PRESSURE SYSTEM. R/S VALVE CLOSED: Supplementary valve lift inhibiting loading (3AG) in upper chamber 3A, through open ports Z and Y (3ATG) of relay valve 4C and ports Y1/Z2 of diverting cock 4CDC and valve 3AT. Augmented valve lift assisting servo pressure (R3G)withheld from the lower chamber 3B by closed port X of relay valve 4D with ports Y and Z venting chamber to atmosphere (3BTG) and (3BG).

ON DESIGNED VALVE LIFT ASSISTED OPER ATION AT PILOT ACTIVATION AND R/S VALVE PRESET RELIEVING PRESSURE. R/S VALVE OPENS: Relay valve 4C operates-, venting upper chamber 3A to atmosphere (3AG) through ports Y and X, closing servo supply port Z (3ATG). Relay valve 4D operates, augmenting element in output of regulator R3SP has vanished in response to fall in feedback control from upper chamber and preset spring loading servo pressure only is fed through relay valve ports X and Y to the lower chamber 3B, (R3G), (3BTG), and (3BG), and venting port Z is closed.

R/S VALVE CLOSES: When the fluid system pressure falls to the pilot blowdown setting, the pilot closes down, the relay valves revert to their original condition, valve lift assisting pressure is again witheld at port X of relay valve 4D, and lower chamber pressure falls to atmospheric, gauges (3BG) and (3BTG) showing (Zero), supplementary valve member loading is restored to upper chamber, additive to the available closing bias of the valve spring.

VALVE LIFT ASSISTED OPERATION, AS ABOVE, BUT WITH VALVE MEMBER LIFT IN HIBITING LOAD MAINTAINED BY MISCHANCE WITHIN THE ACTUATOR UPPER CHAMBER.

R/S VALVE OPENS: Maintained loading in upper chamber 3A, fed back to the regulator R3SP pressure control diaphragm, augments the servo output (R3G) beyond that determined by the preset spring adjustment. Operation of relay valve 4D closes it's venting port Z and opens ports X and Y to admit augmented servo pressure to lower chamber 3B. The arbitrary maintained pressure is now common to both actuator chambers and is self cancelling, the available valve lift assisting pressure in the lower chamber being that provided by preset spring adjustment of regulator R3SP.

VALVE LIFT ASSISTED OPERATION AT PRE SET DESIGNED RELIEVING PRESSURE SET TING BUT DURING WORKING PRESSURE WITHIN THE FLUID PRESSURE SYSTEM.

There may be mandatory occasion for this test, at intervals between runs of simulated monitoring. It is not appropriate to here discuss combinations of parametric pressures and it is assumed, as illustration, that supplementary loading servo pressure is not less than R/S valve relieving set pressure minus fluid system working pressure. Before activating the servo system, it will be necessary to ensure operation of the R/S valve utilising available means; OPERATE ISOLATING/VENT ING VALVE 3AT, to withold supplementary servo supply to, simultaneously venting upper chamber 3A. (3AG) falls to atmospheric, showing (Zero). Isolate feed back connection SRP from upper chamber to additive loading diaphragm of regulator R3SP at three way cock 3AIC, substituting, at three way cock R21C a pressure connection taken from supplementary pressure servo line (R2G).On induced pilot activation, relay valves operate and, R/S VALVE OPENS: Relay valve 4C servo supply inlet port Z closes and ports Y and X open to exhaust through isolating cock, ports Z2 and Y1, servo pressure trapped between upper chamber valve 3AT and relay valve. (3ATG) falls to atmospheric, (Zero). Relay valve 4D exhaust port Z closes and ports X and Y open to admit augmented valve member lift assisting servo pressure to lower chamber 3B.

Gauges 'R3G), (3BTG) and (3BG) all show augmented assisting pressure. Pilot will automatically close down on active restoration of it's initial (higher than induced) activating setting causing relay valves to revert to their initial condition. However, R/S valve cannot close until the temporary servo system changes made to ensure suitable R/S valve operation have been restored. Therefore on pilot close down:lsolate bled connection from servo supply (R2G) to additive control diaphragm of regulator R3SP at three way cook 3AIC and in it's place restore feed back connection SRP at three way cock 3AIC. Switch off D.C. current at TIMER from solenoid operated valve 3AT on upper chamber 3A, closing venting port and opening port to admit servo pressure to chamber.R/S VALVE CLOSES: Initial servo conditions resumed, as under 'During normal working conditions within the protected fluid pressure system.' In this case as by assumption, the augmenting element in the output of the regulator R3SP is not less than the excess valve member loading due to the R/S valve spring setting over the fluid system working pressure, the effective valve lift assisting pressure is, at least, equal to the preset setting of the regulator spring.

In the foregoing operational cases, complete fluid pressure system relieving cycles are performed, the first two under automatic servo assistance at preset pilot setting level, the third by induced pilot activation during fluid system working pressure conditions.

In the following cases induced pilot activation produces observable relay valves response which demonstrates the efficacy of servo action. This response, as described in GB 2077393 and in examples hitherto, has been fed direct to actuator chambers so as to pneumatically assist R/S valve operation.

Means are now temporarily introduced to maintain a maximum valve member lift inhibiting bias during 'SIMULATED MONITORING', whilst retaining visual demonstration of servo operational changes which would otherwise promote unwanted R/S valve test operation.

SIMULATED MONITORING. Diagram Fig. 3 DURING NORMAL WORKING PRESSURE WITHIN THE PROTECTED FLUID SYSTEM.

R/S VALVE REMAINS CLOSED THROUGHOUT PREPARATION FOR PILOT ACTIVATION (*) A direct servo supply path from regulator R2 to the actuator upper chamber 3A, through the isolating cock 4CIC and Z1-Z2 port of diverting cock 4CDC, maintains the preset supplementary valve member loading. Pilot instigated monitoring operations on the relay valve 4C will be observable on the servo supply fed through it's inlet port Z and extending through port Y to the closed side port Y1 of the diverting cock and which is isolated from the 'direct' servo line to the upper chamber.

Lower chamber ISOLATING/VENTING VALVE 3BT must be 'operated' from 'normal' to isolate servo augmented valve lift assisting pressure from the chamber.

Supplementary supply pressure (R2G) appears in upper chamber (3AG) and in relay valve 4C outlet line Y to Y1, (3ATG).

Augmented valve lift assisting servo supply (R3G) is withheld at the closed inlet port X of relay valve 4D. Gauges between relay valve and lower chamber (3BTG) and (3BG), both show (Zero).

ON INDUCED PILOT ACTIVATION Relay valve 4C responds, closing inlet port Z against servo supply and opening ports Y and X to atmosphere. Response of relay valve demonstrated by simulated fall to (Zero), (3ATG) of supplementary valve lift inhibiting pressure in upper chamber, Supplementary supply pressure, bypassed round relay valve 4C, remains in upper chamber (3AG). Relay valve 4D also responds, closing discharge port Z and opening ports X and Y to pass augmented servo supply as far as the closed inlet port of the lower chamber isolating/venting valve 3BT, as demonstrated on (3BTG). Pressure in lower chamber remains (Zero), shown on (3BG).

RESTORE SYSTEM TO AUTOMATIC CON TROL, FUNDAMENTAL DIAGRAM FIG. 2, GB 2077393.

Close down pilot. Switch off D.C. current from solenoid operated lower chamber valve 3BT at Timer, restoring chamber to normal service. Isolate servo supply bypass round relay valve 4C and open up servo path to upper chamber 3A through relay valve ports Z and Y, thence ports Y1-Z2 of cock 4CDC.

ALTERNATIVE SIMULATED MONITORING(}*) Direct supplementary loading maintained in the actuator upper chamber as ("), above, BUT with lower chamber ISOLATING VALVE 3BT NOT OPERATED, so that, on pilot activation the chamber will serve to function to promote valve member lift assistance. Isolate feed back connection SRP from upper chamber 3A, thereby also venting the additive output control chamber SCD/U of regulator R3SP, Fig. 5, by changeover of three way cock 3AIC, thus limiting the servo supply pressure to that of the preset adjustment.

ON INDUCED PILOT ACTIVATION As before ("), relay valve 4C responds, closing inlet port Z against servo supply and opening ports X and Y to atmosphere. Response of relay valve demonstrated by simulated fall to (Zero), (3ATG) of supplementary valve lift inhibiting pressure in upper chamber.

Relay valve 4D also responds, closing discharge port Z and opening ports X and Y, admitting servo valve lift assisting pressure to the lower chamber 3B, shown on (3BTG) and (3BG). This method reduces the valve lift inhibiting load during simulated monitoring by the amount of spring preset valve lift assistance.

RESTORE SYSTEM TO AUTOMATIC CON TROL, FUNDAMENTAL DIAGRAM FIG. 2 GB 2077393.

Close down pilot. Isolate servo supply bypass round relay valve 4C.and open up servo path to upper chamber 3A through relay valve ports Z and Y, thence ports Y1-Z2 of cock 4CDC. Restore feed back connection SRP at cock 3AIC between upper chamber and regulator R3SP additive control chamber.

SIMULATED MONITORING, DERIVED FROM CASES (*) AND (""), Diagram Fig. 4. DURING NORMAL WORKING PRESSURE WITHIN THE PROTECTED FLUID SYSTEM. R/S VALVE RE MAINS CLOSED THROUGHOUT.

Supplementary pressure is fed continuously directly from regulator R2 to upper chamber 3A, under all servo conditions. Therefore relay valve 4C and its bypass system is dispensed with.

PREPARATION FOR PILOT ACTIVATION (""") Supplementary valve member servo loading pressure already in upper chamber 3A, shown on (3AG) Lower chamber ISOLATING/ VENT ING VALVE 3BT must be 'operated' from 'normal' to isolate servo augmented valve lift assisting pressure from the chamber. Augmented servo output from regulator R3SP is witheld at relay valve 4D closed inlet port X.

Gauges (3BTG) and (3BG) both show (Zero) from relay valve to lower chamber.

ON INDUCED PILOT ACTIVATION No change in maintained supplementary valve member loading in upper chamber, shown on (3AG). Relay valve responds, closing discharge port Z, admitting augmented servo valve lift assisting pressure through ports X and Y, as far as the closed servo supply inlet port of the lower chamber ISO LATING/VENTING VALVE 3BT, where it is witheld from the lower chamber. Gauge (3BTG) shows response of relay valve 4D, and (3BG), showing (Zero), indicates no valve lift assistance. This result is similar to (*) above, the full 'normal' valve member lift inhibiting load being applied during monitoring.

RESTORE SYSTEM TO AUTOMATIC CON TROL Close down pilot. Switch off D.C. current from lower chamber solenoid operated ISOLA TING/VENTING VALVE 3BT, rendering chamber suitable for pressure tight service. Upper chamber shows supplementary valve member loading on (3AG). Lower chamber shows (Zero) pressure on (3BG) and (3BTG) due to relay valve reverting to 'normal' with servo supply port X closed and ports Y and Z open to atmosphere. R/S valve will now function at preset pilot/valve spring adjustment.

ALTERNATIVE SIMULATED MONITORING TO (***) Fig. 4.

Supplementary pressure is fed continuously directly from regulator R2 to upper chamber 3A, under all servo conditions. Therefore, relay valve 4C and it's bypass system is dispensed with.

PREPARATION FOR PILOT ACTIVATION (****) Supplementary valve member servo loading pressure already in upper chamber 3A, shown on (3AG). Lower chamber ISOLATING/VENT ING VALVE 3BT NOT 'operated', so the chamber functions as if to promote valve lift assistance. Isolate feed back connection SRP from upper chamber 3A, thereby also venting the additive control chamber SCD/U of regulator R3SP, Fig. 5 by changeover of three way cock 3AIC, thus limiting the servo supply pressure to that of the preset adjustment.

ON INDUCED PILOT ACTIVATION No change in supplementary valve member loading in upper chamber Relay valve responds, closes discharge port Z, and admits spring preset servo valve lift assisting pressure through ports X and Y to the lower chamber 3B, shown on (3BTG) and (3BG).

This result is similar to (**) above, the full valve member lift inhibiting load being reduced on monitoring by the amount of spring preset valve lift assistance.

RESTORE SYSTEM TO AUTOMATIC CON TROL Close down pilot. Restore feed back connection SRP at cock 3AIC between upper chamber 3A, and regulator R3SP additive control chamber. Upper chamber shows supplementary pressure on (3 AG). Lower chamber shows (Zero) pressure on (3BG) and (3BTG), due to relay valve reverting to 'normal' with servo supply port X closed, and ports Y and Z open to amosphere. R/S valve will now function at preset pilot/valve spring adjustment. Diagram 4 may also be used for R/S VALVE TEST OPERATION during fluid system working pressure conditions: PREPARATION FOR TEST Upper chamber ISOLATING/VENTING VALVE 3AT must be 'operated' by switching on D.C, current to solenoid at Timer, thereby venting the chamber to atmosphere, gauge (3AG) showing (Zero).Supplementary servo pressure is already led to the additive control diaphragm chamber of regulator R3SP. Augmented pressure output from regulator shown on gauge (R3G), witheld at closed inlet port X of relay valve 4D with ports Y and Z venting the lower chamber 3B, gauges (3BG) and (3BTG) showing (Zero).

ON INDUCED PILOT ACTIVATION Relay valve responds, opening inlet port X and closing venting port Z, so admitting augmented valve lift assisting servo pressure to the lower chamber, shown on gauges (3BG) and (3BTG). Pressure in upper chamber remains at (Zero), on (3AG). As the supplementary pressure element in the regulator R3SP output, hence also in the lower chamber, is at least, as great as the excess of the R/S valve spring loading over that of she fluid system pressure, it is clear that the preset spring adjustment of the regulator provides at least minimal power to operate the R/S valve.

TO CLOSE R/S VALVE AND RESTORE SYS TEM TO AUTOMATIC CONTROL Close down pilot. Switch off D.C. current from upper chamber solenoid operated ISOLA TING/VENTING VALVE 3AT at Timer, closing vent to atmosphere and admitting supplementary servo pressure to chamber, shown on (3AG). Relay valve responds to pilot closing down, closing inlet port K against servo supply and venting lower chamber to atmosphere through ports Y and Z, gauges (3BG) and (3BTG) showing (Zero).

The above operational R/S valve test is less detrimental than the use of manual valve member lifting gear which is mandatory on certain fluid applications. Frequency of tests involving breaking of valve member seating seal should be minimal.

Periodic monitoring lends itself to a 'clipboard' style of rapid checking procedure, employing a standard prepared data sheet covering full range of servo operating changes etc., which would be signed and dated to give a record of the immediacy and efficacy of the servo system.

Although pneumatic pressures involved are relatively low and are readily observable, the possibility of leakage across control diaphragms and it's effect should be noted: R/S valve actuator diaphragm, if slight will retard operational changeover, if severe, R/S valve will revert to self operation.

Diaphragms in simple reducing/relief regulators can be replaced 'in situ' very quickly and without shut down. A small spring loaded relief valve in line from each regulator, R2 and R3SP will Prevent any possibility of dangerous pressure build up, whatever the cause. Such a relief valve may be combined with the low pressure alarms R2LA and R3LA.

With respect to relay valves 4C and 4D, leakage across the control diaphragms, de pending upon severity, would tend to servo operate the R/S valve. If either of these must be removed, 4C can be isolated by a direct servo path to the upper chamber 3A through isolating cock 4CIC and diverting cock 4CDC, maintaining supplementary loading on the valve member whilst closing Z and Y1 to the relay valve. Relay valve 4D may be isolated at 4DIC. Control lines from pilot may be isolated at pilot supply valve 0.

The conventional three way cocks shown in the diagrams may be advantageously replaced by 'quick operated', two member, socket and plug couplings, supplied with either both or single member self sealing. The relay valves may be fitted with rapid 'make and break' connections at all pipe entries. Isolating cock 3AIC may be replaced by single member seal socket and plug coupling. The by pass network round relay valve 4C would require a two member self sealing coupling in order to maintain supplementary R/S valve member loading during monitoring. One socket would be located on servo supply line preceding relay valve inlet port Z and one at the otherwise blanked off outlet port Y. A plug member carried on a hose, forming a flexible link between the 'rigid' piping to the upper chamber, being engageable in either of the foregoing sockets.

The former coupling would provide a direct line to the upper chamber, bypassing the relay valve, the latter providing servo supply to the relay valve and thereby automatic control of supplementary valve member loading.

Frequent operational testing of high duty relief and safety valves can be detrimental to valve seating contact surfaces despite rapid and positive pneumatic assistance in valve member opening and closing. A policy of monitoring and simulating the immediacy of R/S valve response whilst maintaining supplementary valve member loading and pressure tightness ensures longer intervals before necessity for operational tests and minimises need for shutting down a fluid pressure system for R/S valve servicing.

1. A means to monitor the efficacy of pneumatic servo assistance applied to conventional relief and/or safety valves by a double acting actuator providing valve member lift inhibition or lift assistance, as directed by pilot(s) activation and as described under patent number GB 2077395: simulated monitoring instigated by induced pilot activation during normal working pressure conditions within the protected fluid pressure system, operational changes in servo pressure that under designed higher pressure conditions would prompt valve member lift assistance, as demonstrated on suitably located pressure gauges, but because of temporary precautions during monitoring, cannot influence the valve member which, under monitoring, remains seated under supplementary loading.

R/S simulated monitoring is showm as the response of the relay valves to pilot activation.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. on gauge (R3G), witheld at closed inlet port X of relay valve 4D with ports Y and Z venting the lower chamber 3B, gauges (3BG) and (3BTG) showing (Zero). ON INDUCED PILOT ACTIVATION Relay valve responds, opening inlet port X and closing venting port Z, so admitting augmented valve lift assisting servo pressure to the lower chamber, shown on gauges (3BG) and (3BTG). Pressure in upper chamber remains at (Zero), on (3AG). As the supplementary pressure element in the regulator R3SP output, hence also in the lower chamber, is at least, as great as the excess of the R/S valve spring loading over that of she fluid system pressure, it is clear that the preset spring adjustment of the regulator provides at least minimal power to operate the R/S valve. TO CLOSE R/S VALVE AND RESTORE SYS TEM TO AUTOMATIC CONTROL Close down pilot. Switch off D.C. current from upper chamber solenoid operated ISOLA TING/VENTING VALVE 3AT at Timer, closing vent to atmosphere and admitting supplementary servo pressure to chamber, shown on (3AG). Relay valve responds to pilot closing down, closing inlet port K against servo supply and venting lower chamber to atmosphere through ports Y and Z, gauges (3BG) and (3BTG) showing (Zero). The above operational R/S valve test is less detrimental than the use of manual valve member lifting gear which is mandatory on certain fluid applications. Frequency of tests involving breaking of valve member seating seal should be minimal. Periodic monitoring lends itself to a 'clipboard' style of rapid checking procedure, employing a standard prepared data sheet covering full range of servo operating changes etc., which would be signed and dated to give a record of the immediacy and efficacy of the servo system. Although pneumatic pressures involved are relatively low and are readily observable, the possibility of leakage across control diaphragms and it's effect should be noted: R/S valve actuator diaphragm, if slight will retard operational changeover, if severe, R/S valve will revert to self operation. Diaphragms in simple reducing/relief regulators can be replaced 'in situ' very quickly and without shut down. A small spring loaded relief valve in line from each regulator, R2 and R3SP will Prevent any possibility of dangerous pressure build up, whatever the cause. Such a relief valve may be combined with the low pressure alarms R2LA and R3LA. With respect to relay valves 4C and 4D, leakage across the control diaphragms, de pending upon severity, would tend to servo operate the R/S valve. If either of these must be removed, 4C can be isolated by a direct servo path to the upper chamber 3A through isolating cock 4CIC and diverting cock 4CDC, maintaining supplementary loading on the valve member whilst closing Z and Y1 to the relay valve. Relay valve 4D may be isolated at 4DIC. Control lines from pilot may be isolated at pilot supply valve 0. The conventional three way cocks shown in the diagrams may be advantageously replaced by 'quick operated', two member, socket and plug couplings, supplied with either both or single member self sealing. The relay valves may be fitted with rapid 'make and break' connections at all pipe entries. Isolating cock 3AIC may be replaced by single member seal socket and plug coupling. The by pass network round relay valve 4C would require a two member self sealing coupling in order to maintain supplementary R/S valve member loading during monitoring. One socket would be located on servo supply line preceding relay valve inlet port Z and one at the otherwise blanked off outlet port Y. A plug member carried on a hose, forming a flexible link between the 'rigid' piping to the upper chamber, being engageable in either of the foregoing sockets. The former coupling would provide a direct line to the upper chamber, bypassing the relay valve, the latter providing servo supply to the relay valve and thereby automatic control of supplementary valve member loading. Frequent operational testing of high duty relief and safety valves can be detrimental to valve seating contact surfaces despite rapid and positive pneumatic assistance in valve member opening and closing. A policy of monitoring and simulating the immediacy of R/S valve response whilst maintaining supplementary valve member loading and pressure tightness ensures longer intervals before necessity for operational tests and minimises need for shutting down a fluid pressure system for R/S valve servicing.

1. A means to monitor the efficacy of pneumatic servo assistance applied to conventional relief and/or safety valves by a double acting actuator providing valve member lift inhibition or lift assistance, as directed by pilot(s) activation and as described under patent number GB 2077395: simulated monitoring instigated by induced pilot activation during normal working pressure conditions within the protected fluid pressure system, operational changes in servo pressure that under designed higher pressure conditions would prompt valve member lift assistance, as demonstrated on suitably located pressure gauges, but because of temporary precautions during monitoring, cannot influence the valve member which, under monitoring, remains seated under supplementary loading.

R/S simulated monitoring is showm as the response of the relay valves to pilot activation.

2. A continuous feedback signal from the

upper chamber valve member closure load to the relevant output pressure control diaphragm of the regulator controlling lift assistance pressure to the lower chamber, creates an equal response in the regulator output additive to a preset spring loading component, on designed pilot activation at R/S valve/pilot 'in service' relieving pressure and supplementary pressure in the upper chamber falling to zero (gauge), the augmenting element in the regulator output vanishes in response, and lift assistance is by preset spring adjustment only, if due to pilot/relay valve misfunction supplementary or arbitrary pressure is not, when intended, voided from the upper chamber, a like augmented servo supply will be fed to the lower chamber from the regulator. These two pressures being self cancelling, lift assistance is by preset spring adjustment,

3. A reducing/relief regulator, having dual control diaphragms, initially spring loading but also accepting an additional pneumatic pressure loading, the output of the regulator being the sum of the two component pressures, the regulator output responding to possible variation in the augmenting pressure control, but in it's absence providing a consistent output at the preset spring controlled pressure,

4. A means to ensure that a double acting pneumatic actuator will operate as designed, independent of pressure conditions within the valve menber loading actuator chamber.

5. A system of monitoring, that by maintaining the (normally) closed valve member pressure tightness under supplementary loading, the need for a fluid pressure system shutdown is minimised.

6. A means as in all the foregoing claims and as illustrated in Figs. 1, 2, 3, 4,