GB2129167A - Valve system - Google Patents

Abstract

The present invention relates to a pneumatic valve system for controlling a gas-holder cut-off valve, preferably of the diaphragm operated type which is electrically controlled by strikers on the gas-holder. The system comprises six auxiliary pilot valves 41, 42, 43, 44, 45 and 46 which are of the spring-loaded, diaphragm-type pneumatically actuated valve type. Valves 41, 44 and 45 are normally open while valves 42, 43 and 45 are normally closed. The pneumatic lines comprise lines 65, 65a, 65b, while lines 63 and 67 are connected to atmosphere. Solenoid switch 56 switches line 59 between lines 63 and 65a while solenoid switch 57 switches line 61 between lines 67 and 65b. The valves are arranged to actuate the holder cut-off valve 20 in a predetermined sequence. <IMAGE>

Description

SPECIFICATION Valve system The present invention realtes to a valve system for controlling a gas-holder cut-off valve particularly a cut-off valve of the traditional diaphrahm operated type.

Figure 1 shows a sectional view of a typical diaphragm-operated gas-holder cut-off valve (HCV) shown in the closed position with the valves 1 and 2 of the HCV situated within the valve body 3 and resting on their respective seats 4 and 5 against which the valves 1 and 2 form a seal.

The valves 1 and 2 are attached to the lower end of the main spindle 6. The spindle 6 extends upwardly through the valve body 3 and through the diaphragm chamber 7. The main diaphragm 8 is attached to the main spindle 6 at the point where the spindle 6 passes through the centre of the main diaphram 8. The main spindle 6 extends upwardly to protrude through the top of the main diaphragm chamber casing 9 where it is connected to the inner end of a counter-balance lever 10. The main diaphram chamber 7 is divided by the main diaphragm 8 into two separate chambers 11 and 12, one chamber 11 being above the diaphragm 8 and the other below it. The chamber 7 is closed at its lower end by the auxiliary diaphram 1 3 through the centre of which the main spindle 6 passes and is attached thereto.

The upper and lower chambers 11 and 12 respectively have gas tight seals which separate them from each other, from the atmosphere and from the valve body 3. Gas can be passed independently into and out of the upper and lower chamber 11 and 12 by way of pipework 14 and 1 5.

In use the HCV is situated in the pipe 1 6 which forms the common main 1 7 and the gas holder inlet/outlet 18.

To open the HCV it is necessary to raise the valves 1 and 2 vertically off their seats 4 and 5 to expose the orifices which allow the passage of gas through the valve body 3 in either direction. To raise the valves 1 and 2 off their seats 4 and 5 there must be a force acting upwardly on the main spindle 6.

This force must be of a sufficient value to overcome the combined weight of the valves 1 and 2 and the main spindle 6.

Such a force may be achieved by the application of gas pressure into the lower diaphragm chamber 1 2 in order to create a positive differential pressure between the upper and lower faces of the main diaphragm 8. This positive differential pressure must be of sufficient magnitude to provide an upwardly acting force to overcome the combined weight of the valves and spindle assembly. The HCV is however provided with a counter-balance lever 10 which has a weight carrier 1 9 attached to its outer end and weights can be loaded onto the carrier in order to counter balance the weight of the valves and spindle assembly. This is necessary in practice because the weight of the valves and spindle assembly is high in relation to the area of the main diaphram 8.If counter balance weights were not provided then the gas pressure required to lift the main diaphragm 8 and thus open the valves 1 and 2 would be impractically high. The practice of counter weight balancing is commonly referred to as "weight loading". In practice HCVs are weight loaded to a pressure of approximately one half inch water gauge.

This means that with equal gas pressures in the lower and upper diaphragm chambers 11 and 12, the HCV will be closed because the downward acting force produced by the weight of the valves and spindle assembly is greater than the downward acting force produced by the weight loading attached to the opposite end of the counter balance lever 1 0. To open the HCV therefore gas must be applied to the lower diagphragm chamber 1 2 at a pressure of at least one half inch water gauge higher than the gas pressure applied to the upper diaphragm chamber 11.

Conventionally HCV' are operated by means of pneumatic valves which are mechanically actuated by the movement of the gas-holder during its filling and emptying cycles. Figures 2 to 5 are schematic diagrams showing an HCV 20 located between a common main 1 7 and the gas holder inlet/outlet 1 8 with a pair of pneumatic valves A and B arranged to control the HCV 20 by means of auxiliary pipework 21, 22, 23, 24 and 25. Pipework 21 connects the upper chamber 11 of the HCV chamber 7 to the valve A, pipework 22 connects valve A to valve B, pipework 23 connects the common main 17 to the valve B, pipework 24 connects the holder inlet/outlet 1 8 to the valve B and pipework 25 connects the low chamber 12 of the HCV chamber 7 to the valve B.

Valves A and B conventionally take the form of rotating-cock valves which are mechanically actuated in the manner schematically shown in Figure 6. In practice valve A is a rotating three-way valve which in use takes up one of two positions depending on the position of the three radial arms or levers 11, 12 and 13. The valve A either connects pipework 21 to pipework 22 as shown in Figures 2 and 5 or it connects pipework 21 and therefore the upper diaphragm chamber 11 to atmosphere as shown in Figures 3 and 4.

Valve B is a rotating four-way valve which is in use also takes up to one of two positions depending on the position of the two radial levers 14 and 15. In one position shown in Figures 2 and 3, the valve B connects the pipework 24 and hence the holder inlet/outlet 1 8 to the pipework 25 and therefore to the lower diaphragm chamber 12 as well as connecting the pipework 23 and therefore the common main 1 7 to the pipework 22. Alternatively as shown in Figures 4 and 5 the valve B connects the pipework 24 and therefore the holder inlet/outlet 1 8 to the pipework 22 as well as connecting the pipework 23 and hence the common main 17 to the pipework 25 and therefore to the lower diaphragm chamber 12.

Valve A is actuated to change position by means of two spaced striker plates S, and S2 (see Figure 6), which are mounted on the shell of the gas-holder. As the gas-holder moves down from its high position to its low position during emptying and up from its low to high position during filling these plates Sa and S2 sequentially strike one of the levers It, 12, 13 to cause them to rotate and change position so actuating valve A.

Similarly valve B is actuated to change position by means of one striker plate S3 (see Figure 6) mounted on tye shell of the gas holder between plates S1 and S2. As the holder moves down and up respectivley upon emptying and filling the plate S3 strikes one of the levers 14 and i5 to cause it to rotate and change the position of the valve B.

Referring to Figures 2 to 5 and Figure 6 (which shows the positions of the striker plates and levers during the entire emptying and filling sequence), Figure 2 shows the position of the valves A and B with the HCV 20 closed when the gas holder is at the normal high (full) position. The anaiogous position of the striker plate S, and the levers It to 13 and 14 and 15 is shown in position (a) Figure 6.

In Figure 2, the lower diaphragm chamber 1 2 is connected via a valve B to the holder inlet/outlet 1 8. Therefore, if the pressure in the common main 1 7 falls below the pressure in the holder 1 8 by an amount exceeding the preset weight loading i.e. one half inch water gauge a positive differential pressure will be created between the lower diaphragm chamber 1 2 and the upper diaphragm chamber 11 causing the HCV 20 to open. At this stage the HCV 20 will only remain open as long as the pressure in the common main 1 7 remains lower than the holder pressure.If the pressure in the common main 17 rises again to the same value or greater than the holder pressure then the positive differential pressure between the diaphragm chambers 12 and 11 will cease to exist and the HCV 20 will close. By this means the holder is protected from being overfilled. If the positive pressure differential is maintained the HCV 20 will remain open and gas will be removed from the holder to the common main 18 and the holder will lose height. As the holder loses height, the striker plate S1 shown in Figure 6 will move from position (a) to position (b) thereby striking lever Ii and rotating it to the position shown in Figure 6.

To simplify matters the holder is assumed to be a conventional three-section spiral type holder so that as shown in Figure 6 the striker plates move at an angle of approximately 450 to the vertical. Rotation of the lever 1, will actuate the valve A and move it into the position shown in Figure 3.

In Figure 3 valve A now connects the upper diaphragm chamber 11 to atmosphere while the lower diaphragm chamber 1 2 remains connected to the holder inlet/outlet 18. Since holder pressure is always higher than atmospheric pressure by a figure in excess of one half inch water gauge, the HCV 20 will now remain open regardless of the pressure differential between the common main 1 7 and the holder inlet/outlet 18. The HCV 20 will remain open in this manner as long as the holder is between normal high (full) and low (empty) limits.

As the holder continues to lose height due to escape of gas the striker plate S3 shown in Figure 6 will move from position (b) to position (c) thereby striking the lever 14 of valve B and rotating it to the position 3 in Figure 6. This will rotate the valve B to the position shown in Figure 4.

In Figure 4 valve A still connects the upper diaphragm chamber 11 to atmosphere but now the commom main 1 7 rather than the holder is connected to the lower diaphragm chamber 1 2 by way of the valve B. Nevertheless since the pressure in the common main 1 7 is always greater than atmosphereic pressure by at least one half inch water gauge, the differential pressure between the lower chamber 12 and the upper chamber 11 will be maintained to maintain the HCV 20 open. The HCV 20 will remain open as long as the holder is between the normal high and low limits.

As the holder continues to descend with the continuing removal of gas the striker plate S2 shown in Figure 6 moves from the position (c) to position (d) thereby striking lever 13 and rotating it to position (d) in Figure 6. This causes valve A to rotate to the position shown in Figure 5 in which the holder has now reached its normal low position.

In Figure 5, the upper diaphragm chamber 11 is now connected to the holder inlet/outlet 18 while the lower diaphragm chamber 12 is connected to the common main 1 7. This will cause the hitherto positive differential pressure between the lower diaphram chamber 12 and the upper diaphram chamber 11 to be reversed and the HCV 20 will close.

The HCV 20 will remain closed until the pressure in the common main 1 7 rises above the pressure in the holder by an amount exceeding the weight loading i.e. one half inch water gauge. This will cause a positive differential pressure to be created between the lower and upper diaphragm chambers 12 and 11 and the HCV 20 will open. At this stage the HCV 20 will only remain open as long as the pressure in the common main 1 7 remains higher than the holder pressure by at least one half inch water gauge. If the pressure in the common main 1 7 falls to the same level as, or lower than the holder pressure then the positive differential pressure between the lower and upper diaphragm chambers 12 and 11 will cease to exist and the HCV 20 will close. By this means the holder is protected from being taken below the normal low (empty) position. If however, the positive differential is maintained the HCV 20 will remain open and gas will pass into the holder from the commom main 1 7 causing it to gain height as it fills with gas. As the holder starts to gain height the striker plate S2 moves from the position (e) in Figure 6 (which is the same as position (d)) to the position (f) in Figure 6 so that lever 12 is struck by the plate S2 and rotated to position (f). This causes valve A to rotate once again to the position shown in Figure 4.

This will cause the upper diaphragm chamber 11 to be connected to atmosphere by way of valve A while the lower diaphragm chamber 12 is connected to the common main 1 7. The HCV 20 will remain open regardless of the pressure differential between the common main 1 7 and the holder since the pressure in the common main 1 7 is always higher than atmospheric pressure by at least one half inch water gauge. The HCV 20 will remain open as long as the holder is between its normal high (full) and low (empty) limits.

As the holder continues to gain height with the infusion gas, the striker plate S3 moves from position (f) in Figure 6 to position (g). The plate S3 strikes the lever i5 of valve B and rotates it to position (g) in Figure 6. Valve B rotates to the position shown in Figure 3.

In Figure 3 valve A still connects the upper diaphragm chamber 11 to atmosphere but rotation of valve B causes the holder inlet/outlet 18 to be connected to the lower diaphragm chamber 12. Since the holder pressure is always higher than the atmospheric pressure by a figure in excess of one half inch water gauge, the HCV 20 will now remain open regardless of the pressure differential betweeen the common main 17 and the holder. The HCV 20 will now remain open in this manner as long as the holder is between its normal high (full) and low (empty) limits.

If the holder continues to gain height due to the infusion of gas thereinto, the striker S will move from position (g) to position (h) in Figure 6 and will strike level 12 to cause it to rotate from position (g) to position (h). This will cause valve A to rotate to the position shown in Figure 2 in which the holder is in its normal high (full) position.

In Figure 2, the upper diaphragm chamber 11 is connected to the common main 17 and the lower diaphragm chamber 12 is connected to the holder inlet/outlet 1 8. This will cause the hitherto positive differential pressure between the lower diaphragm chamber 1 2 and the upper diaphragm chamber 11 to be reversed and the HCV 20 will close until a new emptying cycle is initiated.

The above description relates to a holder which is only controlling its own associated HCV with which in practice every gas holder on a station is fitted except when, in rare cases, there is only one gas holder on site. On sites however where there are two or more gas holders, the heavier or heaviest of these holders and almost invariably therefore the last holder to reach its normal high position is selected to control the station volumetric governor which itself controls the filling of the holders. In this case the striker plate S would be omitted from this holder to prevent the closure of the HCV at the normal high holder position and therefore to enable the HCV to remain open.

Similarly, if a holder were the lighter or lightest of the holders on site, it would almost invariably be the last holder to reach its normal low position. This holder would then be selected to control the station boosting equipment or booster which pumps or draws gas out of the holders and into the distribution system. In this case, the striker plate S2 would be omitted from this holder to prevent the closure of the HCV at the normal low holder position to enable the HCV to remain open.

In practice the pneumatic valves A and B are physically located on the ground or attached to some stationary steelwork at the base of or immediately adjacent to the holder. Holder cut-off valves are often sited a few metres distant from the associated holder to which they are connected and occasionally a considerable distance from the holder. Therefore, the auxiliary pipe runs which connect valves A and B to the HCV are often quite lengthy. Long auxiliary pipe runs carrying gas at the low pressures involved leads to very low gas flow rates and a consequential slow operation of the HCV.

It is therefore an object of the present invention to provide a pneumatic valve system which overcomes the above disadvantages.

According to the present invention, there is provided a pneumatic valve system for controlling a gas-holder cut-off valve in such a way that the cut-off valve is caused to open in response to the differential pressure between the common main and the holder or atmosphere or between the holder and the common main or atmosphere wherein the valve system is controlled electrically.

Preferably the valve system is pneumatically actuated by valve means which is electrically controlled.

Suitably the valve means is electrically switchable between positions where the valve means is connected to atmosphere or to a pneumatic supply system.

An embodiment of the invention will now be particularly described with reference to the Figure 7 which shows a schematic diagram of the valve system.

The valve system comprises six auxiliary pilot valves 41,42,43,44,45 and 46 which are springloaded, diaphragm-type pneumatically actuated valves.

Pilot valves 41 and 42 are, in use, connected on one side to the common main 17 by pipework 47.

Pilot valves 43 and 44 are connected on one side to the holder inlet/outlet 18 by pipework 48. Pilot valve 41 is connected on its other side to the other side of pilot valve 43 by way of pipework 49. Pilot valve 42 is connected on its other side to the other side of pilot valve 44 by pipework 50. Pilot valve 46 is connected on one side to a point intermediate pipework 49 by means of pipework 51. Pilot valve 45 is connected on one side to atmosphere by pipework 52.

Pilot valve 45 is connected on its other side to the other side of pilot valve 46 by means of pipework 53. The upper diaphragm chamber 11 of the holder cut-off valve 20 is connected by pipework 54 to a point intermediate the pipework 53. The lower diaphragm chamber 1 2 is connected to a point along the length of pipework 50 by pipework 55.

The pilot valves 45 and 46 are actuated by a solenoid-type valve 56 while,the pilot valves 41 and 44 are actuated by a similar solenoid type valve 57.

The valves 56 and 57 comprise electrically powered three-port two-way normally closed valves.

Valve 56 has an outlet port 58 from which there extends a pneumatic impulse line 59 to actuate pilot valves 45 and 46 by movement of their internal diaphragms (not shown).

Valve 57 has an outlet port 60 from which there extends a pneumatic impulse line 61 which is branched at 61 a and 61 b to provide actuation respectively for pilot valves 41 and 43 and 42 and 44 by movement of their internal diaphragms (not shown).

The outlet port 58 of the valve 56 is switchable between a port 62 which is connected to an atmospheric line 63 and a port 64 which is connected to a branch line 65a of a pneumatic impulse supply line 65. The impulse line 59 is therefore switchable between atmospheric pressure and the pneumatic supply pressure.

The outlet port 60 of the valve 57 is switchable between a port 66 which is connected to an atmospheric line 67 and a port 68 which is connected to another branch line 65b of the pneumatic impulse supply line 65. The impulse line 61 is therefore switchable between atmospheric pressure and the pneumatic supply pressure.

The pilot valves 41,44 and 46 are normally open valves, that is, if the impulse line connection to their diaphragms is open to atmosphere, then the internal spring (not shown) will hold the valve in the open position. The valves can only be closed by applying gas pressure to the impulse line.

On the other hand pilot valves 42, 43 and 45 are normally closed valves, that is if the impulse line connection to their diaphragms is open to atmosphere, then the internal spring (not shown) will hold the valve in the closed position. The valves can only be opened by applying gas pressure to their impulse lines.

The solenoid valve 56 shown in Figure 7 is in the de-energised state, that is, no current is passing through its coil 69. When the valve 56 is energised the outlet port 58 will be disconnected from the atmospheric port 62 and will be connected to the pneumatic supply port 64. This will cause gas to flow to the diaphragms of pilot valves 45 and 46 causing valve 45 to open and valve 46 to close.

The solenoid valve 57 is identicai in operation to solenoid valve 56. When the coil 70 of this valve is energised to disconnect the outlet port 60 from the atmospheric port 66 and connect it to the pneumatic supply port 68, the gas flows to the diaphrams of the pilot valves 41,42,43 and 44 causing valve 41 to close, valve 42 to open, valve 43 to open and valve 44 to close.

In operation therefore, when valve 56 is in the de-energised state the upper diaphragm chamber 11 of the holder cut-off valve 20 is connected to the common main 17 by way of pipework 54, open valve 46, pipework 51, pipework 49, open valve 41 and pipework 47.

When valve 56 is in its energised state however the upper diaphragm chamber 11 is connected to atmosphere by way of pipework 54 and 53, the now open valve 45 and the pipework 52.

Therefore the action of the solenoid valve 56 and its associated pilot valves 45 and 46 is analogous to the action of valve A shown in Figures 2 to 5.

In addition, when valve 57 is in the de-energises state the lower diaphragm chamber 12 of the holder cut-off valve 20 is connected to the holder inlet/outlet 18 by way of pipework 55, open valve 44 and pipework 48.

On the other hand, when valve 57 is in the denergised state, the lower diaphragm chamber 12 is connected to the common main 1 7 by way of the pipework 55, pipework 50, the now open valve 42 and the pipework 47.

Therefore the action of the solenoid valve 57 and its associated pilot valves 41 and 44 is analogous to the action of valve B shown in Figures 2 to 5.

The electrically controlled valve system shown in Figure 7 can therefore be used in a manner analogous to the mechanically actuated valve system shown in Figures 2 to 5 to control the cut-off valve of a gas holder.

In this case it will be necessary for the state of the valves 56 and 57 during the filling and emptying cycles to correspond closely to the state of mechanical valves A and B during their use. The Table on Page 20 shows the necessary sequence of valve states during an emptying cycle with the corresponding connections of the lower and upper diaphragm chambers and the position of the holder.

The filling cycle should be read in the reverse direction.

To actuate the valves 56 and 57 in the correct sequence an electric control circuit is necessary to generate appropriate sequential signals according to the position of the holder. One such control circuit is described in our copending UK patent application no.

In a station with two or more holders, the state where both valves 56 and 57 are OFF should be omitted for the holder controlling the volumetric governor. Similarly the state where the valve 56 is OFF while valve 57 is ON should be omitted for the holder controlling the booster. This ensures that when the holder controlling the volumetric governor reaches its normal high position and the holder controlling the booster reaches its normal low position, their respective holder cut-off valves remain open.

The impulse gas supply is derived from a secure low pressure source ie. a main which is connected to the inlet side of the gas station's district pressure regulator. Pilot valves 41 to 46 and all their associated auxiliary pipework can be kept close to the associated holder cut-off valve. Therefore the auxiliary pipewrok can be kept short with a resultant improvement in gas flow rates and thus faster operation of the holder cut-off valve.

Since the system is electrically controlled it is capable of greater flexibility of operation than is obtained with the conventional mechancially actuated system previously described.

The greater flexibility obtainable with this system is fully detailed in our co-pending UK Patent Application No. 6230387 where the system is incorporated into an electrical control circuit for controlling a site having two or more gas holders.

TABLE Valve 56 Valve 57 LDC is UDC is Holder State State connected to connected to Position OFF OFF Holder Common Main Normal High ON OFF Holder Atmosphere Intermediate (1) ON ON Common Main Atmosphere Intermediate (2) OFF ON Common Main Holder Normal Low LDC = Lower diaphragm chamber UDC = Upper diaphragm chamber The intermediate holder position is between the normal high and low positions.

Intermediate (1) position will be at least slightly higher than intermediate (2) position.

Valve 56 is ON when its coil is energised and OFF when the coil is de-energised.

Valve 57 is ON when its coil is energised and OFF when the coil is de-energised.

The coil 69 of valve 56 may be energised by applying a voltage of the correct polarity between the terminals 71 and 72 of the coil 69.

The coil 70 of valve 57 may be energised by applying a voltage of the correct polarity between the terminals 73 and 72 of the coil 70.

Claims (4)

1. A pneumatic valve system for controlling a gas-holder cut-off valve in such a way that the cutoff valve is caused to open in response to the differential pressure between the common main and the holder or atmosphere or between the holder and the common main or atmosphere wherein the valve system is controlled electrically.

2. A system as claimed in Claim 1 in which the valve system is pneumatically actuated by valve means which is electrically controlled.

3. A system as claimed in Claim 2 in which the valve means is electrically switchable between positions where the valve means is connected to atmosphere or to a pneumatic supply system for actuating the pneumatic valves.

4. A system substantially as hereinbefore described with reference to Figure 7.