GB2292836A

GB2292836A - Device for detecting the presence of gas in the liquid output of a pump

Info

Publication number: GB2292836A
Application number: GB9417544A
Authority: GB
Inventors: Richard Bradford
Original assignee: S B SERVICES
Current assignee: S B SERVICES
Priority date: 1994-09-01
Filing date: 1994-09-01
Publication date: 1996-03-06
Anticipated expiration: 2014-09-01
Also published as: GB9417544D0; GB2292836B

Abstract

A device for detecting the presence of gas in the liquid output of a pump comprises a housing 1 defining a fluid chamber 12 and connected via upper and lower ports 14, 15 to a main pipe section 2. Pipe section 2 is connected in use to the outlet side of a pump via its upper end 4. A float 20 in the chamber 12 carries a magnet 23 which operates a reed switch 24 mounted on the top of the housing 1. If there is air in the liquid output of the pump it enters the chamber and causes the float to drop. This switches off the switch 24 which in turn switches off the pump. <IMAGE>

Description

DEVICE FOR DETECTING THE PRESENCE OF GAS IN THE OUTPUT OF A PUMP The invention relates to a device for detecting the presence of gas in the liquid output of a pump such as a diaphragm pump. Diaphragm pumps are frequently driven pneumatically by compressed air to pump liquids. If the diaphragm becomes perforated, compressed air will pass through it onto the liquid side and be discharged with the liquid output. This in itself is not a major problem, but if the perforation becomes enlarged, liquid will eventually pass to the air side of the diaphragm and will thus be discharged in the exhaust from the pump. If the perforation becomes large, the quantity of liquid discharged in the exhaust will also increase with serious consequences if the liquid is toxic or difficult to clear up such as paint.

Air may also get into the output of a pump if it is sucked in through the liquid inlet and in this case the pump may become damaged.

The present invention provides a device for detecting the presence of gas in the liquid output of a pump so that the pump can be turned off before serious damage or injury can occur.

According to the present invention, there is provided a device for detecting the presence of gas in the liquid output of a pump for liquid, comprising: a housing defining a fluid chamber; a first port in the housing in fluid communication with the upper part of the chamber and a second port in the housing in fluid communication with the lower part of the chamber; the first and second ports being adapted to be connected, in use, to the outlet side of the pump with the first port connected above and upstream of the second port; a float located within the chamber and moveable in accordance with the level of liquid; and a switch operated by the float.

In a preferred embodiment the pump concerned is a diaphragm pump driven by compressed air and the switch is a magnetically operated reed switch which controls the supply of compressed air to the pump. The switch is located on the top of the device and is operated by a magnet carried on the float. This arrangement is particularly useful in an environment where electrical switching cannot be tolerated such as where volatile and combustible liquids are involved.

Embodiments of the invention are described below with reference to the accompanying drawings in which: Figure 1 is a vertical section through a device in accordance with the invention; and Figure 2 is a plan view of the device.

A device for detecting the presence of gas in the liquid output of a pump (not shown) is shown in Figure 1 and comprises a housing 1 connected to a main pipe section 2 mounted vertically. Pipe section 2 is connected to a further pipe section 3. In use, the device is connected via the upper end 4 of the main pipe section 2 to the outlet side of a pump. It should be noted that upper ends 4,5 of pipe sections 2 and 3 are at a level above the housing 1.

Housing 1 is formed by a central tubular section 6 and upper and lower end blocks 7 and 8. Passages 9 and 10 in the end blocks communicate with the hollow interior of the central section 6 to define a chamber 12 within the housing 1. A first upper port 14 in the housing communicates with passage 9 and the upper part of the chamber 12 whilst a second lower port 15 communicates with passage 10 and the lower part of the chamber.

The housing is connected to the pipe section 2 by connections in the form of connecting blocks 16,17 having bores 18 and 19 which lead from the pipe 2 into the ports 14 and 15. As can be seen, the ports 14,15 are thus connected, in use, to the outlet side of the pump with the first port 14 connected above and upstream of the second port 15. The blocks 16,17 are welded or otherwise coupled to the pipe 2 and are connected to the housing 1 through bolts (not shown).

Mounted within the housing 1 in the chamber 12 is a generally cylindrical float 20. The float can move up and down within the chamber according to the level of liquid in the chamber and is guided by a surrounding ring of rods 22 extending upwardly from the lower end block 8.

The float 20 carries a magnet 23 at its upper end. A magnetically actuated reed switch 24 is mounted on the top of the housing 1 and is operated by movement of the float.

Operation of the device is as follows. In use, the top end 4 of main pipe section 2 is coupled to the outlet side of a liquid pump. In the example of the present embodiment the pump is a pneumatically operated pump such as a diaphragm pump, and the pneumatic supply to the pump is connected to the reed switch to be controlled thereby. The pipe section 3 is connected in use to further pipes for delivering the output of the pump to its desired location.

If the pump has not been in use, the chamber 12 will be at least partly full of air at atmospheric pressure and there may be little or no liquid in the chamber. Thus the float will have dropped in the chamber to a position in which the reed switch is put into an "off" position by the magnet. The switch 24 must thus be bi-passed to start the pump, for example a bi-pass button may be pressed by an operator.

Once the pump has been started, the chamber 12 will quickly fill with liquid which will purge the air from the chamber in a few seconds. When the chamber has filled up, the float will rise to a position in which the magnet puts the reed switch into an "on" position. The operator can then release the bi-pass button. If this few seconds delay is not acceptable, a bleed valve can be provided in the housing in communication with an upper part of the chamber. It is important that the pipe section 3 extends to a point above the chamber 12 since otherwise the chamber will not fill with liquid during start-up.

Once the pump has been running for a few seconds, the system will become stable with the chamber full of liquid, the float high in the chamber, and the reed switch in its "on" position. Because the housing is in parallel with the pipe section 2, it does not cause a significant fall in the output pressure of the system.

If the pump should become perforated, or should draw air in through its liquid inlet, the liquid output from the pump will contain gas under pressure. When this gas enters the chamber 12 through port 14 or port 15 it will accumulate at the top of the chamber and will expand to drive the liquid level downwards. This causes the float to drop and for the reed switch 24 to switch the pump off. The reed switch can also be arranged to operate a warning light, alarm, or other means for indicating that there is air in the liquid output.

Thus the device can be used to switch a pump off when gas is present in the output liquid. The device may be supplied to the user complete with pipe sections 2 and 3 and connections 16 and 17. Alternatively, the housing may be supplied alone to be fitted to existing pipework or otherwise plumbed into the user's system. In these latter circumstances it will be important for the user firstly to fit the housing to the pump outlet side so that the port 14 is connected both above and upstream of the port 15 and secondly to ensure that the pipework downstream of the device returns to a level above the device. Normally the device will be supplied with connections 16 and 17 and with the main pipe section 2, but without pipe section 3.

Figure 2 is a view of the device from above showing only the housing 1, connecting block 16, and pipe section 2. The circles shown in phantom indicate how main pipe sections of different diameters may be provided according to the rating of the pump. As can be seen from Figure 2 the housing 1 is of square section and the connecting blocks 16,17 are rectangular.

Claims

1. A device for detecting the presence of gas in the liquid output of a pump for liquid, comprising: a housing defining a fluid chamber; a first port in the housing in fluid communication with the upper part of the chamber and a second port in the housing in fluid communication with the lower part of the chamber; the first and second ports being adapted to be connected, in use, to the outlet side of the pump with the first port connected above and upstream of the second port; a float located within the chamber and moveable in accordance with the level of liquid; and a switch operated by the float.

2. A device according to Claim 1, further comprising: a main pipe section mounted alongside the housing, having upper and lower ends and having an inlet at its upper end for connection to the outlet side of the pump; a first connection connecting the first port to the main pipe section; and a second connection connecting the second port to the main pipe section.

3. A device according to Claim 1 or Claim 2, wherein the switch is a reed switch mounted on the housing outside the chamber and is operated by a magnet carried by the float.

4. A device according to Claim 3, wherein the float is generally cylindrical with its axis upright and is constrained for vertical movement within the chamber; the magnet being carried at the top of the float and the reed switch being mounted on the top of the housing.

5. A device according to any preceding claim, wherein a bleed valve is provided in the housing in communication with the chamber at an upper part thereof.

6. A device according to any preceding claim, wherein the switch controls the operation of the pump such that when the float falls due to the presence of gas in the chamber, the switch turns the pump off.

7. A device according to Claim 6 for use with a pneumatically operated diaphragm pump, wherein the switch controls the pneumatic supply to the pump.

8. A device according to any preceding claim, wherein the main pipe section has a lower end which is connected to a further pipe section which extends to a point at a level above the chamber.

9. A device substantially as described herein with reference to the accompanying drawings.