GB2357553A - Monitoring of float operated devices - Google Patents

Abstract

A float operated device such as a pressure powered pump is provided with a monitoring device 32. A proximity sensor 36 which is connected to the monitoring device 32 is disposed within the chamber 2 of the pump. The sensor 36 is activated by a permanent magnet 40 mounted on an operating link 28, so that the magnet 40 activates the proximity switch 36 on each stroke of the pump. The monitoring means includes a display panel 46, on which data obtained from the sensor 36 may be displayed. For example, the display panel 46 may display a cumulative total of cycles performed by the pump, or a cumulative volume of liquid displaced by the pump.

Description

2357553 MONITORING OF FLOAT OPERATED DEVICES This invention relates to the

monitoring of float operated devices, and is particularly, although not exclusively, concerned with the monitoring of the operation of pressure powered pumps.

A typical pressure powered pump is disclosed in GB-A-2302916. It comprises a chamber having an inlet and an outlet for a liquid, such as condensate from a steam utilizing installation. Flow through the chamber from the inlet to the outlet is controlled by non return valves. The selective admission and exhaust of a motive fluid such as steam is controlled by a float which follows the level of liquid in the chamber. At the top of its movement, when the chamber is substantially filled with the liquid, an inlet valve for the steam is opened, and the liquid is driven through the outlet of the chamber. When the float is at the bottom of its movement, the motive steam inlet is closed and an exhaust valve is opened to vent the chamber to atmosphere. This allows further condensate to enter the chamber through the inlet, so repeating the cycle.

Pressure powered pumps are capable of working for long periods without maintenance. However, the absence of moving parts outside the chamber makes monitoring of the operation somewhat difficult. Such monitoring is useful not only to ensure that the pump is working correctly, but also to establish the number of cycles of freight movement which the pump has undergone in order to'determine when servicing or an overhaul may be desirable.

It is known to monitor the operation of pressure powered pumps by positioning a pressure.sensor within the chamber. The pressure sensor responds to the pressure variations within the chamber during a cycle -2 of operation of the pump, so that pump cycles can be counted. The pressure sensor may take the form of a piston provided in a cavity communicating with the chamber which piston operates a mechanical counter each time a pressure increase within the chamber occurs.

However, such a device permits the loss of fluid from the chamber. This not only leads to a loss of efficiency, but also impermissible if the fluid to be pumped, or the motive fluid, is toxic or otherwise hazardous.

Pressure powered pumps have also been monitored by means of electronic pressure sensors, but these are expensive. This is so particularly if the interior of the chamber is never vented entirely to ambient is pressure, because the pressure sensor then needs to respond to changes in absolute pressure. The cost of such devices tends to be prohibitive in relation to the value of the pressure powered pump itself.

Pressure powered pumps are often used in potentially explosive atmospheres, since they are intrinsically safe in such environments. The cost of adapting pressure sensor technology for safe use in explosive atmospheres is unacceptably high.

According to the present invention there is provided a float operated device comprising a chamber accommodating a float which is movable within the chamber in response to changes of liquid level within the chamber, the float being connected by an operating link to a valve assembly, a proximity sensor being disposed within the chamber for providing signals to monitoring means outside the chamber, the proximity sensor being responsive to displacement of the float.

The use of a proximity sensor means that monitoring of the operation of the device can be achieved at relatively low cost, and the inherent safety of pressure powered pumps in explosive atmospheres can be retained.

In a preferred embodiment in accordance with the present invention, the proximity sensor responds to an activating element which is movable within the chamber upon movement of the float. Preferably, the activating element is provided on the operating link. In one form of pressure powered pump, for example that disclosed in GB-A2302916, the operating link extends upwardly from a lever which pivotally supports the float, to the valve assembly, which is positioned above the maximum liquid level in the chamber. The activating element can thus be fitted to the operating link so that it moves, during each cycle of pump operation, to a position above the maximum liquid level. This means that the proximity sensor itself can be positioned in the chamber above the maximum liquid level.

Preferably, the sensor is mounted on a probe which extends downwardly into the chamber from a top cover, the proximity sensor itself being connected by suitable leads to a monitoring device fitted to the top of the chamber.

The proximity sensor may comprise a reed switch and the activating element may comprise a permanent magnet.

The monitoring device may incorporate a display for indicating the accumulated number of strokes undergone by the float operated device. In the case of a pressure powered pump, each cycle represents a defined volume of liquid displaced through the chamber, and so the display can be adapted to provide an indication of the cumulative volume of liquid displaced. The monitoring device may also include a failure alarm so as to respond to abnormal signalling from the proximity sensor, for example the absence of a -35 signal for a predetermined length of time.

The monitoring device may be connected to a remote 4- server or PC of an energy management system.

For a better understanding of the present invention and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:

Figure 1 is a sectional view of a pressure powered pump; and Figure 2 shows, on an enlarged scale, a monitoring device and sensor of the pressure powered pump of Figure 1.

The pump shown in Figure 1 is a condensate pump for returning condensate in a steam system to the boiler.

The pump comprises a pumping chamber 2 having a is condensate inlet 4 and a condensate outlet 6. Check valves (not shown) ensure one-way flow through the pumping chamber 2 in the direction of the arrows A.

The chamber 2 has a cap 12 which has steam inlet and exhaust passages (not shown) in a valve block 14.

Valve members for closing the inlet and exhaust passages are operated by a float 22, acting through an overcentre mechanism 24. In operation, starting from the position shown in full outline in Figure 1, the steam inlet passage is closed and the exhaust passage is open. Condensate, under a relatively low pressure, enters the pumping chamber 2 through the inlet 4. This causes the float 22 to rise and, when it reaches a high level, as shown in dotted outline in Figure 1, the overcentre mechanism 24 will snap over. This will cause the valve members of the inlet and exhaust passages, which are operated in unison, to be displaced so that the steam inlet passage is opened and the exhaust passage is closed. Steam under pressure can then enter the pumping chamber 2 to discharge the accumulated condensate through the outlet 6. The float 22 accordingly falls, the overcentre mechanism 24 snaps back to its previous position, and the sequence begins again.

The float 22 has a float arm 25 by which the float is pivotably supported on a support bracket 26 projecting downwardly from the cap 12. The float arm is pivotably connected by an operating link 28 to a slotted link 30 of the overcentre mechanism 24.

A monitoring device 32 is mounted on the cap 12.

A probe 34 is secured in a sealing-tight manner at its top end to the cap 12, and extends downwardly into the chamber 2. At its lower end, the probe carries a proximity sensor 36 in the form of a reed switch. The sensor 36 is connected by leads 38 to the monitoring.

device 32. As shown in Figure 1, the support bracket is 26 is hollow, and the probe extends within the interior of the support bracket 26, and thus is isolated from the interior of the chamber 2.

The operating link 28 carries an activating element in the form of a permanent magnet 40. As can be appreciated from Figure 1, the magnet 40 is moved, during an operating stroke of the pump, between a lower position shown in full outline, and an upper position shown in dotted outline. In the upper position, the magnet 40 is positioned adjacent the sensor 36 in sufficient proximity to actuate it to cause a pulse to be sent to the measuring device 32.

The monitoring device 32 comprises a housing 42 which is supported on the cap 12 by a bracket 44. The monitoring device 32 has a digital display panel 46.

As the pump operates, each operating cycle results in movement of the magnet 40 into and out of a position next to the proximity sensor 36. Consequently, each cycle of the pump causes a signal to be sent to the monitoring device 32. The display panel may be arranged to display a cumulative total of such pulses.

Since the flow throughput of the pump may not be at a constant rate, the number of operating cycles performed by;the pump provides a reliable indication of the amount of wear which may have occurred in the moving parts. Consequently, the display on the display panel 46 provides a useful indication of the need for servicing or overhaul of the pump.

Furthermore, since each cycle of the pump represents a defined volume of liquid displaced, the monitoring device 42 may be adapted to display, on the display panel 46, a figure representing the cumulative displaced volume. This can be done simply by multiplying the number of cycles by the volume displaced on each cycle. Where the pump is used to pump condensate in a steam utilising process, the is quantity of condensate discharged from the system and the rate of condensate discharge can be useful parameters in an energy management system. For this purpose, the monitoring device 42 may be connected to a remote computer forming part of an integrated energy management system.

In addition, the monitoring device may be equipped with an alarm, so as to generate an alarm signal should abnormal conditions arise. For example, the alarm could be set up so as to provide a signal should the p roximity sensor 36 remain inactive for a predetermined length of time. Thus, the alarm will signify that the pump has not completed a full stroke in that period, which can mean either that the pump has failed or that condensate flow has ceased.

Although the present invention has been described in relation to a pressure operated pump, it will be appreciated that the monitoring device 32 could be employed in other kinds of float-operated device.

Also, although the magnet 40 has been shown fitted to the operating link 28, the magnet could be provided on another part of the pump which moves during an operating cycle.

Claims (13)

1. A float operated device comprising a chamber accommodating a float which is movable within the chamber in response to changes of liquid level within the chamber, the float being connected by an operating link to a valve assembly, a proximity sensor being disposed within the chamber for providing signals to monitoring means outside the chamber, the proximity sensor being responsive to displacement of the float.

2. A float operated device as claimed in claim 1, in which the proximity sensor is responsive to an activating element which is movable upon movement of the float.

3. A float operated device as claimed in claim is 2, in which the activating element is mounted on the operating link.

4. A float operated device as claimed in claim 2 or 3, in which the activating element is a permanent magnet.

5. A float operated device as claimed in any one of the preceding claims, in which the proximity sensor comprises a reed switch.

6. A float operated device as claimed in any one of the preceding claims, in which the float is mounted on a lever which is pivotable about a pivot point fixed within the chamber.

7. A float operated device as claimed in claim 6, in which the operating link extends between the lever and the operating means.

8. A float operated device as claimed in any one of the preceding claims, which is a pressure powered PUMP.

9. A float operated device as claimed in any one of the preceding claims, in which the moni-toring means includes a display indicating cumulative operating strokes of the float.

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10. A float operated device as claimed in claim 9, when appendant to claim 8, in which the display indicates the cumulative volume displaced by the pump.

11. A float operated device as claimed in any one of the preceding claims, in which the monitoring means includes a failure alarm.

12. A float operated device as claimed in any one of the preceding claims, in which the monitoring means is connected to a remote energy management system.

13. A float operated device substantially as described herein with reference to, and as shown in, the accompanying drawings.