GB2213622A

GB2213622A - Control for delivery system

Info

Publication number: GB2213622A
Application number: GB8728626A
Authority: GB
Inventors: Robert Edward Bannister
Original assignee: Fospur Ltd
Current assignee: Fospur Ltd
Priority date: 1987-12-08
Filing date: 1987-12-08
Publication date: 1989-08-16
Anticipated expiration: 2007-12-08
Also published as: GB8728626D0; GB2213622B

Abstract

An hydraulically operated ram pump comprising a piston P arranged to reciprocate within a cylinder C is equipped to give an early indication of the failure of the pump. A first detecting means HP is arranged to provide an output signal indicative of whether the piston is moving towards or away from the cylinder end wall W, and a second detecting means CP is arranged to provide an output signal indicative of the pressure within the cylinder. The signals are supplied to a comparator E which compares them with a predetermined pattern, and activates an alarm A in the event of a deviation from that pattern. <IMAGE>

Description

CONTROL FOR DELIVERY SYSTEM This invention relates to the control of a delivery system and more particularly for detecting a failure within a pumped delivery system. In particular it relates to the detection of a valve failure within a system pumped by a ram pump.

There are many problems involved in identifying pump failure, and these are compounded in installations where a battery of such pumps are connected in parallel. One known method of detecting failure uses microwave doppler effect devices to determine the velocity of the substances within the pipes connected to the pump. A disadvantage of such devices is that they are not directionally sensitive. This means that they are unable to distinguish between a substance that is sloshing back and forth within the pipe (as occurs when a valve fails) and a substance that is moving in one direction. Thus, such devices are required on both the inlet and outlet sides of the pump.

It is an object of the invention to provide pump failure detection means for a pump, which means are reliable, cheap and gives early indication of a failure.

According to one aspect of the invention there is provided apparatus arranged to deliver a substance, the apparatus comprising a cylinder having an end wall, a piston reciprocally movable in the cylinder, an inlet valve and an outlet valve being present in the cylinder, an inlet line connected to the inlet valve and an outlet line connected to the outlet valve, the piston being movable by means of pressurised hydraulic fluid applying pressure to an end thereof characterised in that first detecting means are present to determine whether the piston is moving towards or away from the cylinder end wall, second detecting means are present to determine the pressure within the cylinder, and comparator means to compare the outputs of the detecting means and compare them with a predetermined pattern and to sound an alarm in the event of any deviations from the predetermined pattern.

In order that the invention may be well understood it will be illustrated with reference to the following diagrammatic drawings in which Figure 1 shows schematically a ram pump during the suction cycle according to the invention, and Figure 2 is the same as Figure 1, but showing the pump during the compression cycle.

In the drawings Figure 1 shows schematically a ram pump which comprises a cylinder C having an end wall W and within which a piston P reciprocates. The piston P is moved by pressurised hydraulic fluid, which is supplied via hydraulic line HL to the outside face of the piston P, the top as shown. An inlet line I leads to one side of the cylinder C adjacent the end wall W and includes an inlet valve IV.

Opposite the inlet is an outlet line 0 including an outlet valve OV. As shown in Figure 1, the pump is in the inlet stage with inlet valve IV in the open condition and the outlet valve OV in the closed condition.

A cylinder pressure transducer CP is mounted on the side wall of the cylinder C and is arranged to detect the pressure within the cylinder. A hydraulic pressure transducer HP is connected to the hydraulic line HL and is present to determine the hydraulic fluid pressure within the line and thus the position of the piston P within the cylinder. The outputs of the two transducers (CP, HPY are connected to an electronic circuit E which is connected to an alarm A, actuated in the event of a pump failure.

In use, the piston P reciprocates within the cylinder C under the pressure of hydraulic fluid within the hydraulic line HL. When the pressure within the cylinder C drops because the piston P is moving away from the end wall W, the difference in pressure between the inlet line I and the cylinder C urges the inlet valve IV from its seating to allow the substance to enter the cylinder. When the piston P is at the end of its stroke, it starts the pressure cycle.

As the piston P is urged downwards the pressure within the cylinder C increases such that the pressure is greater within the inlet and outlet line (I, O) than within the cylinder. The inlet valve IV closes and the outlet valve OV opens to allow the passage of the substance along the outlet line 0.

Commonly there are three types of failure, inlet or outlet ball valve failure and non-priming of the pump, i.e. when it is pulling air.

In the event of inlet valve failure, a substance e.g. a slurry, taken into the cylinder will be pushed out again through the same valve. Thus, on the pressure stroke there will be no pressure developed within the cylinder. In the event of outlet valve failure, a substance ejected through the outlet valve on the pressure stroke will be sucked back in again on the suction stroke and the pressure will remain relatively high on the suction stroke. In the event of a priming fault, the cylinder will never become pressurised on the pressure stroke.

In use, and in the absence of any failures, the cylinder pressure transducer (CP) detects relatively elevated pressure during the pressure stroke and relatively reduced pressure on the suction stroke. The hydraulic pressure transducer (HP) detects relatively elevated pressure within the hydraulic line when the piston is moving downwards and relatively reduced pressure when the piston is moving upwards. The hydraulic pressure transducer is thus present to detect in which stroke the piston is in.

Thus, for example, the outputs from the two transducers should both indicate elevated pressure at the same time and then reduced pressures at the same time. The electronic circuit means E compares the two values and initiates an alarm A if there is any deviation. The electronic circuit E may incorporate timing means that enable the cylinder pressures to stabilise between suction and delivery strokes., such that a true reading may be made.

The transducers may be replaced by pressure switches. The invention is seen to good effect when the ram pump is a Willett pump operating at the rate of about 10 litres per stroke and up to 30 strokes per minute, especially when a battery of such pumps arranged in parallel is used and in the event of failure leakage can occur from one pump to the next.

Claims

1. Apparatus arranged to deliver a substance under pressure, the apparatus comprising a cylinder C having an end wall W, a piston P reciprocally movable in the cylinder C, an inlet valve IV and an outlet valve OV being present in the cylinder C, an inlet line I connected to the inlet valve IV and an outlet line 0 connected to the outlet valve OV, the piston P being movable by means of pressurised hydraulic fluid applying pressure to an end thereof characterised in that first detecting means HP are present to detect whether the piston P is moving towards or away from the cylinder end wall W, second detecting means CP are present to sense the pressure within the cylinder C, and comparator means E are present to compare the outputs of the first and second detecting means with a predetermined pattern and to sound an alarm A in the event of any deviation from the predetermined pattern.

2. Apparatus according to Claim 1 characterised in that the first detecting means comprises a hydraulic pressure transducer HP located within the hydraulic line HL through which pressurised hydraulic fluid is supplied to the end face of the piston P.

3. Apparatus according to Claim 1 or 2 characterised in that the second detecting means comprises a cylinder pressure transducer CP mounted on the inside wall of the cylinder C.

4. Apparatus according to any preceding Claim characterised in that the outputs of the transducers HP, CP are connected to comparator means comprising an electronic circuit E.

5. Apparatus according to any preceding Claim characterised in that a battery of cylinders C according to Claim 1 is present, the cylinders being arranged in parallel and means are present to prevent leakage from one cylinder to another in the even of a failure in one cylinder.

6. Apparatus according to any preceding Claim characterised in that the cylinder and piston P is a Willett type ram pump.

7. Apparatus arranged to deliver a substance substantially as described with reference to the drawings.

8. A method of rapidly detecting a failure in apparatus comprising a pumped delivery system characterised in that the apparatus is according to any preceding Claim and the first detecting and second detecting means HP, CP provide signals to a comparator E which compares the sensed signals with a predetermined pattern and activates an alarm A in the event of a deviation from a predetermined pattern.