RU2333463C2 - Method of controlling proportioning plunger pump and device to this effect - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: invention relates to proportioning of liquids by using a plunger pump driven by a synchronous drive normally used in petroleum, chemical and other industries. The proposed method of controlling the said pump capacity by bypassing a portion of liquid back into liquid tank the pump intake valve is kept open during a preset time interval from the start of suction and with the plunger discharging stroke, and after the said time interval the inlet valve is closed, while the remaining liquid is forced by the plunger via the exhaust valve to the pump outlet. The method allows, also, the determination of an instant and total liquid flow rate.

EFFECT: providing an automatic or remote control over proportioning plunger pump capacity and controlling its actual capacity allowing for transient processes.

4 cl, 2 dwg

Description

The invention relates to the field of fluid metering when using a plunger pump with a synchronous motor, which is used in the oil, chemical and other industries.

A widely known method of regulating the performance of the pump, used in series-produced pumps of the type ND, which consists in changing the stroke of the plunger by moving the drive eccentric by the screw of the reading device manually or by an electric servo drive. The disadvantage of this method is that the manual drive does not allow you to automate the process, and the electric servo drive, although it allows you to automate the process, but the cost of the servo drive is comparable to the cost of the pump and the quality of regulation is very low, because due to backlash in the mechanical transmission of the gearbox and the motor run-out, the control accuracy is low. In addition, this method does not allow to measure the amount of pumped liquid, for this it is necessary to install an additionally very expensive flow meter for pulsating flows in series with the pump [1].

There is another method for regulating the performance of the pump by periodically turning it on and off [2]. Although this method allows automation of changes in pump productivity to be carried out without large expenses, the operating mode of the pump is very difficult, because frequent engine starts can lead to overheating and complete failure, and the quality of regulation will be rougher and worse than in the previous method [2].

There is also known a method implemented in the device according to the patent of Russia 2171790 [3], in which part of the liquid is passed from the pump outlet to its input. This method does not have a rigid connection between the position of the plunger and the moment of switching on and off the flow breaker and therefore does not allow precise control of the amount of injected fluid. Monitoring can only be carried out averagely after a considerable pump runtime.

The second disadvantage of this method is that the flow is interrupted on the pressure side of the pump, where the pressure reaches hundreds of atmospheres, therefore, the organ that interrupts the supply must be sufficiently durable and energy-intensive, and therefore expensive.

The third disadvantage of this method and all of the above is that they carry out indirect management and control, i.e. it all comes down to changing the stroke value or the number of strokes of the plunger, but the result is not controlled (pump pumping liquid or not? Is it working or not? Is liquid coming in or not?). These methods do not distinguish between idle and useful pump operation.

Technical result: the invention solves the problem of automatic or remote control of the change in the productivity of the plunger metering pump and control of its real performance, taking into account transients, the technical condition of the pump and the physical characteristics of the injected medium.

To achieve the specified technical result, a method for controlling and monitoring the performance of the metering pump by transferring part of the liquid back to the supply tank is proposed, which means that when the pump plunger is pumped for a predetermined time from the start of the suction moment, the pump inlet valve is forcibly kept open, bypassing some of the liquid through it back to the tank, and after this time, the inlet valve is closed and through the exhaust valve the remainder of the liquid is pushed push the plunger to the pump outlet for the consumer of the dosed liquid, and changing the preset time, change the liquid dose or the number of liquid doses, while the moment of suction start is fixed at the moment of pressure drop after the injection cycle, the time of the injection cycle is determined from the moment the pressure arises in the cylinder cavity until it disappears , recalculate it in units of volume per unit time based on the design data of the pump (cylinder diameter, plunger stroke, plunger full stroke time), determine the total time all x injection cycles for the entire period of the pump and based on its design data are converted to volume units.

The implementation of the above method is carried out by a device for controlling and monitoring the performance of a plunger metering pump with a synchronous electric drive, consisting of a cylinder, plunger, inlet and outlet valves, in which the inlet valve is made forcibly controlled (for example, by an electromagnet) and a pressure sensor is installed in the cylinder cavity.

The implementation of the method is carried out by the device shown in figure 1, consisting of a cylinder 1, a plunger 2, an intake valve 3, an exhaust valve 4, a pusher of an electromagnet 5, an electromagnet 6, a pusher of a plunger 7, a guide sleeve 8, a return spring 9, an eccentric 10, the shaft of the gearbox 11, the gearbox 12 itself, the synchronous motor 13, the pressure sensor 14 and the controller 15.

The device operates as follows. When you turn on the motor 13, it through the gearbox 12 and the shaft 11 begins to rotate the eccentric 10, which, reaching the largest diameter, moves the pusher 7 and through it the plunger 2 to the extreme right position. With further rotation of the eccentric 10, its diameter decreases, and the pusher 7 and the plunger 2 are returned to the leftmost position by the spring 9. The process of moving the plunger 2 after each full revolution of the eccentric 10 is repeated and thus the plunger 2 moves from one extreme position to each full revolution another and comes back.

When the plunger 2 moves from the extreme right to the left position, cylinder 1 is filled through the inlet valve 3, reaching the leftmost position, the plunger 2 will begin to move in the opposite direction to the right, but the inlet valve remains open and the liquid starts to be discharged through the inlet valve 3 back to capacity until a command from the controller to the electromagnet 6 arrives and until it releases its pusher 5, valve 3 cannot close. As soon as the pusher 5 releases the valve 3, it closes under the influence of the liquid pressure and this pressure will open the exhaust valve 4, through which the liquid will begin to flow to the consumer.

Thus, changing the time of the open state of the inlet valve and dumping part of the volume back to the inlet through it, the value of the useful dose of liquid passing to the consumer through the pressure valve 4 is changed.

The start (moment) of the countdown is the start of the suction (filling) of cylinder 1 with a plunger 2, for which a pressure sensor 14 is installed directly in the cylinder 1, which detects the moment of pressure drop after the injection cycle and gives a command to count down the set time, after which a command to allow valve closure 3.

The countdown of time intervals, the processing of information from the pressure sensor and the issuance of commands to the electromagnet are carried out by the controller 15.

Figure 2 shows a graph of the performance of the pump from the moment of closing the suction valve

trab = T - (T / 2 + tset - tper),

where T is the pump operation period, consisting of one suction cycle and one discharge cycle;

trab - discharge time;

tset - set time for fluid bypass through the inlet valve (tset <T / 2);

tpere is the transition time associated with the opening and closing times of the valves, depending on the inlet and outlet pressures, viscosity of the medium, etc. (tpere = tper + t2 per).

For a specific pump ND2.5 / 400 T-const and equal to 1.6 seconds.

The discharge time is 50% of the total working time, i.e. after 1 hour of operation, the injection will be 0.5 hours (1800 seconds).

а из пропорции

следует

- это мгновенный расход в пересчете на 1 час,Pump productivity Q = 2.5 l / h = 2500 ml / h, which implies that the maximum single dose is

and out of proportion

should

- this is the instantaneous consumption in terms of 1 hour,

- суммарный расход за все время работы.

- total consumption for the entire time of work.

The proposed device allows, in addition to the above method, to implement other methods of controlling the performance of the pump.

To implement the method used in the prototype, it is necessary to set the specified time in multiples of T / 2, but in this case, a number of advantages of the proposed method are retained, such as the ability to determine the average instantaneous and total flow rate of the injected fluid and diagnostics of the valve status.

Information sources

1. Unit electric pump dosing single-plunger type ND with power up to 0.55 kW. Operation manual ND1.01.150 RE CJSC “Dosing pumps and systems", Tula, 2004

2.http: //www.pomp.ru/products/26.html.

3. RF patent No. 2171790 of 2001.08.10. Block for the preparation of chemicals of block plants.

Claims (4)

1. A method of controlling and monitoring the performance of a plunger metering pump with a synchronous electric drive, consisting of a cylinder, plunger, intake and exhaust check valves, by transferring part of the liquid back to the supply tank, characterized in that when the pump plunger is pumped for a predetermined time from the beginning the suction moment, the inlet valve of the pump is forcibly kept open, passing part of the liquid through it back to the tank, and after this time the inlet valve is closed and through the exhaust valve, the remainder of the liquid is pressed by the plunger to the pump outlet to the consumer of the dosed liquid, while changing the set time, the liquid dose or the number of doses of liquid is changed, while the moment of suction start is fixed at the moment of pressure drop after the injection cycle. 2. The method of controlling and controlling the performance of a plunger metering pump with a synchronous electric drive according to claim 1, characterized in that the injection cycle time is determined from the moment pressure arises in the cylinder cavity until it disappears, it is recalculated in units of volume per unit time, based on structural pump data (cylinder diameter, plunger stroke, plunger full stroke time). 3. The method of controlling and controlling the performance of a plunger metering pump with a synchronous electric drive according to claim 1, characterized in that the total time of all pumping cycles for the entire period of the pump is determined and based on its design data are converted to volume units. 4. A device for controlling and monitoring the performance of a plunger metering pump with a synchronous electric drive, consisting of a cylinder, plunger, intake and exhaust valves, characterized in that the intake valve is made forcibly controlled (for example, by an electromagnet), and a pressure sensor is installed in the cylinder cavity.

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