Pump station above artesian well-schematic diagram of pump control, bactericidal units

Automation for downhole pumps

Automation of production is the use of such technological devices

and equipment in which control and monitoring functions previously performed

man, transmitted to various special devices and automatic devices.

By automation in this case is meant a set of command relays,

power electrical part and various types of protection, the task of which is to protect

electric motor and submersible pump of ECV type itself from failure. Most

Two main pump control schemes are widespread:

working medium (water) in the collecting storage tank and pressure in the pressure tank

pipeline.

Level Control

The first scheme is used when the pump is operating on a collecting reservoir or a water tower, from where water is already supplied to the consumer by pumps of the second lift .

Special level sensors (electrodes) are installed inside water tanks,

which use a level control relay to monitor the lower (pump actuation);

upper (pump shutdown during tank filling) levels. Application in this

the scheme of float switches instead of electrodes is less reliable, due to their

a small working resource. Emergency device is required

overflow in case of overflow of the tank (overflow alarm is usually not

applied).

This scheme is typical for large water wells, when from one

the capacity is supplied to the whole settlement or

village.

The main advantage that is achieved with this approach is a stable mode of operation

pump. Hydraulics constant: rated flow is supplied to the height determined by

the depth of the well, the height of the tower and additionally provides for another 1-2 m - for the outflow.

One cycle corresponds in flow to the full volume of the tower, taking into account the current flow rate

water disassembly. The possibility of short-term start-ups is excluded, that

extends the life of the equipment. It is quite competent to select a pump for

required parameters, once qualified to perform commissioning, and stable

system operation is ensured.

Pressure monitoring

According to the second diagram, the pump is controlled by commands from the pressure switch installed on the

pipeline. Two parameters are set on the relay itself: pump start pressure and

the pressure at which the pump is to shut down. This scheme is characteristic of

individual wells and usually used together with membrane tanks,

designed to maintain the required overpressure in the network,

compensation for hydraulic shocks and low costs. It is extremely important to produce

correct setting of relays according to pump characteristics and volume

membrane tank. So that the pump does not turn on too often, the specified limit

pressure must lie in

middle zone of pump operating characteristic. Hysteresis of values is selected as

rule, in the range of 1.2-2.5 bar, taking into account data on the maximum permissible number

pump actuations within a certain period of time.

The pressure switches used in this scheme can be roughly divided into household and industrial ones. The first, for example, MDR relays from Condor, XMP (Telecanique), etc.,

have powerful contact groups capable of withstanding current up to 16 A, but are not equipped

adjustment scale with indication of adjustable pressure range. Such relays are adjusted using a pressure gauge. The advantages of this type of relay are their

relative cheapness and possibility of application in power circuits (directly for pump control). Disadvantages - low adjustment accuracy and small working

resource - due to the influence of large starting currents. Industrial relays, e.g. FF4

Condor and KPI (Danfoss) are characterized by increased accuracy and reliability, but have low-current contacts and require switching through an external starter. The type of relay affects the selection of further electrical circuit and automation system .

When using household devices, it is enough to directly connect the pump through its contact groups to the network. The simplicity and cheapness of this option attract many

buyers, however, this does not give other advantages. Moreover, such savings

incurs additional operating costs to replace prematurely retired

relay building (contacts burned or oxidized). At the same time, the user himself, putting a new

relay is unlikely to be able to restore the previous settings and check the operating mode that, in

in the worst case, can cause the pump to fail. Well-known saying "stingy pays twice"

does not work here: you will have to pay three times when the pump breaks down - for lifting the pump, repairing and,

for the third time, for lowering the pump into the well and putting into operation. The operation of the pump with industrial relay requires intermediate devices (various versions of control cabinets with or without additional protection devices).

Pump protection

As practice shows, the main reasons for the failure of the downhole pump are operation at increased or reduced supply voltage in the electric network, overload of the electric motor and operation in the "dry" mode, i.e. without water. Any manufacturer indicates in the technical documentation of the pump the requirements for supply voltage (this is standard 1 × 230 or 3 × 400 V) and permissible deviations relative to the nominal.

A radical way to ensure high-quality power supply to the pump is to use variable voltage stabilizers of appropriate power, which is costly.

Most often, voltage control relays are installed in the automation system. These devices shut down the pump during voltage drop and overvoltage, and can also control the sequence and asymmetry of phases (for three-phase motors). The presence of a time delay on the switch provides protection against frequent voltage surges in the network.

The motor is protected from overload by means of thermal current relays, which disconnect it when the set current value is reached. It is very important that the current relay tuning range corresponds to the rated pump current.

Pump protection against "dry" stroke can be carried out in two ways: directly - by the water level in the well using sensors (electrodes) or floats and indirectly - by the current value or shift of the current and voltage phases of the motor using special relays. In some engines, such as Grundfos MS 3 SQ pumps, this protection is already standard built-in. The disadvantage of indirect protection is precisely its "secondary": the relay operates only when the flow part and bearings are already left without water,

lubricating and cooling them. If the pump capacity exceeds the production rate of the well itself, such a situation can occur several times a day, which negatively affects the life of the pump. In this situation, it is strongly recommended to use a level monitoring electrode relay that allows the pump to be shut down before an emergency occurs.

Depending on the particular situation, various combinations and types of protective devices may be used to control and protect the downhole pump.

both by the pump equipment manufacturers themselves and by others

manufacturers.

The main processes that can be performed at pump stations by automation devices are:

1) reception and transfer of control pulse for start and stop of pump units;

2) time delay both before start-up after receipt of command pulse and between individual processes;

3) actuation of one or several pump units in the established sequence;

4) creation and maintenance of the required vacuum in the suction pipeline and pump housing before its start-up;

5) opening and closing of gate valves on pipelines at the specified moments during starting and stopping of the unit;

6) control over the established mode of operation during start-up, operation and shutdown;

7) pump shutdown in case of violation of the set mode and actuation of the standby unit;

8) transfer of pump operating mode parameter to control room;

9) protection of the unit against electrical, thermal and mechanical damages;

10) control of heating and ventilation in the pump station room;

11) protection against unauthorized persons entering the station;

12) actuation and disconnection of drain pumps and pumps supplying water for cooling and sealing of faecal pumps glands;

13) inclusion of mechanized rakes.

The integrated automated control diagram of the pump station usually consists of the following separate parts: pump inlet automation diagram; gate valve automation diagrams on the pressure pipeline; pump electric drive automation diagrams; interconnection diagrams providing the sequence of the system as a whole and implementing the necessary interlocks, as well as automatic protection of the unit and signaling.

The serial production of typical automatic pump unit control stations greatly facilitates the design, acquisition of the necessary equipment, installation and operation of automatic pump station devices. Kharkov Electromechanical Plant produces about 20 types of unified PEH control stations. Oryol Instrument Plant developed and began mass production of automatic control stations UNO1, SUNO-2 l UNO3, suitable for automatic control of depth pumps of any type. Station UNO1 is used to control electric motors with power up to 55 kW, UNO2 - up to 125 kW, UNO3 - from 125 to 250 kW.

SUNO2 station can be applied also to control of horizontal pumps for what the RK.Z relay controlling filling by pump water before its start-up is entered into the scheme.

Diagram of automatic control stations provides:

1) local, automatic and telemechanical control of the pump unit;

2) control of pump operation by means of contact pressure gauge or jet relay;

3) interlock preventing starting of the electric motor in the absence of water in the tank for wetting of the ES pump bearings before its start-up; to do this, a 1CW water availability indicator is installed (for pumps of other types, a jumper is installed instead of the indicator);

4) disconnection of the electric motor in case of violation of normal operation mode of the pump unit, in case of water flooding of the pump station pavilion or in case of bearing overheating;

5) alarm at emergency stop of pump unit and opening of pump station pavilion doors.

At local control the control panel selector switch is set to "Local" position. At that contacts of selector switch 1 - 2 are closed. The unit is controlled by "Start" and "Stop" buttons (Fig. 13.7). In case of local control, the pump operation monitoring circuit is switched off. During automatic control the control panel selector switch is set to "Automatic" position. At that contacts of selector switch 7 - 8 are closed and contacts 1 - 2 are opened, disconnecting local control. At telemechanical control the control panel selector switch is set to "Telemechanical" position. At that contacts of selector switch 5 - 6, 9 - 10 are closed and contacts 1 - 2 of local control are opened. For automatic control, jumpers are placed on the terminal panel of the control station between terminals 5 - 5a, 15 - 15a. The opening contact of the automatic control sensor is connected to terminals I and 15, and the closing contact is connected to terminals 11 to 23.

At telemechanical management after giving of a command impulse "to Include" on a chain: "the Z terminal - contacts of PU 5 - 6 - crossing point 7 - 7a - the disconnecting contact of RPL - crossing point 89 - 5" works the relay of inclusion of RCP. By its closing contact, the ILV relay includes a control relay of the thrust reverser, which is self-blocked by its closing contact through the opening contact of the thrust reverser. The other closing contact of the thrust reverser turns on the starter coil and prepares the circuit of the control relay of the IH pump operation.

RP control relay operates with a time delay of 5 s. This ensures restoration of pump unit operation in case of short-term voltage loss. Simultaneously with actuation of starter L, 1RK monitoring relay starts operating. If the pump pumps water, contacts of the jet CP1 relay will be opened and relay 1PK will be returned to a starting position. If during operation of the pump the water supply decreases, the contacts of the relay CP1 are closed, the relay RK will operate and its opening contact will turn on the emergency relay PA. To release, turn off the machine and find out the reason for the unit shutdown. Similarly, the unit is disconnected when the bearings are overheated, the pavilion is flooded or the pavilion door is opened.

Figure 13.8 shows the diagram of automated control of pump units at the sewage pump station.

The main circuit of automatic control of pump units "of sewage pumping stations is to prevent overflow of the receiving tank above the specified level. Liquid level is controlled by electrode switch * ERSU2. The electrode sensors are installed on a special metal structure in the receiving tank, and the signal units are installed on the wall of the grid room (see Figure 13.1).

Pumps are started when the gate valve is open. When the level of waste liquid P3 is reached, the 4D actuation electrode through the intermediate relay 1RU and the magnetic starter L-1 turns on the first working pump. In addition, the 1RU intermediate relay through the L-2 magnetic starter will turn on the seal seal pump and the KEP1 instrument for automated control of mechanized rakes. If the liquid level continues to rise, at the level of P2, the electrode for actuation of the DD through the relay 2RU and the magnetic starter L-3 will turn on the second working pump and the second device KEP2. If the second pump does not operate, then at further increase of the liquid level in the receiving tank to R2, the 2D actuation electrode will switch on the standby pump unit.

Electrode 1E signals that the emergency level of liquid in the tank is reached and through the RP relay provides a pulse to close the gate valve in the receiving and emergency chamber.

The intermediate relay of the switchgear of the electrode sensor includes a magnetic pump starter, in addition, the switchgear relay is blocked in the ON state through the corresponding trip electrode (LED for the second pump and 4D for the first pump). Such interlock ensures the sequence of disconnection of the operating pumps.

When the level of waste liquid in the tank and the outlet from the liquid of the electrode 2E decreases, after a given time delay, the RVP relay turns off the standby pump unit. When the level drops to P%, the second pump goes out of operation and the CEP2 device is switched off through the contact of the 2PU relay. When the level drops to Rg, the 4D electrode exits the liquid and the first working pump goes out of operation. Relay 1RU which through the contacts in control circuits of pumps of hydroconsolidation of sealing glands and the KEP1 device switches off them from work is at the same time cut off power.

For mechanized grate rakes, local and automated control is provided according to the time program obtained using the command electro-pneumatic device KEP12U. Time of operation and pause of mechanized rakes is established by experience of operation of sewage pumping station. The KEP12U device allows you to change the start and stop time from 3 minutes to 18 hours.

In case of rake pinching, limit moment clutch is actuated in grille penetrators, electric motor is switched off and sound signal is turned on, at the same time alarm lamp supplies signal to control panel.

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