Automation for submersible pumps

By Admin | Heating
26 May 2016
Under automatic in this case means a set of command relays, power electrical parts and various types of protection, whose main task - to protect the motor and the pump itself from failure.The most widespread two basic schemes pump control: the level of the working medium (water) in the storage tank and the pressure in the pressure pipe.

control the level of

first scheme is used for the pump on a water tower or a filling capacity, where water is supplied to the consumer is already the second lift pumps.Inside the tanks are installed special level sensors (electrodes) that are using monitoring relays monitor the lower level (including pump) and upper (pump off when filling the reservoir) levels.The use of this scheme float switches instead of the electrodes is less reliable due to their small work resource.Be sure to provide an emergency drain tank overflow (overflow warning it usually does not apply).This scheme is typical for large township well as from one water tank made of a holiday village, the
village, the village.

main advantage that is achieved with this approach, - a stable operation of the pump.Hydraulics is constant nominal flow is fed to a height determined by the depth of the well, tall towers and further provides 1-2 meters - on the spout.One cycle corresponds to the total volume of consumption of the tower with the current flow of demand.The possibility of short-term start-stop, which prolongs the life of the equipment.It is enough to choose wisely the pump under the required parameters, once qualified to make commissioning and stable operation of the system is ensured.

control pressure

In the second scheme, the pump is controlled by commands from the pressure switch installed on the pipeline.In relays are set two parameters: the pressure switch on the pump and the pressure at which the pump should be shut down.This scheme is typical for individual wells and is usually used in conjunction with membrane tanks, designed to maintain the required excess pressure in the network, compensation for water hammer and low costs.It is extremely important to make the correct setting the relay in accordance with the characteristics of the pump and the volume of the membrane tank.To pump is not too often defined pressure limits should lie in the middle zone of the performance of the pump.Hysteresis values ​​selected usually in the range of 1.2-2.5 bar based on the data about the number of pump starts at a certain period of time.

relay pressure applied in this scheme can be divided into domestic and industrial.First, for example, the relay MDR firm Condor, XMP (Telemecanique) et al., Have powerful contact group, capable of withstanding current up to 16 A, but are not equipped with dials indicating the regulated pressure range.Setting of the relay is carried out using a pressure gauge.The advantages of this type of relay is their relatively low cost and the ability to use in power circuits (for direct control of the pump).Disadvantages - low accuracy settings and small service life - due to the influence of large inrush currents.Industrial relays, for example, FF4 companies Condor and KPI (Danfoss), characterized by high accuracy and reliability, but have a low-current contacts and organizations require switching via an external contactor.Relay type influences the choice of the further circuitry and systems automation.

When using household devices rather directly connect the pump through its contact groups to the network.The simplicity and low cost of this option attracts many buyers, but other advantages it gives.Moreover, such savings entails additional costs in the operation to replace a failed prematurely relay (scorched or oxidised).At the same time the user by placing a new relay, unlikely to be able to restore the old settings and check the mode of operation, which in the worst case, can lead to failure of the pump.The famous saying "miser pays twice" does not work here: to pay at the pump will have to break three times - for the lifting of the pump and repair, for the third time, for lowering the pump into the well and commissioning.To work with an industrial pump relay needed intermediate devices (different versions of control cabinets with additional protection devices or without them).

Pump protection

Practice shows that the main causes of failure of the downhole pump is operating at high or low voltage power mains, motor overload and work in the "dry" course, iewithout water.Any European manufacturer indicates in the technical documentation of the pump requirements for the supply voltage (in Europe the standard is 1 230 × or 3 × 400) and tolerances with respect to the nominal value.

radical way to provide high-quality power to the pump - is the application of AC voltage stabilizer of suitable capacity that expensive.The most common automation system installed voltage control relays.These devices shut off the pump when the voltage drops and overvoltage, and can also control the sequence and phase unbalance (for three-phase motors).The presence in the relay time delay by inclusion provides protection from the frequent surges.

Motor protection against overload by means of thermal current relay, disconnect it upon reaching the set value of current.It is important that the setting range of the current corresponds to the relay nominal current of the pump.

Pump protection from 'dry' progress can be done in two ways: directly - by the level of water in the well by means of sensors (electrodes) or floats and indirectly - by the value of current or the phase shift of the current and voltage of the motor using special relays.In some engines, for example, MS 3 SQ pump company Grundfos, this protection is already integrated as standard.The disadvantage of indirect protection is precisely its "secondary": The relay is activated only when liquid end and the bearings have remained without water, lubricating and cooling them.If the pump capacity exceeds the debit of the well, this situation may occur several times a day, which negatively affects the life of the pump.In this situation it is strongly recommended that you use the electrode level switch, which allows you to disable the pump before an emergency.

Depending on the particular situation to control and protect the borehole pump can be used different combinations and types of protective devices, produced both by manufacturers of pumping equipment and other manufacturers.Consider staying at the products on the market today.

They can be divided into three groups: puskozaschitnoy devices collected on the basis of printed circuit boards - QA / 50B, QA / 60C firms Maniero, SK-701 Company Wilo, etc .;control units on the relay technology - SK 277 (Wilo), «Hydromat» H110-H311 («Gidrolans"), etc .;control system based on microprocessor devices - SPCU3 (Control) MP204-S (Grundfos), SK-712 (Wilo) or similar.

devices based on printed circuit boards are functionally and structurally finished product and require an external device - often through proper pump starter and transmitters (level, pressure switches, etc.).However, they differ in a large set of controlled parameters and functions (thermal overcurrent protection, surge protection, control 'dry' progress through the electrodes and the load of the motor and the like), which, however, do not always use.Thanks completeness change the logic of the device is practically impossible.In some devices, there is no possibility of changing the values ​​of certain parameters of operation.In the event of failure of the board should be replaced entirely, which is comparable to the cost of the new device.

spectrum on the market of devices on the relay technique is quite wide - from the most simple example, SQSK (Grundfos), to multi-pump control cabinets, which are produced directly on the requirements of the customer.SQSK module is a regular starter in plastic casing.Its function - only switching of the pressure switch with a current of up to 4 A. In practice, this unit is no longer protects the pump itself and the pressure switch.No alarm condition or settings.Requires installation of the external circuit breaker.

Control and Protection N110 manufactured by "Gidrolans" has a plastic waterproof housing dimensions 310 × 230 × 130 mm, with hinged removable transparent cover, protection class IP65, sealed cable glands for connection.The module includes a contactor with adjustable thermal overload current protection, voltage monitoring device with built-in digital voltmeter, showing the value of the supply voltage, the lamp signaling modes of operation, the circuit breaker for the internal control circuit, a two-position mode switch to "On. / Off.".

As an option, the unit can be equipped with one or two level switch RM4LG company Schneider Electric and terminals for connecting electrodes.Hardware "filling" of the device protects against all major threats to the downhole pump: When working with an overload current protection is triggered;when loss or power surges monitoring relay interrupts the control line and the pump does not turn on until the voltage returns to normal;restart when power is restored automatically.The digital voltmeter shows the operating voltage, indicating the reason for failure, which is convenient for the end user.

advantages of this type of devices are their relative simplicity and reliability, rapid modernization and adaptations for non-standard applications in case of failure of some parts changed only refused to detail.

Control and protection of submersible pumps on the basis of microprocessor controllers - the most difficult.They allow you to control the parameters of the pump such as the insulation resistance, the motor temperature, phase asymmetry and phase sequence, protects the pump from the high and low voltage, overload and the "dry" course, enables you to record the time of the pump and the amount of electricity consumed.There is the possibility of communication and control pump operation through standard interfaces with a modem or a computer.These are the most expensive devices, and apply them to the recommended pump high power and performance, when the cost of possible repairs of the pump may far exceed the cost of the automation.Setting up and putting into operation of the above devices are virtually impossible without specialists.

In the case of control systems of frequency inverters, observe the minimum speed of the motor.This characteristic is indicated in the technical documentation to the pump and is typically 20-30% of face value.In the case of non-compliance with this requirement, there is a high probability of failure of the thrust bearing of the motor pump.

addition to the above, special attention should be paid to the class chosen by control dust and water resistance, depending on the installation location (see. GOST 51321.1-2000 "Devices complete low-voltage distribution and control").

"Aqua-Therm" № 3 (37) 2007