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Articles


01.07.2012

Safety cushion: Application of Control & Protection stations for deep-well pumps

In installing submersible pumps quite often the Customers are inclined to forget that in order to ensure reliable and long life of the pump it is necessary to control uninterruptedly work process-related parameters, to exclude influence of negative factors added by the supply mains, not to admit operation of the pump in case of water shortage within the well.
Authors :
Anton Afanasyev, Program director
Alexander Kostyuk, Program Director, Doctor of Physics and Mathematics
Sergey Sokolov, principal engineer
Publication :
  • Magazine "WaterMagazine", №6 (58), June 2012

Continuous service of the pump beyond the operating range results in drop of its lifetime by many times. For example, during jobsite evaluation of the wells of the one of district water-pumping sources it has been revealed that, in practice, the pump ECV 10-65-110 consumes 53 kW instead of power rating of Р1=33,4 кW. Arising from this is the reason for carrying out replacements of the pump every 1,5-2 years of operation in place of standard three-five operating years for the ECV pumps. Such example is not a single one. 

Therefore the correct selection of the pump and further application of Control & Protection Stations (Control Panels) are especially important. Constant control over electrical parameters of pump operation allows to take notice of all operational deviations. Deviations to a greater or lesser extent than nominal parameters indicate that the pump operates outside the operating range. High power consumption is an indicative that the pump is overloaded and, most probably, it has been selected with overrated head. On the contrary, too low power consumption gives evidence of insufficient head of the pump, in this case the electric motor is likely to be overheated due to decrease in speed of the cooling flow.

It is necessary that the control station makes it possible to control parameters of the supply mains and consumption current in the course of pump operation.

It is also important to take control of insulation resistance of the motor winding in order to prevent insulation failure.

Only the proper choice of the control station of high quality, designed by the pump Manufacturer with due account for operation practices of the submersible pumps, and its correct setting may provide guarantees for the User on correct operation of the pump motor without overloading: thus preventing early pump breakdown. Reliable protection prolongs lifetime of the pump by way of avoiding its operation beyond the operating range.

All above-indicated requirements are fully supported by updated line of HMS Control L3 panels for submersible pumps. Entered in the said line are stations designed for pump units having a power of up to 132 кW. The new modern controller of native design ensures precision measurement of the parameters, convenient settings and visual display of pump operation.

The use of state-of-the art accessories offered by leading world manufacturers guarantees safe trouble-free operation of the station over entire period of operation.

Depending on specific water-supply scheme at the using activity of the Client the station can be used for delivery of water to the reservoirs, network operation of the pump (keeping of pressure according to the pressure sensor), and pumping water out of the reservoirs. Since the drainage function is available one should use the HMS Control L3 panel to control not only deep-well pump units, but submerged drain pumps as well. In order to control the level of water within the tank (or line pressure) use can be made of different types of the sensors: electrocontact manometers, pressure sensors, float switches, electrodes.

Output signals of dispatching control and also provisions for remote mode of operation make it possible for the operator to control the operation of the pump by using remote panel (operator stand). In case of necessity the said signals may be transmitted by communication interface Modbus or by radio channel (optionally).

Standard climatic version U2 and wide range of operation temperature from -40°С up to +40°С allows to locate the  control stations in the halls or under the shed without additional heating.

Standard protection functions of the control stations may be completed at option with:

  • protection of the station and pump at uprating of supply voltage
  • protection against pulse overvoltage during lightning
  • additional temperature sensor for the motor winding
  • emergency switch positioned on the door of the control cabinet

The family-related control stations HMS Control L3 are also offered with included soft start of the pumps. The cost of the said control station is higher than the cost of traditional stations with direct start. But in this case the Consumer acquires prime advantages of the soft start & stop features:

  • Cutting in starting currents by 2-3 times. Drop in peak loads imposed both onto the motor and on the supply mains. Contactless and noiseless switching, absence of overloads allow to increase the reliability of motor-starting devices.
  • Lowering of electrical losses within the electric motor.
  • Lowering of mechanical loads imposed onto the pump & motor components. Reliability growth by way of elimination of the impact loads onto the most responsible elements of the unit design (impellers, bearings of the pump and electric motor).
  • Because the start-up of the deep-well pumps is not always supported with closed condition of the gate valve as required: so it causes overloading of the electric motor, and in this situation the proposed smooth speed enhancing feature may prevent these effects.
  • Avoidance of the transitional regimes which might appear during direct start-up – namely, «floating-up» of the impellers and backspacing of the rotor.
  • Elimination of water hammers in the pipes and gate valves at the moment of starting & stopping the system. If the non-return valve is not enabled, so abrupt rise of pressure (hydraulic impact) may lead to breakup of the impeller and diffuser.

Besides, some Consumers observed that the quality of supplied water just after elimination of hydraulic impacts because of soft starting & stopping the pumps is to be improved. (“Deficit was left in the past”, issue of magazine “Water Magazine”, №2(54), February, 2012, pages 4-6).

So, as experience shows, the use of the HMS Control panels with soft starting makes it possible to prolong working life of the motor and pump.

Despite the specific advantages of soft starting, bear in mind, that the time of starting shall be limited and reach 3 seconds maximum. This is due to the fact that the deep-well pumps are provided with plain bearings, the standard lubrication duty of which requires minimum acceptable rotary speed.

As a rule, there appear to be advisable to use soft starting for the pumps having a power more than 7,5 кW. For more greater deep-well pumps (ECV10, ECV12) the soft stating is always required. It is also essential feature if the pump is operated with frequent starts and stops.

Therefore, practical use of control & protection stations of high quality offers advantages to the User on operation of pumping equipment, among which are the following ones:

  • increase in lifetime of the equipment
  • improvement of quality and reliability of water service of the Client
  • accident prevention
  • simplification of work and maintenance, guarantees for safety of the personnel