Operation & Maintenance Process Equipments

Canned motor pump and Typical start-up procedure.

Canned motor pump over view

Canned motor pump or sealless pumps they are developed to eliminate the liquid leakage to the atmosphere. This leakage is usually toxic or dangerous to the environment or very expensive.

The two categories compete against themselves magnetic drive pump and canned motor pump this article will manly target canned motor 'pump start-up procedure please (see Figure 1). Canned motor pumps use product lubricated bearings. These bearings are usually cooled and lubricated by the pump liquid.

A canned motor pump (CMP) is a combination of a centrifugal pump and a squirrel cage induction motor built together into a single sealed unit. A portion of the pumped fluid is allowed to reticulate through the rotor cavity to cool the motor and lubricate the bearings (see Figure 1).

Preparation of canned motor pump for start-up.

Never start up the pump without pumping medium!  This will lead in all cases to destruction of the slide bearings.

  1. If the pump is to be cooled or heated, open the corresponding stop valves and regulate the flow; allow the steady-state temperature to be reached in heated pumps. If monitoring equipment is used, adjust the monitoring equipment. The shutdown temperature of the temperature probe depends on the operating temperature of the pumping medium, and it should be 10 to 15°C higher than this temperature.
  2. Correct priming and venting of canned motor pumps are essential for proper operation and pump start-up.
  3. Open the stop valves on the suction side in the by-pass lines.
  4. If the pump is vented to the discharge line then open the stop valve on the discharge side completely once, and then closed almost completely again before pump startup.
  5. If the pump cannot be vented into the discharge line, for example if a non-return valve is used or if other pumps are already operating in the same discharge line, the pump must be vented by means of a separate air bleed cock on the discharge side or the by-pass line.
  6. When liquids are pumped which form gases or vapor which must not escape, the pump is vented into the suction vessel through piping which can be sealed off.

Canned motor pump start-up procedure.

  1. Close the priming and venting lines.
  2. Open the valve in the discharge line slightly.
  3. Open the valve in the inlet/suction line completely.
  4. Start the motor.
  5. Check the direction of rotation of the canned pump. To check direction of rotation: If the canned pump does not reach the required discharge head as listed in the technical specifications and it has been ensured that all air or gas has been removed from the pump (by starting again if necessary), the pump is operating in the wrong direction. In this case, change the phase sequence of the power supply and check discharge head.
  6. When the manometer indicates pressure, open the discharge gate valve until operating pressure has been attained.

Attention! The pump should operate for only short periods when the discharge gate valve is closed (excessive heating).

7. The pump flow and power requirement of the pump increases with decreasing discharge head.

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