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Air Supply Considerations for an Air Motor on a Molten Metal Pump


Air Supply Considerations for an Air Motor on a Molten Metal Pump

Our pumps are offered with air motor options. Air motor benefits include:

  • No electrical connections and associated complexities.
  • Pump speed is easily controlled by regulating the air pressure.
  • The pump can be run from a nitrogen bottle during maintenance or emergencies.
  • Air motors run cooler than ambient temperatures.
  • Air motors are lighter weight than their equivalent horsepower electric motor.

Air Pressure – All our pumps use air motors with a maximum recommended air pressure of 100 psi (690 kpa). A combination of pressure and volume determines motor speed. In most cases, maximum motor speed is not desirable, so a regulator is required to moderate the pump speed.

Air Volume – The necessary volume of air (cfm/lpm) is a function of the horsepower rating of the motor. This table provides reasonable guidelines:

hp cfm table

The illustration below shows an ideal air supply setup for an air motor used in a high-temperature application:

molten metal pump air supply setup

Important considerations:

  • The master valve is used to cut off the air supply for servicing the air supply components including the filter, regulator, oiler, etc.
  • The master valve location may be selected based on safety considerations. Closing the master valve or the quick acting valve will stop the operation of the pump.
  • The factory air supply may be “CDA” or clean, dry air. If this is the case, eliminating the filter/separator is acceptable.
  • The quick acting valve is typically a simple quarter turn ball valve located for ease-of-use and operator safety.
  • A flow meter may be installed in series with the pressure regulator to provide additional operating information.
  • The line oiler provides lubricant to the air motor. Due to the high temperatures of this application, the oiler must be located away from the molten metal bath.
  • In most applications, it is desirable to use a flexible air hose between the oiler and the air motor. We recommend a 1” (2.5cm) air hose.
  • The flexible air hose should not be subjected to convective heat flow from the metal bath, so a length of steel pipe is used to span the molten metal bath.
  • Maximum airflow is crucial:
    • Use only FULL FLOW VALVES such as ball and gate valves.
    • Do not use needle valves. These will restrict flow.
    • Do not use quick-couplings. These also restrict peak flow.

IMPORTANT NOTE – Maximum airflow is the only way to ensure proper air motor operation and significantly reduce the risk of freezing the pump.