Diaphragm Type Metering Pumps

Madden Metering PumpWhat spare parts should be stocked for a metering pump if we don’t know much about metering pump construction?  We have prepared the following list to help you understand the common service parts of a metering pump to help the pump specifier to document the needs of your application.

In our previous blog articles on specifying a metering pump we stressed the importance of matching the liquid to be pumped with wetted end materials of construction that can safely and economically handle the liquid.  What are the spare parts that are normally stocked to replace parts that wear out after prolonged service?

  • Madden diaphragm metering pumps can be relied on to pump critical chemicals for industrial operations 24/7/365 for a number of years.  But there is a limited service life for some of the parts, particularly the wetted end parts that come in contact with the liquid being pumped.  No one wants to deal with a pump that goes down, and they typically do that on a Saturday evening or during a holiday period.  Having the correct parts on hand to enable the maintenance people to make quick repairs is essential to keeping critical plant operations going.
  • The Madden diaphragms are heavy duty molded rubber construction with Nylon fabric reinforcement.  We offer diaphragms in Neoprene, Hypalon, Viton, Teflon faced Viton and Teflon faced Neoprene.  The service life of the diaphragm is determined by chemical compatibility and the flex or fatigue life of the diaphragm.  Neoprene offers the best flex life, and Neoprene diaphragms may go as many as 100,000,000 strokes.  Being more rigid, Teflon offers lower fatigue life, but Teflon has more universal chemical compatibility.  Madden offers the Type DDB double diaphragm option for pumping dangerous liquids that could damage equipment or the environment in the event of a diaphragm leak.  The primary diaphragm that comes in contact with the liquid has a molded in threaded fastener that connects the diaphragm to the piston.  The secondary, or back up diaphragm has a hole in the middle of it.  Stocking a pair of diaphragms for the eventual replacement that will be required is recommended.
  • Valve seats take the constant impact of the seating of the valve check ball, as well as the action of the chemical being pumped.  When valve seats, and valve balls as well, become worn the seating of the check valves is compromised, and the output of the pump will be subject to deterioration.  Keeping a supply of valve parts on hand for replacement of both the inlet and outlet check valves that are integral with the pump is recommended.  In addition to the seats and valve check balls there are Teflon valve cushions and valve gaskets that will be needed for the valve repair.
  • For liquids that are abrasive, such as diatomaceous earth slurries, or suspensions of lime or calcium carbonate or other solids suspensions, Madden offers several valve seat options for the MF Series and MH Series pumps to extend the life of the valve seat.  Obviously you would want to stock spares of these valve seats if abrasive wear is an issue for the pump.
  • For Madden model MF series and MH Series another recommended spare part is the flexible shaft for the output adjustment knob.  Those parts can become damaged if the adjustment knob is turned when the pump is not operating, and there is also the fatigue factor of millions of piston strokes on that part.

Those are the major spare parts components recommended for a Madden metering pump.  While all parts are available in the Madden factory inventory for pumps going back to 1960, you will want to have spares on hand for immediate replacement when parts are worn out.  For more information on the Madden pumps click on this link.  For additional help in specifying a metering pump for your  application, consult the Madden Pump Selection Guide on our website, call us, or send us an email inquiry.  We are always quick to respond.