Many manufacturers offer pumps in standard materials that can be shipped quick at a minimal cost.  For some applications, this may be an attractive option.  For many applications in corrosive and/or erosive environments, a carefully planned design that considers the environment and requirements of the pump may reduce costs and fallout later.

Factors to consider when designing a pump

  • Pressure – This is the force per unit area for the fluid to flow through the pump.
  • Properties of the fluid – The visible and chemical properties of the fluid heavily impacts the pump and corrosive consideration and are imperative in design. If a fluid carries solids through the pump and the swiftness of the momentum is too slow, the result could be settling.  Conversely, there may be a high rate of metal loss on the pump if the momentum is too high.  Ideally, there should be an equalization of pressure and flow to avoid erosion.
  • Temperature – An often overlooked factor is the temperature of the fluid. Sometimes, certain parts of the pump that experience higher temperatures can face corrosion more than the rest of the pump.
  • Size – The size of the pump plays a part in what materials should be chosen.

Materials that impact pump use and maintenance

Usually castings are used for pump bodies.  Selection of the right alloys is particularly important because some alloys are harder to cast than others.  Often, the corrosive and mechanical properties of cast alloys and wrought alloys are different.

In the pulp and paper industry, massive amounts of water and other fluids are processed through the pumps in place.  Alloys that work harden under these conditions are especially important. Though it is possible to determine an alloy’s resistance to corrosion with a variety of tests, there are fewer when it comes to determining its erosion resistance.  ASTM G76 is one of these tests that determines erosion as well as cavitation.

Other factors that can affect erosion    

Other factors can affect the erosion rates of alloys in pumps.  Besides pressure, flow, and temperature, the pH, gasses, and the diameter of the pipe itself may affect erosion corrosion.

Turbulence is caused by high momentum, impediments in flow, or a change in direction. When flow is turbulent, corrosion becomes a steady cycle.  The oxide layer is being continuously washed away.  The swiftness of the fluid compared to the size of the pipe, results in this wear.  At normal temperatures, nickel alloys are highly resistant to corrosion from moderate changes in pH.

Alloy K500 (N05500) is a nickel-copper alloy which combines the excellent corrosion resistance of Alloy 400 with the added advantages of greater strength and hardness. Typical applications for Alloy K500 products are chains and cables, fasteners and springs for marine service, pump and valve components for chemical processing, doctor blades and scrapers for pulp processing in paper production, oil well drill collars and instruments, pump shafts and impellers, non-magnetic housings, safety lifts and valves for oil and gas production, and sensors and other electronic components.

Alloy 6B is a cobalt-based alloy with outstanding resistance to most types of wear. Its wear resistance is inherent and not the result of cold working, heat treating, or any other method.  Alloy 6B is well suited for valve parts, pump plungers, doctor blades, knives, wear plates and bearings.

We inventory an extensive range of bar in Alloy K500 and Alloy 6B. Download our full Data Sheets and login to Request a Quote.  Our industry experts are always available to answer all your questions about how we can help you with your alloy needs.