Material
Materials for industrial pumps – materials for components in contact with media
The selection of suitable materials is crucial for the reliability, service life, and durability of industrial pumps. Particularly critical are the components in contact with media, i.e., those components that are in direct contact with the pumped medium. These include:
- Pump housing
- Impeller, paddle wheel, or rotor
- Drive shaft and shaft seal
- Internal coatings, linings, and seals
These parts must be chemically, thermally, and mechanically resistant to the pumped medium (temperature, pH value, solids, etc.) and the operating conditions (especially pressure). Numerous materials are available for manufacturing the various components in order to achieve maximum resistance and durability. Conversely, this also has a positive effect on lower costs due to less maintenance/repair or even unscheduled breakdowns and downtime.
Metallic Materials
Metals are the first choice in many applications because they offer high mechanical strength and temperature resistance. Different alloys are used depending on chemical resistance:
- Grey Cast Iron: Cost-effective, good castability, suitable for neutral media, but limited corrosion resistance.
- Stainless Steel: Good resistance to many chemicals, widely used in chemical, food, and water technology, also high corrosion resistance.
- Bronze: Corrosion-resistant, especially in seawater applications and with slightly aggressive liquids.
- Duplex Steels: Higher corrosion and stress crack resistance, particularly suitable for chloride-containing media.
- Hastelloy: Nickel-based alloy, extremely resistant to oxidizing and reducing chemicals such as hydrochloric acid, sulfuric acid, or chloride-containing solutions.
- Titanium: Excellent resistance to highly oxidizing acids and aggressive media such as glycolic acid, long service life with low corrosion rate.
- Nickel, Monel, Inconel: Other high-alloy materials for special applications, such as high temperatures or extremely corrosive environments.
Non-metallic Materials (Plastics and Composites)
In many cases—especially with highly corrosive media—plastics or lined components are used:
- PP (polypropylene): Chemically resistant, inexpensive, limited temperature resistance.
- PVC (polyvinyl chloride): Good resistance to acids and alkalis, limited temperature and pressure resistance.
- PVDF (polyvinylidene fluoride): Higher chemical resistance, suitable for strong acids.
- PFA (perfluoroalkoxy alkanes): Excellent resistance to almost all chemicals, temperature and diffusion resistant – often used for linings in chemical pumps.
- PE (polyethylene): Good abrasion resistance, especially when exposed to solids.
- ETFE, ECTFE (Tefzel, Halar): Fluoropolymers with broad chemical resistance, especially for demanding applications.
Fiber-reinforced plastics (FRP, GFK) or composite materials (e.g., SiC composite ceramics) are also used when a combination of chemical resistance and mechanical strength is required.
Ceramic Materials
Ceramics or Silicon Carbide (SiC) are often used for highly abrasive or corrosive pumped media:
- Ceramics (e.g., aluminum oxide, zirconium oxide): Excellent abrasion resistance, extremely hard, chemically inert.
- SiC (silicon carbide): Extremely wear and corrosion resistant, often used for mechanical seals, bearing seats, or as a lining.
Material Selection for various Components
- Pump housing: Must be resistant to both the pumped medium and external influences (e.g., cleaning agents, environmental influences). Often made of metal, even in plastic pumps.
- Impeller/paddle wheel: Bears the main load during pumping – therefore high requirements for chemical and mechanical resistance. Materials often used depending on the medium: stainless steel, Hastelloy, plastic (e.g. PVDF), ceramic.
- Drive shaft: Must withstand high mechanical loads, often made of stainless steel, duplex or Hastelloy. For critical media, it is designed with a protective coating or as a shaft sleeve.
- Seals and shaft seals: Often come into contact with aggressive media. Materials such as PTFE, FKM (Viton), EPDM, or ceramics are selected depending on the application.
Selecting the right material for pump components is therefore essential for trouble-free and long-lasting operation. It must always be made in close coordination with the medium to be pumped, the process conditions, and the requirements for service life. Today’s wide variety of materials makes it possible to find a suitable solution for almost any pumped medium—from inexpensive gray cast iron to high-performance materials such as PFA, Hastelloy or Titanium.
