In chemical-handling applications, pump material selection can have a significant impact on the efficiency, performance and lifespan of equipment.
In this article we explore materials used for common pump components and their suitability for dosing and transferring chemicals and abrasive fluids in water-treatment processes.
From swimming pools to power generation, operators must make a number of vital considerations during pump selection to ensure parts are compatible with the media to be transferred or injected.
Failure to do so inevitably results in component and system failure, which, as well as causing expensive and inconvenient unplanned downtime and increased maintenance requirement, can have damaging consequences such as contamination or environmental harm.
Seal materials
Nitrile rubber (NBR) is among the commonest solenoid valve seal materials, largely due to its low compression set which means it maintains its shape post-compression. NBR has superb temperature resistance from -30°C to 120°C and is being best suited to handling mild chemicals.
EPDM is one of the most water-resistant rubber materials and is compatible with caustic solutions, dilute acids and alcohols as well as having good resistance to cracking, abrasion and ageing. The material withstands temperatures from -50°C to 150°C while retaining its flexibility, which is why it is commonly used for diaphragms, ball checks and O-rings.
PTFE, with its extreme corrosion resistance to most acids, alcohol, detergents and solvents, is well known for its superior chemical compatibility and is commonly found in diaphragms, ball checks and O-rings. PTFE’s exceptional temperature range from -260°C to 260°C means it maintains performance in extreme conditions while its low friction coefficient makes it ideal for the production of seals.
Hytrel® is a versatile thermoplastic elastomer popular in diaphragm production for its resistance to oils, fuels and hydrocarbon-based solvents. Hytrel has excellent protection against flex fatigue, retains its properties at high temperatures and offers superb durability – ideal in industrial applications where reliability is essential in demanding conditions.
Santoprene® is a trademarked thermoplastic rubber resistant to a wide range of solvents and chemicals including alcohols, ketones, glycols and esters. Commonly used for the production of peristaltic tubing, the product has the same levels of flexibility and durability associated with natural rubber compounds.
Polypropylene is a general-purpose material commonly used for seats due to its high chemical compatibility that offers resistance to media such as citric acid, formaldehyde and sulfuric acid. The robust material also provides good protection against water absorption, wear, heat and stress cracking – essential qualities in seal production.
Chemical resistance
PVDF, as well as its excellent capacity for withstanding high temperatures, boasts strong chemical resistance to acids, bases, organic solvents, chlorine and bromine. These characteristics mean PVDF is often used for wetted pump parts – including seats and heads – in pressure-driven water and wastewater-treatment processes.
Aluminium components are used in a broad range of applications due to their resistance to solvents and hydrocarbons. As well as excellent corrosion resistance, aluminium benefits from low density – ideal for systems requiring high strength but lightweight components.
Viton®, often used to manufacture O-rings, offers excellent resistance to caustic and acidic media, hydrocarbons and oils and also withstands solvents such as ketones and acetates. The material is highly durable against oxidation and heat up to 204°C and has a tear resistance of 20 kg/cm, making it robust and reliable.
High corrosion resistance
Stainless steel is highly resistant to corrosion and can therefore handle most acidic media depending on the concentration and type of acid, temperature and steel grade. For example, grades 316 and 317 offer resistance to phosphoric acid at most concentrations; grade 904 offers resistance to high concentrations of sulphuric acid; and types 304L and 430 are resistant to nitric acid.
Whatever your pump application, make component material selection a key consideration when ordering equipment to ensure you achieve the performance, longevity and cost-effectiveness you require.
