Food grade pumps for food processing

There is no rag on a food line, so the wastewater failure list does not transfer. Four things shorten a pump's life here, and heat is the one that catches people out.

1. Temperature. Frying and hot-fill duties are the hard ones. The hotter the medium, the harder it is to seal, and the choice of pump narrows to what can be sealed at that temperature against that product. Temperature and medium together drive the sealing arrangement. Flow and head do not.
2. Cleaning. With no clean-in-place regime, or a weak cleaning procedure, you get product contamination. Crevices, dead legs, a rough internal finish and a head that will not drain are where it starts. Strip a pump down to clean it and you add a reassembly step, which is where gaskets get pinched and seal faces get marked.
3. Speed in an abrasive medium. Run a positive displacement pump too fast on anything abrasive and the wet end wears out early. Abrasive and shear-sensitive media both want pumping slowly, so the pump gets a size bigger and turns a good deal slower for the same flow.
4. Pressure. High discharge pressure shortens the life of a food pump the same way it shortens any other, and on a hygienic build it usually shows up at the seal first.

Viscosity sits underneath all four, and food is the sector where it moves most. The question we ask is whether the medium is water, or as water. Product runs from thin brine to starch that barely moves, and the same product changes as it heats and cools through the line. Design for the worst case, not the typical one. Size on the medium as it behaves at the warm end and you get a pump that stalls every cold start.

One more is a system fault rather than a pump fault. A food factory came to us with repeated suction inlet blockages across a bank of pumps and asked us to replace the lot with something bigger. The pumps were sized correctly. Changing the inlet size fixed it, and the pumps stayed where they were. Look at what the pump is connected to before you condemn the pump.

Select the type against the medium, then size the unit against the duty point. Doing it the other way round is how the wrong pump gets specified accurately.

The trade rule of thumb is roughly 3–4% solids. Below that a centrifugal pump is usually right; above it, move to positive displacement. Viscosity pushes the same way, and on a food line viscosity is normally what decides it.

• Thin product, higher flow. Brine, juice, wash water and CIP return. A hygienic centrifugal pump is cheaper to buy, cheaper to run and simpler to clean. It will shear a delicate product and it will struggle as the medium thickens.
• Viscous or shear-sensitive product. Sauces, emulsions, creams, fruit preparations, starch. A rotary lobe pump displaces product instead of beating it, and holds its flow rate to within a few per cent as the discharge pressure moves. Run it slowly for shear-sensitive media.
• Very thick product. Where the medium barely flows, a progressing cavity pump will move it. The trade-off is dry running: take the liquid away and it burns through the stator and damages the rotor, which is a rebuild rather than a seal change.

Positive displacement costs more up front and turns more slowly. It also gives you more wetted parts to clean and a discharge that needs relief protection. What you buy for that is tolerance. A positive displacement pump will move broadly whatever you can get into it, from water to very thick product, and it holds its rate while a centrifugal's flow swings with pressure. On a line where the product changes through the day, that is usually worth the money.

Air-operated diaphragm pumps have a genuine place, and it is narrower than their popularity suggests. They earn it where there is compressed air and no electricity. Compressed air is expensive to produce, so the running cost sits well above an electric drive. The air supply's cleanliness and filtration become failure points of their own, and the air valve can freeze and stop the pump. Where electricity is available, we would specify electric.

We size across the hygienic ranges we carry, including Alfa Laval and Vogelsang, and we will tell you when the duty is better served by something we do not sell. If you already know the model and just want it shipped, we are not the cheapest way to buy it.

Certification belongs to the manufacturer, not to the distributor. We can tell you which standard applies to your process and get you the certificate for the build you are buying. We cannot certify a pump, and neither can anyone else selling you one.

• EHEDG (European Hygienic Engineering & Design Group) publishes hygienic design guidance and runs a certification scheme for equipment that cleans in place, with no crevices or dead legs holding product.
• 3-A Sanitary Standards set hygienic design criteria for food and dairy processing equipment.
• Food-contact material compliance covers the wetted path: the stainless grades, the elastomers in the seals and gaskets, and any lubricant that could reach product.
• ATEX Directive 2014/34/EU applies where flammable dust or vapour is present, which on a food site usually means flour, sugar, starch or alcohol. The area is classified into zones; the equipment is certified for use in a zone. A pump is not "Zone 1 rated".

Ask for the certificate against the specific build, including the elastomer and seal specification, rather than accepting that the product family is certified. Tell us which standard your process is audited against and we will put that question to the manufacturer before you order.