A pump can turn a good process into a problem. If it pulses, it upsets dosing. If it shears, it damages the product. If it cannot be cleaned, it becomes a quality risk. Selecting a sanitary pump is therefore about much more than flow and pressure, and it starts with a clear description of the fluid.
Start with the fluid, not the catalog
Write down viscosity at the real process temperature, the size and hardness of any solids, whether the product is abrasive, whether it is shear sensitive and whether it foams or contains gas. A pump that handles water very well may be a poor choice for a thick paste, and the reverse is also true. Viscosity often changes with temperature and with shear, so both the hot and cold conditions deserve a look.
The main pump families
Centrifugal pumps are simple, economical and excellent for thin liquids at a steady flow. Their weakness is that flow falls away quickly as viscosity or discharge pressure rises, and their high tip speeds can be hard on delicate products.
Rotary lobe pumps use two rotors that turn without touching. They move viscous and particulate products gently, can run in both directions for emptying lines and clean in place well. Twin screw pumps offer similar advantages with very low pulsation and good suction lift, which makes them popular for difficult transfers.
Progressing cavity pumps push product along a helical rotor inside a rubber stator. Flow is steady and proportional to speed, which makes them useful for metering and for fluids with a wide viscosity range, including those with soft solids.
Diaphragm pumps use a flexing membrane and compressed air or a mechanical drive. They run dry without damage, handle abrasive slurries and tolerate solids, at the price of pulsation and lower efficiency. Peristaltic pumps squeeze a tube, so only the tube touches the product. That is ideal for dosing, aseptic transfers and corrosive or abrasive media, although tube life needs to be planned.
Hygienic design details
- Surfaces polished to a stated roughness and free of crevices
- Full drainability, with inlets and outlets positioned so no product stays behind
- Approved elastomers for product contact, in line with FDA and USP requirements
- Clean-in-place capability with enough velocity to scour the pump interior
- Quick disassembly with clamps for manual cleaning and inspection
Do not forget the system
Suction conditions decide whether a pump performs as promised. Long, narrow or restricted suction lines, high fluid temperature and low tank levels can lead to cavitation or air ingress. Discharge piping determines pressure demand. A pump that looks perfect on paper can fail if the pipe run is longer than assumed or a valve sits partly closed.
Speed control is a further advantage. With a variable frequency drive, one pump can serve several products and be tuned for gentle handling or fast emptying. It also allows cleaning at a higher velocity than production, which shortens washdown time.
Drum and container transfer
Not every transfer is a fixed installation. Drum and container pumps let operators empty barrels and totes without lifting them or spilling. Options with pump tubes that reach to the bottom and drain completely reduce losses on expensive ingredients, and the design of the motor and tube can be matched to the material being pumped, from thin solvents to thick concentrates.
Total cost of ownership
The purchase price is usually a small part of what a pump costs over its life. Energy use, seal and wear part replacement, cleaning time, downtime and product loss all add up. A more expensive pump that keeps a line running and wastes less product can easily pay back within a year or two. When we compare pumps for a customer we therefore ask about maintenance staff, spare parts holding and how often the plant changes products.
Trials, references and spare parts
Ask the manufacturer for a trial unit or a demonstration with your own product whenever the fluid is difficult. A few hours of testing will show flow, pulsation, temperature rise and cleaning behavior far better than a data sheet. Ask for references from plants making similar products, and find out which wear parts are recommended as spares. A pump with a two-week delivery time for a rotor or a stator should be backed by at least one spare on your shelf.
Our pump partners are listed on the pumps page, and we work with them to arrange demonstrations and trials. To discuss a specific application, get in touch.