In our latest project, we were asked to supply a high capacity solid transfer pump to a client who operated a food facility which handled rendered animal products.
They needed a rugged, reliable pump which would handle a 50/50 mixture of water and dry solids consisting of dry meat, bone and tissue solids.
What is rendering?
All industries create by-products that need to be reused, reprocessed or disposed of. Animal production and slaughter is no different, and this kind of by-product presents particular challenges.
Rendering pumps help make the material safe and suitable for reuse in a wide range of applications. In addition, renderers deal with catering waste and unsold animal products that could also become a health hazard.
It’s a highly sustainable solution to food waste – recycling meat processing leftovers for other essential uses and saving landfill space.
Recycling is fairly new, but this is a tradition that goes back centuries. Rendering animal by-products became a widespread and efficient practice in the 20th century meat industry. But it actually dates back hundreds of years to when animal skins provided shelter and clothing, and tallow from animal fat was made into soap and candles.
What was the project brief?
Our client was looking to pump a 50/50 mixture of water and dry solids consisting of dry meat, bone and tissue solids at around 350L/min at 2 bar.
The mixture had a viscosity of around 50,000cPs which is similar to ketchup or mustard. In addition, the formulation of the liquid and its consistency meant that it flows slowly so a pump with a built-in hopper was required.
Having a hopper built into the high capacity solid transfer pump ensures that the mixture doesn’t clog and the hopper pump is not damaged through either dry running, or having oversized solids clogging the inlet.
Rendering pump hoppers can be customised for a variety of liquids and applications. They act as a first stage in the process, feeding the pump with more 
manageable pieces and making sure that mixtures that don’t flow are fed into the pumping mechanism evenly.
Hoppers are available in a variety of designs:
Bridge breaker
These are used to slice large solids found into more manageable pieces which can be accommodated by the pump without processing. Fluids which rat hole, prevent free flow or obstruct pipework often need breaking up and kept moving via the use of paddles.
Rat holing is a common flow problem where material becomes stuck in the rendering pump hopper. Rat-holing causes a funnel flow effect, where the material flows freely above the outlet, but the material that isn’t directly above it doesn’t move and sticks to the hopper sides. If this material can’t be shifted it leads to product being wasted and more downtime as the hopper pump has to be cleaned more often.
Auger feed
An auger is a flat spiral-shaped screw that runs from one end of the hopper to the other, controlling the flow and mechanically forcing the material into the pump inlet. It’s specifically designed for dry solids and sludge which don’t flow freely and need feeding into the pump. It’s an essential part for this particular rendering plant application.
Motorised wheel
When materials such as liquid mortar, resins, mud, blocks of fat or butter are pumped they can plasticise meaning they change shape rather than break up. This means that clogs form and block the rendering pump inlet. These need to be removed manually, again, resulting in more downtime. Manufactured from metal, a motorised wheel rotates 360°within the hopper to stop solids building up and clumping together.
Robust Seal System
We fitted the high capacity solid transfer pump with a seal quench which is a device that applies pressurised oil to a mechanical seal’s outboard faces to keep them clean and free from contamination. This helps to maintain seal integrity. This was important as the hopper pump would be handling large solids up to 41mm wide at high concentrations.
Rendering pump speed is another vitally important factor during the pumping of solids. So we designed the pump to have a reduced pumping speed of 130rpm using the gearbox. This meant that the unit would suffer less wear and tear, and give many years of problem-free pumping to the client.
If you’re looking to pump a liquid that doesn’t flow, contains large amounts of solids and easily solidifies, a hopper-fed progressing cavity pump could be the best solution for you. To find out more, speak to North Ridge Pumps on 01773 302 660 or visit www.northridgepumps.com to see how we can help.
