One of the most critical processes in the production of margarine and shortenings is the transfer of the oil/water emulsion into a scraped surface heat exchanger to chill and crystallise the product.
The success of this process impacts on the entire production cycle and on the end product,so it is essential that the fluid is pumped into the heat exchanger at a constant pressure and flow.
Cheshire-based Amtech Developments Ltd,which supplies food processing and packaging equipment to companies around the world,has recently started fitting Cat Pumps triplex plunger pumps to its shortening,margarine and low fat spreads production equipment for this duty.The first recipient to benefit from this pump type is a Nairobi-based food processing plant manufacturing shortening.Here,Amtech has replaced an existing positive displacement pump feeding the heat exchanger with a Cat Pumps'model 3841 Stainless Steel 38 Frame block-style pump.
In margarine production the emulsifier is melted at about 90ºC and is then mixed with oil to form the oil blend.This blend is then transferred to an emulsion mixing tank and a specific volume of pasteurised water phase(typically containing salt and milk powder)is added,resulting in an emulsion.Now at a temperature of around 40ºC,this emulsion needs to be rapidly chilled in a(Convector)Scraped Surface Heat Exchanger in order to crystallise the fat content.It is here that the high pressure triplex plunger pump comes into operation,pumping the oil/water emulsion at pressures typically between 20 and 70 bar through the crystallisation equipment.Once reduced to a temperature of between 10 and 15ºC,the crystallised fat turns the emulsion into a semi-solid(plastic)product.In this form,considerable force is required to keep an even and steady product flow through to the packaging line and it is the pump that overcomes the high back-pressure and ensures a smooth and continuous flow of product through to the packaging line.In the case of shortening,no water phase is required,so it is typically just the oil/emulsifier blend that is pumped into the heat exchanger for rapid chilling.
The advantage of Cat Pumps'3841 triplex positive displacement plunger pump lies in its high efficiency,high pressure capability,and constant volumetric flow rate irrespective of pressure.Also,where an application requires a variable flow rate,it is well suited to variable speed control as the output is a linear function of the rpm,thus avoiding the need for a complex algorithm to run the variable frequency(inverter)drive.
In margarine production,the pump is located downstream of the pasteuriser,and Amtech were satisfied that this Cat Pumps model is sufficiently hygienic to suit the equipment user's process and cleaning regime.Even though in the case of the shortening process the pasteurisation stage is not involved,a decision was made to supply the 3841 pump with fully machined stainless steel manifolds,valves and seats.
"Neither shortening nor margarine are difficult products to pump",comments Bob Willis of Amtech."However,what the process requires is a pump that can operate against a high back pressure and for many centrifugal and positive displacement pumps this would exceed or be at the top end of their performance range.We were aware that Cat Pumps have been used on other similar projects so when it came to selecting a suitable pump for our customer's production plant in Kenya,it was the obvious choice.The pump is critical to the whole process,as it is the pump that controls the process.The quality of the shortening is affected if the pump does not provide its duty.With many shortening and margarine plants running 24/7,there is a great deal for the pump to do,making reliability,accuracy and maintainability a pre-eminent demand."Amtech Developments Ltd.works in conjunction with Ivarson Inc.based in Wisconsin,USA to supply a full range of margarine and shortening processing and packaging equipment.Bob confirms:"The Cat Pumps product supplied for the shortening plant in Kenya is already up and running and giving the end user the performance expected,and we are very pleased with the outcome."