PRODUCTION | ENERGY MANAGEMENT
the energy spend is discretionary. “This means that you choose to spend it either because you do not have the skills or the real desire to do something about it. The actions taken vary depending on where you are in the development cycle. Beginner sites can start with services management and then move on to more complex process-oriented projects. Experienced sites should be looking at process-oriented projects from the start,” he says.
Target services “Services use, such as compressed air and chillers, will be a high proportion of energy use in a compounding plant, but only because the process is quite efficient. These are some of the first places to look for improvements and there are many things that can be done to reduce services use. These include reducing compressed air leakage and the generation pressure, as well as restricting the use of compressed air for drying or product movement. A further option is to increase the chiller operating temperature or eliminating chiller use altogether with air blast cooling. After the services have been checked, the main extruders
Potential extruder energy savings within the compounding plant:
n Always opt for the AC motor + VSD option in new extruders. Motors should be IE3/IE4 rated (or NEMA equivalent). Retro- fitting can be examined, with payback likely between 1-2 years.
n Check that the extruder is right for the job and is operating close to the design speed.
n Check the loading on the extruder motors and modify the gear ratios to optimise performance. If pulleys are used, this can be as simple as using pulleys of a different diameter.
n If belt drives are used then optimise the belts. Belt types vary greatly in efficiency and toothed belts are the most efficient. Standard V-belts should be replaced with more efficient belts.
n If a gearbox is used then do not exceed the maximum torque allowance. Use the correct oil and make sure it is at the correct temperature.
n Check extruder controls to make sure that heating and cooling are working efficiently together and not competing against one another.
n Check the barrel heater ammeters. If the heaters are constantly on, then shear heating is not providing all the heating required and insulation could well be beneficial.
n Extrusion dies, transfer pipes, screen changers/melt filters and almost everything downstream of the extruder screw tips can be insulated with either flexible or with board type insulation.
n If using ventilation fans above extruders, then use controls to stop these when the extruder is stopped.
Source: Tangram Technologies 18 COMPOUNDING WORLD | February 2020
and process need to be examined for improve- ments.” Kent says that a major change in extruder
operation has been the development of AC + VSD drive systems, which are much more efficient than the older style DC drives. AC + VSD are now being challenged by Permanent Magnet (PM) motors as these are smaller, more energy efficient, have negligible rotor losses and potentially eliminate transmission system losses. However, he points out that it is good people with experience who make the systems and processes work, and says that applies to making older machines more energy efficient and saving money.
The role of experts There are energy management consultancy specialists available that could benefit compound- ers, if used well. “Professional energy managers and consultants will never know a compounder’s site and process as well as they do,” Kent says. “However, the difference is that an energy consult- ant will know where to look and what to expect, as well as knowing what the important things are and where to make the savings. Nevertheless, there are many people and organisations offering energy consultancy and obviously they are not all equal. If your energy management consultancy focuses on the lights - around 5% of the energy use in a compounder plant - and says nothing about the machines, which account for around 66% of the energy use, then you know that you have got the wrong one,” he advises. “Energy management is not a new task, it has simply risen in importance. Site managers have always been given people, machines and materials and told to make good products. Energy is now simply part of this mix and has a higher priority. It is always possible to see if a plant is well managed by looking at the site, the machines and the people. In a well managed facility, the site and machines are clean, everything is well-maintained and the profes- sionalism and enthusiasm of the people is evident. Sites with good energy management look the same. Conversely, it is also possible to observe that a poorly managed site and one with poor energy management look the same. Energy management is an indicator that says as much about a site’s general management capability as about the technical issues of energy management,” according to Kent.
Lean manufacturing US-based producer of twin-screw co-rotating extruders, turnkey production extrusion systems, extrusion wear parts and components ENTEK says
www.compoundingworld.com
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