Energy Management in Rubber Processing - Part 1 - The Basics




The first in a series of energy efficiency worksheets by Dr. Robin Kent for the Carbon Trust to help the rubber industry reduce costs through efficient use of energy.

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Reducing Energy Costs - The First Steps

The introduction of the Climate Change Levy has already increased the cost of electricity for rubber processors and this is unlikely to be the last rise in the cost of energy. Industry generally treats the cost of energy as ‘somebody else’s problem’ (to be ignored) and regards the cost of energy as an overhead and a fixed cost. In reality, the cost of energy is everybody’s problem and it is a variable and a controllable cost.

Most rubber processors could easily reduce energy costs (without large investments) and increase profits through good energy management practice. This set of Worksheets aims to show how to reduce energy usage and increase profits.

Energy is a variable and a controllable cost

The vital questions

Before starting to reduce energy costs it is necessary to understand where, when, why and how much energy is being used. This information provides the benchmarks and signposts for improvement.

Where are you using energy?

The main electrical energy users in rubber processing are motors and drives, heaters, cooling systems and lighting systems. A simple site energy distribution map will reveal where energy is being used, and if only a single meter is being used for the whole site then it can be very cost-effective to install sub-meters to obtain further information on the areas of high energy use. Sub-metering allows the calculation of the cost of energy for each operation and the identification of areas of high energy usage - key factors in reducing energy costs.

A first step is to produce an energy map of the site to locate areas for monitoring and improvement targeting.

When are you using energy?

The time of day that energy is used is also important and total demand plotted versus time gives invaluable information on how to reduce energy costs. Data for demand versus time plots are normally available free from the electricity supply company. Look for unusual peak variations and energy use when there is no production. 

A demand graph also helps to find the ‘base load’ - the load used for heating, lighting, compressors and pumps when there is no production at all, The base load is a prime target for energy saving.

Tip: Another way to find the base load is to record the meter readings (in kWh) and production volumes (in kg) at the end of each shift. Plot the amount of rubber processed against the energy consumption. From the graph, the energy use at zero production gives an idea of the base load.

Reducing the base load is a sure way to make savings.

Typical Site Energy Usage over Time

Why are you using energy?

Ideally, energy should be used only to produce good product and the most important energy benchmark is the energy used to process good product (in kWh/kg). This is the specific energy consumption (SEC) and is found from the slope of the graph produced to find the base load. It can be compared to the industry averages to provide targets for energy reduction.

Is energy being used to keep machines idling when they could be turned off? Are heaters running that are not being used? Are compressors running just to pump air out of leaks? Finding out why you are using energy will reveal a wide range of possible steps for reducing energy use.

How much energy are you using?

Electricity charges are based on a combination of factors (see Key Tips) and an initial survey will reveal areas for potential savings. Sometimes actions as simple as changing the tariff can reduce costs at no cost! ‘Peak demand lopping’ can be very effective to reduce short peaks in the maximum demand.

Key tips for reducing the cost of electricity

Maximum Power Requirement (MPR) is the maximum current a site can draw at the supply voltage. Reduce the cost by:

  • Staggering start-ups.
  • Matching the MPR to the requirements.
  • Getting the MPR right for new premises to avoid costly charges.
  • Negotiating an annually based MD instead of an MPR charge.

Maximum Demand (MD) is the current drawn at the supply voltage averaged over half an hour. Reduce the cost by:

  • Staggering start-ups.
  • Giving machinery time to stabilise before starting up new processes.

Power Factor (PF) is a measure of the phase shift created by machinery. Lightly loaded machinery tends to have a high phase shift, and a low power factor. Improve the power factor by running electric motors efficiently to get power factors close to 1.

Load Factor is a measure of the hours per day that the user draws from the supply. Reduce the cost by:

  • Running for greater than a single shift.
  • Carrying out some operations outside the main shift pattern e.g. regrinding.

Use less energy. See future Worksheets in this series.

Get free advice and help

Energy management will save money and make you more competitive. Start your energy management programme today and reap the benefits of improved profits by cost-effective investment and management.

The Carbon Trust provides free resources for energy management and cost reduction in rubber processing to UK companies. A handbook ‘Practical tips for energy saving in the rubber processing industry’ gives essential information on how to start reducing energy costs.

Get the information, save the money and become more competitive!

'Energy Management in Rubber Processing' Series.

The "Energy Management" series is designed to give plastics processors an insight into how to manage a valuable resource. 

Part 1 - Reducing energy costs - the first steps (This Section)
Part 2 - The rewards
Part 3 - Compounding

Part 4 - Moulding

Part 5 - Extrusion

Part 6 - Motors and drives

Part 7 - Compressed air

Part 8 - Buildings

Download the complete series as an Adobe Acrobat file.

Last edited: 11/03/10  

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