Cleaning bins with a little less power!
For Industrial Washing Machines Limited (IWM) supplying bin washing machines is nothing new – the company is one of the UK’s leading manufacturers of these products. But when it was asked by Eurotec Environmental to provide a bin washer for a hospital application where the capacity of the electrical supply was very limited, the design team at IWM had to do some careful thinking to devise a way of reducing the electrical loading of the machine without compromising its performance.
In essence, the specification of the machine required by Eurotec Environmental – a company that specialises in delivering sustainable eco-friendly waste management solutions – was very straightforward. It had to be able to wash either two 360 litre bins simultaneously, or a single 720 litre bin. The throughput needed was eight cycles per hour, each cycle comprising two of the smaller bins or one of the larger ones.
Because this was a hospital application, the highest standards of cleanliness and hygiene had to be observed, so the machine had to provide a hot wash, followed by either a hot rinse, or a cold rinse with addition of a chemical sanitising agent, as selected by the operator. The heaters and pumps had to be electrically operated, as no other source of heat or power was available.
The challenge, however, was that the electrical supply available in the area where the machine was to be installed had a maximum capacity of just 40 A, well below the peak current requirement of the standard IWM bin washers that would otherwise meet Eurotec’s specification.
To address this challenge, IWM’s design engineers carefully examined the machine’s operating cycle and found that it would be possible to reduce the peak power requirements in two ways. The first was to wash the inside and outside of the bins separately. This allowed a smaller pump to be used than would have been needed to supply water to the jets washing the inside and the outside of the bins simultaneously.
The second measure used to reduce the peak current requirement of the machine was to interlock the operation of the water heaters with the pump, in such a way that if the heaters were operating, the pumps would not run, and vice versa. This had no effect on the overall efficiency of the machine because with the low throughput needed, it was perfectly practical to turn the heaters on for short periods between washes to maintain the wash water at the required temperature.
Aside from these special adaptations, the design of the bin washer followed IWM’s standard practice. This includes the use of hygienic corrosion resistant stainless steel for all major structural components, and a wash system based on continuous high-pressure jetting with a water-detergent mixture that is re-circulated from a heated tank to minimise the usage of both water and detergent. Recirculation also reduces heating requirements, making the machine more energy efficient.
On completion of the new machine with its special customisation, IWM carried out extensive trials to make sure that it would be suitable for operation from the limited-capacity electrical supply in the hospital. These trials confirmed that the maximum load under worst-case conditions was 36 A, well below the specified limit of 40 A. The trials also demonstrated that the modifications had in no way reduced the effectiveness of the machine and that, after washing, the bins consistently met or exceeded the hospital’s strict specifications for cleanliness.
“IWM did an excellent job on this project,” said Terry Hewitt of Eurotec Environmental. “Although the limited electrical supply could have been a big problem, the IWM team rose to the challenge and found a practical and cost-effective way of dealing with it. The results are excellent – we’re delighted, and so is the end customer.”