By Andrew Perks, FSAIRAC
It’s quite interesting how our place in the industry has morphed into such diverse services.
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Andrew Perks is a subject expert in ammonia refrigeration. Since undertaking his apprenticeship in Glasgow in the 1960s he has held positions of contracts engineer, project engineer, refrigeration design engineer, company director for a refrigeration contracting company and eventually owning his own contracting company and low temperature cold store. He is now involved in adding skills to the ammonia industry, is merSETA accredited and has written a variety of unit standards for SAQA that define the levels to be achieved in training in our industry. |
Primarily we are a safety/compliance company, but customers out there are looking for a service from a non-aligned company to meet their own specific and various needs. We got involved with a project recently which I think will pique your interest.
Do you ever wonder how people control product flow and cooling requirements when there are massive product loads at peak times in a production season. We all know it is not financially possible to size your cooling system to deal with these peak loads which can be two to three months a year. It doesn’t make sense to size your plant for 25% of your year’s production requirements – but how to cope?
A case in point was a fruit packhouse in the Overberg that seasonally struggled with these heavy loads. On the face of things, it looked like there was sufficient cooling capacity, but they were not getting the results they were looking for. It’s one thing having the muscle in the plant room but getting the cooling effect where you want it is another thing.
We sat down with the client to first understand the dynamics of their operation. It is interesting when someone looks at a process from a different perspective. One of the major problems is production people. Their job is to get product into cold stores as quickly as possible. Cooling the product – that’s someone else’s problem. So, the first thing we did was to get everybody together to try to understand each other’s job and priorities.
This was a big site with regular and controlled atmosphere cooling rooms spread all over the place. Initially we set out to establish what the cooling capacity was in each room so as not to overload the room. This was obviously directly related to the room’s base load when there was no cooling requirement and the additional capacity available for product cooling. With this in hand we drew up a complex spread sheet to illustrate each cold room’s cooling capacity depending on availability.
At this stage the production people were getting a bit antsy – all they wanted to know was where to put the product to get the best cooling. However, the beauty of the developed spreadsheet was that it showed how much product to put into appropriate rooms considering the impact of varying incoming temperatures while ensuring pull down times for the product and the availability of cooling capacity. As the load varies so do the results from the spreadsheet, re-directing products to other cold rooms for maximum efficiency.
It took some time to pull the spreadsheet together, but the results were encouraging. The information computed covered the following:
- The inputs were product incoming temperature (a variable), chilling time and final product temperature
- Cold room characteristics, cooler capacity, base loads in the room and remaining product cooling capacity
- Heat load information such as hysters, heat of respiration, fan power load, lighting, transmission through panels and air changes
- General, holding capacity of the room; and ultimately
- How many bins can you cool, and the volumes in each room
Feedback from the client after the season was encouraging and some comments are as follows.
“We loaded per average 150 bins per room per day during the hottest receiving months and the results was evident that the CA stores managed a lot better to keep up with the heat load. As the season progressed and the sites holding capacity increased the system managed to keep up more than adequately with the demand.”
Having done the spreadsheet, knowing what the impact would be in each cooling room and what variables could be introduced into the calculations played a major role in ensuring the season was a success.
Suddenly all the mystery was out of the procedure and the client knew exactly what he had and what he could do with it to get the best results. Job done.
Stay safe.