Why is your cold store floor rising?
Above Image: Heater mat being covered by a thin concrete layer at a newly built freezer store in the UK.
In a newly commissioned Danish freezer some years ago, a Storax mobile refused to move. After some initial panic, it was found that the obstacle was a ridge in the concrete floor. As the floor had been checked for level after initial curing, the newly formed ridge was surprising.
The floor had a glycol heater mat beneath the underfloor insulation and every circuit had a flow meter outside the building so that movement of the glycol mixture heated by the refrigeration system condensers could be easily checked.
A bumblebee had become lodged in a flow meter obstructing the flow of glycol and allowing ice to form in the subfloor and creating the problematic ridge through “frost heave”. The bee was removed, the ice melted and the ridge disappeared without cracking the concrete floor.
In Australia, 200mm pipes are laid under freezer floors and air pumped through them to stop ice from forming in the subfloor. At one freezer the pipe did not have sufficient fall, condensation puddled and froze obstructing the pipe eventually causing the cold store floor to rise. At one local store, similar air vents were blocked to prevent rat ingress. That floor rose by 900mms……..
In South Africa, while some recent stores have installed glycol systems, most rely on electrical heater mats which normally consist of three circuits of wire a little like a hot blanket on a bed. The wires lie in a sand bed which may or may not be held together with a weak cement mix. The circuits end in a control box which turns them on only if the temperature beneath the cold store floor dips beneath 4 degrees C.
4 degrees C is interesting as water with impurities can freeze at higher temperatures than zero. Some chill stores have found this out to their cost, as heater mats were considered unnecessary. As the business changed temperatures were dropped to minus 0.5 degrees C and the rooms kept running year round instead of being switched off in the summer months. After several stores experienced frost heave, heater mats and underfloor insulation have now become part of the building design.
While it may sound obvious, check that the heater mats are on when the chamber is commissioned. We have seen at least three stores where the floor rose through frost heave because the heater mats had not been turned on. In one instance the floor subsided. In the others the movement had already cut the wires.
I have visited one store where the heat mat cables had been cut by accident and attempts were made to drill right under the floor in the insulation to replace the wires. I don’t know if the plan worked.
What I have found somewhat surprising is the number of times when management don’t immediately know where the heater mat control panel is situated and how it works. Only last week we had to help a customer who found that his heater mat control panel needed fixing.
This was only identified after the floor began to rise.
It is critical that heater mats get checked regularly and that management understands their purpose. In freezer stores, especially those with mobile racking systems, keeping the floor level is so essential that annual floor level checks are recommended.
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Close your freezer store doors during stock take
Above: A Storax mobile base close to an entrance of a freezer store. The ice build up occurred over a period of time.
When taking stock in a freezer store it is common practice to turn off the evaporator fans and leave the door(s) open. This provides more comfort for the stock takers but causes another problem in mobile racked stores.
When air humidity is high, the warm moist air enters the cold room door as the dry but relatively heavy cold air flows out at the bottom. With the fans off the moisture in the air tends to move to the coldest place it can find which is the racking and the floor. Steel mobile racking wheels have a sufficient co-efficient of friction with the steel rails in the floor to move even when heavily loaded.
However add just a few microns of ice and the situation changes resulting in the wheels turning but mobile base not moving.
In serious cases the solution is to scrape the rails with wire brushes, especially those which support driven wheels so as to provide the necessary traction. This is a frustrating exercise but if one closes the door, turns on the fans and runs the refrigeration system with a low suction pressure the mobiles will probably move more easily the next day. This happens because the thin ice sheet on the floor sublimates to the evaporators via the moving air as they will now be colder than the floor.
But it’s better to keep the door closed even while stock takers are inside.
Keep your freezer store workers warm for longer with Delf Freezerwear
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Cleaning Frozen Juice Concentrate From Cold Store Floors
We were curious as to how cold stores around the world deal with built up ice and more particularly, frozen juice concentrates spills. Their methods as it turns out are not that different to those of South African freezer stores.
Stephen Neel of the GCCA spoke to Jason Dick of Dick Cold Storage, a cold store in Columbus Ohio, USA, and asked him about the steps they take to get rid of frozen pineapple juice built up on their cold store floors.
These were his suggestions:
“Using a hand held paint scraper, or extension pole scraper, Remove all three dimensional residue from the spill site. This may require scraper(s), rags, waste can. Elbow grease at its finest.
After the three dimensional residue has been lifted, there are a few solvents that can tackle the remaining stickiness and cosmetic staining deposits that remain. I prefer two different chemicals:
– The first chemical I recommend is a product called Suma Freeze / Gel / Helada. This product is supplied by an American based company called Diversey, Inc; and can be bought online from companies of the likes of Amazon. You need to make sure to vacate all storage food items in close proximity before usage and cleanup.
– Secondly, I also recommend using a more archaic chemical traditionally known as RV Antifreeze. While not typically sold to be used as a cleaning solvent, it is non-toxic, and does not gum-up when exposed to harsh temperature. Make sure to vacate all storage food items in close proximity before usage and cleanup.”