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Are all refrigeration compressed air dryers the same?

In the UK each year thousands of products are sold to dry compressed air. One of the most common is the refrigeration dryer which can achieve a 3°C pressure dew point. This means that provided the compressed air system stays above this temperature there will be no further condensation of water out of the compressed air. The fridge type is popular because it is adequate for general purpose compressed air and is relatively low cost, easy to maintain and well supported by manufacturers and distributors. This piece of equipment is often vital to the production in terms of both output and quality.

So why do purchasers of these products treat them as commodities? Are all fridge dryers the same and price and delivery should be the top if not only criteria when deciding which brand to select? “Certainly not!” says Chris Norris, Service Manager at BEKO TECHNOLOGIES. “What purchasers should be looking at is first and foremost, what dew point is required, then what is the life cost, reliability, maintenance cost and warranty offered.” So if we take a look at each of these in more detail we can see that there can be big differences between offerings for this important product.

To select the dew point is usually fairly simple. Machinery manufacturers will often specify the dew point required for correct operation or even better give an ISO 8573 classification which includes permitted particulates and hydrocarbon contents. If this information is not to hand then the very easy way is to call BEKO or an equivalent compressed air consultant and advice will be given based on many years of experience. There are some industry norms and specifications too, so if you are a food manufacturer and wish to comply with the British Retail Consortium/British Compressed Air Society Code of Practice then compressed air not coming into contact with the product can be 3°C pressure dew point but would need to XCHARX 40°C for air in contact with the product. The dew point performance has to be the most important parameter otherwise why buy a dryer. So are all refrigeration dryers reaching the same dew points? BEKO believe not because as a measurement company too, we are frequently measuring dew points on all brands of dryers. We see a common thread here says Norris, there are some products which at the rated flow and the not too arduous British

temperatures are hitting 7°C not 3°C. This could simply be because there is a family of fridge type dryers using a thermal mass principle which allows the fridge compressor to stop to save energy but allowing the dew point to rise. However a fridge type dryer can typically be selected for a General Purpose type compressed air as a rule of thumb. This means to operate pneumatic tools, general spraying, blasting, pneumatic cylinders and simple valves and actuators will generally work well at this level of drying.

Life costs vary significantly across the competitive offerings in the UK. When calculating the life cost it is important to add the capital, installation, electrical input and maintenance costs with another cost which often gets omittedXCHARXthe cost of the pressure loss through the dryer which can be significant and can increase if maintenance is neglected. BEKO’s 1000 cfm dryer for example has a total power input of 3.1KW and a pressure drop of 0.19bar looking at two competitive specifications (catalogue data) one has a total power of 4.5KW and a pressure loss of 0.2bar and a second has a power input of 4.3KW and a pressure loss of 0.38 bar. The first one will cost circa £1000 more to run (based on 8600 hours and 10p/kwh) than the BEKO and the second because of high pressure drop will cost conservatively £3000 more because of high pressure drop and input power. So “buyer beware” these products which look very similar need much more than price and delivery questions.

The other parameters are not as dramatic but can still hide some pitfalls. Maintenance costs on fridge dryer plants should be very low and limited to cleaning and filter changing but the minute the product loses gas we are into the new regulations as to who can do maintenance on the products and for most industrial units it means an FGAS qualified person. The warranty is interesting, BEKO offer 3 years with no red tape, simply proof of following the manufacturer’s instructions and correct installation which is important for ventilation. This is not the longest warranty on offer but is probably the simplest. One manufacturer has come from offering a 5 year warranty down to 1 year statutory simply because of cheapening the product. BEKO received an order for a fridge dryer last year because the client knew that with the acidic atmosphere on site the coated heat exchangers of the BEKO DRYPOINT RA would have a normal product life of many years. He knew from bad experience of a competitive product and good experience form BEKO’s range. Another important parameter is the maximum inlet temperature permissible. In the UK we see 30°C occasionally but the temperature in a badly ventilated compressor room could easily be 40°C giving a 50-55°C inlet temperature to the dryer and consider a compressor with a dirty built-in after cooler could add another 5°C easily and we are at the maximum for many fridge dryers. If the purchaser is sending plant to Southern Europe for example then the scenario is even worse. All this from a 60°C maximum which until the risks are considered seems like overkill. It is in fact for this reason that BEKO’s DRYPOINT RA range has a 70°C maximum.

So when a compressed air dryer is needed the last questions should be price and availability after a review of the real issues outlined in this article and the information on the latter tow parameters used simply in making out the order. BEKO’s General Manager Steve Riley says’

“Fridge dryers are a very important part of our business today. We have come from nowhere to a very significant market share for the free standing products in the last 5 years and of course it helps other sales when you have satisfied customers. We are also confident from our measuring business that our dryers are pretty much on the specification for 3°C dew point. Our simple no quibble warranty is attractive to customers too. We have good stocks, 79 units today in Bromsgrove and the prices are competitive hence our increasing reputation for this product”

 

BEKO Technologies Ltd

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