BOC improves refrigerant plant efficiency

The ability to put refrigerant plant back into an efficient state is increasingly sought by contractors and plant operators, particularly when UK energy costs continue to increase and EU regulations call for stricter monitoring of refrigerant use and recovery.

BOC Refrigerants specialist engineers regularly encounter ‘system busting’ instances of refrigerant contamination. Based at Immingham, Lincolnshire the team of comprises four engineers led by refrigerant services manager, Colin McNicholl. Aside from recovery, the team analyses hundreds of liquid refrigerant samples taken from the plants around the UK which combined with a review of system data, gives a detailed picture of how a system is performing.

Key to BOC’s response is the ‘Zugibeast’ (after inventor Kevin Zugibe) which separates contaminants from refrigerant, cleans and returns it while the system operates, critical for large chemical, petrochemical and food plants. The portable ‘Beast’ works next to the chiller or refrigeration machine processing two tonnes of refrigerant per hour (ten times faster than any other system in the UK) and works by using the plant's refrigerant charge to ‘deep clean’.

Refrigerant is distilled so the cleaning action does not suffer from blocked filters encountered with filtration processes, which reduces cleaning rates and contaminant carry-over when filters have been consumed. The molecular sieve in the dryer vessel can be used to reduce moisture levels to less than 10ppm by weight. Oil and debris are also extracted.

In the last 12 months BOC has carried out seven major plant rectifications with the Zugibeast. In that time McNicholl and his team have encountered a range of problems across a variety of industries. Says McNicholl, “one of the trickier challenges was the flooding of a 6,000kg refrigeration system on board a fishing trawler where a condenser tube had leaked allowing a tonne of seawater into the fish freezing system charged with 6.5 tonnes of R22.”

“Dehydration is never easy”, he explains, “moisture gets trapped in pockets throughout the system and each model of chiller presents its own, unique challenges. With the trawler, BOC’s decontamination system was able to remove most of the moisture and get the system back up in running in four days rather than the six weeks it would otherwise have taken”.

Moisture contamination was also a problem at a food storage plant in Wales where the refrigeration plant was failing to meet its design loads.

At 50 parts per million moisture can cause copper plating, which affects compressor reliability and shortens the life of the system. Too much moisture in the circuit can cause blocked expansion valves, leading ultimately to compressor nuisance trips and reduced plant reliability.

BOC used a two-stage rectification process. Liquid dehydrant was pumped into the system and allowed to mix and circulate with the refrigerant for 24 hours. A BOC superdrier was then connected in series with the pumped liquid line.

“The additive acts as a carrier, picking up any moisture present and dropping it off for the desiccant to absorb,” explains McNicholl. “As the refrigerant charge was circulated, moisture was extracted through a series of desiccant change outs inside the superdrier”.

The unit was quickly working at normal pressure and with fewer compressors on line, power consumption and fuel costs were reduced as was the need for maintenance. Overall the food customer has seen a 20% improvement in the operation of the equipment.

Oil logging in the evaporator of a large, low temperature refrigeration plant in the North East of England resulted in reduced capacity and efficiency.

The three-stage, 12 tonne chiller refrigeration system was designed so that oil could be skimmed off the refrigerant surface in the evaporator. Because the skimmers were not working as they should, oil was building up in the refrigerant side of the evaporator with a resultant loss in capacity and efficiency.

Using the Zugibeast the BOC team pulled contaminated refrigerant from the evaporator and returned it clean. Regular sampling during the process showed that oil content in the refrigerant was reduced to less than 1% and in all, 820 litres of oil was removed from the system.

BOC refrigerants have also cleaned an R22 refrigeration system at BP’s oil refinery at Grangemouth, Scotland. Two hundred litres of oil was stripped from the refrigerant and particulates were flushed from the system evaporators. Now, the plant is chilling product down to -54degC having never previously got below -47degC.

Says McNicholl, “There are a range of methods for tackling the various problems encountered by plant managers across the UK,” adding, “because we have the tools to analyse the system at the outset, put things right and check everything again afterwards, we have built up a wealth of knowledge and expertise in this area.”