MechChem Africa January-February 2022

⎪ Heating, cooling, ventilation and air conditioning ⎪

35 °C ambient in 45 to 50 °C ambient tem- peratures, one of two things can happen. Either the whole system will trip because the temperatures are outside the system’s operating envelope, or the unit will find a balance point at a much lower net cooling capacity. To put this into numbers and compare apples with apples, if we take a system rated to provide 3.5 kW of cooling in a 35 °C ambient with a cabin tempera- ture of 25 °C, and operate it in the design conditions we use, the system will only provide 2.8 kW of cooling, which will resul t in a cabin temperature of

centre. The remaining fine dust is then col- lected in a HEPA cartridge filter capable of removing over 99.95% of sub-micrometre particles. “These are add-ons however, so when there is no need to include them, we don’t. We design into the application and we only size and include components based on what is needed,” says Spies. In addi t ion, the cool ing f in spacing needs to be larger to limit dust build up, which will quickly impair the cooling ca - pacity of inadequately designed systems, again causing less heat to be rejected, lowering the effective cooling capacity. “Another issue is that the draw down time is exponentially longer for systems designed for 35 °C. Even with our systems, it might take 10 to 20 minutes to reduce the inside temperature of a closed cabin, which can be 20° above ambient , to a comfortable level for the operator. With smaller systems, getting down to comfort- able temperatures will take much longer, and the engine must be on for that period, so the operating costs are higher. “Anyone who has to report on HSE stan- dards needs to take particular note of this. Having a comfortable cabin temperature is a legal requirement, not just a nice thing to do for employees,” says Spies. “Simply put, it is not sensible to pay money for a lower cost system that will

30 to 32 °C,” notes Miller. “ The c onve r s e i s a l s o t r u e o f o u r s y s t em , i f ou r Booyc o s y s - tem i s used at 35 °C ambient, it will provide 4 . 3 kW o f cooling and be ab l e to coo l the cabin down to around

not work in the conditions. And if someone claims that a lower cost system is the same as ours, be cautious! If it costs much less it is not likely to work – and it certainly won’t work for long.” warns Miller. “There is a difference. Beware of being duped,” he concludes. q

18°C” “ In pr i nc i p l e , our sys tems include larger and more expensive HVAC sub-systems because these are necessary to do the job. They are not over- engineered, they are purpose engineered,” continues Spies. “In addi t ion, our systems are more robustly built to cater for the off-road nature of the equipment we are cooling: dump trucks, drill rigs, dozers and exca - vators, for example. All these machines often have to cope with excessive vibration levels. From experience, we know that only welded structures can cope with these harsh conditions, and we use thicker gauge (2.0 mm) steel plate. Tar road-systems rely on a less-expensive pop-rivetted structure and much thinner sheet sections, which, under vibration, get destroyed in very little time,” he adds. Dust is another issue. It is everywhere and, for health and safety reasons, Booyco often includes scavenger fans and HEPA filters to maintain the air quality inside the cabins. The scavenger fan creates cyclonic air flow that allows the coarse dust to be gathered from the outer area of the fan, whi le the cleaner air flows though the

SPECIALISED MOBILE AIR CONDITIONING

011 974 8640

info@booyco.co.za

www.booyco.co.za

101 Newton Road, Meadowdale, Germiston, South Africa

January-February 2022 • MechChem Africa ¦ 27