Motors shielded in hazardous environments

Heating, ventilation and air conditioning (HVAC) contracting company 52 Engineering, a member of the South African Refrigeration and Air Conditioning Contractors Association, has employed various methods to protect motors from the dangerous and harsh environments in which they function.

of 52 Engineering John Parry explains that unprotected motors used in factories burn out, owing to the insulation breaking down as a result of excessive heat build-up. An additional consequence is that the copper inside the motors corrodes.

In wire-drawing factories, such as factories manufacturing steel wire rope and welding rods, there is a lot of fine steel dust in the air, he points out. Once the dust gets inside the motors, flashover occurs and causes the motors to burn out, Parry adds. A flashover can also occur when the brushes in the commutators of direct current traction motors touch each other because of an unusual movement.

The company has used various methods of protecting motors, such as using the forced motor ventilation system, which includes a filter, a fan and ducting conveying clean air to the motors.

Parry recounts that it takes about six weeks from the design stage to the finishing stages to set up the forced motor ventilation system on site, depending on the size of the motor. The system is designed to the size of the motor and the air volume that needs to flow through.

“The forced motor ventilation system uses air from outside the hazardous area and then passes it through dust and, occasionally, chemical filters. This ensures that the air is as clean as possible before it is blown into the motors,” he says.

The system was installed for toilet paper manufacturer and supplier Twinsavers at its factory in Klipriver, in Gauteng. The installation was prompted by the inevitability of stray tissue paper settling on and getting drawn into previous motors, subsequently blocking cooling passages and overheating the windings.

Tissue paper is also found outside the factory, which resulted in the need for air used outside the factory to be filtered before it could be blown into the motors.

The forced motor ventilation system at one of energy and chemicals company Sasol’s highly flammable explosives areas in Sasolburg was also used by 52 Engineering.

It was decided to install the air conditioner in a housing and then duct the fresh air from outside the hazardous area into the housing. This was done to protect the evaporator motor and printed circuit board by maintaining a positive pressure in the housing.

Meanwhile, 52 Engineering provides HVAC for the mining, commercial and industrial sectors as part of its service offering. The company emphasises good service and high-quality products, and can provide full design solutions, construction management, installation and servicing for clients.

The company can service HVAC applications, as well as fulfil other requirements involving specialised designs solutions, for office buildings, medical centres, retail centres, manufacturing facilities, churches, schools, substations and laboratories. It can also issue certificates of conformity for air-conditioning installations, which is a legal requirement in South Africa.

Parry concludes that 52 Engineering employees are qualified tradespeople, all of whom have refrigeration handling licences that are renewed by the South African Qualification and Certification Committee for Gas every three years.