Two orders received for air-duct heaters

24th September 2004 By: ongezwa manyathi

Johannesburg-based market leader in the trace heating business Bartec Barlian’s MD Fritz Boettiger tells Engineering News that the main function of trace heating is to make up for heat loss in pipes, vessels, and hoppers. The company has had particular success with its hot-water systems, used in hotels, hospitals, upmarket apartments, domestic households, banks and office blocks. The hot-water system provides a solution for buildings which have more than one floor. Boettiger says such buildings would typically have one geyser in the basement and complicated piping which goes through each floor and to all the points of use. “The problem here is that once the water leaves the geyser it gets cooler and, as a result, has to be circulated to keep it hot, resulting in extra and often unnecessary piping,” informs Boettiger. “Our solution involves laying a heating cable along the hot-water pipe from the geyser to all the points of use,” informs Boettiger. This self-limiting heating tape keeps the water in the pipe warm and it is designed to maintain the water at a certain temperature. He says the advantage is that there is almost instant hot water in a tap on each floor and this eliminates water wastage. The other advantage is that it is self-limiting so it will never overheat and comes with a lifespan of more than ten years. Boettiger says that it is almost maintenance-free and would only require maintenance if it is damaged by a knock during construction. The tapes can be installed on existing pipelines but Boettiger says that it is usually used on new piping installations. Further, senior project engineer Neil Syrett informs that the company recently received two orders for its air-duct heaters. The heaters are to be installed in Gauteng for companies involved in the food industry. Syrett says that the heaters, which are still at the engineering stage, are required to raise 7 860 kg of air an hour from ambient temperature to a delivery temperature of 150 ˚C. “The hot air is blown through maize to decrease the moisture content to about 3%,” he says. The heater outlet has a cross-sectional area of 0,56 m2 and the duct is 2,2 m long. Syrett also tells Engineering News that the company has received a similar order from Kwazulu-Natal. He says that similar heaters are used in the air-pollution control industry. Further, because of the many electrical power failures across South Africa due to limited capacity, existing power stations are currently being recommissioned. One such power station is Camden, which currently has one of its six units being refurbished. Syrett says that once this unit is successfully commissioned the other units will also be refurbished in a similar way. He explains that, for this project, electrical trace heating will be used on the pipelines to maintain the heavy fuel-oil at 25 ˚C at all times. “In the event that the trace heating is switched off, it has been designed in such a way that it is able to raise the product in the pipe back to 25 ˚C within 24 hours,” he says. A 500-m pipeline will be used for one circuit and 1,5 km of trace-heating tape will be used on this pipeline. Syrett says that the heavy fuel- oil will be pumped into six bulk- storage tanks. He informs that the oil has to be heated to avoid it from becoming too thick. The fuel will be used to initially fire up all the boilers in all the units. “What happens is that the low-pressure pump sucks the heavy oil from the storage tanks. “The oil is then pumped to a high-pressure pump via inline heaters and then through to the boilers,” informs Syrett.

He says the heavy fuel-oil is also used to support the coal if there is unstable firing in the burners. “Because a constant-wattage heating cable is used there is a need for temperature control, and controllers are mounted locally on the pipelines,” he adds. The first unit (unit 6) will be commissioned in 2005. He informs that the company has put in a bid to Camden in order to maintain the surface of 64 hoppers at 150 ˚C using electrical trace heating. Further, project engineer Filip Castro informs that the company uses thyristor control in industrial heaters, especially for variations of control of heat. “Eighty per cent of the plants in industry are auto controlled so the advantage of the thyristor control is that it regulates the temperature to the desired heat accurately,” says Castro. He says that, in the past, electrical contactors were used but their disadvantage was that they had only minimum or maximum switching (on – off) and nothing in between. The thyristor is a soft-start controller and has a longer life expectancy. Moreover, customers can gradually raise temperature from minimum to maximum depending on the process in the plant and get 20% more lifespan on their heating elements. Further, Engineering News learns that the company is currently working on a do-it-yourself hot-water kit. “We want to make it possible for the person in the street to be able to install trace heaters,” says Boettiger. He says that the kit, a first for South Africa, and designed by the company, will come with a 30 m roll of electrical trace-heating tape PSB 33 (33 W/pm), 50 m aluminium tape roll, 5 terminations, 4 m roll of fibre tape and an easy-to-follow instruction manual. It is an easy-to-install kit.

“The heat emitted by the tape will be evenly distributed over the pipeline by the aluminium tape,” he informs. Trace heating is already used around the world in countries with colder climates for snow melting and ice prevention. The trace-heating tape used for frost protection and freezing is also used in the refrigeration industry to enable drainage and to be able to open the big fridge doors and prevent them from freezing shut. Boettiger concludes by saying that the challenge facing the industry – like any other industry – is the strong rand. “The strong rand has slowed down import-replacement manufacturing and export manufacturing and this affects us because our customers are involved in these industries,” says Boettiger. He says that, when the company designs and manufactures products it keeps to one of its slogans of keeping the product flowing. “The biggest application for trace heating is keeping the product flowing,” he concludes.