In reaction to stricter environmental regu- lations being placed on many industries in South Africa, the trademarked Clyde Bergemann Dome Valve is increasingly being specified for use in waste management applications, owing to its resilience in harsh environments, says materials handling company Clyde Bergemann.
“Industries like mining, as well as pulp and paper, especially those near suburban areas, were recently put under greater pressure by both government and environ- mental interest groups, as well as the need to comply with International Organi- sation for Standardisation requirements, to manage the by-products of their businesses in an environmentally sound manner.
“To do this, the industries often need to have mechanical or automated systems in place, which is something we are able to design and manufacture for them,” says Clyde Bergemann director Jeremy Kirsch, citing an ash-handling system, designed and commissioned last year at platinum giant Impala Platinum’s refinery in Enstra, Springs, as a prime example.
Impala Platinum (Implats) is so satisfied with the system that it is considering using the Clyde Bergemann Dome Valve on a coal conveying system leading to the Enstra burners when upgrading the plant in the 2013/14 financial year, Clyde Bergemann sales engineer Craig Smith points out.
Apart from stricter environmental regulations, Implats decided to install the ash- handling system to capture and store the ash from its coal-fired boilers. The ash will be sold, as it has recently gained value.
“Companies are using ash to manufacture cement-based products. This is a growing industry, which targets smaller companies rather than power stations, as the ash collec- tors do not have the resources to collect the hundreds of tons of ash produced daily at power stations.
“Owing to these two factors, Implats wanted an effective ash-handling system that would transport the ash to a storage facility quickly and without mess,” he says.
He notes that the company previously had a mechanical ash-handling system, which was not effective because it required frequent maintenance and emitted a lot of fly ash in windy seasons.
“Mechanical ash-handling systems are common but problematic. Owing to the abrasive nature of the ash, normal valves used for this application require a lot of maintenance and often still fail. This means the ash is not being contained and dealt with effectively, which can have a negative environmental impact,” says Kirsch.
The Clyde Bergemann Dome Valve was used on the automated system designed for Implats and Smith identifies valves as an intricate part of the system.
“The valves play the most important role in the system we installed for Implats; essen- tially, they allow the system to operate as a closed pressure vessel conveying system.
“On any system, like the one we installed at Implats, the air-material interface is the most critical location on the system; hence, the specific design of the valves, which isolate the material and maintain a pressuretight seal, while also eliminating any metal-on-metal contacting parts,” he says.
The ash from the boilers falls into hoppers positioned above the valves and when they reach a level probe, an actuator opens the valves and the ash flows through the valves to reach the conveying system.
The Clyde Bergemann Dome Valve opens completely, leaving the full bore unobstructed, allowing material to flow through it without causing any wear or abrasion, as there is no contact between the material and the dome.
It also has an airtight seal, owing to the inner seal inflating and pushing on the dome when the valve is closed to ensure that pressure from the pipe or vessel to which it is connected does not force any material through the valve when it is closed.
The valves are manufactured mostly from cast iron and different types of steel, depending on the application requirements. Kirsch notes that the company has three local suppliers for cast iron and several others for the steel components.
“We try to support local industries as much as possible and promote the growth of these industries, especially those companies that have high broad-based black economic- empowerment ratings and those that qualify for the enterprise development incentive requirements of the Accelerated and Shared Growth Initiative for South Africa,” says Kirsch.
The Clyde Bergemann Dome Valve is manufactured in standard sizes ranging from 50 mm to 500 mm, although Kirsch says the company can manufacture bigger sizes for special applications which require higher volumes of material. The inner seal is usually made from silicone or neoprene to ensure the valve withstands high temperatures.
“The steam and ash from Implats’ boilers are about 200 ºC, which the Clyde Bergemann Dome Valve is designed to withstand owing to the choice of materials used to manufacture the valves, such as silicone and cast iron.
When used in an environment with higher temperatures, a water cooling system is used to cool the dome and top plate, which enables the valve to work effectively,” says Smith.
He notes that the company has also used water cooling on the body of the valves for special applications in the platinum smelting industry, where the temperatures exceed 300 ºC.
“It was of the utmost importance that the system we designed could withstand high temperatures, did not leak or allow any fugi- tive air to enter and create a reverse air flow back into the boiler. This would have caused the combustion process to be disturbed and the ash to fly around the boiler room, creating a mess. It was equally important that the system could run for long periods between maintenance intervals, as Implats needed a more manageable system,” explains Kirsch.
The Clyde Bergemann Dome Valve is designed to withstand harsh environments, needing maintenance only every six months. Smith notes that another client of the com- pany, which also operates a platinum refinery, has been able to achieve operating periods of up to one year between maintenance for these valves by doing small checks every few weeks.
“Although these valves are made to last for long periods between maintenance, they still need to be checked periodically for small things like greasing the nipples.
“It is sometimes difficult for our clients to understand and that is why they begin to encounter problems after six to eight months because they have not checked the valves during that time,” notes Kirsch.
“Many of our other clients in Enstra, mostly from the pulp and paper industry, have heard about what we did for Implats and are also interested in installing a similar system at their plants,” says Smith.
This year, Clyde Bergemann has also used the Clyde Bergemann Dome Valve for several applications, including the conveying of sugar, platinum concentrate, copper concentrate, lime and limestone.
“We also installed these valves on massive storage silos, containing up to 5 000 t of material. The valves were used at the opening of the silo to control the flow of the stored material,” notes Smith.