Aug 03, 2012
Rubber company develops new pressure vessel lining methodBack
1st Wear Corrosion Protection Rubber|Africa|Design|Testing|Africa|Australia|Germany|South Africa|The Netherlands|Building|Chemicals|Cured Rubber|Metal|Metal Fatigue|Products|Rubber|Rubber-lining Pressure Vessels|Uncured Rubber|Andre Van Rooyen|Required Technology
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The method involves putting uncured rubber into the vessel and using the vessel as the curing unit, as opposed to using rubber that has already been cured, or putting the vessel in an autoclave to cure the rubber.
“Uncured rubber is soft and pliable, making it easy to work with and to mould it to the shape of the vessel, as opposed to cured materials, which often require the use of elastomeric fillers at joints.
“Using the vessel as the curing unit has many advan-tages. The rubber bonds better to the metal and forms perfectly to the shape of the vessel, which is important when the vessel is used to hold chemicals that will corrode the metal,” says Van Rooyen.
Other advantages are that uncured rubber is cheaper than cured rubber and, owing to the better bonding properties of the rubber, less repairs are needed. This can also potentially extend customers’ guarantees.
The method was applied successfully to a pressure vessel for an Australian company, which is using the vessel as an acid washing column, in December last year.
“It took me about a month to carry out the tests and ensure this method was possible. I suggested it to the customer. The company was satisfied, so much so that we will soon be lining a second vessel, using the same method.
“The second vessel is in the design phase and should be delivered to us at the end of this year or early in 2013,” says Van Rooyen.
He is hoping to increase awareness of this new method in South Africa, as it will ben-efit businesses that use vessels.
Although the method is suc-cessful, Van Rooyen says there were challenges during the development phase.
“Laws on the use of pressure vessels in the country have become more stringent in the last five years, so much so that a swimming pool pump is now considered a pressure vessel.
“We have government-approved inspection auth-orities (AIAs), which have to certify a vessel and provide a government plate for it before it can be used. If a pressure vessel does not have a manufacturer’s plate on it, you will have to redesign and recalculate that vessel, with an AIA as a wit- ness, as well as with a design engineer to do the recalcula-tions,” he explains.
He adds that redesigning a pressure vessel entails the design engineer doing detailed drawings of the vessel, material identification and X-rays on all welds.
“This can cost anything from R75 000, just for the design engineer’s part of the job. The result is that many vessels are used illegally in the country, which can be potentially dangerous.
“So the method becomes tricky on older vessels, as they will need to be redesigned and recalculated. Factors like metal fatigue and corrosion also have to be taken into consideration when working with older vessels,” says Van Rooyen.
He does not believe in throwing away or destroying older vessels.
“They should be recalculated and downgraded to work at a lower pressure, but many people and inspectors do not know that this can be done.
“We do it all the time at WCP Rubber. We have a vessel that had been manufactured in 1966 that is still fully operational after we downgraded it to work at a pressure of 8.5 bar instead of its designed 10 bar,” he notes.
Another challenge is that many well-qualified professionals in the industry have emigrated to countries like Australia. The few who are left, he says, demand high salaries that rubber lining companies often do not have the budget for.
Van Rooyen believes developing new methods is a way for South Africa to compete with the world.
“Africa has some of the best raw materials and minerals in the world, readily available at all times. We also have the required technology; however, our ability to produce innovative products is hampered by our high labour costs and lack of experts.
“If we use our materials and technology to our advantage, we can fulfill our potential and attract more business to our shores. “This will mean more money and economic growth for the country, as well as fewer strikes and fewer unhappy workers,” he says.
Van Rooyen plans to introduce another new development that he believes will transform the rubber industry.
“I have contacted some people in Holland and Switzer-land, as I plan to develop a way in which a building can be used as a curing unit. “It will be something similar to a bunker that is able to withstand enough pressure to be used as an autoclave. “This would mean any piece of machinery could be rubber-lined and cured,” he says.
He notes that this has been attempted once before in the early 1940s, in Germany, but a conclusion was never drawn and the attempt was unsuccessful.
“I believe it is very possible and it will open doors for the rubber industry. “We may have the funds available to purchase a factory or building of some kind in the future and will hopefully be testing this then,” states Van Rooyen.
Edited by: Chanel de Bruyn© Reuse this Comment Guidelines (150 word limit)
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