When Vesconite Bearings’ team visited knife-gate valve manufacturer A.C.Valves to fully understand how its client was using low-friction wear-resistant Vesconite polymer guide strips in knife gates, the company was manufacturing two valves for a South African gold mine that had experienced a break-down.
By Phillip de Villiers — Vesconite Bearings
The 20” valves had been requested the day before and the mine’s supplier was due to pick them up on the day of Vesconite’s visit to the company, which can manufacture 200 – 300 knife gate valves a month depending on the size of the valve.
A.C.Valves director Colin Scott notes that the gold mine required two narrow-design Wafer Ring Flange (RF) bi-directional valves, which are the company’s most popular design and the design that uses the guide strips.
The valves, which handle light and medium slurries, are relatively thin and are designed in keeping with mining company plant designs that require small compact plants.
The Wafer RF valves consist of two cast iron pieces with a stainless steel gate that lies sandwiched between the two. A PTFE rod with an O-ring acts as a scraper at the bottom of cast-iron valve halves and a rubber seal fits onto the blade.
Three strips, meanwhile, are fitted on to the valve casing and act as guide strips, describes Scott.
“The strips give a longer life to the blade. It prevents metal-on-metal wear, which would otherwise result in scratches on the blade which, when it was retracted into the stuffing box, would cause leakages,” he elaborates.
The goal is to manufacture quality products that will not breakdown and cause downtime and un-scheduled shut downs for unexpected replacements and maintenance.
“We have had no complaints about the guide strips and there has not been a case where the valve has failed due to the guide strips,” Scott continues. “I have been using it for 10 years and it has worked perfectly.”
Customers are in the mining industry, require robust knife-gate valves of different sizes depending on the size of their plants and need reliable valves that do not result in the loss of any commodity-containing slurry.
Other customers include those in the water industry. These also have demanding requirements since valves are specified to remain in situ and have no maintenance requirements for 20 years.