South African valves manufacturing company Mitech last month installed a combination shut-off and control valve test station at the company’s factory in Kempton Park, Johannesburg.
The test station was imported from Netherlands-based valve testing unit manufacturer Ventil through Ventil’s South African agent, AT Technical Services, for a total cost of about R1-million.
Mitech engineer Stefan Pfeffer explains that the new unit will perform a variety of tests on the company’s products to validate criteria, such as valve leakage class and pressure rating. Once testing is complete, the unit will print out a certificate stating the valve has passed the test.
“Customers are then given the final certificate to prove the valve adheres to the specifications it was designed for,” he notes.
Pfeffer also points out that Mitech’s globe control valves, pneumatic linear actuators and rotary pneumatic actuators were awarded safety-integrity level- (SIL-) 3 certification, in February this year.
He explains that an SIL rating refers to a product’s capability to reduce process risk through the implementation of safety functions and “is a measurement of performance required for a safety-instrumented function”.
Mitech was awarded the certification through functional safety certification company exida, following a comprehensive audit of Mitech’s manufacturing and design processes. The certified products were assessed using a failure modes, effects and diagnostics analysis (FMEDA) methodology, which exida executes using subsets of the IEC 61508 require- ments.
Pfeffer explains that exida collects a significant amount of field data to perform a proven- in-use analysis to validate the accuracy of the FMEDA results. To achieve an SIL 3 capability rating, the highest rating achievable, a company must demonstrate and prove that its respective products have been in use for a minimum of 30-million collective hours. “In the case of the Mitech’s products, the SIL 3 certificate states that the products will have a useful, safe life period of about 15 years, based on the FMEDA results.”
As part of the certification, exida also prepares a safety case for companies, which enables them to compile a safety manual for products that fall under an SIL application.
In light of this, Mitech has since developed its own safety manual, which is dispatched with all its globe control valves, pneumatic linear actuators and rotary pneumatic actuators.
Pfeffer notes that Mitech has also been placed on exida’s safety automation elements list – a database of companies and products that are SIL-certified.
He points out that, owing to this inclusion, the company is now eligible to supply its products to large companies globally that require products to be SIL-certi- fied, such as petrochemicals group Sasol.
Diversified Product Offering
Meanwhile, Mitech launched its new rubber-lined butterfly valves, which are available from size 80 mm nominal bore to 1 800 mm nominal bore, at the beginning of this year.
Rubber linings are used in valves to prevent media such as water from coming into contact with the body material of the valve. This allows the body of the valves to be made from significantly cheaper materials, such as cast iron or mild steel, instead of high-quality materials, such as stainless steel.
Pfeffer notes that, while the company has always supplied rubber-lined butterfly valves, this is the first time Mitech is manufacturing these valves.
He adds that Mitech started developing the prototypes of its rubber-lined butterfly valves at the end of last year and, following extensive testing, validation and cost analysis on the valves, the company found that it could provide a high-quality product at a competitive price.
“The addition of rubber-lined butterfly valves has diversified Mitech’s product offering and we have noticed that there is significant demand for butterfly valves, particularly at water works and for certain petrochemical applications,” Pfeffer says.
He notes that most butterfly valves used in the water and wastewater industry, come with some form of rubber lining, usually made from ethylene propylene diene terpolymer (EPDM), which offers significant liner performance, but is a challenging material to successfully develop linings with.
Pfeffer points out that, to address this challenge, Mitech developed a dual process of moulding and lining the valves with EPDM to ensure a successful bond. “The butterfly valve is first lined with EPDM, which is then cured at temperature. The pressure provided by the mould, at the given temperature, allows the rubber to be moulded into the desired shape. The curing process allows the EPDM to be successfully bonded to the valve body.”