Air Products South Africa, a producer and supplier of gas and chemical products, recently commissioned a large refurbishment project. A compressor used for direct supply of nitrogen by pipeline to two of Air Products Vanderbijlpark’s largest customers in the Vaal Triangle failed, requiring new components.
The project was awarded to Actom Turbo Machines, and stipulated a period of three months for completion. At the same time, Air Products decided to refurbish the 2 500 kW 11 kV 2 pole AC induction motor that drives the compressor. This project was awarded to Marthinusen & Coutts, Actom Turbo Machines’ sister business unit.
“Three months is an extremely tight timeframe as it is about a third of the time that would normally be allocated for such a complex task, especially taking into account that we had to manufacture the replacement impellers and pinions by a reverse-engineering process, which was necessitated by the short turnaround time as set,” says Chris Bezuidenhout, MD of Actom Turbo Machines.
“In addition, we had to ensure that the tolerances between the various components were strictly adhered to, these being especially critical in this instance as the compressor is a four-stage high-speed unit operating at speeds of between just below 20 000 r.p.m. and in excess of 33 000 r.p.m.”
Both the first- and second-stage impellers and pinions had to be replaced by newly manufactured units. “We manufactured all these to a tolerance with a margin of error of 0.02mm, which is well within the norm to ensure extra protection against any risk of damage during operation,” Bezuidenhout says.
All the rotating components – the gear set, impellers and pinions – were balanced in accordance with the international ISO 1940 specification. The compressor was then assembled and delivered to site where it was installed together with the motor modified by Marthinusen & Coutts. Actom Turbo Machines also conducted laser alignment and fault-finding on all pipe stresses before making ready for commissioning, followed by a rigorous step-by-step start-up procedure.
“The start-up procedure is critical to protect the machine against possible damage during the run-in period. This is concluded by running a surge curve to confirm that the unit has been run-in successfully and is operating optimally,” Bezuidenhout explains.
The work performed on the motor included a modification to the rotor to reduce the excessive vibration that the unit experienced when Marthinusen & Coutts assessed it at its main electrical rotating machines repair and refurbishment facility in Cleveland, Johannesburg.
Image credit: http://www.actomturbo.co.za/about-us/
