SPC
Mild Steel replaced by brass
Improved corrosion resistance
Notes:
Included in their extensive product range is a series of heat exchanger coils for cooling exhaust gases or for heat recovery in a "run around system". The product comprises of a bank of finned copper tubes through which flow a suitable refrigerant or coolant, while the gas to be cooled passes over their surface. The copper tubes are held in position by end plates 1.6mm thick which have holes of pre-determined pitch punched in them. The tubes are finally secured by locally expanding them to fill the end plate holes. The complete assembly is then electro-tinned to provide sacrificial corrosion protection.
For conventional applications the end plates are pre-galvanised mild steel strip and the tube fins are aluminium. However in harsh environments, typically with contaminated industrial air flows and swimming pool systems the electro-tinning soon flakes off, exposing the galvanising which breaks down causing the mild steel to corrode rapidly. In addition, the surface take-up of electro-tinning on galvanised steel is poor giving a blistered orange peel effect, and spoiling the general aesthetics of the product. Similarly the electro-tinning does not adhere to the aluminium tube fins and chlorine laden atmospheres typically found in swimming pools rapidly corrode the unprotected aluminium.
The company's engineers' solution to this problem was to replace the pre-galvanised mild steel with brass end plates, and when necessary the aluminium tube fins with copper. The whole assembly is then electro-tinned as normal giving a better bonded and much smoother surface finish on both the end plates and tube fins.
Although the brass end plates are 60% dearer, the final price of the assembly is typically only fractionally more expensive (4%) and the following benefits have been achieved. Firstly brass is well adapted to electro-tinning and although the tinning still flakes off it takes longer. Secondly the material exposed is brass which resists corrosion for longer than the galvanised mild steel. These combined give the product a life expectancy of three times the original thus saving on replacement and installation costs, which compensate for the small increase in the cost of the original unit many times over.
The better quality product, both technically and aesthetically has also led to increased sales.