Cast Iron Welding Services Ltd
Large numbers of Cast Iron components are condemned to the scrap heap and expensive replacements purchased due to many engineers beliefs that the material cannot be weld repaired successfully. Cast Iron Welding Services Ltd based in Coalville, Leicestershire have built an enviable reputation and extensive customer base for the weld repair of cracks, fractures, corrosion and erosion to a variety of components ranging from works of art, historical/heritage landmarks to critical industrial machinery.
A casein point is when they received a call from a middle east oil refinery enquiring if it was within their scope to rebuild ‘some’ pump casings which are used to pump sea water to cool various machines and plant involved in the refining process. These are no ordinary pumps and this is no ordinary requirement….Originally installed over 60 years ago and housed in a purpose built pump house, a total of 7 Ingersol-Rand Cameron Pump Division, 24 inch high lift suction pumps are,(during the summer months when ambient temperatures are in excess of 40 degrees Centigrade) all required 24/7. Each of the pumps are driven by a turbine and have external bearing housings and cartridges. The internals of the pump were in reasonable condition, but the casings were suffering from excessive and extensive corrosion particularly in and around the original stuffing boxes and wear ring locations both of which were corroded to the point of being non-functional.
In considering the way forward, the refinery explored the possibility of purchasing new direct replacements, but, they were obviously no longer available. Alternative pumping solutions would require extensive civil engineering works with inevitable disruption and ancillary expenditure. They eventually decided that during the winter months when ambient temperatures dropped to around 30 degrees and only 5 of the pumps were required that they would send both a top and bottom casing weighing 2 and 3 tonnes respectively to CIWS in the UK, for restoration to original profile of the wear ring locations and a modification to the stuffing boxes to accommodate mechanical seals. Upon receipt in CIWS workshops a detailed dimensional, crack detection & ultrasonic inspection determined that large areas of the joint faces of the two halves required rebuilding, and in addition a number of the threaded bolt holes were stripped of their threads.
A critical part of this inspection process was the removal of a small piece of material from the component which was sent to an independent test house for analysis to determine its chemical composition . To weld repair Cast Iron successfully it is necessary to pre-heat the entire component to approx 600 degrees C. and to maintain temperature during the process, once the castings reached 600 degrees Cast Iron Welding Services restored/rebuilt the pump housings utilising their process known as “Gas Fusion Welding” a manual operation utilising oxcy-acetelyne and most importantly the weld material identical to the parent metal.
A consequence of the pre-heat and weld temperatures involved in the process is that of distortion, the amount of distortion (that may or may not take place) is largely dependent upon the amount of work stresses within the component, following the weld process it was necessary to undertake post weld machining, this included….minimal skim to joint faces, light skim to bearing location flange, reinstating the hold down threaded bolt holes, assembling the two halves and proof machining of wear ring and mechanical seal locations, this to prove the integrity of the weld but to leave 3 mm on all diameters for final machining to be undertaken when returned to the middle east.
The first pump was repaired in 2007 and successive pumps are being repaired each year.
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Tel+ 44 (0) 1530 811308