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Caveat Emptor – Shoddy Repairs

Centri-Force is the leading repairer and supplier of refurbished Separators and Decanter Centrifuges in the UK and has over the years witnessed what can only be described as frightening repairs which have been conducted by those who do not fully appreciate the huge forces involved when a Centrifuge is running.

From time to time we witness machines coming into our workshop for repair/overhaul only to discover that whoever conducted the repairs previously have had very little understanding of what they are dealing with.

Z42 Bowl 1Recently we have had a Flottweg Z42 Decanter arrive for overhaul, our team of engineers stripped the machine and compiled an in-depth report on its condition listing what was required; the report shocked us, we thought we had seen it all.

While investigating the rotating assembly our attention was drawn to the obvious markings around the circumference of the bowl on the parallel section near to the mating flange. We stripped the bowl completely for further investigation and used dye penetrant to confirm our suspicions.

We concluded that at some time in the machines life the parallel section flange where it mates onto the taper section has been replaced and whoever conducted this repair had removed the original section and welded on a ‘new’ piece of material. Furthermore the inside of the bowl had a metal strip welded around the inner circumference covering the weld on the bowl wall. When we tested the weld using the dye penetrant (inside and outside) we discovered that there was no integrity of the weld at all.

Z42 Hub 2When we looked at the large end hub we noticed pitting around the circumference of the centre shaft. We again tested this with dye penetrant to discover that at some point previously the shaft had been removed (outboard side only) and had been replaced by a ‘new’ piece of material.

Again we were shocked that a considerable amount of the assembly weight is acting on this section of shaft which as we found was only being held together by a few millimetres of weld penetration.

The previous repairer had taken a huge chance. The customer had taken a huge risk but thankfully the machine had not come apart when running.

We brought this to the attention of the customer and highlighted the potentially huge risks involved in conducting these low cost repairs.

Although the customer had at some time been persuaded by competitive repair costs it has in fact cost him more overall because of longer downtime. We advised replacing the bowl section and also the large end hub, both parts were marked dangerous and it was stressed to the customer that these parts should never be used. They are now safely consigned to the bin.

At Centri-Force all of our engineers are trained to fully inspect every component part of the customer’s machine giving piece of mind that when we return a machine it is fit to run, is reliable and above all safe.

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