In-situ Cleaning of a Heavily Contaminated MV Alternator in Nigeria

Our alternator specialists have just completed the in-situ cleaning of a severely contaminated medium-voltage alternator in a power plant in Nigeria, Africa.

The alternator has been in operation for around 32,000 hours in a very dusty environment without ever having been cleaned. Eventually, the winding temperatures reached unacceptable levels so that the unit’s load had to be reduced. A visual inspection by the plant’s operator and insulation testing by a specialized company revealed that the windings were very dirty and that the insulation values were too low. The Polarization Index (PI), which was calculated to be 1.4, was unacceptably low. The manufacturer of the alternator, Leroy Somer, specifies the PI to be at least 2.0 while we recommend not less than 3.0.

The specification of the alternator is as follows:

Manufacturer: Leroy Somer Type: AC Alternator
Nominal Power: 7600 kVA Nominal Voltage: 11000 V
Nominal Speed: 750 rpm Frequency: 50 Hz

Condition of the alternator before cleaning:

Condition of the alternator after cleaning:

5000 Volt Megger readings before and after cleaning:

QuantiServ’s technicians achieved a superb result without using any harmful chemicals or CO2 at all. Only water and a special formula of water-soluble, non-toxic detergent was used.

The power plant operator was highly pleased with the result of our cleaning work. He was told by more than one party that the rotor had to be withdrawn from the stator for cleaning. That we did it in-situ saved him a lot of time and money.

This case shows well the outstanding effectiveness of QuantiServ’s alternator cleaning method. So far we have not yet come across an alternator that we could not clean in-situ and where dismantling was required!

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In-situ machining of lateral surfaces on a 20V32 engine block in Bangladesh

Lateral surfaces before and after in-situ machining

Lateral surfaces before and after in-situ machining

In-situ machining of lateral surfaces on a 20V32 engine block in a power plant in Bangladesh

In October 2016, QuantiServ received an urgent request to carry out in-situ machining on a 20-cylinder 32-bore engine block in a power plant in Bangladesh. During the replacement of the crankshaft it was noticed that both lateral surfaces of main bearing cap number 5 showed signs of severe fretting and were in need of machining.

Immediately, in-situ machining equipment was prepared at QuantiServ’s Dubai workshop and was sent to site. Once the equipment had arrived at site, QuantiServ’s engineers from Dubai performed in-situ machining on the engine block to achieve a clean surface that was free from damage. The in-situ machining process was constantly monitored by laser to ensure perfect alignment and adherence to very tight machining tolerances.

The main bearing cap was sent to a local workshop in Bangladesh for machining and installation of compensation plates. This process was supervised by QuantiServ’s engineers. Once the machining was completed, all mating surfaces for the main bearing cap were checked with marker blue to ensure a perfect fit.

Once the work was completed, a final check by laser on the assembled bearing cap showed that both the bore alignment and diameter fully conformed to the engine maker’s specification.