Nuclear Power Plant Emergency Diesel Generator Block Repair

The operational requirements for emergency diesel generators (EDG) installed in nuclear power plant are very strict and demanding. In case of an emergency event leading to the loss of off-site power, a nuclear power plant’s EDGs are meant to supply independent, redundant power. From this follows that they have to start reliably and quickly  under any condition and must be able to take on load almost instantaneously, which generally means within about 10 Seconds. This is tested regularly under real-life conditions, according to the prevailing nuclear codes, standards and regulations.

This testing regimen of sudden load changes puts an enourmous thermal loading on most of the EDG’s internal components and on its auxiliary systems. Excessive wear and tear is therefore to be expected and is indeed a small price to pay for ensuring plant safety.

For years, QuantiServ has been supporting nuclear power plant operators and contractors serving them with specialist services throughout the long service life of the plants. We are happy to play a small, but nevertheless important role in ensuring safe and reliable electricity supply from whatever source.

The enclosed pictures show the machining of an impressively large, 20-cylinder engine with a rated output of 4000 kw, a cylinder bore of 240 mm and a stroke of 230 mm. It suffered from a small internal defect, caused by wear and tear, that we successfully remedied in our workshop in The Netherlands in 2020.

Cooling Water System Reverse Engineering

After 25 years of intermittent operation and of being exposed to the elements, the cooling water radiators of an 3500 kW emergency diesel generator installed in a thermal power plant in Macau had degraded considerably. Thus, the power plant owner decided to replace them.
Unfortunately, the original documentation and specification were not available anymore. Therefore, QuantiServ reverse engineered them and got 12 new elements made by a specialized manufacturer.
The new radiators have just been installed and commissioned and will provide reliable cooling for many years to come.
Although this was a small case, it illustrates the important advantages that reverse engineering provides. Many of the industrial plants that we maintain and repair on behalf of our customers have a lifetime of many decades. But that does not mean that the documentation always survives that long, or that spare parts are still available. And sometimes even the OEM himself, or his sub-supplier, may not exist anymore.
It is thus comforting to know that QuantiServ has the skills, tools and experience to reverse engineer and reproduce all kinds of machinery components, even very complex ones and entire systems.

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 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.