Conventional cleaning methods are Solvents and Steam / Water Jet blasting with lots of time consuming manual labor.

Contaminants like carbon,  oil,  cement ,  paper, rubber, etc. (depending on the industry the generator / motor is used in) need to be removed over a period of time as these contaminants lower the insulation resistance of the windings and can even cause mechanical failures in extreme situations.

Solvent Cleaning

Solvents are sprayed over  the areas to be cleaned, while the surface is rubbed  with a nylon brush or blunt insulated stub to remove contaminants that have adhered to the surface of the windings. Solvent soaked swabs are then used to access areas between adjacent coils and areas in which a brush / stub cannot be used.

Solvent cleaning  requires the cleaned component to  be heated  post cleaning  to remove all traces of solvents. Solvents often affect the outer layer of varnish and as such, application of a finishing varnish after the dry out is mandatory.

The short falls in this cleaning method are:
Solvents are toxic. Collection and disposal of  secondary  waste is a major  deterrent. Solvents  affect the outer  layers of  insulation. The abrasive action of brushes, stubs and swabs worsens the situation. It is difficult  to clean the  inter  spaces of  adjacent coil sides and  between  top and bottom  half coils on  the  overhangs of windings.  Contaminants  lodged  in crevices  are  not easily removed.  Drying out  of  the machine  requires  the use of a  temperature controlled oven. This calls for dismantling of the machine and transportation to a service facility.  Such operations carry with them the associated risks and costs.

In-situ cleaning, if carried out , will require that the machine is heated using hot air blowers or  passage  of electric current  through the windings. These methods are potentially hazardous. Typically the man power required for a large machine is ten people over a  4 - 6 day period.

Steam / Hot Water Jet Cleaning

With this method of cleaning the windings are cleaned with steam or hot water mixed with a mild detergent.
The cleaning results are good, however the major draw backs of this method are:

A perfect post cleaning dry out of the windings  is mandatory. This involves dismantling and  transportation of  the equipment to  a service  facility.  In-situ cleaning is therefore ruled out. Further, this method of  cleaning  has to be carried out judiciously to ensure that  there is no excessive abrasive action  that may cause damage. Application of a fresh coat of finishing varnish after the dry out is recommended. All in all, lots of down time and very costly.

ABB, GE, SIEMENS and ALSTOM generators and large motors, to name but a few in Europe, Asia/India and the Americas, are cleaned in-situ with our Crystal Particle cleaning method. It presents the owners / operators of such equipment with several advantages.

Dry Ice Crystal Particle Cleaning provides a "cleaner clean"

The  inter space  between  adjacent  coils and  between  top / bottom  half coils on  the overhangs are very thoroughly cleaned.  It  has particularly  been  noted  that contaminants trapped in crevices and on overhang tie-ups are very well removed.

There is no abrasive action  because of Dry Ice Blasting,  if  correctly carried  out. Application  of  a post clean up  finishing  varnish  is not necessary in most cases. Heating of  the  windings after clean up  is  not  required  (using good quality / dry  blast  cleaning  air.  See: Products - Air Supply / Compressors).  It  is  however recommended, that hot air is lightly blown over the cleaned area  using a hand  held  hot air  blower  to remove  traces  of  light surface condensation, if present. Low insulation resistance values, if attributed solely to contamination, improve considerably after the Dry Ice Crystal Particle cleaning operation has been completed.

Typical example, demonstrating before and after readings, are:

 GENERAL ELECTRIC, DC Motor, 4000KW, 700 Volt, 5800 Amperes, Excitation Voltage: 125 Volts. Speed: 150/375 RPM

Another important issue is accessibility and maneuverability of Heavy Electrical Rotating Machinery on site.

An Indian petro-chemical  company is employing CO2 blast cleaning, since dismantling and shifting of the machine is not possible within the given shut down period of 72 hours. CO2  cleaning  is extremely useful  as well,  when machines to  be cleaned are located  in areas  where overhead  cranes are not available.  In India  for example,  power plants with diesel generators, have only a 5 ton overhead crane  to facilitate the engine overhaul. Dismantling of such machines for overhauling is an onerous task and Dry Ice Crystal Particle cleaning in-situ provides a perfect solution.

CAUTION !

Dry Ice Blast Cleaning in the Heavy Electrical Rotating Machinery industries requires a well trained machine operator. Without proper training and  CO2 Safety  Instructions,  Dry Ice Blast Cleaning should not be carried  out in this industry. The values  of generators and motors are too high to be negligent and allow unnecessary risk. CMW’s sales agents in Europe, the Americas and Asia /India provide hands  on training at reasonable cost.  Usually done on-site  in an actual service  job situation;  i.e. the on-site training pays for itself !