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Rebuilt motor program

The UL Listing Mark on a newly manufactured piece of equipment indicates compliance with nationally recognized safety requirements. A device with a UL Listing Mark that has been subsequently "rebuilt" is an entirely different story. Whether it's due to previous damage, or due to the rebuilding process itself, modifications make continued compliance with UL requirements uncertain. In response to these concerns, UL's HazLoc engineering staff has the ability to establish certification programs to determine whether or not any piece of rebuilt equipment continues to comply with the applicable UL HazLoc requirements.

UL already has a number of active certification programs for rebuilt hazardous locations equipment (also referred to as reconditioned, remanufactured or refurbished equipment). The most common of these address HazLoc motors and generators and HazLoc industrial and process control equipment (including programmable logic controllers, auxiliary devices, and magnetic motor controllers). As the need arises, additional rebuilt programs for other UL HazLoc equipment can be established.

Regarding the UL program for rebuilt motors and generators, this is by far UL's most active program for the rebuilding of HazLoc equipment. There are over 600 companies throughout North America, Europe, Asia and Latin America authorized by UL to rebuild UL HazLoc motors and generators. The following will provide details on how UL's rebuilt motor program works, highlight some of the more significant aspects of the program, and explain how to request an application to get started in the program.

How the program works

The main part of this program consists of a review of your motor rebuilding facility. UL's hazardous locations staff will visit your facility to:

  • Determine that the materials to be used are adequate. Materials include: motor insulation materials, lead wires and lead sealing compound. The motor insulation materials shall be rated Class F(155) or better except that minor insulation components such as tie cord may be Class B(130).
  • Establish that a minimum amount of measurement equipment is available to inspect the joint and shaft path widths, clearances, roughness, etc.
  • Determine that dielectric voltage-withstand test equipment is available to test the insulation properties.
  • Review the machining and manufacturing equipment to verify that they are suitable for the type of rebuilding work that may be necessary.
  • Explain the requirements of the program, including the methods and procedures to be employed during the rebuilding process.

Major program information

  • The motor to be rebuilt must have been UL Listed for use in hazardous locations when new. Either (1) the UL Listing Mark nameplate must be attached to the motor, or (2) a letter from the original equipment manufacturer must be obtained that references the specific model or serial number and states (a) that the motor was UL Listed for use in hazardous locations when new, and (b) the hazardous location classes and groups for which it was originally built.
  • The motor can only be rebuilt for any one or any combination of the hazardous location classes and groups for which it was originally built. A motor cannot be rebuilt for any hazardous location class or group for which it was not originally built.
  • All motors and all auxiliary electrical circuits are to be subjected to a dielectric voltage-withstand test.
  • Control circuit temperature limiting devices (thermostats) are to be installed in every motor; except a motor that (1) was originally built for use in Class I, Group D only, (2) did not include thermostats, and (3) the OEM windings are not being replaced.
  • A motor cannot be re-rated without the original equipment manufacturer's information, except that the voltage and current may be changed. If a motor is rewound, the new winding is to have the same construction as the winding that was removed (wire gauge, number of wires per coil, coil groupings, etc.).
  • The dielectric voltage-withstand test equipment is to be calibrated at least annually.
  • Measurement equipment (inside and outside micrometers or vernier calipers) that has a precision of at least 0.001 in. and is large enough to measure the stator frame, end shield joint diameter is needed.
  • Motors that incorporate motor-circuit temperature limiting devices (thermal protectors) are not eligible to be rebuilt unless the original equipment manufacturer's information is available.
  • Motors for use in Class II, Group E hazardous locations are not eligible to be rebuilt unless the original equipment manufacturer's information is available.
  • Motors intended to be supplied by a variable frequency inverter drive are not eligible to be rebuilt unless the original equipment manufacturer's information is available.
  • Damaged or deteriorated parts may be replaced or repaired. Replacement parts shall be obtained from the original equipment manufacturer. Parts may be repaired by welding or brazing. If the Class I enclosure is welded or brazed, the weld or braze shall be gas-tight as verified by means such as X-ray. Shafts may be metalized, and shaft openings, bearing caps and end shields may be sleeved. Bolts, tie rods, cap screws, etc., may be replaced with hardware having equal or higher tensile strength.
  • All electrical repair must be done at the rebuilding facility (no field work or outside vendor work). Mechanical repair may be done by others. However, it will be the responsibility of the rebuilder to verify that the construction complies with the requirements as if the work was done in-house.

Getting started

To initiate an investigation of your facility, request an application form. Sign and return it to UL, along with the specified preliminary deposit. After the application and deposit are received, UL will establish a project and one of UL's hazardous locations staff will contact you.

Questions?

We hope that this program overview provides sufficient information for you to make a decision about becoming a UL rebuilder of electric motors for use in hazardous locations. If you have any questions or comments on this service, or any other UL rebuilder service, please contact hazloc@ul.com. We look forward to working with you.