Chuck Yung
Senior Technical Support Specialist
Electrical Apparatus Service Association
St. Louis, MO
Field service work can be challenging due to unfamiliar surroundings, potential hazards, and the lack of usual tooling. Chuck Yung's paper "Field Service Work, Techniques & Cautions," presented at the EASA Convention 2017, provides valuable insights into making field service work easier and safer. Yung emphasizes the importance of personal protective equipment (PPE), including Nomex clothing, steel toe footwear, hardhats, safety glasses, and goggles. He also highlights the necessity of lock out, tag out procedures to ensure safety when working on equipment that might start unexpectedly.
Cleaning motors on-site can be efficiently done using dry ice, which is environmentally friendly and reduces disposal concerns. Bearing replacement, particularly for sleeve bearings, requires meticulous attention to cleanliness and fitting. Yung suggests using oil instead of Prussian blue for fitting sleeve bearings and monitoring velocity with a portable vibration analyzer to detect early signs of bearing issues.
Cold stripping the stator is necessary when a motor cannot be removed from the site. Techniques such as wedge removal using a hacksaw blade or circular saw, and coil removal using custom pry bars, are discussed. For large machines, Yung recommends using a crane or hoist with a spreader bar and J-shaped jig to facilitate coil removal. Preheating the stator or using a DC supply to heat each coil can also aid in the process.
Portable ovens made from hard foam board and aluminum duct tape are effective for drying or curing windings on-site. Yung advises monitoring temperature with RTDs or thermometers and controlling oven temperature with dampers. He debunks misconceptions about drying windings with welding machines and the risk of burst insulation at high temperatures.
On-site machine work, such as machining shafts, commutators, or slip rings, can save customers time and money. Portable key mills and Dynabrade belt sanders are useful tools for these tasks. Yung provides tips for machining slip rings in place, emphasizing the importance of positioning the belt sander correctly to avoid debris contamination and ensuring the belt direction opposes the ring direction.
Yung concludes by stressing the importance of safe work practices and appropriate protective equipment in field service work. His paper offers practical techniques and cautions to help service technicians navigate the challenges of field service work effectively.
Key Points Covered:
- Importance of personal protective equipment (PPE)
- Lock out, tag out procedures for safety
- Cleaning motors on-site using dry ice
- Bearing replacement techniques, especially for sleeve bearings
- Cold stripping the stator and coil removal methods
- Portable ovens for drying or curing windings on-site
- On-site machine work, including machining shafts and slip rings
- Debunking misconceptions about drying windings with welding machines and burst insulation
Key Takeaways:
- Field service work requires meticulous attention to safety and cleanliness.
- Personal protective equipment is essential for protecting technicians.
- Lock out, tag out procedures ensure safety when working on potentially live equipment.
- Dry ice is an effective and environmentally friendly method for cleaning motors on-site.
- Proper techniques for bearing replacement and cold stripping the stator are crucial for successful repairs.
- Portable ovens made from hard foam board and aluminum duct tape are effective for drying windings on-site.
- On-site machining of shafts and slip rings can save time and money for customers.
- Misconceptions about drying windings with welding machines and burst insulation at high temperatures are debunked.
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