Entries by Mike.Lake

Casing Repairs (Part 1: Cracking)

This three part Turbine Generator Tip discusses the most common steam turbine casing problems: cracking, distortion and erosion. Most units can be repaired by grinding, welding or by pre-stressed mechanical methods. Finite element calculations show that in many cases, repairs can overcome some of the original design weaknesses and extend useful life by up to […]

Crane Safety Revisited

Just when you think you have all the bases covered, the “impossible” happens. During a lift on one of our recent outages, the idler pulley and mounting bracket for the drive on the overhead crane fell approximately 25 feet. Fortunately no one was injured. We have discussed the need for pre-outage crane inspections in previous […]

AC & DC High Potential Testing Fact & Fiction

Which is better: AC or DC Testing? Will these tests hurt my generator? Here are the facts: DC high potential test equipment is relatively small and easy to transport. AC equipment is comparatively difficult to transport (large and heavy). DC testing stresses the dielectric in a different manner than AC. DC tends to stress the […]

Hose Connector Failures

Once again we are inviting comments on a recent safety concern and TGM’s efforts to remedy it.  A 1” air hose came loose from the connector fitting.  The hose whipped across the floor, narrowly missing two mechanics, before a quick thinking mechanic shut off the supply. Our hoses were equipped with the fitting shown on […]

Direct Current High Voltage (Potential) Testing

Direct current high voltage testing can be divided into two categories: Proof testing and Controlled Over-Voltage testing. Proof testing qualifies an insulation system to hold a specific voltage. By definition, it is a pass-or-fail evaluation – there is no diagnostic value. Acceptance proof testing is performed on new stator winding as part of in-process and […]

Exploding Sockets Revisited

Recently, one of our sockets exploded while loosening a bolt using a HyTorc hydraulic wrench. No one was injured, but we take these incidents seriously, generating a “Near Miss” report and subsequent corrective action. We discussed exploding sockets in a previous Safety Tip, which you can review in the May 8, 2012 post (see below). […]

Polarization Index (PI) Test

A Polarization Index (PI) test is generally performed at the same voltage as the Insulation Resistance (IR) test.  Where the IR test is performed for a period of one minute, the PI test is performed over a period of ten minutes. This gives the absorption (polarization) current ample time to decay, and reveals a more […]

Proper Manual Lifting

Back pain constitutes about 10% of occupational injuries and is the most common reason to take leave from work.  Each year about $50 billion is spent on treatment in The U.S. alone, making it the third most expensive condition after heart disease and cancer. With this in mind, an ounce of prevention is worth a […]

Insulation Resistance (IR) Test

The Insulation Resistance Test measures the integrity of the generator’s winding insulation, and therefore the likelihood of developing a ground.  A test voltage is applied to the generator and the current flow required to maintain that voltage is measured over a period of time (typically one minute).  In simplest terms, the less current flow, the […]

Starting Over

We’re embarrassed. We had our first recordable accident after 909 days (over 500,000 hours). Just when everything was going so right. We had the toolbax safety meeting at start of shift to discuss the day’s hazards. We had the Job Safety Analysis for the task to be performed. We had top management buy-in and a […]