Global machining specialist Hydratight has become the first company to use electrical discharge machining (EDM) for maintenance work on a live nuclear reactor pipeline system.
The company completed the technically challenging campaign for a major energy company at a US power station as part of post-Fukushima upgrades. The use of EDM avoided an expensive unplanned shutdown of the reactor for the operator and took 48 hours off the reactor outage schedule.
Hydratight’s EDM process used a heated solid electrode to accurately cut a hole within the reactor feed water line then removed microscopic cuttings using back-flushing and vacuums. It prevented 99.5% of foreign material exclusion (FME) particles, such as drill cuttings and debris, from entering the reactor, which can cause contaminations and lead to unplanned outage.
Mike Riordan, Hydratight’s nuclear speciality services manager, said: “This was a milestone achievement on a live nuclear reactor pipeline system and has resulted in safety enhancements in line with the industry’s post-Fukushima requirements. The work has created another way to feed water into the main line if there is ever a power loss to the reactor.”
The line had water pressure of 120 PSI and electrical conductance exceeding 3,500 micro-siemens. Hydratight’s speciality services deployed customized tooling to negotiate a 15-inch-long, 1-inch wide pipe as an entry point to reach the spot where the ¾-inch EDM penetration was to take place.
EDM is typically deployed as an alternative to mechanical methods, such as drilling and hot-tapping, during planned outages. As well as preventing FME particles from entering process piping, the cutting is highly accurate and can maintain a tolerance of .002-inch when making the hole in the pipe.
“Material contaminations are a major concern for most facilities and electrical discharge machining is a highly accurate and safe way of machining,” added Mr Riordan. “Tool pressure was also a concern on this particular project, so we were able to use a method which was completely contactless.”
Hydratight has offered its services to the nuclear and power generation industries for more than 30 years.
Source:via BIG Partnership via Actuant Corporation
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