Windsor Locks, CT óPneumatically and hydraulically controlled robots used for inspection and repair of the cooling tubes in nuclear reactor heat exchangers make work safer for maintenance technicians at ABB, a manufacturer of power generation equipment. The robots minimize exposure to radiation, especially during inspection of each heat exchanger's 3,500 to 13,000 water tubes.
For greater efficiency, ABB's product development manager Lance Fitzgibbons needed to remove some of the problematic components from his previous robotic system, which used an electric motor pump and served only one robot at a time. "And with the old system, we'd have to wait for the electric pump motor to build up pressure. Then, we'd have to keep it running for long periods of time during the tube inspections," he says.
The old 220V pumps had electric solenoid valves for controlling hydraulic functions of the robot, which compounded ABB's problems. "If the solenoids overheated, they'd shut down and stay open. Then, we'd get leakage of contaminated reactor water into the uncontaminated water supply. The leakage prompted a manual shut-off," says Fitzgibbons. The manual shut-off necessitated a trip into the reactor vessel, which increased the amount of radiation exposure each technician received.
The new robotic system uses a 30:1 air-over-oil intensifier pump from Interface Devices (Milford, CT), which hydraulically and pneumatically controls up to three robots simultaneously. "Because it's an air-over-oil pump, I get instant pressure. And all I need to operate it is shop air," says Fitzgibbons. The new pump eliminates the need for a 220V line and the additional transformer needed to sustain that line.
ABB now uses pneumatic rotary actuators for controlling zero-leakage hydraulic rotary shear seal valves, thereby eliminating use of the solenoid valves and their overheating problem. With no solenoids to stick open, ABB eliminated the amount of leakage it had in its hydraulic system. "We also have a manual override capability now that we didn't have before," says Fitzgibbons.
Additional applications for the pumps include work-holding and embossing.