Horizontal Mounted Actuator Upgrade for Toshiba® Units
MD&A performs repairs on hydraulic systems on all major turbine makes. We’ve built a solid reputation on governor stand repair, and now are forging an equally well-deserved reputation with actuator repairs. Our experts designed a horizontal mounted actuator upgrade.
At our 100,000-square-foot facility in Euclid, Ohio, we stock a large number of components, everything from MHC governor stands to Rexroth® actuators to servos and solenoid valves.
We also take a lot of pride in our repair documentation. In addition to recording the model and serial number, we note any auxiliary equipment like a servo solenoid, which most of the actuators have, before we start the disassembly process.
GE® and Toshiba® both use Rexroth® actuators on their combined cycle units. Toshiba® mounts their actuators in a horizontal position, while, GE® mounts them vertically. That difference can cause a maintenance problem.
Mounting the actuator in a horizontal position causes a lot of stress on the shaft. As the actuator control valve strokes back and forth, it puts a tremendous amount of weight on the seal. All that weight sits on the down side of the spring can retainer. So as the actuator strokes to regulate the speed of the turbine, it causes a lot of stress.
One customer has a large Toshiba® steam turbine that uses these valves and gets about two years out of them before the stress wears away the seal. Then metal-to-metal contact occurs between the ID of the spring can and the OD of the spring can retainer. That causes drag and friction and also lowers the shaft.
As the shaft lowers and the friction increases, the forces put more stress on the guide bushing that’s closest to the spring can. Those seals start to wear away and the equipment may leak fluid into the spring can.
Our technicians have worked on different actuators for different Toshiba® units from large steam turbines to combined cycle units. All examples had the same scoring and the same wear on the lower side of the spring can where the spring can retainer and the spring can meet.
MD&A experts created an actuator upgrade for horizontal mounted actuators where we coat the inside of the spring can, upgrade the seal, and redesign the HP bushing & the LP bushing.
With those modifications, we expect to extend the life of the Rexroth® actuator on the Toshiba® units so that they need service no more than once every four years, roughly doubling the current outage interval.
MD&A Bearings, Seals & Hydraulics division, since 1984, has refurbished and upgraded hydraulic control components, such as actuators. We can offer a short cycle turnaround because of our inventory of components, along with our team’s knowledge.
Email This article | Print This Article