A detailed incoming inspection was performed for the HP/IP and LP rotors and found relevant indications in the LP rotor steeples at L-1 (stage 20) through magnetic particle inspection, in addition to minor damages identified on the HP/IP rotor.

Finding indications in the last-stage LP rotor steeples (also known as fir-tree grooves) is a common issue.  Basically, the steeple indications are caused by corrosion fatigue (when a material degrades due to the combination of corrosion and cyclic stresses).

Repair of the LP rotor included removal of the L-1 steeple indications by hand tooling, followed by blending and polishing. There were 3 steeple indications that were noticeably deeper than the rest. The approximate depth of these deeper indications was 3 mm (0.12”) located on the convex side of the steeple.

A finite element analysis was performed to verify the structural integrity of the steeples after grinding. Based on the analysis, the L-1 steeple repair was found to be acceptable. After all rotor repairs were complete, the rotors were balanced, and the journals were strapped lapped prior to leaving the workshop.

Incoming inspections were also completed on the HP/IP and LP diaphragms.  The HP/IP diaphragms arrived at the workshop with the lower half appendages removed for reverse engineering. Minor damages were noted on the LP diaphragms including horizontal joint erosion and foreign object damage to the partition trailing edges on all stages, as well as damage to the steam seal face on stages 17-21.

Repair work to the HP/IP diaphragms included installing new appendage rings with honeycomb seals, which were supplied by MD&A Parts.  To ensure proper fitting, the appendage and bore packing fit diameters were machined round prior to the installation of the new appendages. Additionally, the dowel pins were removed, and the horizontal joint was skim cut.  Dowel pin holes were then enlarged, and oversized dowel pins were installed.

New bore packing (with honeycomb seals) for stages 2-9 and 11-15 were also supplied by MD&A Parts.  The bore packing was test fitted after appendage installation.

Minor repairs were performed on the LP diaphragms including horizontal joint weld repairs and removal of broken studs. After all diaphragm repairs were complete, new horizontal joint hardware was supplied by MD&A Parts and test-fitted before the diaphragms left the workshop.

Through MD&A’s state-of-the-art repair facility and quick access to replacement parts, an extensive inspection and necessary repairs were completed by our experts in a timely manner that allowed the unit to be quickly returned to the site.

Call MD&A today for any turbine repair at +1 (314) 880-3000 or use our Contact form.

The post Rotor Steeple Indications and Diaphragm Repairs appeared first on MDA Turbines.

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.

Call our MD&A Bearings, Seals & Hydraulics division today at (800) 446-4776 or use our Contact form.

The post Horizontal Mounted Actuator Upgrade for Toshiba® Units appeared first on MDA Turbines.