The projects shown here deal with the changing of the throttle valve seats on various Westinghouse steam turbines. Similar operations are performed to change the main stop valve seats on many General Electric turbines, though some of them are bolted in, and some are welded. The work is similar but perhaps easier on a GE turbine because the valves are usually oriented vertically, and not horizontal as are these Westinghouse valves.
The work generally consists of the following:
Cut the seal weld from the old seat and pull it out. Machine the gasket face and spigot fit bore in alignment and perpendicularity with the axis of the seat bore. Skim cut the seat bore to establish size and roundness. Machine the new seat to proper sizes, shrink, and install. Complete the seal weld.
Uintah Machine has worked on quite a few Reheat Stop Valves (RHSV or RSV). Those shown here are on Westinghouse turbines. Besides on site work like this, we also work on the bearing end caps and the yoke brackets (AKA “mummy case”) in the shop.
Pressure Reducing (or Relief) Valves (PRV’s) function to divert the water and pressure from the turbine should an untoward incident take place, and they are designed to open in an instant when tripped, thereby preventing serious pressure spikes in the penstock. The photos below show various boring bar setups used in the rebuild of these valves.
We also bolted in stainless liner plates below the seat ring of one of these PRV’s where the wall of the valve had been largely destroyed by the forces of cavitation. This part of the valve was mostly spherical, and so it was necessary to build a special hydraulic drill that would adjust to all angles or elevations and rotation in order to get the holes radial to the center point of the sphere.
Uintah Machine changes out nozzle blocks when required to do so. The photos shown here depict jobs on a couple of different Westinghouse turbines. The general procedure is to remove the old bolts (shearing the retaining pins in the process), remove the nozzle blocks, then machine the interface with the nozzle chambers. Thereafter the new blocks are lapped in to contact with the nozzle chambers, bolted up, and the bolt heads pinned.
Uintah Machine has rebuilt many Westinghouse steam chests. They range in size from as small as 2 1/2″ or so ID, up to 5 3/4″ ID in the throat. Most of the steps to the process are shown here in photos.
Uintah Machine also when called upon changes out the inserted governor valve seats that are inserted from the bottom of the steam chest before the steam lines are welded on on some of the older Westinghouse units.