Components of Reliability
Journal Bearings
Our journal bearings are split at the horizontal centerline for easy access and
replacement without removing the rotor. These bearings are bronze-backed and
babbitt-lined
for long life. In most cases, journal bearings are interchangeable at both the inlet and
exhaust ends. They are normally ring-oiled, but can be arranged for pressure lubrication
when you require. Depending on your operating conditions, optional ball bearings may
eliminate your need for cooling water.
Impro Seals
Impro Seals are optional mechanical-type seals which provide a positive seal against oil
leakage and the entry of dirt and gland-leakage steam into the bearing housings.
Prevention of contamination by the seals helps prolong the bearings' life.
Rotor Assembly
We design and build rotors to withstand the most stringent requirements of API 611 and API
612. For all applications, we machine wheels from a single steel forging with two rows of
single blades. This provides 50% more hub area at the shaft than with two single wheels.
The special web-shaped design also restricts excessive heat transfer from the rim to the
hub. For high-speed applications optimizing wheel and rotor dynamics, solid rotors are
available.
Carbon Ring Packaging
To minimize steam leakage, Dresser-Rand's gland sealing arrangement features an
angle-type, carbon ring design with a packing case that is an integral part of the turbine
case. Inconel springs hold the rings in place. Our unique stainless-steel spacer rings
provide a continuous flat face for the vertical surface of the carbon ring to seat
against. The slanted outside diameter produces a positive seal at the spacer ring.
Thrust Bearings
While our impulse design produces minimum internally generated thrust, a thrust bearing is
required to firmly fix the rotor in its axial position and to withstand coupling thrust by
load transmission. Dresser-Rand thrust bearings accommodate these requirements with ample
capacity and high reliability. Depending on your requirements, we offer either a ball
bearing or a double acting, self-equalizing, tilting pad thrust bearing.
Blades
For moderate temperature applications, we make blades from stainless-steel drawn stock,
manufactured to API 612 specifications. For more demanding conditions, we machine blades
from solid stainless-steel bar stock. Blade roots and shape are selected based on each
turbine's operating conditions.
Labyrinth Gland Packaging
We use labyrinth packing made of relatively soft metallic material as an option when back
pressure or turbine speeds dictate their use. The packing is segmented and assembled
concentric to the turbine shaft and held in place by multiple coil springs. With our
precise machining capabilities and the characteristics of the soft packing, no shaft
sleeves are required. This segmented packing design allows for movement under upset
conditions, maintaining the integrity of the steam path.
Mechanical Seals
These optional, dry-running seals replace labyrinth or carbon-ring gland-seal systems.
They create a high-pressure region that forms a barrier to steam flow as the turbine
rotates. The seals reduce leakage so that gland ejectors and condensors are not required.
These seals decrease steam consumption and lower maintenance costs.
Safety Trip Systems
Our emergency valve and trip mechanism is entirely independent of the governor. It
utilizes a piloted venturi-type trip valve and provides positive trouble-free closure to
shut off steam to the turbine in case of overspeed. The pilot feature allows the mechanism
to be easily and quickly reset against full steam pressure.
Governors
Our SST standard governor is the NEMA Class A Woodward TG governor. This governor combines
accurate speed control with simple economy. It is a self-contained governing system,
hydraulically powered for high output. Optional governors include the Woodward PG and
UG,
which meet NEMA D requirements. Electronic governors with pneumatic/hydraulic actuators
offering more control, flexibility and remote speed adjustment as well as other operating
modes are also an option.
Trip and Throttle Valve
The trip and throttle valve has two separate and distinct functions. It acts as a
quick-closing valve when tripped manually or automatically by the overspeed governor or
other safety devices. It also operates as a hand throttle of the steam for starting and
bringing the turbine up to speed. This arrangement is optional throughout the complete SST
line, but standard on our 500 HS, 700 S and 700 HS models where high operating pressures
require it.
Casings
Our turbine cases are designed with metal-to-metal horizontal joint sealing and optimized
wall thickness that keeps distortion and misalignment to a minimum. The casings fully
conform to ASME Section VIII and NEMA for allowable stress levels. Each section of the
turbine casing is hydrostatically tested to rigorous API Standard 612 requirements and is
a true API metal-to-metal horizontal split design.
Hand Valves
Hand valves help maximize efficiency by increasing or decreasing the nozzle area through
which steam can flow. Optional automatic hand valves control the nozzle area to match the
turbine output with a minimal amount of throttling without any operator intervention.
The valve logic is furnished through an electronic governor which can be set to open or
close the valves in a predetermined sequence.
Stationary Steam Path
Components
We individually drill and ream our standard nozzle rings to fit customer requirements. We
design them to be independent of the turbine case which makes replacing them easier during
turbine rerates.
When efficiency demand requires it, we use the innovative Profiled Ring and Vane
(PRV)
process to construct nozzle rings and diaphragms. PRV nozzle rings, with their special
end-wall profiling, offer efficiency advantages over conventional designs.
