Our turbine cases are designed with metal-to-metal horizontal joint sealing for a wide
range of steam pressures and temperatures.
Rugged Casing Design for any Application
These casing components are modular designs, selected from
standardized components. The inlet or high pressure section of the casing is cast carbon
or low alloy steel; a combination of cast steel and fabricated steel construction can also
be used. We select casing materials based on your specific application and manufacture in
compliance with industry standards. Dresser-Rand continues to pioneer casing designs that
properly accommodate expansion, corrosive influences, thermal stresses and sealing
capabilities called for in today's high pressure and high temperature steam applications.
Each section of the turbine casing is hydrostatically tested to rigorous API Standard 612
requirements.
Horizontally Split Casing
Horizontally split centerline allows ease of maintenance and service through the removal
of the upper turbine half for internal inspection. Careful attention to the selection of
fasteners and joint assembly tools, plus features like removable by-pass piping for lower
half admission help to reduce maintenance time and costs.
Customized Stationary Steam Path
Components
We use an innovative Profile Ring Vane
(PRV) to construct
both nozzle rings and diaphragms. PRV diaphragms, with their special end wall profiling,
offer efficiency advantages over conventional diaphragm designs.
Our diaphragms precisely match the pressure, temperature,
steam flow and required pressure drop across each stage. Special features, such as
windshields, water catchers and inter-stage drains, are used as required by stage
conditions to minimize erosion.
Blading
Designed for Performance and Reliability
Blade design is a critical factor in achieving consistent,
reliable and efficient steam turbine performance. At Dresser-Rand, our team of experienced
design engineers use the latest in computer-aided analysis and solid modeling coupled with
extensive laboratory and field testing to develop efficient and reliable blade designs.
We've developed and field-proven a large selection of efficient, heavy-section blade
profiles. Optimal blade selection for all conditions of service is available.
Depending upon stage conditions, stress factors and design
requirements, blades are final assembled using a shroud band made from a stainless steel
strip and precision riveted to the blades in five to six blade packets. Our stainless
steel shrouds contribute to the proper blade damping, minimize steam leakage over the
blades and increase strength and rigidity of the rotating blades.
Each stage of all variable speed mechanical drive steam
turbines is analyzed with Campbell and Soderberg (modified Goodman) diagrams. Our
engineers developed and implemented Singh's Advanced Frequency Evaluations (SAFETM)
analysis program, which clarifies any interference appearing in the Campbell diagrams and
lets us more accurately forecast blade behavior. This analysis program has become the
standard around the world for avoiding harmful harmonic resonances.
Rotors Tailored to Your Application
Because the rotor is the single most important component of
any turbine, ours receive special attention. We concentrate our years of turbine
experience on its design, materials, workmanship, assembly and testing.
Solid Rotor Feature
It was Dresser-Rand's utilization of the solid rotor that lead directly to out ultra-high
shaft speeds in modern steam mechanical drives. Our large solid rotor, designed and
constructed in compliance with the latest API Standard 612 specifications, provides for a
smooth running unit throughout the operating range. As a result, we are able to narrow
wheel hubs and minimize bearing spans to reduce stress to conservative levels and to
markedly improve turbine rotor stability.
Automatic
Control Valves
for Maximizing Efficiency
Dresser-Rand provides both heavy-duty cam operated governor
valves and a less complicated bar lift designed for use on low to moderate inlet
pressures.
Automatic Valve Features
We individually size and sequence valves for optimal efficiency at your specified
operating points. To prevent spinning, chattering and sticking, valve stems are positively
held with controlled vertical movement. To seal valves against leakage, surface hardened,
stainless steel bushings guide the valve into lapped seats. Control valves are precisely
positioned by a powerful low pressure oil servo system and are designed to positively
close on any trip signal.
Governing
Controls Precision Matched to Your Needs
For added reliability of the total design and enhanced rotor
dynamics, we use electronic control and overspeed trip devices. By eliminating mechanical
connections required for conventional mechanical systems, maintenance time and costs are
minimized.
Dresser-Rand's basic governing system includes digital
electronic speed and/or process control. The system includes a redundant speed pickup,
digital governor and an electro-pneumatic valve actuator. Electro-hydraulic actuators are
also available.
Bearings Designed to
Handle the Load
Proven bearing designs are used to maintain machine
reliability under demanding operating conditions.
- Pad backing can be low carbon steel, the most common, or
high-thermal-conductivity material such as chrome-copper alloy.
- The lining is a tin-based babbitt material.
- Each bearing has two spring-loaded temperature sensors,
including both the upstream and downstream sides of the thrust bearing.
- All bearings can be inspected or removed without disturbing
the upper half of the turbine casing or rotor.
- We provide X-Y radial vibration probes for each bearing area.
- We provide rotor axial position probes.
Thrust Bearings
Our thrust bearings, built on the Kingsbury principle, withstand heavy thrust loads with
very small friction losses and a low rate of wear. The babbitt-surfaced, multi-segment
shoes pivot during operation, providing a tilting action that forms a wedge-shaped oil
film between the rotating thrust collar and the bearing surface. The thrust load
automatically distributes in either direction equally to the several shoes, maintaining
internal alignment as well as holding the rotor in its axial position. This means less
maintenance to wearing parts.
Journal Bearings
For proper rotor dynamics in critical service applications, we use tilting pad, center
pivot, and axial aligning pad type journal bearings. We pay careful attention to actual
support stiffness, instead of infinite stiffness, to predict and design the rotor and
support systems.
Low Loss Bearings
The latest directed lube bearing technology minimizes mechanical and parasitic losses, and
reduces lube oil flow requirements, yet maintains conservative bearing pad temperatures.
Extensive testing in our laboratory and in the field proves the effectiveness of these
state-of-the-art bearings.
Shaft Packing for
Increased Steam Path Efficiency
To minimize steam leakage and maintain peak efficiency, we
use labyrinth packing where the shaft passes though the casing end glands and
diaphragms.
Made of a relatively soft metallic material, our labyrinth
packing is segmented and assembled concentric to the turbine shaft and held in position by
multiple coil springs.
Due to our precise machining capabilities and the
characteristics of the soft packing, no shaft sleeves are required. Its segmented packing
design allows for movement under upset conditions, maintaining the integrity of the steam
path.
Gland Seal System
In addition to appropriate packing, as part of our steam sealing systems we provide our
turbines with a gland seal system. Dresser-Rand's standard scope of supply includes
leakoff manifold, gland condenser, air ejector and condensate tank.
Turning Gears for Large
Turbines
If necessary, a rotor turning gear is used during cooling
down periods to keep temperatures uniform along the shaft to eliminate distortion and
shaft bow. The turbine can be started during cooling-off periods, without fear of shaft
bow being present or increasing the time required before start-up. A double extended motor
shaft with wrench is provided for manual operation.
Testing for your Assurance
The key to reliable turbine generator performance is superior
quality control. You can have confidence in the reliability of our equipment because we
regularly conduct ultrasonic, magnetic particle, and hydrostatic tests, as well as test
for fatigue and tensile strength. In addition, we constantly check for the accuracy of all
our production measuring tools, using the most up-to-date equipment. In fact, all our
procedures are process-documented and certified to meet ISO 9001 requirements. At
Dresser-Rand we give all our turbines a no-load mechanical run test, and when appropriate,
run a no-load test in accordance with API Standard 612. Our test facility includes
high-pressure boilers, surface condensers and water brakes to facilitate the mechanical
spin test and various part-load procedures.
