Case Study – Nuclear Power Plant: Steam Turbine Inner Casing Closure

Product: Hydraulic Rod Tensioner & Hydraulic Rod Nut

PROVIDING

  • Greater loads within restricted footprints
  • Shortened turnaround times
  • Easy adaptation for retrofitting to studs not extending above nut

Problem

Solution

1. Insufficient loading using conventional torqueing methods cased warped flanges

2. Leakage between stages due to gap between flanges (known as “smile”)

3. Labor-intensive operations led to over-budgeted turnarounds

4. Contaminants in the steam path

1. Simultaneous tensioning of studs provided precise loading allowing full flange closure

2. Developed sufficient clamping to overcome warping of inner casing

3. Labor hours drastically reduced – turnaround reduced by one month

4. Water-charged hydraulic nuts eliminated contamination concerns

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Case Study – Reciprocating Equipment Components: Compressor Crosshead

Product: Hydraulic Tensioning Nut

PROVIDING

  • Increased clamping uniformity and repeatability
  • Reduced assembly time compared to torqued hardware and external tensioning

 

APPLICATIONS & FEATURES

  • Stud thread size range from ¾” up to 6”
  • Capable of generating loads up to 85% of stud yield strength
Hydraulic Tensioned Nut Tool

Problem

Solution

1. Difficult and unpredictable pre-loading of crosshead hex jam nuts using turn-of-the nut method

2. Difficult crosshead alignment

3. Piston rod bending and fatigue failures

4. Piston rod and crosshead slide life

1. Replace original jam nuts with HTN to achieve uniform and predictable pre-loading

2. HTN incorporates spherical washer for ease of alignment

3. Design features prevent piston rod bending and fatigue failures

4. Uniform loading provides longer life piston rod and crosshead slide

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Case Study – Rotating Equipment Casing: Steam Turbine Casing Closure

Product: Hydraulic Rod Tensioner

PROVIDING

  • Ease of cover flange face blue check inspection
  • Greatly reduced installation times vs hydraulic torqueing

 

APPLICATIONS & FEATURES

  • High temperature service (950°F)
  • Limited spot face and high residual load applications
  • Easily retrofitable to existing requirements

Problem

Solution

1. Torqueing of nuts in a defined sequence resulted in insufficient load leading to the warped flange condition

2. Warped casing from in-service use made closure difficult

3. Long assembly times using traditional torqueing methods

4. Space constraints

 

1. Improved clamping load and uniformity from hydraulic tensioning successfully closed the warped flange

2. Independent loading easily performed to close gap

3. Reduced assembly time from 2 days to 3 hours

4. Tensioning system with washers fit within existing spot face and tensioned to an installed residual stud stress of 45,000 psi.

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Case Study – Valve Cover Assembly: Steam Turbine Control Valve

Product: Custom Designed External Tensioning

PROVIDING

  • Improved gasket sealing
  • Elimination of galling
  • Reduced turnaround time

Problem

Solution

1. Non-uniform load distribution using traditional torqueing methods of valve cover assembly

2. Improper gasket sealing

3. Routine valve servicing is time consuming

4. High risk of valve cover studs

1. Custom-designed four-leg tensioner bridge with external tensioners and 3” diameter x 17” long studs to replace hydraulic wrenching tooling

2. Studs incorporate internal tapered threads that mate directly to tapered tensioner puller screws to achieve elongation

3. Tensioners operating in tandem hydraulically stretch studs to achieve a residual 30,000 psi stud stress after relaxation

4. Tensioner bridge allows installation in a tightly nested hex cap nut pattern

5. Achievement of accurate preload quickly with uniform pressure distribution for proper sealing

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Case Study – Nuclear Power Plant: Steam Turbine Inner Casing Closure

Product: Hydraulic Tensioning Nut

PROVIDING

  • Greater loads within restricted footprints
  • Shortened turnaround times
  • Easy adaptation for retrofitting to studs not extending above nuts

 

APPLICATIONS & FEATURES

  • Unique Metal-to-Metal Seal Design
  • Tolerant to harsh environments
    • Applications up to 500°F
    • Water charged for special application
  • Multi-bolt Tensioning
    • Simultaneous “Daisy Chaining” provides uniform clamp loads and shorter assembly time.
  • Accommodates confined spaces and envelope restrictions.
  • Inherent Safety
  • Forces act along bolt axis and not thought torque reaction arms.
  • Compact Standard Sizes and Custom Designs
Hydraulic Tensioned Nut Tool

Problem

Solution

1. Non-uniform load distribution between casing halves with traditional torqueing methods and multi-jackbolt torque nuts

2. Resulting leak paths and sub-marginal acceptance tests

3. Extended delivery and commissioning times due to numerous adjustments required to achieve clamping uniformity

1. Uniform and repeatable clamping pressure

2. Trouble-free acceptance testing as leak paths are eliminated

3. On-time delivery and start-up

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Case Study – Rotating Equipment Casing: Centrifugal Compressor Casing Closure

Product: Hydraulic External Tensioner

PROVIDING

• Elimination of galled threads

• Uniform and repeatable loading

• Shorter turnarounds

• Reduced acceptance test periods

 

APPLICATIONS & FEATURES

• Standard tensioning solution for exposed threads above exiting hex nuts

• Modular design – common load cell with interchangeable puller screws available in any size thread and pitch

• Thread sizes ¾” to 4” for loads up to 615,000 lb

• Simultaneous tensioning as any number of tensioners can be linked together

Problem

Solution

1. Non-uniform load distribution between casing halves with traditional torqueing methods and multi-jackbolt torque nuts

2. Resulting leak paths and sub-marginal acceptance tests

3. Extended delivery and commissioning times due to numerous adjustments required to achieve clamping uniformity

1. Uniform and repeatable clamping pressure

2. Trouble-free acceptance testing as leak paths are eliminated

3. On-time delivery and start-up

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