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MOV/Gearbox Overtorque Protection Presented By:Denise Lane Mech. Engineer Agua Fria Generating Station (Ex: Limitorque Actuators) Power Generation Best.

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Presentation on theme: "MOV/Gearbox Overtorque Protection Presented By:Denise Lane Mech. Engineer Agua Fria Generating Station (Ex: Limitorque Actuators) Power Generation Best."— Presentation transcript:

1 MOV/Gearbox Overtorque Protection Presented By:Denise Lane Mech. Engineer Agua Fria Generating Station (Ex: Limitorque Actuators) Power Generation Best Practice’s Meeting October 31, 2007

2 Presentation Elements MOV/Gearbox Safety Concern Refresher –Crystal River –Common Causes of Failure –Valve Wrench/Cheater Bar Usage Mechanical Overload Protection Device –Operating Principle –Information & Calculations –Installation & Cost

3 MOV/Gearbox Safety Concerns Crystal River - 01/2004 – BFP Iso Valve Killed 20 Yr. Employee Valve Wrench To Close Gears Cranking to Open Cracked Actuator Housing

4 MOV/Gearbox Safety Concerns Valve Failure Root Causes –Using a Valve Wrench/Cheater Bar on the Handwheel –Holding In the Motor Control Contactor –Setting the Torque Switch Too High –Beating on Valve Body to Unseat Valve –Removing Stem Locknut Under Pressure –Electrical Shock

5 Safety – Handwheels & Valve Wrenches Handwheel Torque > Motor Torque Wheel Radius & Max. Hand Forces Limit Torque −Designed for Max. Allowable Actuator Rating

6 Safety – Handwheels & Valve Wrenches Valve Wrenches/Cheater Bars −Benefit - Decreases Hand Force Needed to Seat or Unseat Valves −Drawback - Uncontrolled Length Increases Induced Weak Link Stress −Drawback – “Slipping” Safety Concern

7 Safety Concerns Weak Links Can Stretch & Separate –Yoke & Actuator Housing Cover Bolts –Causes Actuator &/or Valve Housing Ejection –“Missile” Safety Concern –Not Just Limitorque –More Often Now

8 Overtorque Protection Collar – How It Works

9 Protection Collar – Other Styles Top Mounted D82 Model D82TM-INT SMB-000 Integral part of Limitorque actuator

10 Protection Collar – Information Needed Valves –Make & Model/Style –Stem Diameter & Threads/Inch Actuators –Make & Model/Style –Shaft Diameter –Keyways Width x Length x Depth Length Extended Through Handwheel Collar? Extruded or Inlaid?

11 Protection Collar – Calculations Needed Formula Derivation – (4) Steps –Parker/Winsmith Gear Speed Reducers Limitorque SMB-00 Actuator Supplier –Pinnacle Actuation MOV/Gearbox Safety Training –SRP Engineering -

12 Protection Collar – Calculations Needed Determine Actuator Parameters Limitorque SMB-00 = 260 ft*lbs Max. Input Aura Motor = 260 x 0.6 = 156 ft*lbs Max. rpm = hp x 5252/Torque −Min. Angular Speed < Step 3 Ensures Max. Torque Not Exceeded

13 Protection Collar – Step 1 Information Actuator Nameplate Service Factor Maximum Allowable Torque Input Motor Manufacturer Safety Factor

14 Protection Collar – Calculations Needed Gear Output = Min. Torque to Open/Close Valve Wedge Diameter = Valve Diameter Seating Force = Line Pressure x Seating Area x Valve Turning Hardness Factor Required Output = Total Thrust x Stem Radius

15 Protection Collar – Step 2 Information System Line Pressure Valve Internal Diameter Valve Stem Diameter Valve Friction Coefficient: −Gate = 0.3 Packing Friction Coefficient −Graphite = 3,000 psig incl. S.F.

16 Protection Collar – Calculations Needed Supplied Gear Output = Max. Actuator Torque Input = hp x 5252/rpm Stem Speed = rpm/Drive Sleeve Bevel Gear Ratio −Must be > Step 1 Min. Calculated Speed Input Gear Torque = Output hp x 5252/Stem Speed

17 Protection Collar – Step 3 Information Motor hp Motor rpm Motor Efficiency Drive Sleeve Bevel Gear Ratio

18 Protection Collar – Calculations Needed Required Torque < Overload Protection Cutoff < Max. Actuator Torque Vector = Moment Arm Length About System C.G. Hand Force = Cutoff Torque x Vector Max. Bar Length Allowed = Cutoff Torque - Avail. Hand Torque_____ Hand Force Needed – Avail. Hand Torque

19 Protection Collar – Ease of Installation/Pricing $1,000-$1,500 Ea. Dependent on Qty. & Style Greg Bennett – “Relatively Easy” Kirk Mason – “Very Easy” “Piece of Cake” Successfully Tested

20 Collar Installed on FWH Extraction Valves No CollarsCollars

21 Questions?


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