MOV/Gearbox Overtorque Protection

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

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

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

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

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

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

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

Overtorque Protection Collar – How It Works

Protection Collar – Other Styles

Top Mounted D82 Model D82TM-INT SMB-000 Integral part of Limitorque actuator

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?

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

Protection Collar – Calculations Needed

Step 1.

Actuator Input Parameters

Maximum Actuator Torque Input Minimum Actuator Angular Speed Input 156 12 17 ft*lbs rpm rpm for 0.7 hp Motors for 1 hp Motors

Note: NO Actuator Torque shall Exceed 260 ft*lbs for SMB-00 In Addition, the Motor Supplier Limits Motor Parameters Further to 60% of this Value = 156 ft*lbs

•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

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

Protection Collar – Calculations Needed

Step 2.

Operating Output

Max. Steam Pressure to Overcome in Fully Open Line Flexible Wedge Diam.

Flexible Wedge Seating Area Stem Diam.

Stem Loading Area Seating Force Stem Load Stem Packing Friction Max. Seating & Unseating Thrust

Max. Gear Torque Output Required

445 6 29 1.50

1.77

3,838 786 3,000 7,624

88

psig in in.^2 in in.^2 lbs.

lbs.

lbs.

lbs.

ft.*lbs.

•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

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.

Protection Collar – Calculations Needed

Step 3.

System Supply Adjustments

Max. Horsepower Worm Gear Input RPM - All Motors

Motor Torque Input Max. Speed Reducing Gear Ratio Supplied

Constant Valve Stem Speed

Motor Efficiency

Max. Output hp 0.7

1,700

2.2

80

21.25

0.61

0.427

hp rpm

ft.*lbs.

rpm hp Max. Gear Torque Output 106 ft.*lbs.

•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

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

Protection Collar – Calculations Needed

Step 4.

Torque Overload Protection Required Handwheel Shaft Length & Wheel Radius Vector Rim Pull Force Needed

Available UnLevered Torque per AS2638

Max. Extension Lever Required 95 ft.*lbs.

0.96

98 ft.

lbs.

56 ft.*lbs.

11.96

in.

•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

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

Collar Installed on FWH Extraction Valves No Collars Collars

Questions?