NRC MOV Course

NRC MOV CourseTheory of OperationCollege of Engineering

Theory of Operation of MOVsObjectives Identify common valve types and their typical serviceapplications. Describe the mechanical components that make up rising-stemvalves. Describe the mechanical components that make up rotatingstem valves. Describe the major electrical and mechanical components thatmake up common motor actuators. Describe the electrical and manual modes of operation ofmotor actuators and trace the path of the rotational forcesthrough the device.College of Engineering

Introduction An MOV is a combination of two separate devices,usually provided by two separate manufacturers.– Valve Assemblya mechanical device to optimize a desired fluid controlfunction, such as isolation or throttling.– Actuatoran electrical/mechanical device used to position a valveassembly from a remote location. The basic parts of a valve assembly have commonnomenclature regardless of the type of valve.– valve body, bonnet, disc (pressure boundary)– seat, stem, and yokeCollege of Engineering

Valve Assembly Basic PartsYokeStemBonnetValve BodyDiscSeatCollege of Engineering

Rising-Stem Valves Rising-Stem Valves are those designs operated bypushing or pulling the valve stem. The valve stems do not rotate. The valve stems are threaded and matched to astem nut to convert the rotational output of theactuator to linear movement of the valve stem. Most common designs are gate and globe valves.College of Engineering

Gate Valves Gate valves are used to start or stop flow, but arenot intended to regulate or throttle flow. The name “gate” comes from the appearance of thedisc in the flow stream. Gate valves are most often found in flow isolationapplications– Used at any system pressure– Common in large diameter, higher pressure pipingsystems.– Often have a closing safety function such ascontainment isolation or an opening safety functionsuch as emergency core cooling.College of Engineering

Typical Gate ValveCollege of Engineering

Gate Valve Disc Designs Gate valve discs may be parallel or wedge design.– Parallel discs have seating surfaces that are parallelto each other and perpendicular to the flow path.– Wedge discs have angled seating surfaces whichform a “V” shape that wedges the disc between theseat rings.– Wedge discs can be solid, split, or flexible. Gate valve discs typically provide seating on boththe upstream and downstream seats.College of Engineering

Gate Valve Wedge DiscsCollege of Engineering

Globe Valves Globe valves are used to stop, start, and regulate fluid flow. The name “globe” is derived from the shape of the disc whichcan be similar to a globe. The disc more often looks more like a plug.– (can lead to confusion with true plug valves which arequarter-turn valves) Globe valves can be designed so that, a large flow area isrealized around the disc with small stem movement.– This allows a quick opening or closing function. Globe valves and be designed so that the flow area graduallychanges with stem movement.– This gives the globe valve good throttling ability for use inregulating flow.College of Engineering

Globe Valve Orientation Globe valves can be installed with flow over orunder the disc. Closing against the direction of the fluid flow (flowunder disc) impedes closing but aids in opening thevalve. Closing in the same direction as the fluid flow (flowover disc) aids closing but impedes opening thevalve. This characteristic makes globe valves well suitedfor fail-open or fail-close valve applicationsCollege of Engineering

Typical Globe ValveCollege of Engineering

Quarter-Turn Valves Quarter-turn valves are those designs operated byturning the valve stem 90 degrees. Valve discs rotate with the valve stem to open orclose the flow path. Valve stems are driven directly by the rotationalmotion of the actuator. Most common designs are ball, plug, and butterflyvalves.College of Engineering

Ball And Plug Valves Ball and plug valves are used to stop or start fluidflow. The names are derived from the shape of the discwhich resembles a ball or a plug. In the open position, the ball/plug provides anunobstructed flow path through the valve. In the closed position, the ball/plug is turned 90degrees, blocking the ports and stopping fluid flow.College of Engineering

Ball And Plug Valves Advantages:– Little resistance to operation– Differential pressure has little effect on operatingloads– Quick opening and closing– Designed for any system pressure. Disadvantages:––––Higher costRapid wear and corrosion of seatsInability to regulate flowWeight of the ball or plug in large diameter systemsCollege of Engineering

Typical Ball ValveCollege of Engineering

Typical Plug ValveCollege of Engineering

Butterfly Valves Butterfly valves are used to stop, start, and regulatefluid flow. The valve stem extends completely through thevalve body. The disc is a flat or slightly curved disc attached tothe valve stem. The disc is rotated 90 degrees about an axis at aright angle to fluid flow The seats are typically a soft, resilient seat made ofrubber or neoprene.College of Engineering

Butterfly Valves In the fully open position, little resistance to flowexists and pressure loss is minimal. In the fully closed position little seat leakage occursprovided the resilient seat is in good condition. At intermediate positions, throttling of the fluid flowoccurs although the flow regulating characteristicsare not as good as that of globe valves. Butterfly valves are used in low pressure systems,such as circulating water systems. They are inexpensive and fairly easy to maintain.College of Engineering

Typical Butterfly ValveCollege of Engineering

Valve Actuators The actuator operates the valve stem and discassembly. Actuators for valve assemblies can be––––––manual handwheelsmanual leversmotor operatorspneumatic operatorshydraulic operatorssolenoid MOV Actuators used in US nuclear power plants areelectro-mechanical devices, manufactured by– Limitorque– RotorkCollege of Engineering

Limitorque SMB ActuatorsCollege of Engineering

Limitorque Actuator on a TypicalGate ValveCollege of Engineering

Limitorque SMB Load RatingsTypeSizeSMBSMB00000SMBSMBSMBSMBSMBSMB01234 & 4T *5 & 5T *NuclearCommercial MaximumMax ThreadedRating, ft-lb Rating, ft-lb Thrust, lbStem Dia., 4* The “T” in the size designation means a torque only application, no thrustcapability.College of Engineering

SMB Modes of Operation Electrical operation has electrical control for actuatormotion. The actuator and valve are protected by thetorque switch. Manual operation still has the indication, but thetechnician controls position. The two modes are separated by a clutchingmechanism which prevents simultaneous operation.College of Engineering

SMB-00/000 Power TrainsElectric Power TrainMotorHelical Gear SetWorm ShaftWormManual Power TrainWorm GearHandwheelClutch KeyClutch KeyDrive SleeveStem NutValve StemCollege of Engineering

Limitorque Actuator Gear TrainCollege of Engineering

SMB-000 MotorCollege of Engineering

SMB Helical Gear Teeth 72706072College of Engineering

SMB-000 Exploded ViewCollege of Engineering

SMB-000 Electric Power TrainCollege of Engineering

SMB-000 Electric Power Train – SideViewCollege of Engineering

SMB-000/00 Worm Shaft GearAssemblyCollege of Engineering

SMB-000/00 Worm and Worm GearCollege of Engineering

SMB-000 Drive SleeveCollege of Engineering

SMB-000/00 Declutch MechanismCollege of Engineering

SMB-000 Actuator Drive SleeveCollege of Engineering

SMB-00 Actuator Drive SleeveCollege of Engineering

SMB-000/00 Drive Sleeve ExplodedCollege of Engineering

SMB-00 Top-Mounted Manual PowerTrainCollege of Engineering

SMB-00 Side-Mounted Manual PowerTrainCollege of Engineering

SMB-000/00 Handwheel Worm GearAssemblyCollege of Engineering

SMB-000/00 Worm/Belleville SpringPack AssemblyCollege of Engineering

SMB-000/00 Scissor Action TorqueSwitchCollege of Engineering

Modified Leaf and Knee Type TorqueSwitchCollege of Engineering

SMB-000/00 Limit SwitchCollege of Engineering

SMB-000 HousingCollege of Engineering

SMB/SB-0 thru -4College of Engineering

SMB-0 thru 4 Power TrainsManual Power TrainHandwheelElectric Power TrainMotorHandwheel ShaftHelical Gear SetSpur GearsWorm Shaft ClutchWorm Shaft ClutchWorm ShaftWormWorm GearDrive SleeveStem NutValve StemCollege of Engineering

SMB/SB-0 thru –4 Electric PowerTrainCollege of Engineering

SMB/SB-0 thru –4 Motor PinionArrangementCollege of Engineering

SMB/SB-0 thru –4 Worm ShaftClutch GearCollege of Engineering

SMB/SB-0 thru –4 Worm ShaftExploded ViewCollege of Engineering

SMB/SB-0 thru –4 Worm and WormGearCollege of Engineering

SMB/SB-0 thru –4 Spring PackAssemblyCollege of Engineering

SMB/SB-0 thru –4 Drive SleeveCollege of Engineering

SMB/SB-0 thru –4 Manual PowerTrainCollege of Engineering

SMB/SB-0 thru –4 HandwheelAssemblyCollege of Engineering

SMB/SB-0 thru –4 Worm ShaftClutchCollege of Engineering

SMB/SB-0 thru –4 Worm Shaft andDeclutch MechanismCollege of Engineering

SMB/SB-0 thru –4 DeclutchMechanismCollege of Engineering

SMB/SB-0 thru –4 HousingCollege of Engineering

Limitorque SB ActuatorsCollege of Engineering

SB Belleville Spring CompensatorHousing Cover AssemblyCollege of Engineering

SB Spring CompensatorCollege of Engineering

SB Belleville Spring Assembly WithBearing CartridgeCollege of Engineering

SB Belleville Spring Assembly WithSpring CartridgeCollege of Engineering

SB Spring CompensatorsSB-0SB-1SB-2SB-3SB-4College of Engineering4 Springs14 Springs5 Springs10 Springs4 Springs

HBC ActuatorCollege of Engineering

HBC –0 Thru 3 Exploded ViewCollege of Engineering

HBC –0 Thru 3 Operator Top andSide ViewsCollege of Engineering

HBC –4 Thru 10 ActuatorCollege of Engineering

Limitorque LubricationCollege of Engineering

Limitorque Lubrication Lubrication of the actuator internals is critical to theproper and sustained operation of the equipment.– Reduces wear– Removes heat– Resists moisture Major wear areas include– Bearings - drive sleeve, spring pack, and worm shaft– Sliding surfaces – drive sleeve splines, worm shaftsplines, worm and worm gear teeth– Motor pinion and drive gearCollege of Engineering

Limitorque Recommendations For SMB and SB actuators––––––Not corrosive to steel gears, ball or roller bearingsMust contain an EP additiveNo grit, abrasive or filler materialSuitable for the environmental temperature rangeNo separation at temperatures up to 300 FMust not cause Buna-N or Viton to swell more than8%– Good resistance to moisture– Good resistance to oxidationCollege of Engineering

Recommended Lubricants Exxon Nebula EP-0 for all units through SMB-4 Prior to SMB/SB/SBD serial number 295809, SunOil Co. 50 – EP For Nuclear service inside containment, ExxonNebula EP-1 is the only qualified lubricant. For limit switches, Beacon 325 or Mobil Mobilgrease28 is used Lubricants should never by mixed.College of Engineering

New Lubricants Exxon Mobil has discontinued the manufacture ofNebula EP greases. Nuclear industry has identified the MOV Long Lifegrease for future use. ANSI bench tests have satisfied the Limitorquerecommendations for actuator lubrication.College of Engineering

Rotork ActuatorsCollege of Engineering

Rotork “A” Range ActuatorsCollege of Engineering

Rotork “A” Range ActuatorCollege of Engineering

Rotork Actuator Size and OutputTorque ValuesRotork “NA” type actuators are “A” Range actuators qualified for duty innuclear power plants.Torque, lb/ft at rpmActuator50 Hz:60 4045120225400750375625110095090NACollege of Engineering150015001250

Rotork Actuator AssemblyCollege of Engineering

Rotork Category 1 ActuatorCollege of Engineering

Rotork Stator AssemblyCollege of Engineering

Rotork Torque Switch MechanismCollege of Engineering

Rotork Add-on PakCollege of Engineering

The actuator operates the valve stem and disc assembly. Actuators for valve assemblies can be –manual handwheels –manual levers –motor operators –pneumatic operators –hydraulic operators –solenoid MOV Actuators used in US nuclear power plants are electro-mechanical devices, manufactured by –Limitorque –Rotork