ML19317E674
| ML19317E674 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 04/30/1975 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML19317E672 | List: |
| References | |
| 07054, 7054, NUDOCS 7912180838 | |
| Download: ML19317E674 (11) | |
Text
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April 1975 s.
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BRANCH TECHNICAL POSITION APCSB 9-1 OVERHEAD' HANDLING SYSTEMS FOR NUCLEAR POWER PLANTS A.
BACKGROUND Overhead handling systems are used for handling heavy items at nuclear power plants.
The handling of heavy loads such as a spent fuel cask raises the possibility of damage to the load and to safety-related equip =ent or structures under and adjacent to the path on which it is transported should the handling
'systsm suffer a breakdown or malfunction.
Two methods are used in nuclear power plants to prevent damage to safety features or release of radioactive material due to dropping of heavy loads, such as a spent fuel cask.
One is protection by physical design of the facility to preclude damage to spent fuel and safety-related systems if a heavy load should be dropped.
The other is to provide an overhead handling
.. system that is designed so that a connected load would not fall in the event of a failure or malfunction.
An overhead handling systen includes all the structural, mechanical, and electrical components that are needed to lift and transfer a load from one location to another.
Primary load-bearing components, equipment, and subsystens such as the driving equipment, drum, rope reeving, centrol, and braking systems require special attention.
Proper support of the rope drums ensures that they would be retained and prevcated frou failing or disengaging from the braking and control system in case of a shaf t or bearing failure.
If the hoisting system (raising and lowering) includes two mechanical holding brakes, each with better than full-load stopping capacity, that are automatically activated when electric power is off or when mechanically tripped by overspeed or overload devices, a critical, load will be safely held or controlled in case of failure in the individual load-bearing parts of the hoisting machinery.
Failure of the bridge or trolley travel to stop when power is shut off or an overspeed or overload condition due to malfunction or failure in the drive system can be prevented and controlled by appropriate safety and limit devices and brake systems.
Since the crane industry has not yet developed. codes or standards that adequately cover the design, operation, and testing for a " single failure-proof" crane, the APCSB has developed a branch position to provide a consistene basis for reviewing equipment and components for such overhead handling systems.
The position below delineates acceptable codes and standards and supplements t'acm with specific recommendations on features that will prevent, control, or stop inadvertent operation or malfunction of the mechanical supporting r.nd moving components of the handling system.
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B.
BRANC11 12c CHNICAL POSITION overheand h nandling systems intended to provide singic failure-proof handling of loacas
- =hould be designed so that no single failure or malfunction will result in dropping or loosing control of the heaviest (critical) loads to b'e handilec 3.
Such handling systems should be designed, fabricated, installed, inspectred-, tested, and operated in accordance with the following:
1.
cc=ncrr:21 Performance Specifications Secparate performance specifications should be prepared for a permanent a.
c=-rane which is to be used for construction prior to use for plant cerscration.
The allowabic design stress limits should be identical f;or both cases, and the sum total of simultaneously applied loads c:nould not result in stress levels causing any permanent deformation cc:her than that due to localized stress concentrations.
b.
rine operating environment, including maximum and minimum pressure,~
tacmperature, humidity and rates of change of these parameters, czaould be specified to determine the venting and drainage required f cr box girder sections.
The specifications should also state the c;r rosive and hazardous conditions th' t may occur during operation.
a Ferecture toughness for the steel structural materials should be c; nsidered.
Plate thickness, with a margin for the lowest operating
_rmperatures, should determine the type of steel that can be used uc_th or without toughness tests.
The selection of steel materials u _11 be reviewed on a case by case bases.
53'e crane should be classified as seismic Category I and should be c.
c;rpable of retaining the maximum design load during a safe shutdown eutrthquake, although the crane ray not be operabic after the scismic The bridge and trolley should be provided with means for e-ren t.
preventing them from leaving their runways with or without the design lead during operation or under scismic loadings.
The design rate Icad plus operational and scismically-induced pendulu= and swinging load effects on the crane should be considered in the design of the trolley, and they should be added to the trolley weight for the design of the bridge.
All veld joints for load-bearing structures, including those susccptible d.
to lamellar tearing, should be inspected by nondestructive examinations for soundness of the base metal and weld metal.
i A fatigue analysis should be considered for critical load-bearing e.
structures and components of the crane handling system.
The cumulative I
fatigue usage factors should reflect effects of cyclic loadings from
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both the construction and operating periods.
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f.
Preheat and postheat treatment temperatures for all weldments should be specified in the weld procedures.
For low-alloy steel, the recommendations of Regulatory Guide l.50 should be followed.
2.
Safety Features The automatic and manual controls and devices ' required for normal a.
crane operation should be designed such that a malfunction of these controls and devices, and possible subsequent effects during load handling, will not prevent the hand 13ng system from being maintained at a safe neutral holding position.
b.
Auxiliary systems, dual components, or ancilliary systems should be provided such that in case of subsystem or component failure the load will be retained and held in a stable position.
Means should be provided for devices which can be used in repairing, c.
adjusting, replacing failed components or subsystems when failure of an active component or subsystem has occurred and the load is supported and retained in the safe (temporary) position with the system immobile.
As an alternative to repairing the crane in place, means may be provided for moving the handling system with lond to a laydown area that has been designed for accepting the load and making
'the repairs.
s 3.
Equipment Scicction a.
Dual load attaching points should be provided on the load block or lif ting device designed so that each attaching point will be able to support a static load of 3W (W is weight of the design rated load),
without permanent deformation other than that due to localized stress concentrations in areas for which additional material has been provided for wear.
b.
Lif ting devices such as lif ting beams, yokes, laddle or trunnion type hooks, slings, toggles, or clevises should be of redundant design with dual or auxiliary devices or combinations thereof.
Each device should be designed to support a static load of 3W without permanent deformation.
The vertical hoisting (raising and lowering) mechanism which uses c.
rope and consists of upper sheaves (head block), lower sheaves (load block), and rope reeving system, should be designed with redundant means for hoisting.
Maximum hoisting speed'should be no greater than 5 fpm.
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d.
The heat and load blocks should be designed to maintain a vertical load balance about the center of lift from the load block through the head block, and should have a dual reeving system.
The load block should maintain alignment and a position of stability with either system and be able to support 3W and maintain load stability and vertical align =ent from the center of the head block through all hoisting components to the center of gravity of the load.
The design of the rope reeving system should be duai, with each system c.
providing separately the load balance on the head and load blocks through the configuration of ropes and rope equalizers.
Selection of the hoisting rope or running rope should consider the size, construction, lay, and means or type of. lubrication to =aintain efficient vorhing of the individual wire strands as the rope passes over the shcaves during the hoisting operation.
The effects of impact loadings, acceleration and c=crgency stops should be included in selection of the rope and reeving system.
The wire rope should be 6 x 37 Iron Wire Rope Core (IWRC) or comparable classification.
The stress in the lead line to the drum during hoisting at the maximum design speed with the design rated load should not exceed 20%
of the manufacturer's rated strength of the rope. The static stress in rope (load is stationary) should not exceed 12-1/2 of the manufacturcr's rated strength.
Line speed during hoisting- (raising or lowering should not exceed 50 fpm.
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The caximum ficct angic from drum to lead sheave in the load block should not exceed 3-1/2 degrees at any point during hoisting and there should be only one 180* reverse bend for each rope leaving the drum and reversing on the.first or lead sheave on the load block, with no other reverse bends oth:r than at the equalizer if a sheave-type equalizer is used.
The fleet angles for rope between individual sheaves should not exceed 1-1/2 degrees.
Equalizers may be beam or sheave type.
For the recommended 6 x 37 IWRC classification wire rope, pitch diameter of the lead sheave should be 30 times rope diameter for the 180* reverse bcnd, 26 times rope diameter for running sheaves, and 13 times rope diameter for equalizers. The pitch diameter is measured from the center of the rope in the sheave groove through the sheave center.
The dual reeving system may be a single rope
'from cach end of a drum terminating at a' beam-type load and rope stretch equalizer with each rope designed for total load, or a 2-rope system may be used from each drum or separate drums with a sheave or beam equalizer, or any other combination which provides two separate and complete reeving systems.
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The vertical hoisting system components, which include the head block, rope reeving systen, load block, and dual load attaching device, should cach be designed to sustain a load of 2W (W is the weight of the design rated load).
A 2W static load test should be perforced for cach reeving system and load attaching point at the manufacturer's plant.
Each reeving system and each one of the load attaching devices should be assembled with approximately a 6 inch clearance between head and load blocks and should support 200% of the design rated load without degradation of the components or permanent deformation other than that due to localized stress concentrations.
Measurements of the geometric configuration of the attaching points should be made bafore and after test folloued by nondestructive examination, which should consist of combination of' magnetic particle, ultrasonic, radiographic, and dye penetrant examinations to verify the soundness of fabrication and assure the integrity of this portion of the hoisting system.
The results of examinations should be documented and recorded for the hoisting system for each overhead' crane.
h.
Means should be provided to sense such items as electric current, temperature, o.verspeed, overloading, and overtravel.
Controls should be provided to stop the hoisting mover..ent within 3 inches taximum of vertical travel through a combination of c1cetrical power controls.and mechanical braking and torque control systc=s should one rope of the dual reeving system fail.
- i. The control systems nay be designed as combination electrical and mechanical systems and may include such items as contractors, relays, resistors, and thyristors in combination with mechanical devices and mechanical braking systems.
The electric controls should be selected t
to provide a maximum breakdown torque limit of 175% of the required rating for a.c. motors or d.c. motors (series or shunt wound) used for the hoisting drive motors.
Compound wound d.c. motors should not be.used.
The control systems provided should consider hoisting (raising and. lowering) of all loads, including the design rated load, and the effects of inertia of the rotating hoisting machinery such as motor armaturcs, shafts and couplings, gear reducers, and drums.
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The mechanical and structural components of the hoisting system should have the required strength to resist failure should "two-blocking" 1/ or " load hangup" 2/ occur during hoisting. The designer should provide means to absorb or control the kinetic energy of rotating machi' ery in the event of two-blocking or load n
hangup.
The location and type of mechanical brakes and controls shauld provide positive and reliable ceans to stop and hold the hoisting drums for these occurrences. The hoisting system should be able to withstand the maximum torque of the driving motor, if a malfunction occurs and power to the driving motor cannot be shut off at the time of load hangup or two-blocking.
k.
The load hoisting drum on the trc11ey should be provided with structural and ccchanic safety devicca to prevent the drum from dropping, disengaging from its holding brake system, or rotating, should the drum or any portion of its shaft or bearings fail.
1.
To preclude excessive breakdown torque, the horsepower rating (HP) of the electrical motor drive for hoisting should provide no more than 110% of the calculated HP requirement to hoist the design rated load at the maxtrum design hoist speed.
m.
The minimum hoist braking system should include one pswer control
' braking systen (no: nachnn cal or drc; brake-type) and two techanical holding brakes.
The holding brakes should be activated when power is off and should be automatically trippad by mechanical ceans on overspeed to the full holding position if a malfunction occurs in the electrical brake controls.
Each holding brake should be designed to 125% - 150% of naximum developed. torque at the point of application (location of the brake in the ecchanical drive).
The minimum design requirements for braking syste=s that will be operabic for emergency lowering after a singic brake. failure should be two holding brakes for stopping and controlling drum rotation.
Provisions should be made for manual operation of the hciding brakes.
Emergency brakes or holding brakes which are to be used for manual lowering should be capable of operation with full load and at full travel and provide adequate heat dissipation.
Design for manual brake operation during emergency lowering should include features to limit the lowering speed to less than 3.5 fpm.
1/ "Two-blocking". is an inadvertantly continued hoist which brings the load and head block assemblies into physical contact, thereby preventing further movement of the load block and creating shock loads to rope and reeving system.
- 2/ " Load hcagup" occurs when the load block or load is stopped during hoisting by entanglement with fixed objects,.thereby overloading the hoisting system.
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The o,namic and static alignment of all hoisting machinery components n.
including gearing, shafting, couplings, and bearings should be maintained throughout the range of loads be lifted with all components positioned and anchored on the trolley machinery platform.
o.
Increment drives for. hoisting may be provided by stepless controls or inching motor drives.
Plugging 3/ should not be permitted.
Controls to prevent plugging should ae included in the electrical circuits and the control system.
Floating point 4/ in the electrical power system, when required for bridge or tolley covement, should be provided only for the lowest operating speeds.
p.
To avoid the possibility of overtorque within the control system, the horsepower rating of the driving notor and gear reducer for trolley and bridbe motion of an overhead bridge crane should not exceed 110% of the calculated requirement at maximum speed.and with the design rated load.
Incremental or fractional inch movements, when required, should,be provided by such items as variable speed or inching motor drives.
Control and holding brakes should each be rated at 100% of maximum drive torque at the point application.
If tuo mechanical bra'.tes are provided, one for control and one for holding, they should be adjusted with one brake in cach systcm for both the trolley and bridge leading the other and should be activated by release or shutoff of power. The brakes shculd also be mechanically tripped to the "on" or " holding" position in the event of a malfunction in the power supply or an overspeed condition.
Provisions should be made for manual operation of the brakes.
The holding brake should be designed so that is cannot be used as a foot-operated slowdown brake.
Drag brakes should not be used.
Opposite whccis on bridgas or trolleys which support the bridge or trolley on the runways should be matched and.have identical diameters. Trolley and bridge speed should be limited.
A =aximum speed of 30 fpm for the trolley and 40 fpm for the bridge is recommended.
3/ Plugging is the momentary application of full line power to the drive motor for the purpose of promoting a limited movement.
4/ The point in the lowest rt.nge o movemen't control at which power is on, brakes
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are off, and motors are not energized.
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The complete operating control system and provisions for emergency controls for the overhead crane handling system should be located in the main cab on the bridge.
Additional cabs located on the trolley or lif ting devices should have complete control systems similar to the bridge cab. Manual controls for the bridge may be located on the bridge.
Remote controls or pendant controls for any of these motions should be the same as those provided in the bridge cab control panel. Provisions should be made in the design for devices for emergency control or operations.
Limiting devices, mechanical and electrical, should be provided to indicate, control, and prevent overtravelling and overspeed or hoist (raising or lowering) and for trolley cad bridge travel movement.
Luffers for bridge and trolley travel should be ir.cluded.
Safety devices such as limit type s' itches provided for malfunction, r.
inadvertent operation, or failurd should be in addition to and separate from the control devices provided for operation.
The operating requirements for all travel movements (vertical and s.
horizontal movements, or rotation, singly or in combination) for permanent plant trcncs should be c1carly defined in the operating manual for hoisting and fcr trolley and bridge travel.
The designer should stablish the maximum working load (%~L).
The L L should not bc less than 85% of the design rated lond (DRL) capacity for the new cranc at time of operation.
The' redundancy provided, design factors, selection of components, and balance of auxiliary-ancilliary and duel items in the design and manufacture should be taken into account in setting the maximum working load for the critical load handling crane syst em(s).
The MWL should not exceed the DRL for overhead crane handling system.
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When the permanent plaht crane is tc be used icr construction and the
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operating requirements for construction are not identical to those required for permanent plant service, the const7uction operating requirements should be defined separately.
The crane should be designed structurally and mechanically for the construction loads, plant service loads, and the functional performance requirements for each.
At the end of the construction period, the crane handling system should be adjusted for the performance requirements of permanent plant service. The conversion or adjustment may include the replacement of such items as motor drives, blocks, and reeving system.
After construction use, the crane should be thoroughly inspected using nondestructive examinations and should be performance tested.
If the 3,ad and performance requirements are different for construction andplantserviceperiods,thenthecraneshouldbetestedforlboth phases.
The crane integrity should be verified by the designer and manufacturer and load testing to 125% of the design rated load required for the operating plant should be done before the crane is used as p,crmanent plant equipment.
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Installation instruction should be provided by the manufacturer.
These should include a full explanation of the crane handling system, its controls, and the limitations for the system, and should cover the requiraments for installation, testing, and preparation for operation.
4.
Mechanical Checks, Testing, and Prevent'ative Maintenance a.
A complete mechanical check of all crane systems as installed should be made to verify the method of installation and to prepare the cranc for testing.
During and after installation the proper assembly of electrical and structural components should be verified.
The integrity of all control, operating, and safety systc=s is to be verified as to satisfaction of installation and design requirements.
The cranc designer and crane manufacturer should provide a manual of information and procedurcs'for use in checking, testing, and crane operation.
The manual should also describe a preventive maintenance program based on the approved test results and information obtained during the testing; it should include such items as servicing, repair, and replacement rbr,uirements, visual ex..minations, inspections, checking, measurements, problem diagnosis, nondestructive exa=ination, crane performance testing, and special instructions.
Information concerning proof testing on compdacnts and subsystems as required.:and performed at the manufacturer's plant to verify component or subsystem ability to perform should be available for the checking and testing performed at the place of installation of the crane system.
b.
The crane system should be prepared for the static test of 125% of the design rated load.
The tests should include all positions of hoisting, lowering, and trolicy and bridge travel with the 125% rated load and other positions as recommended by the designer and manufacturer.
After satisfactory completion of the 125% static test and adjustments required as a result of the test, the crane handling system should be given full performance tests with 100% of the design rated load for all speeds and motions for which the system is designed.
This should include verifying all limiting and safety control devices.
The crane handling system should dc=onstrate the ability to lower and move the design rated load by manual operation and with the use of emergency operating controls and devices which have been included in.the handling system.
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10 The complete hoisting machinery should be allowed to two-block during the hoisting test (load block limit and safety devices are bypassed).
This test should be conducted without load and at slow speed, to provide assurance of the integrity of the design, equipment, controls, and overload protection devices. The test should demonstra'te that when the maximum torque that can be developed by the driving system, including the inertia of the rotating parts at the overtorque condition, will be absorbed or controlled prior to two-blocking.
The complete hoisting machinery should be tested for ability to sustain a load hangup condition by a test in which the load block attaching points are secured to a fixed anchor or excessive load.
The drum should be capable of one full revolution befe:e starting the hoisting test.
The preventive maintenance program recommended by the designer and c.
manufacturer should also prescribe and establish the MWL for which the crane will be used.
The maximum working load should be plainly marked on each side of the crane for each hoisting unit.
It is reconmended that critical load handling cranes should be continuously maintained at 95% of DRL capacity for the 17.3. capacity.
C.,
REFERENCES 1.
Regulatory Guide 1.50, " Control of Preheat Temperature for Welding of Low-Alloy Steel."
2.
" Table of Engineering, Manufacturing, and Operating Standards, Practices, and References," attached to this position.
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e TABLE OF ENGINEERING, MANUFACTURING, AND OPERATION STANDARDS, PRACTICES, AND REFERENCES Association of Iron and Steel Engineers (Std. No. 6).
General items for AISE overhead cranes and specifically for drums, reeving systems, blocks, controls, and electrical, mechanical, and structural components.
American Institute of Steel Construction, " Manual of Steel Construction."
AISC Runway and bridge design' loadings for impact, and structural supports.
AS::':
A crican Society of Mechanical Engineers.
References for testing, materials, and mechanical couponents.
ASTM American Society for Testing Materials. Testing and selection of materials.
American National Standards Institute -(A10, B3, B6, B15, B29, B30 and N45 ANS1 series N series of ANSI standards for quality control).
ANSI consensus standards for design, manufacturing, and safety.
Institute of Electrical and Electronics Engineers.
Electrical power and IEEE ccatrol systems.
A'JS Accrienn Uciding Society (Dl.l.72 - 73/74 revisione).
Fabrication requirements and standards for cranc structure and weldments.
EEI Edison Electrical Institute.
Electrical systems.
Society of Automotive Engineers, " Standards and Recommended Practices."
SAE Recommendations and practices for wire rope, shafting, lubrication,
' fasteners, materials scicction, and load stability.
Cranc Manufacturers Association of Accrican (CMAA 70).
Guide for preparing CMAA functional and performance specifications and component selection.
NEMA National Electrical Manufacturers Association.
Electrical motor, control, and component selections.
Selection of WRTB Vire Rope Technical Board and their manuf acturing members.
rope, reeving system, and reeving efficiencies.
1bterials Handling Institute and their member associations.and association MHI members such as American Gear Manufacturing Association for gears and gear
~' reduc'ers, Antifriction Bearing Manufacturers Association for bearings selection, etc.
Welding Research Council, " Control o,f Steel Construction to avoid Brittle WRC Fracture," and Eulletin #168, "Lamellar Tearing."
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