Document: NRC Regulatory Guide
Document ID: 626cd346-6298-4966-a92d-c5d4b24bbc2b
Document Type: regulatory_guide
Title: Overhead Crane Handling Systems for Nuclear Power Plants
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1303/ML13038A096.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.104
CFR Part: 
CFR Title: 

Content:
stem- should have the re- quired strength to resist failure if the hoisting system should "two block"1I or if "load hangup" 2 should occur during hoisting. The designer should provide means within the reeving system located on the head or on the load block combinations to absorb or control the kinetic energy of rotating machinery prior to the incident of two .blocking oruload hangup. The location of mnechan- ical holding brakes and their controls should provide positive, reliable, and capable means to stop and hold the hoisting drum(s) for the conditions described in the design specification and regulatory positions 1 and 2. This should include the maximum torque of the driving 1"Two blocking" is the act of continued hoisting in which the load block and head block assemblies are brought into physical contact, thereby preventing further movement of the load block and creating shock loads to rope and reeving system. 2 "Load hangup" is the act in which the load block and/or load is stopped during hoisting by entanglement with fixed objects, thereby overloading the hoisting system. 1.104-6 motor cannot be shut off. k. The load hoisting drum on the trolley should be provided with structural and mechanical safety devices to prevent the drum from dropping, disengaging from its holding brake system, or rotating, if the drum or any portion of its shaft or bearings should fail or fracture. 1. To preclude ekcessive *breakdown torque, the horsepower rating of the electric motor drive for hoisting should not exceed 110% of the calculated de- sign horsepower required to hoist the design rated load at the maximum design hoist speed. m. The minimum hoisting braking system should include one power control braking system (not mechanical or drag brake type) and two mechanical holding brakes. The holding brakes should be activated when power is off and should be automatically mechani- cally tripped on overspeed to the full holding position if malfunction occurs in the electrical brake