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:
be retained and prevented from falling or disengaging from their 1.104-2 braking and control system in case of a shaft or bearing failure. Two mechanical holding brakes in the hoisting system (raising and lowering) that are automatically ac- tivated when electric power is off or when mechanically tripped by overspeed devices or overload devices in the hoisting system will help ensure that a critical load will be safely held or controlled in case of failure in the individual load-bearing parts of the hoisting machinery. Each holding brake should have more than full-load stopping capacity but should not have'excessive capacity that could cause damage through sudden stopping of the hoisting machinery. A brake capacity of 125% to 150% of the breakdown torque developed by the motor at the point of brake application has been determined to be acceptable. Manual operation of the hoisting brakes may be necessary during an emergency condition, and provision for this should be included in the design conditions. Adequate heat dissipation from the brake should be en- sured so that damage does not occur if the lowering velocity is permitted to increase excessively. Features should be included in the manual control of the brake to limit the lowering speed. A limiting velocity of 3.5 fpm has been determined to be acceptable for trouble-free operation. Component parts of the vertical hoisting mechanism are important. Specifically, the rope and reeving system deserves special consideration during design of the sys- tem. The selection of the hoisting rope which is a "run- ning rope" should include consideration of size, con- struction, lay, and means of lubrication to provide for the efficient working of the strands and individual wires. The load-carrying rope will suffer'accelerated wear if it rubs excessively on the sides of the grooves in the drum and sheaves due to improper alignment or large fleet angles between the grooves. The load-carrying rope will furthermore suffer shock