Load Moment Indicators and Safety Devices Flashcards
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Read the first 6 Load Moment Indicators and Safety Devices flashcards as text
What is a Load Moment Indicator (LMI) and what information does it provide to the crane operator?
Answer: An LMI is an electronic safety system that measures the actual load on the crane's hoist line and the current boom and radius configuration, calculates the percentage of rated capacity being used, and provides a warning when the crane approaches or exceeds its rated capacity
An LMI uses sensors for load (hoist line tension), boom angle, and boom length to continuously calculate the actual load as a percentage of the current rated capacity, alerting the operator before capacity is exceeded.
If a crane's LMI system shows the crane at 95% of rated capacity but the operator believes the load weighs less than what the LMI indicates, what should the operator do?
Answer: Stop the lift and have the LMI system inspected and recalibrated by a qualified technician before continuing. Do not bypass or override safety devices
LMI systems should not be bypassed or overridden. If the operator believes the LMI is inaccurate, the equipment must be taken out of service and the LMI inspected and recalibrated. The LMI reading may be correct and the operator's load estimate incorrect.
What is the purpose of the RCL (Rated Capacity Limiter) function in a crane's safety system, as distinguished from the RCI (Rated Capacity Indicator)?
Answer: The RCI (indicator) provides information and warnings to the operator, while the RCL (limiter) actively intervenes by automatically stopping certain crane functions when the rated capacity is reached
RCI (Rated Capacity Indicator) is an information and warning system; RCL (Rated Capacity Limiter) adds an active control function that automatically prevents or stops crane motion that would cause an overload condition.
How must a crane's LMI system be verified before being relied upon for production lifting?
Answer: The LMI must be calibrated and verified with a known test load at the beginning of each day's operations, and the system's accuracy must be within the manufacturer's specified tolerance before it is used as the capacity reference
LMI calibration must be verified with known test loads per the manufacturer's procedures. Daily verification ensures the sensors and calculations remain accurate before the system is trusted for production lifting decisions.
What is an anemometer and why might it be required as part of a crane's safety instrumentation?
Answer: An anemometer is a wind speed measuring instrument. It may be required on large cranes, tower cranes, and crawler cranes because wind creates significant additional forces on large loads and boom sections that can cause overload or instability
An anemometer measures wind speed. Wind creates horizontal forces on the load and boom that increase the effective moment, potentially overloading the crane. Cranes operating at height or with large load areas require wind speed monitoring to verify safe operating conditions.
What does ASME B30.5 require regarding the inspection of load moment indicators and other safety devices?
Answer: Safety devices including LMI, ATB, and boom angle indicators must be checked for proper function before each shift, with any deficiency corrected before the crane is placed in service
ASME B30.5 and OSHA 1926.1416 require functional verification of all safety devices, including LMI systems and anti-two-block devices, before each shift begins. Deficiencies must be corrected before the crane is used.