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Handling Inc. Copyright 2020 © R&M Materials Handling Inc. All rights reserved.
8.7
Approaching Theoretical Calculated Lifetime
In order to ensure safe operation of cranes, the proper working and operational condition shall be maintained
according to standard ISO 9927.
This requirement covers also special assessments to be carried out by an expert engineer at regular intervals to
check the remaining Designed Working Period (DWP) of the hoist as stated in standard ISO 12482-1.
8.7.1
General overhaul
In the GO service, the product is assigned with a new, runtime-based DWP, provided that it is safe to continue the
operation. The runtime-based DWP means the lifetime of the interchangeable rotating components of the hoist like
the hoisting gear and the hoisting motor. For instructions on how to perform the DWP calculation, see Appendix
Designed working period (DWP) Calculation.
WARNING
When the Designed Working Period (DWP) of the hoist has decreased to zero
or is counting in the negative, the hoist may only be used after a GO service
has been conducted, or the hoist must be replaced with a new one. Any usage
of a defective hoist can result in serious damage, injury, or death.
CAUTION
When performing the General Overhaul, the construction of the hoist may not
be changed or the supporting structures repaired without permission from the
manufacturer. If there are any deformations, cracks or corrosion in the
supporting structures of the hoist, the parts have to be replaced or repaired
according to the instructions given by the manufacturer.
Only authorized service personnel or an experienced service technician who is authorized by the manufacturer or
the manufacturer
’s representative may conduct a General Overhaul service.
The data and the information about conditions based on which the General Overhaul should be performed can be
provided for a chain hoist by one or more of the following means:
A time counter keeping track of the hoist operational hours (runtime)
Manual bookkeeping/diary/logbook about the use and the operating conditions of the hoist.
Note:
The same hoisting machinery can undergo no more than two GOs before it must be replaced completely.
The chain hoists are designed for a period of use of at least 10 years until the first general overhaul is carried out.
This is based on the condition that the specified group of mechanisms is not exceeded by the actual duration of
service. When the actual duration of service has reached the theoretical duration of service valid for the group of
mechanisms, further operation of the chain hoist is only permissible after a general overhaul.
The theoretical duration of service D (hours at full load h) depends on the group of mechanisms classification of the
chain hoist. The actual duration of service is to be determined annually in accordance with FEM 9.755. During the
annual inspection by our after-sales service, you may have the actual service life determined.
Upon expiration of 90 % of the theoretical duration of service
– if the chain hoists are correctly classified after 8 to
10 years
– the owner must arrange for a general overhaul GO to be carried out. A general overhaul must be carried
out no later than when the end of the theoretical duration of service is reached.
During the general overhaul the following parts must be replaced in addition to the checks and work specified in the
inspection and maintenance schedule:
Gearbox frame, sealing, bearing, gears and oil/grease