“Design Life, Mechanical Life, Structural Life”
A “Major Inspection” is exactly what the name implies.
A “Major Mechanical Inspection” is a strip down inspection of the mechanical assemblies which requires that cranes have all of their mechanical components disassembled, measured, inspected, tested if necessary by NDT methods, then re-assembled and a full set of commissioning tests be done. All of this should be supervised by a competent and qualified engineer who at the end of this process should issue a certificate of suitability for continued service for a period which the engineer deems suitable and prudent (usually not for another full design lifetime).
Similar concepts govern structural design life and “Major Structural Inspections” which will involve NDT of all critical structural members and joints. Obviously, such major inspections (both mechanical and structural) involve considerable expenditure. Sometimes major mechanical inspections alone can cost a very significant proportion of the replacement cost of a new crane for that application. It is therefore sensible and practicable that “Major Inspections” are not undertaken lightly or before they are due. “Major Inspections” should be done only when the crane has reached the measurable end of its design life, or where the design life (classification) cannot be reliably established or when the history of usage is not known. It is best not to spend funds unnecessarily if the life can be reliably and conservatively calculated.
In most cases, Modular Cranes Pty Ltd, because of our background & experience, is able to inspect cranes of various types and gather sufficient information about their past usage to enable us to determine where a crane is in relation to its “mechanical design life” and to determine whether a “Major Mechanical Inspection” is really necessary. When we can determine where a crane is in relation to its “mechanical design life”, we can also say with confidence whether a “Major Structural Inspection” is also required.
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