An API RP 4G Category III inspection requires a thorough visual inspection of all load bearing components and members to determine the condition of the Mast/Derrick, or Sub-Structure, or both. And documented on an inspection checklist. Inspections on well servicing truck or trailer mounted masts should include observation on rig up/rig down operations.
An API RP 4G Category IV inspection shall include the requirements of a Category III inspection and also the following requirements:
- a) Critical joints shall be subject to non-destructive examination.
- b) All equipment shall be disassembled and cleaned to the extent necessary to conduct NDT of all defined critical areas.
- c) All welds (100 %) shall be visually examined.
- d) All welds in critical areas shall be inspected using NDT methods
Global 1 Inspection results from Category III and IV inspections shall be documented and maintained.