Hi Kris,
Maintenance activities on live lines are typically controlled by proprietary procedures. (and) although these procedures may refer to quality control requirements, such as confirming the surface profile. The governing document or action should be safety. Therefore, within the site’s proprietary procedures, there should be limitations or recommendations on air blast pressure and type/make of abrasive. These air pressure limitations are based on
· Age of the equipment, or lines (safety)
· Remaining wall thickness, or pitting (safety)
· Integrity engineering assessments (safety)
· Blast media and pressure to maintain safe operative engagement. (Safety)
Additionally, maintenance on aging substrates typically will not resemble surface conditions on new steel, often showing heavy leaves of surface degradation or pitting. Therefore, taking and recording the surface profile although ticks a box has little value.
Recommendation.
Raise a technical engineering query in advance of the project start, informing that due to the substrate temperature, and from a technical (no method) and safety standpoint (hot surface) surface profile readings are not possible.
Solution.
Due to the air pressure and velocity, hardness of blast media it is reasonable to assume the profile will be achieved, it should be known that this will be a qualitative empirical assessment. Should the project require quantitative assurance then the project will need to supply steel test plates with the same steel composition to the lines. The test plates will be cleaned progressively and used to verify the surface profile.