What sort of minimum inspection should be made once check valves are offered for inspection during shutdown opportunity?

A lot many are measured by HSE;
Lost-time injury
LTIF / LTIR
Total recordable cases TRC / TRIR
DART, Days Away, Restricted, Transfer
Severity, Lost Days /Severity Rate
First aid cases
Medical treatment cases
Near misses
High-potential incidents
Unsafe acts/conditions
Safety inspections ...

GWT ring arrays are clamped externally around the pipe while it remains in service. Low-frequency ultrasonic guided waves propagate axially over long distances, making it possible to screen unpiggable or coated pipe sections (Lyu et al., 2024). While sticky or highly bonded coatings can cause wave ...

Cr gives stainless steel its basic passivity; Mo makes that passive layer much more resistant to chloride attack, especially pitting and crevice corrosion.
In stainless steels, there is a commonly used measure:

PREN=%Cr+3.3(%Mo)+16(%N)

Pitting resistance depends heavily on Mo presence.

Good read for 2013.

Is this book useful for us working in oil & gas? specifically talks about issues within our industry? Both static and rotating equipment?

Credits: Nuate Faith

This is a critical finding.
Has to be reinstated as per design documents and drawings.
There is a potential of supports failure as you observed movements already.
How old are these lines now on these incorrect supporting system?

May help.

Mercury attack is most likely when:
The natural gas or condensate contains elemental mercury, even at very low concentrations (typically in the µg/Nm3 range).
An aluminium plate-fin heat exchanger is installed downstream of the gas stream.
Mercury removal units (MRUs) are absent, bypassed, saturated ...