PetroStreet

Maintenance engineers:
What sort of Belzona repair can be applied on piping pinhole having cooling water service?
What are the major considerations?
Applied in all cases? What are the limitations?

Now when this is cooling water service, you have a lot many options available.
It all depends on the nature of repair to be performed, the kind of curing you are looking forward, and how aggressive is this cooling water service.
Typical systems include:
Belzona 1111 (Super Metal) for rebuilding local metal loss
Belzona 1212 where rapid cure is required
Belzona 1311 where erosion-corrosion is dominant
Belzona SuperWrap II System as the structural pressure-retaining composite

Go for 1111, recommended in this case just because of its expected long term service.

For an actual pinhole leak, simply plugging the hole with Belzona paste is generally not considered an engineered repair.
The structural capability usually comes from the composite wrap system, not the filler itself.
I am not sure whether you have been looking into this.

It is cooling water service, so any of the recommended products by arcpro should work all fine.
Check your conditions while you make the selection.
Do you apply wrapping as well after belzona application?

For an active leak, I would go for Belzona 1212 and reinforcement tape. Or go for a stop kit, Belzona 9611, then apply 1212.