... For example, I asked why it would be necessary to check IP on a newly serviced regulator at 500 PSI first. Your answer was "to establish IP at 500 PSI" or something along those lines. That's not really an answer about why you think it's necessary. I know that it's not, from experience. If you have an actual answer for that, I'd be interested.
From a professional repair technician's perspective - the simplest answer is "It's necessary because it's part of the manufacturers prescribed procedure for servicing this model of regulator."
Liability in the SCUBA industry is - in part - mitigated by following industry standards. When teaching - this means that I comply with my agency's standards - and when things end unfavorably as they sometimes do despite our best intentions - my agency - and more importantly my insurance carrier stand behind me. With respect to regulator service, complying with the manufacturer's training requirements, recommended tools, techniques, service kits, and procedures mitigates the risk of servicing a piece of equipment that may be involved in someone's unfavorable ending. While I may be sued - my insurer's attorney will reasonably argue to a jury that by properly servicing the regulator in the manner prescribed by the manufacture - I was not negligent or liable for the injured party's outcome. If however, I deviate from the manufacturer's procedure - or make up my own process, or substitute alternative parts when servicing a regulator - then my attorney has a much more difficult task explaining why I may or may not be liable for an outcome.
Perhaps risk mitigation or liability isn't something you concern yourself with. From a purely functional perspective, Scubapro's engineers have established (or at least they publish) that the optimal range of IP most favorable for their line of second stages is: 125 - 145 psi. For balanced regulators with an IP inversion - verifying that the IP is near the high end of the range at low supply pressure generally results in a regulator tuned in a manner consistent with their engineering recommendations. E.g. [IP 145 @ SP 500 ... IP 140 @ SP 3000] As the inversion is variable and not always present - starting with a low SP is an efficient way to establish an optimum IP - within the manufacturers specification. I don't see a more efficient procedure for doing this. Without know the amount of inversion to expect - it would be necessary to guess the optimal IP at SP 3000 PSI - and ensure that the IP stayed within the prescribed range when SP pressure was dropped to 500psi.
I suppose you could be asking any number of other questions... Why does Scubapro prescribe an optimal IP range of 125 to 145psi. Why did they choose to manufacture a balanced regulator (the Mk 25) who's IP may experience inversion of 1 to 5 psi over the typical range of supply pressures. What processes in the first stage contribute to this effect. Couldn't I service this regulator in an alternative fashion and improve its performance beyond the manufacturer's expectations? None of these questions are interesting to me - for reasons related to liability. And frankly - I don't know how any of this benefits the DIYer who is wondering what their IP on their Mk25 should be tuned to after servicing - and how they should go about doing so. Frankly, it starts to feel like...
Many of us on this DIY forum got our start at least in part due to the incompetent work by dive shop technicians, who are all graduates of the same weekend seminar you took. Over the years I've listened to a lot of nonsense from supposed professional dive shop techs, so I ask your forgiveness if I seem a little combative to you. I appreciate your participation on this forum, but I'm always wary of 'professionals' who tout their credentials while providing not really insightful (or sometimes simply wrong) information about regulator function.
I don't take you personally. We've all experienced professionals whose execution left us disappointed. I've been disappointed by some of the scuba professionals I've encountered. I'm happy to participate in the forum with the understanding that any recommendations or opinions publicly shared will generally be consistent with those of the manufacturer.
Personally - my interest in regulator / gear service is mostly from self-interest. I sometimes enjoy doing solo technical dives. Sometimes in overhead environments. Sometimes on CCR. Sometimes both. While training for failures is important - my likelihood of a favorable outcome is in part proportional to to the reliability of my gear. I'm passionate about having my gear performing optimally - and I'm happy to share that enthusiasm with others.
