Curt, I have been racking my old brain on stuff 40-50 years past. I finally remembered an incident that indicates that steel pipe is not a panacea either in your case. I was the service tech initially dispatched to the call. Exactly the same application that you have. It was a hospital that had a dedicated 80 PSI boiler and steam system for a lot of sterilizers. One huge one in their central supply department. 100% steam wasted. System was 20 years old and started leaking at threaded joints and welded fittings. Pin holes like yours. Piping was 100% schedule 80 with forged fittings and steel valves (no brass, bronze, or copper in the system except 1.5" makeup water line, steam pipe from 3" to 1/2".
We installed all new piping long side the existing with valves for each branch. Cut over worked smooth and event-less on graveyard shifts when no surgery occurred. I racked up a lot of double time plus my daily service work. We then dismantled the old piping. Many places the piping was the thickness of Schedule 5 and pitted all over. Some elbows were paper thin where velocity had really worked its magic. Disaster waiting to happen. Had some piping samples and condensate samples tested. Piping had a lot of carbon residue and water PH was -3 and loaded with carbonic acid and carbon dioxide.
We had the plant engineer (he was new, only one month) go back on records. The boiler had been re-tubed twice due to pin holing. Conclusion was that the production of steam pulled the carbon dioxide from the makeup water (city water) and created carbonic acid that attacked the piping and boiler. Shut down and inspected the boiler steam side. Pitted throughout, and tubes 5 years old already showing the effects. Next step was reviewing the water treatment: They had a junior engineer that daily checked the chemical auto feeder level and add chemicals, when needed, with chemicals prescribed by a water treatment supplier. No body ever checked the chemistry of the wasted condensate as it was going down the drain (wonder what the sewer system looks like?). Make up water was a considered a fixed entity so no tests were made there either . Makeup water was not heated and went directly to the feed pump; good way to shorten the boiler life with thermal shock.
The new engineer seemed to have good grasp of what we found and went to management with our written report. Due to the critical nature of the system the board of directors contracted my firm to engineer a new system and re-tube the boiler again. At that point I lost contact with with the project. I heard later from fellow workers that they added a DA system to remove dissolved air and other gasses from the water, a heater system using boiler steam to bring makeup water to 212 F before introducing to the DA system, a water softner for make up water, and a whole new chemical feeder system monitored and calibration checks each shift (wonder how long that lasted?).
This experience from the past may be helpful. I think I have exhausted my knowledge base on your problem.
Ron
