I have a procurement specification for vauum jacketed pipe, if this is what you are looking for. If you want detail fabrication specification, you may want to contact someone like CVI Corporation in Columbus, Ohio who specialize in cryogenic hardware. Their telephone number was (614) 876-7381...
If you are talking about high vacuum, in the micron range, you will probably want to use copper or stainless steel, very well cleaned. Same can be said for valves. Components must be free of any contaminent that can off-gass at the low target pressures.
The pitting occurs throughout. Not only at joints, although it is somwhat more prevelent at the joints. Perhaps whatever is creating the corrosive condition is aggrevated by the turbulance at the fittings.
Deejon,
The DHW system has a 1075 gallon tank capacity, heats to a temperature of 125F. The system is one of three or four on this campus. The others all have 16 or more years of service without incurring this type of problem. All on same water source. We have designed many domestic hot...
Domestic hot water system is a recirculating system on a city water source that is typically somewhat hard, but not usually corrosive. Tubing has developed thinning walls and pin hole perforations throughput the system (1" through 2" tubing). There does not appear to be any...