The hydro test is fairly simple.
Every external valve is attached and closed. Each of these valves is considered part of the boiler and must meet spec and be part of the test. The boiler is totally filled with water- no air space at all. Nothing is connected beyond any valve except a water pump to supply the test pressure. It is then pumped up to a pressure of 150% of working pressure- in this case 210 psi. It is held there while the inspector looks around for any leaks. He went over it pretty thoroughly, even crawling under it to get inside the firebox. After a few minutes at the high pressure it is lowered to working pressure- 140psi- and held there as long as the inspector wants, about an hour.
The boiler is required to be warm, as I recall over 70 degrees, We had a kerosene heater blowing into the firebox door for a couple hours to get the whole thing up to a suitable temperature.
The paper trail is extremely complete. Every piece of material that went into the boiler must have orders and invoices showing its exact origin, and each piece must have a certificate that it meets whatever spec is appropriate. Each piece of metal that came into the shop was logged in, and assigned a 2 character code. Each piece was stamped with the code. As a piece was cut off the stock to use it was first stamped with the same code, then cut off and used.
If you look at the boiler now you will see lots of yellow paint marker circles about 1" dia. These identify the code stamp. You can go back to a file and find the exact source of that item, and its certificate that it meets spec. Once the boiler has been approved and stamped these numbers are no longer important- the boiler now has a serial number and an S stamp that certifies all its pieces met spec.
Basically the inspector had to be satisfied that every item in the boiler was made from an approved material, with a clear spec. He actually did this review at several stages during construction, and initialed every order, spec sheet, and drawing.
He also looked at every test report, like the Xrays of welds and the stress relieving to verify the tests were done, and signed.
In addition BRV had to develop a written procedure for every operation. These procedures were part of the early work to get the certification. The inspector was frequently checking to see that these procedures were correct, and were performed correctly. It cost BRV over $30k to achieve this certification, including purchase of a set of spec documents that fill a shelf about 4 feet long. These get updated every 3 years, and more inspections, to the tune of over $10k.
Code work is a very detailed, and costly process. But in the end we have great assurance that every item in that boiler met all the specs needed to insure its safety.
