What's also done, is a Transient Analysis to determine the possibly of formation of vacuum conditions during abnormal operating conditions, eg pump trip. GRP has minimal strength from external pressure, and needs to be protected as such.
Thinking about it, all our underground piping has drains within culverts.
Hydrotesting underground piping after backfilling is ridiculous. Imagine having a leak, and now having to remove all the backfill now to find the source.
For new construction piping you need to be able to inspect the underground section as well during hydrotest. If you now have to provide access, then you have the ability to operate the drain valve.
Chances are you won't need it again after construction.
As SnT man said "all chambers should be capable of being vented & drained independent of process piping. Sometimes necessary to have separate vent & drains just for hydro, depending on vessel orientation."
For horizontal exchangers, process connections can be used as vents and drains.
For...
Let's say, for example, we have a 2 mm diameter pore, with a visible depth of 1 mm. How can ASME now give a blanket statement that ALL surface porosity is unacceptable? Now the contractor will have to repair this innocuous pore, because of this.
I don't agree that porosity can obscure the...
metengr,
"Because surface porosity can result in lower fatigue properties since stresses are highest at a free surface"
You said "it can", then some sized porosity on some thickness weld should have allowed some to be acceptable and then you should have an acceptance criteria?
Weldstan:
You said "Porosity in thin welds may reduce the supporting ligament to such an extent where in service leakage could occur and there is plenty of emperical evidence to support such failure. "
But this condition would occur for both internal and external porosity. it doesn't give me a...
DekDee, I saw this note but it confuses me even more.
(5) These imperfections are evaluated only for welds ≤ 5 mm (3⁄16 in.) in nominal thickness.
I assume it means that for welds below 5mm thick are evaluated. But for welds thicker than 5mm are not evaluated? Does that mean all surface...
Using ASME B31.3 as a reference; why is surface porosity always unacceptable regardless of size, while internal porosity has an acceptance criteria.
Let's assume both are the same size, why does the fact that it's on the surface make it unacceptable?
EdStainless, I was always under the impression that Pickling was the cleaning process. And Passivation being either chemically induced or self passivation, as in the case of Austenetic Stainless Steels.
For my knowledge, What cleaning does passivation entail?
According to ASME Section VIII Div 1, Table UCS 56, for Carbon Steel Welding:
• Preheating nor PWHT is required for plates < 1.25”.
• Preheating (200F min) can be done in lieu of PWHT for plate 1.25 – 1.5” thick.
• Preheating (200F min) and PWHT is mandatory for plates >1.5” thick.
