not sure, but I think each individual part can be designed under either sect I or VIII, but the ensemble device cannot be sold as a unit boiler under sect I unless all parts meet sect I. Sect I has easier QC and inspection requirements than sect VIII, but also mandates a lot of instrumentation and drum nozzle rules not present in sect VIII
3 pressure level HRSG's may have the drum level control valve at the economizer outlet , for the IP and LP drums. This prevents a steaming economizer, and allows use of higher temp water for the spray attemporator. More releif valves are required in this case.
Prior to WWII, it was not unusual to have the different parts of the boiler mfr'd by different fabricators, and the owner might have hand a hand in the design as well. Nowadays, few HRSG's are built in the boiler mfr's shop; almost all HRSG's are built piecemeal by various 3rd party fabricators in Korea.
Tody, the most common use for a sec VIII component in the boiler is when a stainless tubed economizer is used, for heat recovery boilers, fired heaters, and HRSG's. Sect I will not permit a water washed stainless component due to chloride stress corrosion issues, but a duplex stainless tubed economizer may be supplied as a sect VIII component.
Yes, both the Boiler and Steam drum must be ASME certified and stamped. This boiler will be installed in a refinery,and the refinery is not in IRAN!!!
Do you know whether the steam drum can be designed and stamped under sec. VIII, when the Boiler itself is Sec. I?
davefitz,
I want to exclude the Steam Drum from scope of the Boiler Manufacturer. I just want to know if there is any code related problem if manufacturer of steam drum uses Sec. VIII and put U stamp on it, when the rest of the Boiler gets S stamp.
Amir,
Refer to the ASME VIII, Div 1:
U-1(g)(1) Unfired steam boilers shall be constructed in
accordance with the rules of Section I or this Division [see
UG-125(b) and UW-2(c)].
As such, the Steam Drum can be fabricated elsewhere, U stamped and assembled into the boiler ASME Section I.
Howzat,
cheers,
gr2vessels
As I understand it,
If the drum is part of the fired sec. I, you can not stamp it sec VIII-1 period. you can construct the complete boiler and then use a drum separator w/ sec VIII-1 stamp.
...but there is a company's boiler where the steam drum is built-in and it is stamped sec Viii-1.- I will find out for you how they manage to get away with it.
genb
If the steam drum is capable of being isolated by valves from the rest of the unit, then the steam drum will require relief valves as specified by sect I, and the economizer and superheaters will require releif valves as specified by sect I- as if they are seperately fired superheaters or trapped econoizers subject to full BFP overpressure etc.
Sect I also has many other rules associated with the assumption of the drum being part of sect I- eg, gauge glasses, blowdown and blowoff connections, thermal sleeve for feedwater, etc.
It is unusual ( perhaps bizarre) to have an isolatable steam drum, but here are some unusual advantages - I had earlier mentioned the avoidance of a steaming economizer and higher temp spray water in one case, and one can also operate "dual pressure" with a sliding pressure superheater and constant pressure evaporator if a throttle valve is at the steam drum outlet. But it has to be carefully thought out- many years of experience are represented by the sect I rules, and skipping them is an invitation for big problems.
