Steam Drum and Sec. VIII 3

[StaticPressure]

How can a Steam Drum, which is part of a Fired Steam Boiler, be designed under Sec. VIII?
I appreciate any advise.

 

[LSThill]

CHECK CODE CASE

 

[metengr]

Steam drums can be used in HRSG's (heat recovery steam generators).

 

[davefitz]

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

 

[StaticPressure]

Thanks guys,

Isthill:
Would you let me know which Code Case you mean?

Davefita:
If we have intervening valves on interconnecting piping between steam drum and boiler, do we need to consider the drum as a part of boiler?

 

[MJCronin]

Amir,

"...intervening valves on interconnecting piping between steam drum and boiler" (?????!!??)

I have never heard of valves between the steam drum and the "boiler"

Are you fabricating your own homemade boiler "on the fly" ?

Will the eventual product bear any kind od ASME or ISO stanp or seal ?

Will this boiler be installed in IRAN ???

-MJC

 

[davefitz]

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.

 

[StaticPressure]

MJCronin,

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.

 

[gr2vessels]

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

 

[gr2vessels]

Also check out the Code Case 2485 mentioned by lsthill and metengr.

 

[GenB]

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

 

[MJCronin]

Anybody else "sense danger" here or am I just getting old?

Amir, if your "boiler" is located remote from your "steam drum" and are seperated by valves, where do you place the safety valves ?

The purpose of the safety valves is to protect both the boilers and the tubes in the event of a pressure excursion.

.......but you want isoltion valves in-between ?

Why do you need such valves and what code will govern the construction of these valves ?

Is this boiler generating superheated steam ?

Can you get your engineering supervisor to stand up-close to the boiler during start up ????

My opinion only...

-MJC

 

[davefitz]

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.

 

[GenB]

steam drum as part of the boiler can not be separated by valves.- Steam separators can.
There isn't any danger if you follow the Code...
genb

 

[StaticPressure]

Eventually we decided to use Sec. I.
I appreciate for all your comments.

Amir

 

[GenB]

Good, I did not think you had a choice.
a lot of homework was needed
gen blr