Implication of a ASME Sect 1 and Sect 8 steam boiler 1

[vesselguy]

Hi all,

wonder if I can get some pointers on what is the implication of designing a steam boiler to ASME Section I versu Sect VIII. Are the issues related to future maintenance records keeping?

I have read in API RP543 that one could design the boiler to Sect I and register it as Section VIII vessel. What is the implication?

Thanks in advance.

 

[eliebl]

vesselguy,

The differences between the two code sections are small. They essentially have the same rules. It is important to note that if it is designed to section VIII-1 for steam service then many of the requirements for joint design, PWHT, and radiography in UW-2 are the same as the requirements in section I.

Two more areas that cause problems are the materials selection, i.e. SA-350 LF2 is not permitted in Section I (don't ask me why someone would want to use it) and jurisdictional requirements. If it is designed in accordance with Section I and operated in Alberta there are specific operational requirements which must be met.

The differences are not as much in the head and shell thickness as they are in the small details.

Regards,
EJL

 

[metengr]

I believe the Preamble in ASME Section I provides specific guidance for fired steam boilers and unfired pressure vessels that generate steam and are exempt (like heat exchangers. Note, unfired steam boilers can be constructed to I or VIII.

 

[vesselguy]

Gents, thanks for your input.

My fault that I did not made my question clear. My question is pertaining to un-fired boiler HRSG and a steam separator.

I am familiar with the "design" asepct btw the two codes as I've been a design engineer in the design office all this time. I am weak in the operating side. What I was asking is aside from design issues, are there any advantange or disadvantage to register an unfired steam generator and steam drum to Sect 8 instead of Sect 1. Would there be cost or time savings (less hassle) with completing code required/jurisdiction required inspection records, or maintenance records/paper works. Are there other issues I should know about?

The reason I'm asking this is if registering them as a Sect 8 equipment means less hassle for the Operating/maintenance team and resulting in long term cost savings for the company, then I would like to register them as Sect 8 instead of Sect 1 equipment.

 

[eliebl]

If the vessel is to be located in Alberta the HRSG would be expected to be designed as a "boiler" and would have all of the operational requirements as called out in the local regulations. If the system is process steam related and a steam seperator then it would be best not to confuse the issue and design it to Section VIII-1. Depending on the steam generation capacity of the HRSG there would be specific supervision requirements.

The regulatory requirements in Alberta would require that all of the controls on the HRSG would have to be in compliance with Section I regardless of the design code chosen.

One of the pitfalls with the choice of Section I is that there must be someone (company with authorization) to take responsibility and apply the code stamp to the completed boiler. This has caused problems in the past when a boiler manufacturer does not actually build any of the components but subs out all of the individual parts and pieces. None of the subs are willing to complete the master data report for the boiler.

Regards,
EJL

 

[vesselguy]

Hi EJL,
Sounds like you're an Alberta kinda guy. Me too. Yes, I know full well about the "one responsible designer" issue to PE stamp the "boiler", and how to handle that. I was not aware of the point in the second paragraph. Thanks for the heads up.

 

[davefitz]

As I recall, there is a good summary of the differences between sect VIII and sect I in M. D. Bernstein's book on the ASME section I overview. Section VIII has more rigorous QC procedurures than section I, and will allow use of stainelss steel in contact with liquid , while section I will not. To use a SS economizer on a HRSG, one typically supplies that component as a sect VIII part.

Sect I also has many design requirements related only to boilers , such as level instrumentation, relief valves, etc not found in sect VIII. Allowable stresses for tubing within the boiler setting may be higher than sect VIII.

 

[eliebl]

vesselguy,

If this is to be located in Alberta you may want to speak with someone in Design Survey at ABSA about this if you are early enough in the design stages. That way there will not be any surprises come time for registration. For a regulatory agency they are fairly easy to deal with but quite overworked given the billions of dollars being invested in the oilsands.

EJL

 

[ApC2Kp]

To vesselguy,

There are implications from the designation to ASME Sec. I or to Sec. VIII that affect the total cost of ownership, beyond the costs of fabricatied unit due to design code.

There is a plant in Texas with a Sec.VIII gas cooler (read Waste Heat Boiler) that has the water tube bundle past a 180 degree turn in duct work from the (spent acid) burner. Since there was not flame impingement on the tubes, their A.I. agreed in advance to accept it as a Sec. VIII unit. The owner has benefit of an extended time between service inspections, maybe 2 years instead of 1 to 1.5 year intervals.

A nitric acid plant in Louisiana has an ammonia catalytic converter with integral water tube walls and a 200 psi steam drum. It was fabricated by Babcock in France. Since it was stamped to Sec.VIII calling it a heat exchanger, there was a reduced import duty, than if it had been a "boiler".

You will need to confirm with owner and A.I. about any acceptable differences for Section I versus Section VIII, and whether there will actually be any advantage result.

 

[LSThill]

What Code Case allow ASME Section I to be Design and Fabricatin to ASME Sect VIII, DIV. 1?

 

[vesselguy]

ApC2Kp,
I am looking for info such as you stated, "The owner has benefit of an extended time between service inspections, maybe 2 years instead of 1 to 1.5 year intervals." Is this something spelled out in Sect 1 (I confess I don't know Sect 1 well), but I don't recall seeing any requirements in Sect 8 talking about inspection time. Where's that come from? My guess must be from the local boiler branch requirement?

I know the design you're talking about. Its a Waste Heat Boiler from a sulphur plant; I've worked on 2 of them in the past. Real tricky butt welding of the tubes to tubesheet. I've seen them with the gas side (Cr-Mo) designed and registered to Sect8 while the C.S. steam side is Sect 1 (both codes on one exchanger).

 

[vesselguy]

ApC2kp,
How soon I forget. It wasn't called a waste heat boiler; they're called Process Gas Cooler. Doh.

 

[eliebl]

For those interested in the Alberta Requirements the link is

http://www.absa.ca/Forms/AB-506 Pressure Inspection Interval Requirements.pdf

There is a table of inspection intervals for this jurisdiction and you can then compare the "Boiler" to a "Process Gas Cooler".

EJL

 

[vesselguy]

eliebl,
Thank you very much for the link. The info is useful for one of the things I need to know on the operation side. Thanks again.

 

[ApC2Kp]

To vesselguy,

The post by eliebl has the basis for some of the critical considerations by owner and insurance agency. It also implies that some jurisdictions could be different.

The Sec VIII units in Texas and Lousiana are known to me only because of analysis for the piping connected to them. It does look odd to have ASME B31.1 Boiler External Piping connected to Sec VIII vessel and then B31.3 piping at other end. Many of the Waste Heat Boilers in sulfuric plants are firetube boilers with the tube to tubesheet joints you have experienced welding. The Sec VIII gas coooler in Texas is actually watertube design like a few others in sulfuric acid / phosphoric fertilizer industry.

To lsthill,

Perhaps the ASME Code Case 1855 Unfired steam boiler Sec I and Case 2485 Steam Drum in HRSG System would provide basis for decision to use Sec VIII stamp. The piping, safety relief valves, instrumentation, and controls appear to be required as for Sec I unit?

It is more complex than deciding whether an item would be a vessel or large piping. Involvement on international projects adds the differing and sometimes conflicting requirements of other national codes to result in more uncertainty and confusion. The ASMA Code Case 1855 was originated in 1980, so it at least has some history.

 

[vesselguy]

ApC2Kp,
I agree with you on the point about "weird" with 31.1 piping on both sides of a Sect 8 vessel. I don't recall ever seeing that. People usually draw the line using the rule in Sect1 Fig. PG58.3 to define boiler proper and boiler external to make the switch, and stick to that. By that I mean if you define the vessel is going to be Sect8 then the piping coming into the vessel will be 31.1 piping and when it leaves the Sect8 vessel, the piping will be 31.3. Please do correct me if I'm wrong as I don't do much Sect1.

 

[robsalv]

One difference I'm aware of is that section VIII allows pilot operated safety relief valves, whilst section I does not.

As these are not my native codes, I'd be happy to be corrected if this is wrong.

Cheers