Implementing ASME B31.9 - sanity check and advice 1

[Rputvin]

I'm working on a project that my customer has requested ASME B31 compliance for. The most applicable section is B31.9, the skids we're making are small pump stations that include a few valves, a few feet of pipe spool, and the main plate heat exchanger (ASME U/UM stamped) at the center of two sides of piping.

We're moving water at 150psi, 200°F for max design conditions.

The system is mostly carbon steel pipe, A106 seamless, and all of our valves and fittings follow API/ASME/ASTM/ANSI/etc as needed for dimensional and/or pressure. I've gone through ASME PTC 19.3 TW in full for our thermowells and everything is looking to be overkill for the service conditions.

Our shop has a U stamp for ASME BPVC Section VIII, and we have Section IX qualified welders and procedures to do the actual welding and quality control. No worries there, I'm just finding navigating these piping codes a little more confusing than straight up pressure vessels.

Wall thickness requirement is all of .0058" (or thereabout depending on pipe size) and we're using SCH 40 pipe (wall thickness ranging from .14 to .26). Calculated max pressure of the pipe is on the order of ~3500psi.

B31.9 points to B31.1 in several instances, and I've used the two codes to run through calculations for; allowable stress, branch connection strength for our instrumentation branches (lowest one still over 1000psi), longitudinal pressure stress, thermal expansion, expansion & flexibility analysis, bending stress, and some moderate seismic analysis using a=0.3g as the installation isn't in a seismic region. I ran the stress numbers as unsupported piping and the numbers look fine for everything except our non-weld joints (some threaded, some bolted flange) and have added supports as needed. Supports are modeled as "unknown carbon steel" as prescribed in the code as we'd use non-controlled carbon steel angle and tube to make the supports, which are simple rigidly attached and welded to the deck (no slider, rollers, guides, etc). Once again, the numbers are all well below any kind of critical threshold.

The only issue I've got is that the customer is supplying specific pumps and valves, which are cast iron, and I can't find enough information to reliably say they're good to go. The customer has made very similar skids with full CE/PED credentials for European installs. I asked for those full design packages, but they're not sharing. We're essentially taking that design, moving everything from SI to Inch, and changing the piping to conform with our weld procedures/materials/practices.

I haven't gotten as far as cold-spring, hot-and-cold reactions, or some of the more in depth analysis. I originally had it all written off under 919.4.1 eq.8, but the customer's supplied components started showing up and the cast iron bodies don't allow that exception if I consider them part of the design.

The system is pretty much the same thing we've been building for 30+ years, been shipping worldwide, we've just never had to apply codes due to the industries and customers we've been working with. How far does the "System duplicates a successfully operating installation or replaces a system with a satisfactory service record" extend? Does that apply if the existing installations are not ASME compliant? Can I use our existing pump stations and the customer's EU/CE/PED installations to "fill in the gaps" in my ASME B31.9 design package in terms of complete compliance? Alternatively, is it acceptable to call the piping spools up to code and rigidly support the customer supplied cast iron pieces between my spools?

There are a few directions I can go, I'm just not sure what the proper method would be. I don't mind the added work if additional analysis is required, I just don't have a straightforward method for that analysis figured out or I would've done it already.

I've reached out to our Authorized Inspector from BPVC work, and our contacts from Hartford that we work with on Section VIII/IX jobs, but we're on a compressed timeline and the holiday season hasn't been helping in getting a quick response.

Thanks for any help or insight you can provide!

 

[GD2]

RPutvin,
You are correct in selecting the design code of B31.9. The design conditions are within the scope of the code.
I am a bit concern on the usability of the customer supplied cast iron material components and valves. Limitations of materials can be found in Chapter II Part 3 and Chapter III. It allows the usage of Ductile iron to certain degrees but not cast iron. Go through the sections on these two chapters once more. You should find the answer to take a decision.

GDD
Canada

 

[Rputvin]

GDD,
Thanks for the comment.

Chapter II only mentions cast iron to not be used for flammable liquid or gas service. Cast iron isn't a listed material, but it states valves and fittings that aren't listed can be used within manufacturer design conditions. Alternatively it can be qualified by proof test, engineering calculation, or ASME BPVC Section VIII Div 2 experimental analysis.

Chapter III 923.2.1 only says to consider avoiding cast iron if shock loading is present. There isn't any shock loading.

We're using 5 different pumps, two of the models do have temperature and pressure limits on the nameplate (not published in any of the documentation for it though). We've got an OEM account with the manufacturer, hopefully they respond to my inquiries this week. Control valves supplied by the customer are another matter. I might have to pull in some similar valves and use the verbiage of the code to allow me to use those values.

B31.9 specifically doesn't cover pumps, though. Is it improper to consider the pump case another valve/fitting in the system for my purposes? I'm not as concerned with an ASME-rated pump, as I am having a complete design package for ASME B31.9 piping.

 

[GD2]

RPutvin,

Let's refine our term for 'Cast Iron' into better technical name designation. B31.9 allows usage of ASME B16.1 Grey Iron and B16.42 Ductile Iron Flanges and Fittings. These are listed materials in Table 926.1.
As the Customer is supplying valves and pumps, look at the flange specification for both (I guess both of these will have flange connections). If the flange standards are either B16.1 or B16.42 you are covered.
Check the size for meeting the P-T ratings. For size up to NPS12, ASME B16.1 Class 125 should work for the design conditions. For larger size you will need to go for Class 250. If the flanges are B16.42, Class 150 will take you to NPS 24.
B16.1 material is usually A126 Class B, B16.42 is A395 GR 60-40-18.

Depending on the customer supplied B16.1/B16.42 classes, you will need to match B16.5 flanges where applicable (assuming you will be using B16.5 C.S flanges with A106 pipe). Be sure to match the bolt patterns when you connect different material with different flange classes.

Don't overthink - qualifying material through analysis, tests are time consuming, expensive and requires expertise.



GDD
Canada

 

[Rputvin]

Another good post, thanks

The pumps and valves are European based. I finally have an answer that they have PN6/10 flanges, PN10 is equivalent to Class 150 according to some charts, I'll need to verify further since they're technically 10bar (145psi) which is just shy of our max pressure. They also gave me EN-GJL-250 / ASTM A48-250B grey iron as the pump housing material. So you are correct, I can use grey iron numbers. Temp rating is 230°F.

Largest pipe in any of these systems is NPS 4.

The control valves are going to be a bit more difficult to track down, but I've got enough to go on I should be set.

Thanks again!
-Ross

 

[GD2]

Ross,
PN10 flanges are rated at 10 bar but this is the rating at 38 C (100F, Cold condition). If you say it is just a shy from the design pressure of 150 psi, it is incorrect. Pressure and temperature are co-related. Pressure rating for the pump flange will drop at 200F.
This type of mismatching in design conditions are common when equipment are ordered separately by a different group and the piping system is designed by another group. Check the max operation conditions of the system, sometimes the margin set for design conditions overkills.

Get details of all equipment and components supplied by the customer. See if it fits your design conditions. Conversely, if the pump designs are correct, then the piping system could be overkill.

GDD
Canada

 

[Rputvin]

The piping system is overkill, I know that already. Design conditions were set by my company, they're not arbitrarily high. It's all of the oddball stuff the customer is supplying that is the issue.

I'm trying to find an EN chart that has PN10 flanges, but you're correct that they're at their nominal rating at cold conditions and only go down (I think cold for EN flanges is up to 50°C). That's the digging-into I mentioned previously.