Scope Limits of ASME B31 Codes (B31.4, B31.8 and B31.3)

[shehzad305]

Dear Guys,

Greetings & Good Morning.

I need your help to understand the scope limits of B31.4, B31.8 and B31.3 codes. We have NGL line designed and constructed under B31.4 upto our facility fence.Inside the fence the same line is designed and constructed under B31.3.

As per B31.4 Fig. 400.1.1-1 (Attached)the scope of B31.4 piping ends in the plot limits of production of a property Line. We are Producing Petrochemicals, my understanding from the fig.400.1.1-1 is that scope of B31.4 could be upto the ethylene production area inside our facility fence. Am I correct???

How can we define the scope limits of B31.4, B31.8 and B31.3 codes, means to say where B31.4 will end and from where B31.3 will start for example.

The requirements of B31.4 are much more lenient than API-570, B31.4 covers the repairs to inservice damages like API-570, but B31.4 consideres Full Encirclement Pressure Containing Sleeve repairs as permanent while API-570 consideres them as temporary repairs.Why is this difference there between B31.4 & API-570???


Regards.

 

[weldstan]

There are different members with differing needs writing the referenced Codes. B31.3 takes into account a far greater number of service conditions than do either B31.4 or B31.8.

 

[pennpiper]

shehzad305,
In most cases I have been involved in in the past, it was up to the Client to define where he (or she) wanted the Code limits.

Where we had a fenced in process plant (Refinery) and a cross country pipeline, some would dictate the .4 or .8 Pipeline Code ended at the fence and the .3 process plant Code took over inside the fence.

Others dictated the Pipeline Code came inside the fence to a dedicated metering station and Pig Receiving station. All of this was fenced (inside the Refinery fence) and the .3 Code took over at the fence on the other side of the Metering station.

I do not think there is any specific Rule of Regulation in any of the Codes. You need to have your Client give you his thoughts and direction.

Sometimes its possible to do all the right things and still get bad results

 

[Duwe6]

penpiper has it exactly - the exact location of a Code/Spec break is up to the designer. And he listed both of my top choices.

Please remember that if you want a Code or Spec break, you HAVE to do it at a 'feature', like a flange pair or a valve [preferably a flanged valve, for ease of hydro]. It is basically impossible to do a decent break in a featureless run of pipe; what do you hydro to?; what wall thickness and corrosion allowance? Had a Designer/General Const. Mgr think that three different companies could work on the same methane header without any features at their boundaries. Ended up with one firm commissioning the header, but only on one side of the tee in the main 8" line. Until the other contractors were complete enough to commission, the balance of that header was a pipe bomb - fuel/air mixture. Lasted about 3-weeks. Got lucky - no BOOM.

Booms are fun to watch. From a distance. With the area cleared of people.

 

[shehzad305]

Dear Guys,

Thanks for your responses regarding the scope limits of B31 codes.

Lets please talk about the repairs as per B31.4 and API-570 as i mentioned above.

Regards.

 

[LittleInch]

To take your first point / question - "As per B31.4 Fig. 400.1.1-1 (Attached)the scope of B31.4 piping ends in the plot limits of production of a property Line. We are Producing Petrochemicals, my understanding from the fig.400.1.1-1 is that scope of B31.4 could be up to the ethylene production area inside our facility fence. Am I correct???"

Yes you are correct - B31.4 can and commonly does extend inside the fence line of a plot up to a break point. Often this is the plant side of the valve which tees off the pipeline at the pig trap. It is important that the pipeline codes are used up to the point where the pipeline becomes non piggable because sudden or large changes in the ID can cause pigging issues and ultimately simply increase cost for little or no benefit. Design factors sometimes need to increase (0.6 maybe) for the pipeline, but this is still normally much less than the 31.3 pipe. B 31.3 tends to have a much thicker wall than pipeline pipe, it doesn't handle buried pipe very well and can introduce things like PWHT where 31.4/8 doesn't require it. Changing design codes on a pipeline line at the fenceline or some other arbitrary location is, IMHO, poor design and should be avoided. Usually the reason why this happens is that the piping designer holds sway and doesn't like this strange pipeline thing messing about with his piping design....

I'm not familiar with API 570, but can't see why there would be a difference. If maybe you posted the relevant page then we might be able to see whether it is relevant or not.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[metengr]

The main difference between B31.4 and API 570 is that B31.4 is a pipe construction code while API-570 is an in-service inspection, repair, alteration piping code.

 

[shehzad305]

Dear metengr,

Thanks for joing the discussion, i agree that API-570 is an in-service inspection, repair, alteration piping code. But ASME B31.4 also address the integrity assessment and repairs of in-service transmission pipelines.

ASME B31.4 is very lenient for design & construction compared to B31.3 & B31.1 for example and similar for integrity assessment and repairs of in-service transmission pipelines from API-570.WHY????

 

[metengr]

shehzad305
The reference in B31.4 for integrity assessment is only a guide. As weldstan mentioned, when all of the piping codes were originally developed they were developed based on consensus among various code volunteers for design, construction and unique service conditions. Lately, the piping codes have started to take an interest in providing basic recommendations for maintenance and condition assessment of piping systems.

API-570 was strictly developed as an enforceable inspection, repair and alteration code for piping. Yes, you will have overlap between codes. However, API-570 has a rather specific scope and does not deal with design, fabrication nor construction activities.