Pressure vessel vs. piping

[Moersleutel]

Hi

I have an interesting situation where the line between pressure vessel and pressure piping has been blurred. I would like to know if anybody is aware of a rule when to treat a component as a pressure vessel / boiler component / piping. We have a fired heater where some parties want the headers to be treated as pressure vessels and some want them to be treated as piping. The main issues are legal requirements (ie. pressure testing, documentation, etc), welding, design code (ASME Div 1 / B31.1 / API) and NDT.

Regards

 

[davefitz]

The definition of whether to define the component as piping (section I or B31.1 ) or a pressure vessel ( section VIII) is in the opening paragraphs ( scope of section VIII)of section VIII div 1. They provide some simple rules.

 

[MJCronin]

Rudol,

Since you have a "fired heater" I believe that you should review the rules and scope of ASME Section I ( Power Boilers) and not ASME Section VIII

ASME VIII is specifically for "Unfired Pressure Vessels"

If you have a header that cannot be isolated by a valve form the portion of the device that develops pressure, I belive that you MUST use Section I....

Anyone else out there agree/disagree ?

John Breen, are you still out there ???

MJC

 

[sgasociate]

Hi,
The rules of the "Construction" Codes are specific. I think the rules for Section I or Section VIII end at the first circumfrential weld, flanged connection or attachment to the vessel proper.
If you are speaking of interconnect piping from one vessel to another, you need to know what type of system you are running. Steam (B31.1), Oil (B31.3) ect. What is the fluid or medium you are transfering ? What temp/pressure ? Is the Fired Heater a "Code" Vessel ? Is this system under API ?
Let me know and I will try to help.
Sam

 

[tickle]

There are codes out there for the design and fabrication of fired heaters (eg API12k for water bath heaters).

There are rules that relate to the amount of stored energy as to whether a vessel needs to be designed as a pressure vessel (volume x design pressure related).

As previously mentioned there are various rules for the design of tanks and pressure vessels as well.

To respond to your colleagues explain to them the design pressure in the "vessel" In a water bath heater the only item that will be at pressure will be the process tubes and these are generally designed as piping. The water bath needs to be designed only for the head of water and the fire tube for the head of water acting externally.

 

[ijzer]

I do not know which country your heater is located but if it is outside Europe , API 560 is used for Fired Heaters. This standard mentions that parts outside the heater shall be per ASME B31.3 if process (e.g. hydrocarbons) and ASME 1 if steam or BFW.

 

[ctmfab]

Generally, all the following must be met for the component to be designed as a piping component. If ALL these are met it can be designed as a piping component, if not ALL are met it could be designed as a pressure vessel.

1. It can be described by a piping sketch or iso drawing and referenced piping specs.

2. It is not intended for storing or processing fluids. The exception would be items such as mixers, tees, headers, metering devices, or other items that are typically recognized as piping components.

3. Its primary function to transport fluids (gasses included) from one location to another within a system of which it is an integral part (a piping system).

4. It is not intended to act as an air receiver. OSHA requires that new air receivers be ASME stamped.

5. The item will not be subjected to more frequent test and inspection intervals than the remainder of the attached system.

If these conditions are used, you should have a good arguement to design the component as either a piping component or pressure vessel.

 

[objengrs]

John Breen is listed as working with old friends at Pressure Sciences in Pittsburgh, they're on the web. However his email link didn't work recently.