MDMT for black iron pipe 6

[airgasspec]

Am starting a new design project and am trying to find the MDMT for a segment of black iron pipe that's in an exiting system. Was wondering if anyone could provide some assistance.

 

[nickelkid]

What is the design code and material spec?

 

[vesselfab]

The MDMT is set by the plant's enviromental site location and service. Now whether some unknown piece of pipe meets that MDMT is a different story,

 

[airgasspec]

Unspecified. It's an old site and all I know is it's 2" diameter.

 

[gr2vessels]

There is a bit of the problem with your pipe, as I'm not sure, is it a 'black iron pipe' as in a natural gas system, or is it a simple A53 steel pipe painted black, in any service. So, what is it, iron or steel?
And I'm not sure what is the exiting system, is it something related to the high security prison and carrying almond smelling gas or simiar?
cheers,
gr2vessels

 

[nickelkid]

To determine its minimum design temperature of a pipe, just knowing it is "black iron" and "2 inch diameter" is not enough.

 

[stanweld]

What are the operating conditions? Pressure, temperature, fluid service. What is the wall thickness? What is the current (corroded) condition? These are more important in the evaluation of this pipe for continued use.

If the pipe was made prior to about 1975-1980, it could have a ductile to brittle transition temperature above 100F.

 

[airgasspec]

The pipe material is cast black iron. Used currently for gaseous argon/CO2 (98%/2%) Emixal for industrial welding. Proposed change to system with a gaseous argon/O2 (98%/2%) Emixal.

Current operating conditions: 50 psig, ambient temp, pipe is fairly new (within 10 yrs).

 

[nickelkid]

Does the pipe have threaded fittings? Often steel pipe is called "cast black iron".

 

[moltenmetal]

RCHandy is correct: "black iron" is a trivial description for a system of small-bore STEEL piping (2" NPS and less) and threaded 150# malleable (cast) iron fittings. It is doubtful that the pipe itself is of cast material.

 

[MJCronin]

airgass...

This is a guess.....but I bet that I am right..

"Black Iron" small bore pipe is usually A53 Grade B carbon steel.

Use ASME B31.1 to find MDMT properties etc.

Be aware that, if the system uses those cheap-ass malleable iron fittings, you are limited to both a maximum (400F) and minimum temperature by those fittings....not by the pipe.

My opinion only

-MJC

 

[nickelkid]

If this is in a typical bottle filling plant the fittings were probably purchased at Home Depot or equal.

 

[stanweld]

You can safely use a -20 F MDMT for the screwed low carbon steel piping system described if you so inclined. The stress imposed by the design conditions, assuming normal wall thickness for screwed systems is more than likely < 5% of pipes specified minimum yield strength.

 

[nickelkid]

Looking at B31.3 if you have "Type F" (continuous welded)A53 Grade A a +20F minimum design temperature is permitted.

It looks like all other A53 grades and production methods allow a -20F minimum design temperature.