what will you do if carbon steel pipe is installed in place of ltcs _ what is piping
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8/10/2019 What Will You Do if Carbon Steel Pipe is Installed in Place of LTCS _ What is Piping
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Introduction:
Low Temperature Carbon Steel (LTCS) is used in piping
system when there is a possibility of proc ess fluid
temperature falling below -29 degree c entigrade during
operation. In ty pical refinery A 1 06 Gr B material is used
for carbon steel and A 333 Gr 6 is used for LTCS in normal
operation. There is no major difference in between these
two materials in composition. Also no non-destructive
testing is available which c an ensure these two materials.
So if by mistake CS and LTCS mixe s up with o ne anothe r
and some one installs CS in place of LTCS without knowing
the major operational impact whats the solution?
Reason for Mix up:
In construction sites sometimes the material mix up may o ccur. Someone may be wondering how Carbon
steel (CS) and Low Temperature Carbo n Steel (LTCS) material co uld mix up. The main reason is that no
physical identification is possible and There are various possibilities which can arise in a construction site
like:
1. Common surface preparation & painting yard for all materials.
2. In many c ases, the co lour co ding of pipes (Positive Material Identification-PMI) was not followed due to
schedule pressure.
What is Piping An attempt to ex plain pr oc ess piping engineering basic s in detail to help all the pro ce ss piping engineering
professionals around the world.
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7 th October 201 3 An up CS 1 Comment
What will you do if Carbon Steel pipe is
installed in place of LTCS
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3. On fittings, identification marks are written by low stress punch which was not visible after painting.
4. Common store/contracto r/fabrication area in construction site.
5. I gnorance of all concerned about the criticality & impact of mix-up with normal carbon steel.
So what will you do in such situation?
Process piping code ASME B 31.3 provides a guidelines in such situations. There is a provision in ASME B
31 .3 co des that is based on the stress ratio, the minimum allowable temperature of carbon steel materials
can be further lowered without any impact testing.
So whats this stress ratio?
Stress ratio can be defined as maximum of the
a) Nominal pressure stress divided by allowable stress at design minimum temperature.
b) Fo r piping co mpo nent with pr essure ratings, the o per ating pressure div ided by rated pr essure at the
design minimum temperature.
c) Combined longitudinal stress, without stress intensification factor, due to pressure, deadweight, and
displacement strain divided b y allowable stress at the design minimum temperature. (Coincident
Conditions)
Note that Stress Ratio requires computed stresses at minimum temperature and co incident pressures and
No stress intensification factor to be used for stress calculations.
So calculate stress ratio as per abov e guidelines.
Now the code provides a graph (reproduced above) from where you can calc ulate the amount of
temperature reduction with respect to stress ratio. From the figure for a temperature reduction of -17
degree centigrade (to make it -29-17 =-46 degree centigrade) the required stress ratio is 0.65. So if the
calculated stress ratio is within 0.65 then not to be worried. I n case the stress ratio exc eeds 0.65 pro vide
additional support to reduce stress ratio within that limit.
In this way y ou can reduce the pro bable huge impact of material changing (thereby co st) after the erection
of piping is already ov er.
No related posts.
8/10/2019 What Will You Do if Carbon Steel Pipe is Installed in Place of LTCS _ What is Piping
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More In CS
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Nitin
Sunday 27 April 2014, 10:19 pm
nice article!
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