Tube Nipping
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Transcript of Tube Nipping
![Page 1: Tube Nipping](https://reader033.fdocuments.us/reader033/viewer/2022061200/54778645b4af9f766d8b4616/html5/thumbnails/1.jpg)
NIPPING OF F-201 TUBE # 21
PREPARED BY: HAFIZ ABID HUSSAIN / SOHAIL RAZA
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Introduction / Background
• F-201 Catalyst tubes are in service since 1982 and completed a service life of > 227,760 hrs against design of 100,000 hrs.
• Higher life achieved due to lower Tube Metal Temperatures (TMT value around 895 0C against design value of 925 0C).
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Process
Convection
SectionK -201
Vent Stack
Radiant
Section
Reformed
Gas
Natural Gas + Steam
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RADIANT SECTIONF-201 Radiant Section
Refractory Lining
Fire Box
Radiant Tubes
Burners
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Hairpin
Inlet Header
Catalyst Tube
Outlet Pigtail
Hot Collector
Mechanical Description
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1. Tube # 160 April 27, 2003
2. Tube # 228 July 25, 2003
3. Tube # 164 January 22, 2006
4. Tube # 21 June 26 , 2008
Tube Leakage History
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• On June 26, 2008 at 1930 area operator reported high noise
level in A/B chamber of primary reformer F-201 and backfiring
of Burner # 1.4B.
• Burner was immediately isolated.
• On checking through peep door, a black vertical spot was
sighted at the bottom of a tube.
• Burner # 1.5B was also extinguished due to improper burning.
• Coordination / Shift Engineer visited the site and declared
Tube # 21 in Hot collector # 41 as the leaking tube.
• Insulation from pigtails of tubes from 19 to 23 was removed,
TMTs taken and hourly monitoring started.
Tube Leakage Detection
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• Noise level in A/B chamber was 111 dB as compared
to 99dB in C/D chamber.
• TMT of tube # 21 was 8900C.
• Insulation removed from pig tails of tubes # 19 to 23
to check pigtail temperature.
• Pig tail temperature of tube # 21 was initially 7680C,
while at adjacent tubes temperature was 7800C.
• This temperature reduced to 7550C until nipping of
the tube.
Observations / Actions taken
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• B # 1.4B found glowing from inner side.
• Hot spot at external burner plate was increased to
4450C with LS application.
• Burner # 1.4A at opposite end of Tube # 21 was
removed to take observations of the leaking tube.
• A log sheet developed for monitoring of tube
leakage.
Actions taken….
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• Before Tube nipping activity Shop Test was carried out as per standard nipping practices.
• The purpose of shop test is to simulate the actual nipping conditions.
• This is required to:– Check work ability of the equipment to be used on
the job.– Train all the team member for the actual job.
Tube Nipping
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• Plant Emergency Actions were discussed in detail within the group and with other units.
• Safety squad alerted. (Situation was discussed with Deputy Warden)
• Fire truck arranged for rescue purpose.
• Safety talk conducted before job execution.
• Doctor on duty was informed about the job and Ambulance was arranged with dispenser.
• All possible scenarios were discussed with maintenance team and area operators.
• Plant-II coordination Engineer and other units were informed about the activity.
• Lime water arranged at F-201 bottom and top for avoiding dehydration of personnel working in hot environment.
• Ice cooled jackets with complete fire protection suits arranged by the maintenance Engineer for the nipping team.
Safety Precautions Adopted
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– On June 27 tube nipping activity was carried out
from 1930 to 1945 hrs.
– It was nipped first from the bottom pigtail at
13000 PSI and then from top hair pin at 4500 PSI
pressures.
Tube Nipping Activity
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• Noise level in A/B chamber was reduced from 111 to 100 dB.
• Tube color changed to glowing red from top to the leaking
point. Tube bottom portion remained dark.
• Burner plate hot spot reduced from 445 to 900C.
• Temperature at HC # 40/41 were reduced from 788/789 to
782/7750C respectively.
• Flue gas temperature decreased from 1002 to 9800C.
• CH4/CO2 slippages increased from 0.65/0.1100 to 0.78/0.1150 %.
• Syn. gas flow had to increase from Zero to 3200 NMC/hr to
control Syn. machine 1st stage discharge pressure.
Observations After Nipping
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Hairpin
Inlet Header
Catalyst Tube
Outlet Pigtail
Hot Collector
Mechanical Description
Nipping point for outlet pigtail
Nipping point for inlet hairpin
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BURNER# 1.4B GLOWING BEFORE NIPPING
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BURNER # 1.4B BECAME NORMAL AFTER TUBE NIPPING
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BEFORE NIPPING PIG TAIL OF TUBE # 21 IS GLOWING
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AFTER NIPPING PIGTAIL BECAME DARK