NIPPING OF F-201 TUBE # 21

PREPARED BY: HAFIZ ABID HUSSAIN / SOHAIL RAZA

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).

Process

Convection

SectionK -201

Vent Stack

Radiant

Section

Reformed

Gas

Natural Gas + Steam

RADIANT SECTIONF-201 Radiant Section

Refractory Lining

Fire Box

Radiant Tubes

Burners

Hairpin

Inlet Header

Catalyst Tube

Outlet Pigtail

Hot Collector

Mechanical Description

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

• 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

• 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

• 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….

• 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

• 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

– 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

• 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

Hairpin

Inlet Header

Catalyst Tube

Outlet Pigtail

Hot Collector

Mechanical Description

Nipping point for outlet pigtail

Nipping point for inlet hairpin

BURNER# 1.4B GLOWING BEFORE NIPPING

BURNER # 1.4B BECAME NORMAL AFTER TUBE NIPPING

BEFORE NIPPING PIG TAIL OF TUBE # 21 IS GLOWING

AFTER NIPPING PIGTAIL BECAME DARK