INSPECTION AND REPAIR OF THE RECYCLE GAS FURNACE

INSPECTION AND REPAIR OF THE RECYCLE GAS FURNACE

 I will share to you how I carried out the inspection and repair of the pre heater furnace of train 1 and I will explain the methodology that applied to achieving my objectives.

I began to work on this project in 5^th  April to 15^th April 2005. I worked on this for ten days.
I was in rol as “INSPECTION CORDINATOR/ SHUT DOWN” in ORINOCO IRON COMPANY
 

It was  a  repair project. I did  it As a part of the activities programmed for the shut down #08 of the train 1 Modulo #2, I proceeded to carry out the inspection routines and the fixtures in the pre heater furnace pipes.

INSPECTION AND REPAIR OF THE RECYCLE GAS FURNACE

The objective of the project was to inspect and repair the pre heater furnace pipes of the convection  zone, gas plant train “1 modulo #2 of Orinoco-Iron to assure the dependability of this equipment in avoiding unprogrammed shut downs, following the norms of manufacture  for pressure equipments (ASTM section 8, ASME B31.3 and National board Inspection code)

My position at that moment inside the organization was “INSPECTION COORDINATOR/ SHUT DOWNS” . My mission was to execute and to drive the mechanical inspections and tests of equipments, during the intervention of the trains (shut downs), in order to outline recommendations and/or mechanical modifications that guarantee greater readiness of the equipments, following the limits of the superintendence fulfilling the norms as regards to enviroment and security. See the follow diagram:

Diagram of Positions. I am highlighted in green

 

My main duties were the following:

• Basic job duties:

-  Take advantage of the opportunity to thoroughly inspect the mechanical equipment during the shut downs. 

- To ensure the dependability of the inspection of the repaired parts following the manufactures technical specifications.

- To inspect the works carried out by third parties. 

- Technical information of the state of the equipment during the shut downs.

- To follow the official norms on environmental health an safety 

- System of quality ISO 9001:2000 implanted and maintained. 

- Assigned resources preserved against loss, deterioration and waste. 

• Operative duties

-   To perform the reliable inspection of the mechanical maintenance.

-   To recommend high quality information which contributes to decision-making.

-   Recommendations over improvements of equipment during the shut down of trains according to technical specifications.

-   Interface with the units involved with quality control 

-   To make confidential the access information to third parties. 

-   Program of daily activities executed according to that planned.  

-  Identify deviations and correct them in time.  

 

The area of the work was the gas plant, it is the area of production where natural gas is processed to transform it in a gas reducer, using furnace reformers, pre-heater furnace, re-boilers, absorber Column regenerator Column, chemical solutions, vapor, etc. and other equipment that is used in a gas  plant.

The gas reducer is used to make the reduction of the mineral. This contains 29.7 ppm h2s, 5.6% CO, 2.9% CO2, 16.7% CH4, 66.1% h2 and 8.9%N2. this gas is preheated in the pre heater furnace. The gas enters with a temperature of 77 °C and it leaves toward the reactors to 832 °C.  

The reducing furnace is a cylindrical type with vertical coils and it is constituted by the following parts: inlet header, out let header, convection area and radiation area.  

The inlet header takes charge of to receiving the gas reducer from the gas plant and to feed it to the convection area.  

The convection area is an enclosed chamber which holds a group of finned tubes which take charge of getting up the temperature of the gas reducer from 77°C to 455°C before entering the radiation area. 

The radiation area is an enclosed chamber that contains some coils of tubes made of a very special material and inthere the biggest quantity in heat is transferred because they  are as near as possible to some burners. The transmission of heat is given by radiation. This area elevates the temperature of the gas to 832°C.   

The coils are configured so that the gas makes a journey sufficiently long so that it reaches the wanted temperatures. They form three lines, these they are: entrance line, where the gas enters from the convection area, central line and exit line to the out let header. The following outline exemplifies the explained above.  

The out let header takes charge of receiving of all the gas at 832°C from the radiation area and to address it towards the area of the reactors.  

Parts of the furnace. 1: inlet header, 2: outlet header, 3: tube coils 

 

As part of my work list, I have a lot of experience in the inspection and repairing of these types of furnaces, especially those of the radiation area that are those that are exposed to the most severe conditions of pressure and temperature.

The tubes of the radiation area are manufactured of a very special resistant material to the high temperatures of up to 1200°C without melting. This material is the A297 HP nb.  

 I will relate how I carried out the inspection and repair of the pre heater furnace of train 1, for I will explain the methodology that applied to achieving my objectives:  

1) I carried out the plan of inspection of the tubes taking into account the record of them, taking in care the respective norms.

2) I carried out the decision making regarding the repairs to be done after interpreting all the obtained data of the non destructive testing.  

3) I coordinated, inspected and approved all the works carried out to repair the damaged tubes, assuring the dependability, readiness and operability of the equipment.  

It is necessary to highlight the levels of knowledge and professionalism, which have to have to inspect and repair these tubes, are very high.   

The norms of quality for the production are very strict and the good application of them maintains the security of many human lives because the very inflammable gas is managed at 211913m3n/h to 12 bar of pressure and 832 °C.  The knowledge and handling of the engineering techniques is very important, not only in the productive part, but also in the moral aspect. 

As a part of the inspection plan I applied eddy current inspection to the coil tubes involving all parts of the pipes including the elbows to detect corrosion. There is a type of corrosion that is very dangerous called metal dusting. Metal dusting is a destructive form of carburisation which occurs in pipes which drives gases with a carbon activity >1, in the temperature range 400 – 900 deg C. The eddy current can detect carburisation so metal dusting too.

To have a good reference, the three files pipes were marked using numbers and letters  each like its shown next:

Example how one of the  pipe files are market. The pipes are 4” nominal diameter.  

During the eddy current test I found four pipes with high indication of carburisation. They were:

 

Center line:  

Level 0:, 6 B, 8 B, 10 B and 11B   

To verify the wall thickness in the section tubes with high indication, I used a thickness test, using ultrasonic equipment. The ultrasonic equipment is able to take very exact measurement of thickness using ultrasonic waves which go straight through the metal and bounce to the end of the other side of the wall. The equipment  interprets the bounce of the wave face and translate it to distance or wall thickness.  

During the Thickness test I found that the four pipes with high indication of carburisation had low wall thickness. The wall thickness of these was 10 mm and the minimum wall thickness allowed was 5,6 millimetres. I found thickness up to 4,9 mm in scanned areas. 

Finally I used an X rays test in the low thickness areas of the pipes, detecting and verifying that the problem found was metal dusting, as I suspected. In the fallowing image we can see the pipe # 6B.

Localized metal dusting

  To repair it I did not have to cut off  all the pipe, because the metal dusting was very localized just around the weld between the bend pipe and the straight pipe.  I had  to cut off  only 300 mm from the weld  to change only the damage parts of the pipes with metal dusting and weld it again  using a new pipe part. 

Due to the exposure at high service temperatures secondary carbides are formed and ductility material decreases.  This increases the risk of cracking when repairing. The following diagram, shows the method I used to repair  the damage pipes following ASME B31-3. It is considerate like alternative  procedures, because I had to weld new pipe parts with old pipe parts.

Method following reference codes

 

Before any weld process, I preheated the old material to 250 °C and sustain the temperature between 150 and 200°, to avoid cracks due thermal shock.  A welding procedure was done to keep all the essentials variables under control.

During the repairing, I used Spot Check and X ray test to certify the quality of the welding. The welds have to be discontinuities and defects free following the reference code ASME SEC B31-3.

Once all the repairing was finished, a leak test was done and no leaks were found. The furnace started without any problem and is still working. No accidents occurred.

 

- My view of the overall project

When the furnace repair was done, the quality of the welds and materials had to be the best. No mistake could be allowed because the minimum could cause a fatal accident. The minimum leak during running meant a certain shut down. It could became a very high losses of money too. The repair done by me was excellent, and I felt calm because I knew the people (workers) were safe.  

- How the project fared in meeting the goals/ requirements

After the furnace was repaired, it was started up without any problems, no accidents, no leaks, etc, and it is still working. 

- How my personal role contributed to the project

 The fact that I detected metal dusting problems and I repaired the furnace on time, implied that I guaranteed the dependability of the pre heater furnace reliable and in time.  and this was one of my roles.    

To see more of my competences please download my "Competency Demostration Report" pdf clicking here:

 

COMPETENCY DEMOSTRATION REPORT