Crossover Main Replacement - Coke Oven Managers Association

Matthew John
Crossover Main Replacement Project

Introduction
• Morfa Coke Making plant is an Otto Simon Carves’ Twin
Flue Underjet Compound design with twin collector
mains.
• The Ovens were comissioned in 1981 and consists of 84
ovens (2 batteries of 42 ovens).
• As part of the coke making process, volatile gases
released from the coal during the carbonisation process
are exhausted from the ovens to a By-Product plant, via a
gas recovery pipe work system referred to as “crossover
mains” There are four crossover mains in total, two per
battery.
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Introduction
After 33 years of uninterrupted service, each crossover has
typically seen in the region of 1.45 billion m 3 of coke oven gas.
The system has already surpassed its original design life by
some 8 years and the pipe work was in poor condition.
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Introduction
Due to the poor condition of the pipe work and the losses of
containment, we were faced with three options.
1. Repair the current pipe work by “over plating”.
2. Remove the Coke side Gas Collecting Main and
“Crossover mains” altogether and operate the plant on a
single Gas Collecting Main.
3. Remove the Crossover mains and replace with new.
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Introduction
The first two options were not viable, firstly each of the
crossover mains had previously been “over-plated”, and this
would only prove to be a short-term repair.
Secondly even though it was possible to operate the plant on
a single Gas Collecting Main the operating tolerances were
too fine, due to the size of our oven design and size of out
Ascension pipes.
Stopping the coke making process to replace these crossover
mains was not an option, so plans were put together to
change all four mains on a “live gas” system.
This is believed to be a first for Tata Steel Europe if not
worldwide.
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Planning Phase
The planning phase was key to the success of this project.
A project team was formed which was collaboration between
both Process and Engineering personnel from the Coke oven
department, Process Safety personnel and personnel from
the Project department.
A master schedule was produced and a weekly status review
plan was used to provide an easy to read breakdown of the
imminent tasks.
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Planning Phase
Health and Safety
Safety was the main priority of this project and to ensure
there weren’t any accidents, there were a number of safety
measures taken.
The project was carried out in accordance with CDM
regulations and F10 notification was issued to the HSE.
The project team were nominated as both CDM Co-ordinator
and Principal Contractor.
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Planning Phase
Health and Safety
Due to the hazards involved with this project a huge amount
of time and effort was invested in Hazard Identification and
Process Hazard Analysis.
Event trees were constructed to provide good clear
visualisation of the events requiring mitigation, this helped to
develop a comprehensive Process Hazard Analysis.
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Planning Phase
Assembly Drawings
An assembly drawing was constructed covering the entire
scope of the installation including over-plating, temporary
platforms and the interconnection pipe work
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Planning Phase
‘Mock-up’ trial
Another crucial part of the planning phase was the
construction of a ‘mock-up’, simulating the blanking spade
insertion and removal process.
The mock-up included:
•The blanking spade
•Clamping ring concept
•Jacking steel work
•Guide cradle
•and protective curtain.
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Preparation Phase
Jacking Steelwork & Over plating
Before any work could be started a substantial amount of
preparation was required.
Large areas of the collector mains required over plating to
ensure there was enough “mechanical strength” to carry out
the replacement task.
Additional steelwork was erected to provide “jacking points”
for splitting the flanges with hydraulic jacks.
Pressure control and purging operations
Nitrogen purge points and re-circulating gas stabbings were “hottapped”
into the crossover mains to facilitate pressure control and
purging operations.
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Preparation Phase
Ground preparation of surrounding areas
Calculations made during the planning phase of the project
considered the weight of each crossover main assuming they
were totally blocked with heavy tar deposits.
“Gas flow” testing was also conducted as part of the planning
phase; this indicated that each of the crossover mains was
substantially blocked.
The weight of each main was calculated to be approximately
40 tonnes, which resulted in the requirement for an 800T
crane.
Ground surveys were performed in the two crane location
areas and the ground was prepared in readiness for the
arrival of the crane.
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Preparation Phase
Spreader beam
Due to the visibly poor condition of the existing crossover
mains, there was real concern that the horizontal section of
the main could collapse under it’s own weight during the
removal process.
Therefore a bespoke “spreader beam” was designed and
manufactured, that supported the pipe at one-metre pitches to
mitigate this problem.
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Preparation Phase
Coke “Dump Wharf”
The crane location for the work carried out on number two
battery, prevented the use of the existing Coke “dump wharf”.
This was recognised during the planning phase and a new
“emergency coke dump wharf” was constructed.
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Preparation Phase
Interconnecting pipe work
Preparation had to be made for each battery to operate on a
single crossover main while one was being replaced.
This was achieved by the installation of interconnection pipe
work and valves, which enabled the gas make to be re-routed
to the adjacent Gas collecting main.
A pipe work arrangement was “hot tapped” into the ram side
gas collector main and a duplex arrangement was “hot
tapped” into the coke side gas collector main.
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Preparation Phase
Welding inspection & Pressure testing
All the new pipe work, including the service pipe work was
manufactured and tested at Fairwood Fabrications Ltd
workshop.
Before leaving the workshop every weld was 100% MPI
tested and each pipe section pressure tested with
compressed air to one and a half times the maximum working
pressure.
A quality assurance (QA) file complied throughout the
manufacturing process was produced and formed part of the
Health and Safety file.
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Preparation Phase
Expansion Joint
The only design change from the original crossover design was the
inclusion of an expansion bellows.
This was to allow for any thermal expansion likely to have taken place
when the new crossover at ambient temperature is connected to the
working gas system with temperatures around 80° C.
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Crossover Main Replacement
Isolating the first Crossover main
Insertion of the first blanking plate was the first real test of all
the months of preparation and planning.
For each crossover the Ram side leg was blanked off first
followed by the Coke side.
As an output from the Management of change and risk
assessment exercises, a comprehensive checklist was
written to ensure all tasks were listed and signed off when
completed.
A crane and hydraulic jacks were used to split the flanges.
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Crossover Main Replacement
Isolating the first Crossover main
The most critical part of this process was the control of the
gas pressure while splitting the flanges.
To ensure the precise control required for this task, the
system was controlled manually using pressure gauges and
vent pipes to provide a visual indication to the controller.
While inserting the blanking plate the sight of coke oven gas
emerging from the split flange was a good indication that
there was a slight positive gas pressure preventing air ingress
and the threat of explosion.
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Crossover Main Replacement
Isolating the first Crossover main
Guided slots at the front edge of the blanking plate located
around the few loosened flange bolts at the rear of the flange;
to facilitate bolthole alignment.
When all the new flange bolts were loosely fitted, the
crossover main leg supported by the crane was lowered until
the flanges fitted onto the new gasket.
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Crossover Main Replacement
Removal of “Bend Section”
The bend section of the crossover was disconnected form the
horizontal section to prevent slewing as the horizontal section
was lifted out.
An 80 tonne crane set-up on the Ram track side of the
Battery was used to execute the lift.
After disconnection of the flanges and breaking up of the
heavy tar deposit at the flange, the bend was lowered to the
floor.
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Crossover Main Replacement
Removal of “Bend Section”
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Crossover Main Replacement
Horizontal Section Removal
After disconnection of all service pipe work and the flanges
connecting the horizontal section to the verticals, the fully
supported the horizontal section was ready for removal.
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Crossover Main Replacement
Horizontal Section Removal
When the pipe work was lowered to the floor level, it was
clear to see it’s poor condition and the necessity to support
the pipe at one-metre intervals.
Also as the “gas flow” tests performed prior to the work
starting indicated, the pipe cross sectional area was
substantially reduced by deposits effecting gas flow through
the pipe.
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Installing the new Crossover Mains
Installation of the new horizontal section
Prior to the installation of each new horizontal section all the
support steelwork was upgraded to ensure good mechanical
integrity and extend the life expectancy.
The installation process was simply the reverse of the
removal process.
The new vertical legs were lifted and secured into place, and
then the horizontal sections complete with all new service
pipe work and expansion joint was lifted into place.
Maintaining good visual and radio contact with the crane
operator was essential throughout the lift.
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Installing the new Crossover Mains
Installation of the new horizontal section
Scaffolding towers erected on either end of the crossover
proved a safe working area for the installation team to
carefully guide the new pipe into place and install the new
gaskets.
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Installing the new Crossover Mains
Installation of Bend Section
The final section to be fitted is the bend.
The bend section was cut to suit, allowing for the difference in
the new installation fitting to the existing pipe work that is still
operational and carrying hot gas.
The bend was measured and tacked on site then removed
backed to a workshop for completion.
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Installing the new Crossover Mains
Removing the Blanking plates
With the installation of the new pipe work complete the next
phase of the installation was the removal of the spade that
was preventing the gas flow over the new pipe.
Again the pressure control was critical to the success of this
phase, so to ensure the precise control required for this task,
the system was controlled manually using pressure gauges
and vent pipes to provide a visual indication to the controller.
The coke side spade was removed first followed by the ram
side.
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Installing the new Crossover Mains
Removing the Blanking plates
Again the 800 tonne crane was used to split the flanges via
the bespoke spreader beam.
Slowly the spade was removed and the gas pressure was
adjusted as required.
When the blanking spade was fully removed, the bolts were
replaced and the main was lowered back onto the new gasket
and the joint was secured.
At this point coke oven gas was flowing through the new
crossover pipe work and the new main was “live”.
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Summary
The project took 40 weeks to complete from start to finish.
Thousands of man-hours were utilised.
Four new crossover mains were successfully installed.
The project was completed on time, within budget and without
any accidents.
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