Wednesday, July 17, 2024

REHABILITATING A PETROCHEMICAL PLANT MAIN

A very tight time frame and several long installations of up to 1 km and more are only a few of the challenges that a petrochemical plant pipeline renewal project in Spain entailed. To meet these challenges, the pipeline owner decided to renovate the existing asset with the aramid-reinforced pipe-in-pipe system Primus Line®, a trenchless solution, which has the benefits of reduced down times due to its rapid installation. As a result of the swift project execution, the production process was not affected at any time.

The petrochemical plant was built in 1966 to produce petroleum derivatives. Currently, this plant has a production capacity of 120,000 tons of styrene-butadiene-styrene (SBS) and
styrene-ethylene/butylene-styrene (SEBS) per year. For its operation, the plant needs a continuous water flow for cooling and fire protection. Therefore, it has a water supply system made up of a pumping station, and a 6 km long main supply pipe. The first 3,600 m of the pipe has a diameter of DN600 and consists of concrete, reinforced with a sheet metal jacket and asbestos cement. The following 2,400 m are made of asbestos cement with a diameter of DN350.

The industrial water pipe, with an age of nearly 50 years, began to show symptoms of being close to the end of its life due to successive leakages in recent years, particularly in the asbestos cement section.

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The fortuitous leakage of the concrete pipe at the beginning of and under the intersection with a RENFE railway platform accelerated the need to undertake action.

The DN600 pipeline of the initial section runs parallel to the platform of the Santander to Bilbao railway line, so any intervention in this area required special access permits. This is the reason why a construction system that would minimise the damage to that infrastructure had priority.

The petrochemical plant opened a consulting process with companies specialised in trenchless technologies and civil works so they could propose solutions to renovate or rehabilitate the existing pipeline according to exact criteria:

• Renovation works compatible with the plant’s operation
• Maintaining the system’s hydraulic capacity
• Minimal effects on private properties and environment
Three offers with different characteristics were submitted:
• New pipe installed using traditional methods with open trench
• Sliplining with HDPE pipe
• Sliplining with the Primus Line® system

The option of a new pipe by traditional method with open trench was rejected due to its
cost, the need of numerous land permits and the technical challenges at the crossings
with urban environments, railways, roads, and rivers.

The option of renewing the main using sliplining with HDPE pipe was rejected due to
the reduction of the hydraulic capacity, the number of pits required and therefore the
number of land permits required. In addition, the potential installation length of each
section was shorter than the option selected.

The option selected for the works’ execution was the one presented by SinzaTEC, a
company specialising in the trenchless rehabilitation of pipes. SinzaTEC proposed
to reline the existing main using the aramid-reinforced Primus Line® system. The
company’s offer included the renovation with the medium pressure DN500 reinforced
flexible pipe for the DN600 pipe sections and the medium pressure DN350 reinforced
flexible pipe for the DN350 pipe sections.

The decision was taken based on various factors including:
• Practical absence of land permits thanks to the rehabilitation design in long sections
and from existing manholes where drains and vent valves are located
• Possibility of carrying out all the rehabilitation work in windows of 30-hour water
supply cuts, the estimated time in which the cooling storage tanks descended below
the critical level that would have forced production to stop
• Minimal reduction of the hydraulic capacity due to the small wall thickness of the
Primus Liner of only 6 mm for PN16
Project execution

The works’ execution was already planned between 2018 to 2021, following the
investment capacities of the plant, and adapting the work needs to the capacities of the
plant.

The pipe rehabilitation works were carried out based on the following criteria:
• Organisation in phases with short-term tasks based on the scheduled supply cuts
• Minimise the necessary number of connectors by installing long sections depending
on existing elements
• Coordination with Adif, the railway network operator, to eliminate effects on the
operation of the RENFE railway

The activities were planned accordingly and designed to carry out the installation of
the 5,800 m of pipe to be renovated in ten installation sections. The duration of the
execution phases for all sections was short, including two cuts of the supply service
per installed section.

The first supply cut of about twelve hours was scheduled for the removal of the
existing asbestos cement pieces, which required a specific health and safety
protocol. After dismantling these elements, temporary hazard-free pipe pieces
were installed that allowed the supply to be restored and a subsequent simple
disassembly to shorten times in the rehabilitation phase.

The second supply cut of about 30 hours allowed disassembly of the temporary
pieces, carrying out of a camera inspection of each section, installation of the
Primus Liner and corresponding connectors. A cleaning process was not necessary
as the host pipe did not present any debris or sediment.

The two-component resin in the Primus Line® connectors needed to harden for
at least six hours, which in this case coincided with the nightime. Work could be
resumed the next day with the connection of the remaining elements at the ends
and commissioning of the pipe.

After completion of each section, each chamber was reconstructed, and the land
was reconditioned.

Conclusion

The works were carried out with absolute precision as scheduled, so the operation
of the plant was not affected at any time and the pipe was rehabilitated to the
customer’s satisfaction.

In view of these results, it can be concluded that trenchless technologies already
play an important role and will play an even more important role in the future,
since the current policies related to the maintenance of the environment at the
cities and their surroundings require measures to be taken in all sectors to reduce
CO2 pollution and waste, and to eliminate the effects on the environment and on
the daily life of citizens caused by the construction works.

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