Rehabilitation of the main pipeline in a petrochemical plant in Spain

28 Sep 2022

A very tight time frame and several long installations of up to one kilometre and more are only a few of the challenges that this pipeline renewal project entailed. To meet those challenges, the pipeline owner decided to renovate the existing asset with the aramid-reinforced pipe-in-pipe system Primus Line^® – a trenchless solution, that 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 petrochemical 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-kilometre main supply pipe: Its first 3,600 metres with a diameter of DN600 consist of concrete reinforced with a sheet metal jacket and asbestos cement. The following 2,400 metres 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 span due to successive leakages in recent years - particularly in the asbestos cement section. The fortuitous leakage of the concrete pipe at the beginning of and under the intersection with the RENFE railway platform accelerated the need to undertake actions.

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

Consulting process

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 line according to exact criteria:

Renovation works compatible with the plant’s operation
Maintaining the system’s hydraulic capacity
Minimal effects on the private properties
Minimal effects on the environment

Three offers with different characteristics were submitted:

New pipe by traditional method 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 specialised in the trenchless rehabilitation of pipes. SinzaTEC proposed to reline the existing main using the aramid-reinforced Primus Line^® system. Their 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 option selected was determined based on factors such as:

The practical absence of land permits thanks to the rehabilitation design in long sections and from existing manholes where drains and vent valves are located.
The 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 stops.
Minimal reduction of the hydraulic capacity due to the small wall thickness of the Primus Liner of only 6mm for PN16.

Project execution

The works’ execution was already planned in the years 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 amount 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.

Following these criteria, the activities were planned and designed to carry out the installation of the 5,800 metres of pipe to be renovated in ten installation sections, with lengths of 257, 334, 1,060, 757, 555, 636, 157, 498, 587 and 913 metres respectively.

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 require a specific health and safety protocol. After dismantling these elements, temporary hazardous-free pipe pieces were installed that allowed the supply to be restored and a subsequent simple disassembly in order to shorten times in the rehabilitation phase.

The second supply cut of about 30 hours allowed to disassemble the temporary pieces, to carry out a camera inspection of each section, to install 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 needs to harden for at least six hours, which in this case coincided with the night hours. 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 conditioned.

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 addition to this, the use of the trenchless Primus Line^® technology provided the following benefits in the works’ execution in comparison to other rehabilitation/renovation methods:

Safe & reliable

100% quality control during the manufacturing process and before shipping
No curing, steaming or adhesion process
Independent of weather conditions during the installation
50+ year lifetime

Environmentally friendly

Noise reduction
Reduction of CO₂ emissions
Small pits and reduction in road work
Reduced use of machinery
Elimination of effects on the environment, roads, railways

Cost-effective

Reduced project cost
Reduced uncertainty in the budget
Reduction of execution times
Minimum needs of permits, licenses, etc.

Highly flexible

Installation through multiple bends of up to 45° (up to 90° after technical clearance)
Withstands thermal expansion of the host pipe and seismic movement
Fully flexible seamless woven aramid fabric
Installation in difficult-to-access areas

In view of these results, it can therefore 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.