In the last year, La Línea Vertical has incorporated the service of inspecting the inside of gas storage spheres through rope access in petrochemical industries. This is a very physical job that requires specialised personnel to carry it out.
In these inspections, the technicians access the inside of the spheres, which are usually 24 or 25 metres in diameter, by means of a rope positioning system and progress through the interior to reach the welds by means of a system of pulleys, ropes and magnets of up to 15kN or 17kN of anchoring force, which serve to support the positioning of the technicians.
According to Daniel Sierra, one of the LLV specialists who performs this work, first a visual inspection of the inside of the sphere is carried out, followed by a more detailed inspection by means of non-destructive testing. In some cases, if required by the client, our company carries out both the access to the dial and the inspection, while on other occasions, a third company carries out the inspection and our technicians are in charge of introducing it into the dial and moving it inside.
Sergio Santiago, a technician and inspector at La Línea Vertical, explains that the welds inside the spheres are checked with magnetic particles, so that the area is magnetised and an aerosol is applied to carry out a surface and sub-surface inspection of the weld; the thickness of the sheet metal is also measured by ultrasound.
Both Daniel Sierra and Sergio Santiago recognise that it is quite a tough job – perhaps one of the most complicated they do – which requires the intervention of a team of up to seven specialised technicians who work in shifts. On the outside of the sphere, they always have staff from the team, experts in rescue and ready to act in the event of any incident.
In line with our company’s policy of prioritising work safety, in summer, shifts are changed more frequently, so that no technician remains inside the sphere for more than 20 minutes. This is due to the fact that the humidity inside causes a considerable increase in the sensation of heat, which increases exhaustion in the face of such physical work.
Daniel Sierra says that before starting a job of this type, the refinery or petrochemical plant itself must carry out a risk assessment and then the technicians from La Línea Vertical carry out another assessment to check the situation of the sphere, whether there are any product residues and assess whether extra protective equipment is needed. In addition, during the time that the technicians are inside the sphere, they must carry a continuous gas meter in case there is a leak or a lack of oxygen is detected (the inside of the sphere is a confined space).
Sergio Santiago points out that a few years ago, inspections of the spheres were carried out in water: they were filled little by little and the technicians moved around inside in a boat. But since rope access has been incorporated, ‘it saves a lot of time and money,’ he says.
This technician wants to highlight the importance of carrying out these inspections with quality, as these are structures that contain liquefied gas, which is highly polluting and flammable, so any leakage can be fatal, and is generally the maximum safety zone in a refinery. He points out that special attention must be paid to the areas of the pipe fittings, ‘which have a higher concentration of stresses’, and to the junctions with the ferrules, ‘which are very sensitive and more prone to defects’.
La Línea Vertical has carried out numerous inspections of spheres. In some cases, thickness measurements were taken of all the ferrules and crossings, as well as the fittings; in others, the fittings are also inspected, as well as all the welds and ferrules by ultrasound, in each case the customer requests a specific service based on their own inspection plan and needs. This December 2024 we have worked in another area in Portugal, carrying out in this case the work of access and accompanying the inspector.At La Línea Vertical we are very satisfied with the quality and safety of this new service, a pioneer in Spain, of inspections carried out on spheres using vertical techniques; it has been possible thanks to teamwork, as it is a very technical and physical task: it is essential to have the best team of experts in rope access and inspection and perfect coordination between them.