CLAMSHELL BELLOWS BY JOHN CARDWELL LIMITED

The pipework around a water-filled “U-seal” arrangement contained 2-universal pressure-balanced compensators which were fitted when the plant was built. Over time the corrosive coastal environment had caused the attachment welds attaching the bellows tangents to the pipework components in the compensator to corrode causing the gas to escape. The bellows to pipe attachment welds were on the inner surface of the pipe section and so could not be accessed to attempt repair work.

The leaks caused significant operational problems at the plant, in particular blast furnace gas has high carbon monoxide content and the presence of this gas made routine maintenance work in the area difficult because of personnel safety issues.

Working closely with the client John Cardwell Limited proposed a solution incorporating an oversize clamshell bellows arrangement. Site measurements were made and a great deal of care was necessary to ensure that the bellows and associated piping components were correctly sized. It was necessary to ensure that the new clamshell bellows was large enough to clear the existing bellows under installation and operating conditions but also small enough not to foul the hinge pins in the restraining structure on the compensator.
The clamshell design was accepted by the client and a programme of work was established.

Belman Production A/S produced the clamshells in Esbjerg, Denmark, and shipped them directly to site.

The clamshells (which were produced in two halves to enable them to be fitted) were constructed using a 2mm thick nickel alloy (2,4858, Incoloy 825) bellows mounted on vessel-quality carbon steel pipe pieces rolled from plate.
To enable access to carry out the closing weld on installation, the profile of the bellows was designed using a wide convolution pitch.

During the time leading up to the planned installation date the client’s preferred on-site pipework contractor carried out the necessary preparatory work which involved cleaning the existing platework and adding split rings sized to accept the new clamshell bellows. This work was carried out in accordance with the agreed specifications made by John Cardwell Limited and agreed with the client.

Installation was carried out by the experienced Belman installation team who attended site, positioned the clamshells and tack welded the assemblies to the prepared pipework then made the longitudinal butt welds in the bellows and pipe pieces. The final circumferential closing fillet welds of the pipe sections on the clamshells to the split rings and platework were then made by the pipework contractor.

On completion of the work by the Belman team the client’s own non-destructive testing personnel inspected and approved the welds. After this inspection was carried out the final sections of a permanent protective cover (left loose during installation to allow access for the closing welds on the bellows) were fitted.
These covers were an improvement suggested by John Cardwell Limited as part of the initial proposal to protect the bellows element from any mechanical damage.

An advantage of the oversize clamshell arrangement is that it can be fitted with the system on line. On this project the first clamshell was installed whilst the plant was running; the second was fitted some time later during a planned shutdown because the gas leak was worse and use of breathing apparatus would have been necessary to work with the plant live at this location.

At all times the installation team operated within the strict site working regulations, the necessary risk assessments were made and the fitters observed all the heath and safety requirements specific to the work area including, for example, obtaining work permits and wearing carbon monoxide monitoring devices at all times.

The project demonstrates the benefit of the cooperation between John Cardwell Limited and Belman Production A/S to our customers. The proposal was made by John Cardwell Limited who attended site initially to investigate the requirement and produced the designs for the solution. Manufacture was then carried out at the Belman Production works in Denmark (the bellows forming machinery in the Cardwell plant at Stockport does not currently produce this size) and the Danish installation team completed the job.

Throughout the project John Cardwell Limited carried the responsibility for design, scheduling, Quality Assurance, safety and general project management elements and it was necessary to work very closely with both our customer and our associates at Belman to complete the job to the total satisfaction of our customer.