WET News

SEPTEMBER 2016 WET NEWS 15 ONSITE TRENCHLESS TECHNOLOGY cone-shaped device that, within the outer shell, has the facility to install links to which individual pipe towing heads can be attached. However, the job was not going to turn out to be quite as simple as all that. Subsequent to the first meeting and the formulation of the design of the Multi Puller, SDL also added that it wanted to ballast the pipes in the bundle during the pull-in operation in order to reduce the pulling loads, so as to minimise stresses on both the drilling rig and pipes themselves as the installation proceeded. This was not such an easy 'ask'. What further complicated the situation was that the ballasting would not be required until the pipe string was about half way through the pull-in operation of the HDD process. Test Ends A‚er careful consideration of the range of equipment in the PESL armoury, Steve Kent, managing director of PESL, came up with the idea of using their Test Ends, which when suitably modified, could be utilised in the place of standard towing heads The Test Ends comprise a pipe end stop that can be inserted into a pipe and expanded within the pipe to both grip the inner diameter and also form a seal. The Test End normally has a valve attachment that enables water or air to be passed into the pipe and pressurised up to 16 bar. This made them ideal for the purpose required for the HDD installation. The problem was how to get them into the Multi Puller and have them work effectively as pulling heads whilst still enabling them to be used to pass ballast water into the pipes. Ultimately, the mod- ifications to the Multi Puller and the Test Ends involved, within the nose section of the Multi Puller, connecting all the test ends to the towing plate so that they were rigidly held in place. The individual pipes were then placed over the grippers of the Test Ends which were then expanded to hold the pipes in place. As an added security to ensure that in gripping the pipes they did not expand or deform at the towing end, each pipe was fitted with a stainless steel collar to offer a platform against which the Test End could seal and grip. The Test Ends were then connected together so the contractor, when putting water into just one of the 125mm diameter pipes, could fill all the pipes to the same level at TECHKNOW • The Test Ends comprise a pipe end stop that can be inserted into a pipe and expanded within to both grip the inner diameter and also form a seal • The modifications to the Multi Puller and the Test Ends involved connecting all the test ends to the towing plate so that they were rigidly held in place • The Multi Puller has the facility to install links to which individual pipe towing heads can be attached • The individual pipes were placed over the grippers of the Test Ends which were then expanded to hold the pipes in place NEED TO KNOW 1 The HDD profile was designed as a continuous curve from the entry point 2 Once the main boring and reaming work was completed, the pipe bundle was assembled and leak tested 3 To facilitate the reaming stages of the main bore, two pilot holes were drilled 4 SDL wanted to ballast the pipes in the bundle during the pull-in operation to reduce the pulling loads THE VERDICT "During the course of the project a number of day-to-day problems did arise which could have developed into something far worse but for the correct and timely response of Stockton's personnel on site" Paul Lloyd, SSE the same time. Using this design enabled the contractor to not only fill the pipes with ballast as and when required but also meant that the full length of the pipe string did not have to be welded together and laid out before the final pull-in operation could take place. Once the pull-in operation was underway, new lengths of the pipe string could be welded into place as required, with the final lengths being added just prior to the time when the ballast pumping was needed. Having connected together the pipes at the towing head, using just one of the smaller diameter pipes meant that all the pipes could be ballasted at the same time. Pull forces With this plan in place, once the main boring and reaming work was completed, the pipe bundle was assembled and leak tested and the pull-in operation commenced. The operation was successfully completed without incident with the Multi-Puller doing precisely what is was designed for. Darrel Dobbs, HDD superintendent for SDL says of the operation: "I am pleased to say that the pulling head worked well in distributing the ballast water to all attached pipelines during the pull back, and we managed to maintain lower than expected pull forces throughout the entire length of the crossing." Commenting on the new Multi Puller, Steve Kent says: "Given the complexities of the Galway project we were very pleased to be able to assist SDL with this new design of pulling head. As with many of the advances in technology with the modern industry it is o‚en a specific situation that gives rise to the development of a new piece of kit that could now aid other similar projects in the future." Following the successful completion of the project, SSE project manager Paul Lloyd says: "During the course of the project a number of day-to-day problems did arise which could have developed into something far worse but for the correct and timely response of Stockton's personnel on site. Stockton demonstrated a thorough knowledge of this field and an understanding of the critical design issues that must be addressed in order to successfully undertake a complex project of this nature. At all times Stockton's site personnel conducted their business in a safe professional and courteous manner and they were a pleasure to deal with." The Multi Puller is a cone-shaped device that has the facility to install links The Multi-Puller pipe connection design

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