HDD Crossing Across River Ganga for City Gas distribution network 8” x 2400 m in Allahabad CityThe Ganga is the most adorable river in India and is also a lifeline to millions of people who live along its course and depend on it for their daily needs. The River is Mighty, Water Flow is fast and furious and the river width is around 1800m. During the change in course of the river oil and gas pipelines already layed under the river becomes exposed endangering the environment and safety of people. To keep the above into consideration, JV company between Indian Oil Corporation Ltd. & Adani India Ltd (IOAPL) awarded HDD work of installation of 8” dia pipeline under the River Ganga at a depth of 25 meters below the bed level to a length of 2400 meters. Installing a pipe of the given size and length in a remote village near river bank was a challenge in terms of its technicalities, placing of string on rollers but also in terms of logistics. Trenchless Engineering Services Pvt. Ltd. was awarded the entire job including Welding, Testing, HDD installation, the line.
Around The ClockAfter tuned planning and preparation, opening of ROU, villagers land problems, the project kicked off on the 13th March 2016. Given the pipeline was 2400 meters long, it had its challenges in preparing the pipe string in one single length passing over mighty highway bridge. String was then made into three parts of about 800m each. The pipeline was designed for safe Radius of Curvature for lower stresses, easy exit angle for smoother overbend and got approved from the Owners. While the Theoretical Pulling loads were only 47 Tons. TESPL’s rig spread having a pull force of 260 tons was selected for the job as torque requirements to complete pilot hole were large. Assisting the Rig was SC-300 Mud Pump having capacity to pump out 500 GPM to clean 99% sandy formations. Anticipating larger pushing loads towards the end of the crossing S-135 grade 6-5/8” drill Pipe were used for the Pilot Bore. Further, approximately 210m of 12.75” dia casing was installed in the hole to help push the pipe in the initial curvature and to facilitate easing returns flow. The pilot hole was drilled in double shift and was completed on 11th April 2016. The punch out point was 2380m and line deviation was within limits. We need to punch out on the edge of the ROU and we cannot change the deviation as there is no ROU on the right side. Initially TESPL’s planned to start using intersection technology. Even job has to be finished on war footing because of upcoming pious “Kumbha Mela”. At pipe side there were restricted ROU and road elevation immediately at punch out location. TESPL’s have but no choice to go round the clock with one side drilling. Increasing the hole and pull back was done using 14” fly cutter. The same were immediately commenced. Since enlarging the hole increases the probability of hole collapse, reaming and pull back was done on 24 hour basis in adverse site conditions. TESPL crews worked around the clock safely. Any near miss during navigation and drilling unnoticed for the most part beneath the mighty river. Vaibhav Gupta, the Project Manager and in charge of directional drilling and surveying, had complete confidence in the crew and capabilities of the equipment. “We were confident going into the job because of the experience we have with other trenchless installations in the area,” Vipin Gupta, CMD of TESPL says. “But we also had a great deal of confidence in the technicalities of IOAPL.
Staging PullbackAfter completing the pilot bore in about 4 weeks under mighty Ganges, the crew was able to facilitate completion of pull back immediately. We assembled the pipeline in three strings, on rollers. As points where there was a high elevated bridge, the pipe was elevated onto the rollers on the ramp over the pipe to give easy access to traffic on mighty bridge. Manning the 800 meter sections, there were 4 hydras, 1 backo and 1 excavator to ensure smooth flow of pipe into the ground. A high grade Bentonite slurry was continuously pumped through the hole to facilitate hole lubrication and cuttings removals. The 2380m of 8” OD pipeline along with was pulled in near friction less hole in 48 hours at a pull load of less than 40 tons including two golden joints. The speed exceeded the expectations of over the most optimistic members. Accolades from Owners, Industry, Golfers and Businesses Alike
Apart from the initial pilot hole delays because of unpredicted soil, the punch out and pull back went picture perfect.