When a project is selected as the “Job of the Year” you know it was a unique situation that required some serious ingenuity. That’s what the Indian Institute of Trenchless Technology thought when it selected Accord Engineering of Chennai, India, for the award.
Accord Engineering is a well-respected company offering horizontal directional drilling (HDD) services that has enjoyed a stable flow of work over the years to encompass a wide range of directional drilling capabilities.
While it would have been easy for Accord Engineering to stay within its normal range of work, the company knew it needed to expand into larger-diameter projects to ensure future growth. So when the company was presented an opportunity to enter the steel carrier pipeline market, they were intrigued.
Accord Engineering has worked extensively with World Wide Machinery Solutions over the years and decided to involve them early in the process for technical advice and assistance in the project planning and bidding stage.
The company (Accord Engineering) was presented with a project that called for the installation of a 35.5-cm (14-in) steel, high-pressure gas transmission line from Chennai to Bangalore, India. Kazstroy, a Kazakhstan-based gas company, was the project owner.
Accord Engineering was asked to bid on a 680-m (2,231-ft) bore under a meandering river near Chennai. This was the largest crossing in the parcel of work, and Accord Engineering thought the project would require the use of a maxi rig, putting them at a disadvantage in the bidding process.
Working with World Wide Machinery Solutions, Accord Engineering determined that the project could be effectively completed with a 45,360-kg (100,000-lb) machine, which played well for Accord Engineering. The company had recently purchased a Vermeer D130x150 horizontal directional drill that features 59,000-kg (130,000-lb) of pullback force and 17,628 Nm (15,000 ft-lb) of torque, bringing large power to the jobsite in a relatively small and self-contained HDD package.
The project was awarded to Accord Engineering, and the company began the pre-planning process including a soil investigation that identified the soil profile as a mix of silt on top a layer of compacted coarse sand. Based on this information the bore plan was modified to drill a few meters higher than originally planned. The bore averaged 9 m (29.5 ft) in depth through a softer layer of coarse sand.
Accord Engineering used a standard duck bill drill head for the pilot bore, which took two days to complete. Once the pilot bore was finished, a 35.5-cm (14-in) compacting reamer was used, followed by a 60.9-cm (24-in) fly cutter. A fluid mixture of bentonite and polymers was used during the back reams to help hold open the hole in the sandy soil conditions, as well as carry out the cuttings.
Once the 60.9-cm (24-in) fly-cutter pass was completed, a 55.8-cm (22-in) barrel reamer was installed to complete a proving pass and reduce the viscosity of the down hole fluid. Following this pass, the barrel reamer was moved back to the pipe side and connected to the swivel and product pipe. During the pullback, a 7.6-cm (3-in) conduit was installed along side the 35.5-cm (14-in) steel, high-pressure pipe. The conduit would house a fiber-optic cable to control sensors and transmitters designed to detect potential pipeline ruptures and /or leakages. The cable was to be connected to a supervisory control and data acquisition (SCADA) system in the pipeline control room.
When the pullback commenced it was a little high on the pull pressure to start with. So the speed was reduced while the drill operator worked through the bore hole. Once the pullback pressure dropped, the operator increased the speed until they were pulling back a rod every 45 seconds. Overall the project took two weeks to complete.
Greg Ehm is a features writer for Two Rivers Marketing in Pella, Iowa.