Large Diameter PE Laterals: The Supraflow Solution
In the US, distribution companies add Polyethylene (PE) branch connections, services, and by-passes without dramatically restricting gas flow by using hot tapping equipment or installing 3-way tees by squeezing off the main. These current methods perform the job but have their disadvantages such as limited flow capacity, expensive equipment, complicated procedures, risking PE pipe stress cracking, large excavations and labor-intensive.
Current PE Lateral Installation Choices
Installing a 3-way tee provides no flow restriction. Although, the gas must be stopped using multiple squeeze-offs in order to fuse a 3-way tee in-line with the main. The squeeze-off procedure creates a few concerns with larger diameter PE pipes such as:
- Possible need to install a temporary bypass adding labor and material cost.
- Susceptible damage to existing PE pipe at the squeeze points, decreasing pipeline integrity.
- Large excavations are required which increases reinstatement cost.
- Very large squeeze-offs require lifting equipment to maneuver in place, adds to job site mobilization cost.
- Squeeze-off may not completely stop the gas, creating a dangerous work environment.
High-Volume Tapping Tee (HVTT)
The high-volume tapping tee (HVTT) with an Electrofusion (EF) saddle and a self-contained wind-down cutter are one of the easiest fittings to install a lateral connection. However, these tees are only available in 2” and smaller, restricting flow compacity for laterals requiring a high volume of gas. Also, HVTT typically does not have the installation flexibility to accommodate a variety of pipe configurations due to its preferred upright installation position.
PE Saddle Hot Tapping
Large PE lateral branches are most commonly installed by hot tapping through a 2”-8” fused branch saddle using specialized equipment. Some examples include the McElroy Hot Tap tool, T.D. Williamson SHORTSTOPP system and the M.T. Deason POLYTAPP. These systems require a lateral shut-off valve. The drill shaft and cutter travel through the valve to create the tap into the sidewall of the main. However, these procedures have many laborious steps to complete and typically performed by a specially trained crew. The method also requires a large excavation, adding expensive reinstatement costs. Once the tap is complete, the drill shaft is retracted, valve is closed and equipment is removed. Pipe connections are completed. Though, the connection between new pipe and valve cannot be air tested prior to energizing the new lateral. Since air testing against a live valve is typically against procedures, this method introduces an untested connection into the system.
Supraflow Tapping Tee
New to the USA, the Supraflow Tee is a fitting and tapping procedure for installing live 4”-8” branch connections gas-free at high pressure on large diameter PE gas mains without squeeze-offs or disrupting the gas flow. All can be done in a small 3′ x 3′ excavation. Solving many of the drawbacks inherent to the other methods outlined above.The Supraflow developed by Grupo Torre in Barcelona, Spain, around 2010 was in response to growing concerns in Europe over the lack of cost-efficient large diameter PE hot tapping systems. As well as safety issues over the potential damage that squeeze-off causes to PE pipes. Over 9,000 Supraflow tees have been installed in Europe for outlet diameters of 90 mm-160 mm (3”-6”). In recent years, a few major gas utilities in the US, such as CenterPoint Energy have begun to use the tee for branch connections up to 8″ diameters.
The Supraflow fitting can be used with any currently approved branch saddle fitting, making it easily compatible with any company’s pipeline system. It is an intrinsically safe solution for main connections, high flow services and large diameter by-pass installations for 4”-8” branching on 4”-18” PE mains operating up to 150 psi. Tapping is simple and quick using Supraﬂow’s ultra-light drilling equipment. Its exclusive tubular cutter retains the coupon and shavings preventing them from entering the main. The Supraflow is as easy to install as a HVTT, without restricting flow and without the hassle of complicated equipment or squeezing off. The fitting saves money and enhances safety when expanding the PE system with large PE branch connections.