FAQ: Can the same TR FLEX® joint be used for HDD and Pipe Bursting applications and how are the locking segments held into the bell without falling out?
Yes, the same standard TR FLEX® joint is used for HDD and Pipe Bursting. A slight modification of how the rubber retainer is inserted into the cavity is the only difference between standard and trenchless use. The following is a description of the process and detailed instructions can be found in the Trenchless Pipe brochure.
Once the locking segments are installed, the rubber retainer is trimmed to about 5/16" longer than the handle width between the right and left locking segments. Then it is driven in between the segments to the back of the segment cavity; the compresison of the rubber holds the segments into their proper position. The pulling action of pipe extends the joint moving the weld bead into contact with the segments, thus locking the segments into place. The rubber-retainer(s) are only required to hold the segments in place until the joint is extended and serve as a safeguard to keep the segments in place. The 30" - 36" HP LOK® joints use a ductile iron ring that only requires tightening after the joint is made.
FAQ: What type of pulling head can be used with TR FLEX®?
Pulling heads have been made by cutting off a TR FLEX® bell with approximately 12-inches of pipe extending and fitting a steel fabricated cone with “I” hole over the pipe. The assembly is then drilled and bolted with the bolt heads welded to the cone. USP is presently in the process of developing pulling-heads but are not ready for market yet.
FAQ: How should the pipe be wrapped if rock is encountered in the bore path?
Double poly-wrap is recommended either with the first layer being the low-density poly with high-density over the outside or double wrapped with low-density.
FAQ: How much pipe can be pulled at one time?
This depends on many factors such as mud viscosity, borehole stability and diameter, friction coefficient, drill rig size and strength, etc. Formulas for estimating the pull force are estimates; One reason drillers and pipe bursting personnel experience lower pull back forces with Ductile Iron is because only a small portion of the bell can contact the environment it is moving through - the barrel of the pipe is smaller in diameter and does not make contact. Poly-wrapping the pipe can also decrease the pulling force. 1000 to 3000 - foot/pulls (depending on size) are common with Ductile Iron pipe.
FAQ: How much can the pipe be deflected?
The full allowable pipe deflection for each joint is listed in Table 1 of the Trenchless Pipe brochure. However, the industry standard for a curved or radius pull is to limit the radius to half of the deflection capability of the joint. This stipulation as well as drilling the borehole to 1.5 times the bell diameter for curved bore paths, ensures that the pipe will not become wedged in the borehole.
FAQ: How much time does it take to assemble a joint using the "Cartridge Method"?
4" - 20" TR FLEX® Pipe joints take about 15 seconds to assemble with the 24" TR FLEX and 30" - 36" HP LOK® joints taking 1 - 2 minutes.
FAQ: Where can TR FLEX GRIPPER® Rings be used?
Gripper Rings can be used to complete closures and are not recommended for use in the pullin/pull back process.
FAQ: What type of polyethylene should be used with HDD applications?
C105/A21.5 Type 1 - linear low density polyethylene film with a minimum thickness of 8 mils, or Type 2 - high-density, cross-laminated polyethlene film with a minimum thickness of 4 mils.
FAQ: What benefit does spiral winding the tape along the barrel of the pipe provide?
Spiral winding is easier to do in a muddy trench and also does not allow the drilling mud to build up underneath the poly-wrap causing it to balloon. All over-lapped edges of the poly-wrap should be taped except for the over-lapped poly along the length of the barrel, where the spiral winding is sufficient.