FIELD LOK 350® gaskets cannot be used for bridge crossings. The FIELD LOK 350® gasket is a friction restrained joint and due to the fact that bridges are subject to vibration from vehicles traveling over the bridge, there is a possibility that the gasket could work itself lose. U.S. Pipe's recommendation for bridge crossings is TR FLEX® pipe.

To install the gasket correctly in the groove in the bell, it must be uniformly distributed around the interior of the bell circumference. To do this, the gasket must be looped as it is initially placed in the bell. As a general rule:

4" through 12" gaskets generally require one loop. In cooler weather it may be easier to install the 10" and 12" gaskets using two loops placed at the twelve and six o'clock positions.

14" through 20" gaskets generally require two loops but three may be necessary, placed at the twelve and six o'clock positions.

24" through 36" gaskets generally require four loops, spaced approximately 90° apart. Put the bottom loop in first to prevent debris from being introduced into the joint.

42" and 48" gaskets generally require six loops, spaced equally around the circumference of the bell. Put the bottom loop in first to prevent debris from being introduced into the joint.

54" through 64" gaskets generally require eight loops, spaced equally around the circumference of the bell. Put the bottom loop in first to prevent debris from being introduced into the joint.

In cooler weather, it is usually a good idea to warm the gaskets before trying to install them or store them in a warm environment.

Never lubricate the gasket or gasket groove prior to installation of gasket into the bell.

No. Usually, a pipeline flowing constantly maintains a fairly even temperature. TR FLEX® Pipe should always be extended at installation to engage the locking segments which provide joint restraint. When the joint is properly extended, there is sufficient clearance between the face of the pipe plain end and the back of the adjoining bell to accommodate slight changes in length due to thermal effects.

If a TR FLEX Telescoping Sleeve is installed above ground, internal pressure will usually extend the sleeve to its maximum length. In the case of a bridge crossing where the ends of the pipeline are usually fixed, the increase in length often causes the pipeline to snake. A zigzag pipeline is not only aesthetically not pleasing, it can also result in over-deflection at the joints.

The exception to this recommendation is where a pipeline is to cross a lengthy bridge that has been constructed in sections such that the roadbed has expansion joints between sections. Provided the individual pipe on each section are given adequate vertical and lateral support, it may be desirable to add a TR FLEX Telescoping Sleeve at each bridge expansion joint so that the pipeline can accommodate significant movement fo the roadbed.

Understand that if the earthquake is sufficiently large, Mother Nature will always win. However, studies performed after several recent major earthquakes (Kobe, Japan - magnitude 6.9 - 1995, Northridge, CA - magnitude 6.7 - 1994, and Loma Prieta, CA - magnitude 7.0 - 1989) show that ductile iron piping systems suffered significantly less damage than other piping materials.

TR FLEX Telescoping Sleeves and XTRA FLEX®  high deflection fittings have often been used to cross fault lines to increase the survivability of the pipeline. When used for this purpose, the Telescoping Sleeve is installed only partially extended. A dirt boot of polyethylene encasement is taped securely to the sleeve and the mating pipe to prevent dirt from being forced under the gasket and breaking the seal. The pipeline must be carefully backfilled and compacted before applying any internal pressure. This ensures the sleeve will remain partially extended and only move with significant earth movement.

Depending on size, a TR FLEX Telescoping Sleeve that has been installed only halfway extended can accommodate up to one foot of expansion or contraction of the pipeline. This ability to expand/contract coupled with the ability of a standard TR FLEX Joint to deflect up to 5° or an XTRA FLEX Fitting to deflect up to 20° allows the pipeline to survive significant lateral movement when subjected to earth shear.

Yes. The TR FLEX® joint is easily disassembled by following the assembly instruction found in our TR FLEX® Pipe and Fittings brochure. The FIELD LOK 350® gasket requires a disassembly kit that can be purchased through your U.S. Pipe Representative.

Yes, wrapping the TR FLEX® telescoping sleeve and TR TELE FLEX® coupling will prevent dirt from becoming impacted in the joint, and could prevent movement.

U.S. Pipe's primary method of thrust restraint are restrained joints.

A column of liquid moving through a pipeline has momentum or force that tends to separate the joints at changes in direction (bends and tees), stops (plugs, caps, or closed valves), and changes in size (reducers). Some means must be used to prevent joint separation to maintain the integrity of the pipeline. Three such means are thrust blocks, tie rods, and restrained joints.

Thrust blocks are usually poured-in-place concrete.  They must be engineered with full knowledge of the pipeline operating characteristics and of soil type and bearing strength. They must bear against virgin soil, because thrust forces in the pipeline are transmitted through the thrust block to the soil.  Depending on these conditions, thrust blocks can be quite massive. The use of thrust blocks can delay completion of the project to allow the concrete to cure adequately before applying test pressure to the pipeline. If future construction disturbs the thrust block or the surrounding soil, joint restraint and the integrity of the pipeline can be jeopardized.

Tie rods usually involve some sort of fabricated steel harness on either side of the joint held together by tie-rods. This type of joint restraint is generally labor intensive. A tie-rod type of joint restraint must be adequately protected against weakening by corrosion, or else the joint restraint and integrity of the pipeline can be jeopardized.

Restrained joints are designed to hold the joint together against a rated pressure while the pipeline transfers the thrust force to the surrounding soil envelope. In order to calculate the footage of restrained pipeline necessary for the thrust force to be fully dissipated to the soil, it is necessary to know pipe diameter, maximum anticipated internal pressure, depth of cover, soil type, and trench construction type, as well as the configuration (e.g., bend angle) requiring restraint. The calculated restrained footage must be installed on each side of the fitting. Since polyethylene encasement for external corrosion protection reduces the friction between the pipeline and the surrounding soil, the calculated restrained footage is usually multiplied by a factor of 1.5 for pipelines where polyethylene encasement is to be installed.

Mechanical joint retainer glands, both common and proprietary design, are available for use where such devices must be used (e.g., a special valve or meter). However, U.S. Pipe does not recommend their use. Restrained push-on joints manufactured by U.S. Pipe are less susceptible to external corrosion, offer appreciably more deflection, and are much less labor-intensive to install.

While other manufacturers are licensed to manufacture the TYTON JOINT® through 24" diameter, only TYTON JOINTS® conforming to current joint configurations which allow 5 degree joint deflection are applicable with FIELD LOK 350® gaskets.

It is recommended that restrained joint carrier pipe be pulled through a casing. This will ensure that the restraining device is engaged and that all of the slack has been taken out of the joint.

Yes. This is why we have come up with an in the field restrained joint called the TR FLEX GRIPPER® ring (4"-36" only). Larger sizes will have to use the TR FLEX® weld kit or factory made closure pieces.