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.

• After assembling the joint, pull out on the pipe to engage the locking segments.
• Prevent lateral movement on bridge crossings and piers.
• Choose non-rigid joints for underground installations.
• TR FLEX Gripper Rings are not recommended for use with fittings.
• TR FLEX Gripper Rings are not recommended for vertical bends.
• Use rubber retainers between all right- and left-hand locking segments. Bend them to fit in the gap between the segments.
• Right-hand locking segments are painted red, and marked "RH." Left hand locking segments are painted black, and marked "LH."

The standard SBR material is rated to 150°F. EPDM is rated for 200°F and Viton® (fluorocarbon) is  rated to 300°F when used for water or air.

The procedure for installing gaskets is simple.  However, a large part of the reliability of the seal depends on cleanliness of the joint at the time of installation.  Considering the variety of conditions that may be encountered in transit or at the jobsite, it would not be possible to ensure joint cleanliness if the gaskets were pre-installed by the manufacturer.  Pre-installation would also expose gaskets unnecessarily to ultraviolet exposure and even vandalism.

For mechanical joints, the gland should be slipped some distance back from the plain end of the pipe with the lip of the gland facing the bell.  The inside diameter of the mechanical joint gasket is smaller than the outside diameter of the pipe.  Brush the plain end of the pipe and the gasket with an approved pipe lubricant as supplied by the manufacturer.  The gasket must then be stretched over the plain end of the pipe with the thinner side of the wedge facing the bell.  The lubricant allows the gasket to slide more easily into the bell and become equalized as the gland compresses it to achieve a reliable seal.

The TYTON JOINT® and FIELD LOK 350® gaskets have a stiff rim called the heel bonded to a circular cross section called the bulb.  After correct installation, the heel will fit into the first groove just inside the bell.  The bulb will enter the bell first and will be compressed between the inside of the bell at the gasket seat and the outside of the pipe to achieve a seal.  The gasket diameter is larger than the bell opening, so a technique must be followed to allow the gasket to be properly fitted inside the bell.

For smaller pipe, up to about 20”, draw a loop of the gasket towards its center forming somewhat of a heart shape.  While holding the loop with one hand, start fitting the gasket heel into the groove of the bell with the other.  Gradually release the loop while pressing the gasket evenly into position around the inside circumference of the bell.  It may be necessary to firmly seat the loop with the heel of the hand to ensure it is fully seated. 

As pipe size increases, it will be necessary to use an increasing number of loops to facilitate gasket installation.  In the largest sizes, it is not uncommon to have as many as eight loops, evenly spaced around the gasket.  Regardless of pipe size, if the gasket has been properly installed, the leading edge of the rubber should be slightly below the smallest part of the bell opening all around the inside circumference.  If any part of the gasket is sticking up, it must be worked until fully seated, or the gasket must be removed and re-installed.

Once the gasket is properly seated, continue with the assembly procedure to make up the joint.

The FIELD LOK 350® gasket and TR FLEX® joint are both boltless restraints. This saves time by not having to tighten any nuts & bolts as well as preventing possible leaks where a bolt wasn't tightened.

Table 2 of the Guidelines For Use and Application list the maximum deflection for each size available. USP recommends the pipe be pulled in a straight path, however, the pipe can be deflected and “snaked” as long as the bore hole diameter is large enough so that the pipe OD is not dragging against the wall of the bore, thus causing the pull force of the pipe to be exceeded. It is for this reason why long radius or curved pulls are not recommended.

Deflection of the pipe should occur after the plain end has compressed the gasket but prior to the plain end being homed into the bell. See FIELD LOK 350® animation for complete details of assembly.

They are color coded so that you know which one is which. Just remember that red equals right (two r's) and black equals left. See TR FLEX® animation for further details. Each locking segment is also cast with a "LH" or "RH" for left hand or right hand.

SBR gaskets are readily available and are routinely shipped with each order. Gaskets made from other elastomers may require longer lead times and minimum order quantities. The comparative prices are shown below and are approximate; actual prices may vary with size and quantity.

a. EPDM – 2.5 times the cost of SBR
b. Neoprene – 3.2 times the cost of SBR
c. Nitrile (NBR) – 3.3 times the cost of SBR
d. VITON® (FKM) – 62 times the cost of SBR

The Ductile Iron Pipe Research Association (DIPRA) has developed a fact sheet titled "Gasket Materials used for Ductile Iron Pipe in Water and Sewage Service." This fact sheet provides general guidelines in specifying gasket materials for different applications. Here is an excerpt from that sheet:

Pulling back on the FIELD LOK 350® gasket causes the stainless steel locking segments to engage the pipe, activating the restraint mechanism. Pulling back on the TR FLEX® pipe puts the joint in tension as well as taking up the "slop" in the joint. If this is not done, the line will "grow" when pressure is introduced to it which could cause problems.

Yes, it is possible, but it must be done very carefully.

In a standard TR FLEX joint, the locking segment cavity and gasket seat are adjacent to each other. The joint should be retracted to engage the locking segments, a distance that will vary by size but averages less than 3/4".

In a TR FLEX Telescoping Sleeve, the locking segments cavity and the gasket seat are separated by an appreciable distance (depending on size, this can be up to approximately one foot.) Similarly, the location of the weld bead on a plain end for Telescoping Sleeve is considerably further back from the face of the plain end than on a standard TR FLEX plain end. It is these design features working together that allow the collapse and expansion of the Telescoping Sleeve while maintaining a reliable seal throughout the range of longitudinal movement.

The TR FLEX GRIPPER® is used to accommodate field cuts of TR FLEX® Pipe. The Gripper Ring takes the place of both the locking segments and the factory applied weld bead, which would be cut off on a field cut pipe.

If it should be deemed necessary to install a Telescoping Sleeve with a Gripper Ring, it is important to consider two things:

1.  Once the Gripper Ring is tightened around the pipe installed in a Telescoping Sleeve, the ability for significant longitudinal movement is eliminated.

2.  Prior to tightening the Gripper Ring, it must be determined that the pipe has not been pulled out past the gasket, which would prevent achieving a seal.

One way to do this is to measure from the face of the Telescoping Sleeve to a point approximately one inch past the back of the gasket seat. Apply a band of duct tape around the circumference of the field cut pipe with the edge of the tape closest to the face of the plain end located at the distance measured. Insert the gasket and the Gripper Ring, lubricate the gasket and plain end of the pipe and insert the plain end until the edge of the duct tape is flush with the face of the bell. After ensuring the Gripper Ring is square on the pipe, tighten the torque-limiting bolts of the Gripper Ring until the heads snap off.

If at all possible, check to be sure that the gasket is in place and fully compressed between the inside of the Telescoping Sleeve and the outside of the plain end of pipe.