NON-RESTRAINED FITTINGS AND PULLOUT PREVENTION TECHNIQUES

Buried Pexgol pipes and their approved fittings are self-restrained and require no thrust blocking.

Thrust blocks are used to support fire hydrants. Concrete pads are used under metal valves to reduce settlement. Anchor blocks are used when a Pexgol pipe is to be connected to other pipe materials that use bell and spigot connections unless these connections are themselves restrained to prevent pullout.

Generally, it is necessary to anchor the ends of a Pexgol pipeline that transitions into an unrestrained joint pipe system.

Design of wall anchors and thrust blocks

A typical anchoring technique is installing a fixpoint clamp or a Pexgol flanged coupling on the pipe close to the wall, and pouring concrete around it.

Non-restrained fittings

A different situation occurs in certain applications where axial forces which are present in the pipe may pull out the pipe from non-restrained joints.

The axial forces may be a result of the following:

  • Thermal deflection (contraction) due to temperature variations
  • Ground movement and earthquakes
  • Hoop expansion: The internal pressure hoop expands the diameter (ever so slightly) and tends to contract the pipe length in proportion to Poisson’s Ratio.

In dewatering or borehole applications, additional longitudinal forces might be present due to the weight of the pipeline, the weight of the water column, or pump weight. These axial forces could result in pulling out the pipe from a gasket joint or a complete pulling out of the Pexgol pipe from the fitting.

Buried applications

All Pexgol’s fittings that are approved for buried applications are considered as restrained connections and they do not require any pull-out prevention method in buried applications.

Above ground applications

For the applications of horizontal pipelines and inclined pipelines (including dewatering lines) with a slope of up to 40°, the following fittings are restrained by the ground and therefore are considered as restrained connections and do not require any pull-out prevention method:

  • Electrofusion fittings
  • Hela bolt connectors
  • Branch-off saddles

The following fittings are considered as unrestrained connections for above ground applications, and they require a pullout prevention technique:

  • Electro fusion fittings
  • Hela bolt connectors
  • Branch-off saddles

The following fittings are considered as unrestrained connections for above ground applications, and they require a pullout prevention technique:

  • Flanged couplers
  • Pexgol flared end connectors
  • Victaulic PE couplers
  • Aquafast couplers

For dewatering applications and inclined pipeline with slope over 40°, all Pexgol fittings are considered as unrestrained connections, and they require a pull-out prevention technique.

Borehole applications

This is a special application requiring special constrained fittings and consulting.

Pullout prevention methods and devices

Fixpoints: Unrestrained fitting should be protected from pull-out by creating a fixpoint before and after each fitting using our fixpoint clamps.

Floating fixpoint device: In some applications (like Dewatering or inclined pipelines) it might be costly or problematic to install fixpoints in the line.

In that case, if you have of a non-restrained fitting which requires a pullout prevention device, it might be easier to replace the two fixpoints by a floating fixpoint device.

A floating fixpoint device is actually two restraining fittings that are installed before and after the non-restrained fitting. Restraining a non-restrained fitting is achieved by connecting two restraining fitting so that the axial forces can be transferred through the device while bypassing the non-restrained fitting.

In cases of industrial installation over pipe supports, it is usually feasible to use the fixpoint clamps as pull- out prevention devices. However, in cases where the Pexgol pipe is connected to a steel pipe by a non- restrained fitting, it might be convenient to use the fixpoint bridge and install one clamp directly on the steel pipe. Alternatively, a combination of a back-flange and a fixpoint clamp can be used together with the existing steel flange.

Fixpoint Instructions

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