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 GP flanged coupling on the pipe close to the wall, and pouring concrete around it.
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.
- Hoopexpansion: 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.
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:
- 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.
This is a special application requiring special constrained fittings and consulting.
Pullout prevention methods and devices
Unrestrained fitting should be protected from pull-out by creating a fixpoint before and after each fitting using our fixpoint clamps (see pages 57 & 58).
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 transfered through the device while bypassing the non-restrained fitting.
The pictures on page 58 show a few arrangements for a floating fixpoint device, including our fixpoint bridge (see pagess 58 & 75).
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(see drawing on page 58).
The fixpoint clamp is a standard item from Golan. It is available for all pipe diameters from 63 mm. For more details (see page 73).
The drawings show a double flared-ends connection or a double flanged coupling connection protected from pull-out by two fixpoint clamps. The solid blue lines represent a part of the construction that is not supplied by Golan.
Anchoring the pipeline along the line (for example, in case of sea outfall lines) is achieved by casting concrete on a fixpoint clamp.
A Flex Restraint electrofusion fitting by Plasson can be used to replace the fixpoint clamp.
Anchoring the end of an inclined pipeline (for example, in the case of dewatering lines) is necessary for restraining the weight of the inclined pipeline.
Floating fixpoint devices
The central mechanical fitting is protected from pull- out by two external fittings operating in tandem with two loose flanges. Before connecting the central fitting, a loose flange is mounted over the pipe and then the external fitting is mounted over the pipe, far enough from the pipe end to allow the central fitting to be mounted later.
The axial forces are transmitted from one flange to the other flange through the threaded bars. The central fitting as well as the external fittings in the picture are Victaulic connectors but they can be replaced by flanged couplers or any other type of mechanical connectors approved for Pexgol pipes.
The central mechanical fitting is protected from pull-out by two external electrofusion fittings operating in tandem with two loose flanges. Before connecting the central fitting, a loose flange is mounted over the pipe and then the external electrofusion fitting is mounted over the pipe, far enough from the pipe end to allow the central fitting to be mounted later.
The axial forces are transmitted from one flange to the other flange through the threaded bars. The central fitting in the picture is a flared end connector, but it could be a flanged coupling or any other mechanical connector.
The floating fixpoint device in this picture is called a fixpoint bridge. It has two fixpoint clamps that replace the two external fittings and the two loose flanges in the previous pictures.
The two fixpoint clamps are connected by a steel frame that replaces the threaded bars in the previous pictures. For more details (see page 75). The fixpoint bridge is a standard item available by ordering from Pexgol’s fittings catalog (see page 117).
PE100 electrofusion fittings
Electrofusion fittings are used to connect Pexgol cross-linked polyethylene pipes (for example, ISO 14531). The pipes and fitting are joined by electrofusion welding, creating a leak-proof seal. During the electrofusion process, a current is transported through a heating wire. The surrounding material (around the wire) is melted, welding the pipe to the fitting.
Service temperature for the PE 100 electrofusion fittings is limited to 40°C. For higher temperatures Pex2Pex electrofusion couplers can be used.
Golan approves and supplies the following fittings systems and installation tools: Plasson, Friatec, GF/Wavin.
Plasson Plex2Plex Electrofusion Fittings
Electrofusion fittings for high temperature working conditions
In addition to the mechanical fittings, the Pexgol system offers also a high temperature welding system. The items with the brand name Plasson Pex2Pex, are suitable for Pexgol pipes class 15 SDR11 in the temperature range from -50° to +110° and the full pressure ranges of this pipe class. The couplers are not UV resistant and should be protected from UV light.
Table No. 60.1: Plasson Pex2Pex Coupler
Table No. 60.2: Plasson Pex2Pex 90° Elbow
Table No. 60.3: Plasson Pex2Pex tees
Table No. 60.4: Plasson Pex2Pex Brass Connector
Special high temperature electrofusion couplers
When higher working pressures or pipe dimensions are required, for which Plasson Pex2Pex couplers are not available, Golan offers special high temperature electrofusion couplers. Please consult Golan’s application engineer.
Prior to using Plasson Pex2Pex fittings for the first time, please consult Golan regarding local training.
Pex-lined steel fittings consist of a steel flanged fitting lined with thick black Pex coating which extends over the full face of the flanges. This type of fitting can be used as a standard fitting such as a Tee, an elbow, or a reducer. The fittings are supplied with an external epoxy coating. Standard fittings are supplied with wall thickness of Pex layer: 3 – 5 mm for corrosion resistance and up to 10 mm for abrasion resistance.
The fittings are usually supplied with weld-neck flanges. Loose flanges are supplied on request. Shorter fittings (with slip-on flanges instead of weld-neck flanges) are supplied on request.
The elbows in the fittings catalog (page 142) are 1.5XD elbows. Long-radius (3XD) elbows or elbows with a larger radius can be supplied upon request. The minimum length of each fitting is indicated in the fitting catalogue pages 117 to 146. This length can be reduced after consulting Golan.
It is possible to order a non-standard fitting, which is a combination of standard fittings, or a standard fitting with longer legs. For maximum allowable length, consult the application engineer.
Golan supplies straight sections of steel Pex-lined pipes as well, between Pex-lined fittings, in order maintain the same ID on the line. Alternatively, Golan supplies Pexgol pipes with the same or similar ID, or Pexgol reducers to match the ID.
Brass Fittings for Pexgol Pipes Class 15 & 24
• It is recommended to install brass fittings above the ground.
If you must install them, make sure they are protected from corrosion.
• Do not connect brass fittings to steel or galvanized steel pipes or fittings. • All thread outlets are BSPT.
• NTP threads are available upon request.
Branch-off saddles are designed for side outlets of a maximum diameter equaling half of the main pipe’s diameter. They are made from plastic or metal. Plastics saddles may be installed below ground. If you must install metal saddles below ground, make sure the ground is not corrosive for brass or stainless steel saddles. Do not connect brass fittings to steel or galvanized steel pipes or fittings.
Pexgol pipes can be used with plastic saddles such as Plasson mechanical saddles or electrofusion saddles, with restrictions regarding the allowable temperature and pressure range, according to Golan’s recommendations for Pexgol pipe connections.
Golan’s metal saddles are suitable for the full temperature and pressure ranges of Pexgol pipes. Brass saddles with
threaded outlets are used for pipes from 32 mm to 160 mm diameter; see the next page for the installation of saddles.
For diameters bigger than 110 mm, stainless steel saddles with threaded or flanged outlets (according to standard requirements) are available.
All metal saddles are suitable for pipes transporting drinking water.
Saddles with internal rubber lining at the flange outlet are available for corrosive materials that might damage the stainless steel saddles. Golan supplies these saddles on special request.
Prefabricated elbows are produced from Pexgol pipes of all classes according to a proprietary process.
Prefabricated elbows with flared-ends are available in any length between the minimum and maximum values, dimension A. Prefabricated elbows with plain ends are available in minimum lengths according to dim.B.
The length of each leg of a Pexgol elbows is specified according to dimension A or dimension B in table 64.1
Each leg can be ordered with plain ends or with flared ends with or without flanges. The length of each leg can be different.
The elbows are produced with a tolerance of up to +5 degrees and +/-10 mm in length.
For full details see Fittings Catalog (page 117) where the full range of products is available.
When ordering, please specify length A or B, and describe the pipe ends. For example:
ELB16014.6-453D one leg 550 mm with flared end and flange ASA 150, the other leg 420 mm plain end.
The weight of the elbow is calculated by adding the A or B values of the legs, dividing them by 1,000 (to get the total length of the elbow in meters) and then multiplying by the weight per meter of the pipe according to the pipe dimensions tables.
Table No. 64.1: Dimensions of Pexgol elbows
* Available upon request
- Elbow length also includes a straight section to make connection to the elbow easier.
- The dim.A is the length of the elbow with a flared end & flange.
- Elbows with a plain end (for electrofusion or mechanical connector) are available with a shorter length according to dim.B.
- Elbows with longer dimensions A or B are available by special order (after coordination with Golan Plastic Products).
- Larger or smaller radius elbows are available by special order. Elbows with angles not according to standard are available by special order.
Flared End Connectors
The ends of the Pexgol pipe are heated and then flared by a proprietary process, performed at Golan Plastic Products. The final pipe end is similar to a stub end. Flared ends can be also be made at the ends of Pexgol elbows, reducers, etc.
The loose flange is usually mounted over the pipe at Golan during the flaring process. Alternatively, split flanges can be supplied and mounted later. The flanges are available according to table 72.1 Flanges that conform to different standards are available by special request. Detailed drawings of flanges are supplied on request. Plastic coated flanges are available on request.
Pexgol flared end pipes are available in lengths according to customer specifications. They are also available in lengths of 5.80 m to fit into 20 ft containers or in lengths of 11.80 m to fit into 40 ft containers. The elbows with flared ends are available from our catalog according to specified length. Pexgol flared end pipes are available in minimum lengths according to table No. 65.1.
Table No. 65.1: Length (L) for Pexgol stub end
The straight sections with flared ends are produced with a tolerance of +/- 10 mm in length. The elbows with flared ends are produced with a tolerance of up to +5 degrees and +/- 10 mm in length
The catalog number in table No. 65.1 represents a Pexgol stub-end that is a Pexgol pipe class 15 spool with a standard length of 500mm and with a flared end on one side. For example – FLA16014.6 means pipe section 160 mm, wall thickness 14.6 mm, and length 500 mm. For sections shorter than 500 mm, use the length L in the table.
If a different wall thickness is required or a longer section is required, or flared end on both sides, or the section should be supplied with loose flanges, please specify according to the following example:
For a pipe section 160 mm, wall thickness 14.6 mm, length 2500 mm with one flared end & flange – FLA16014.6 2500 mm with flaring and flange ASA 150 on one side.
Please refer to our fitting catalog where the full range of fittings is available.
Pexgol Short Sections with two Flared Ends
The following table lists the lengths of short flared ends Pexgol sections.
The A length is relevant for short sections which are supplied with regular flanges.
The shorter B length is applicable for short sections which are supplied with split flanges that can be mounted after the short section is flared.
The short sections with flared ends are produced with a tolerance of +/- 10 mm in length.
Table No. 66.1: Dimensions of Pexgol spacers
Extra-thin Pexgol Spacers
Pexgol spacers are supplied in any width up to 50 mm.
Pexgol Spigot Reducers
Pexgol concentric spigot reducers are available according to the following table. Other sizes are available by special order. The working pressures and temperatures of the Pexgol spigot reducers are the same as for the d1 side of the reducer. Table 67.1 lists the dimensions of standard spigot reducers. The sizes in the table are a partial list only, and other sizes are available on request.
When using the Spigot reducers to connect them with electrofusion couplers, the end user can shorten lengths L1 or L2.
Table No. 67.1: Dimensions of Pexgol spigot reducers
Pexgol Reducers with Flared Ends and Flanges
The working pressures and temperatures of the Pexgol spigot reducers are the same as for the d1 side of the reducer. Pexgol reducers are supplied with flared ends, with or without flanges. If supplied without flanges, use split flanges that can be installed later by the end user.
The split flanges can be supplied by Golan or by the end user.
The maximum length of each flared end is specified as L1 or L2 according to table 65.1 or any length down to the minimum length L in table 67.1.
The reducers with flared ends are produced with a tolerance of +/- 10 mm in.
Pexgol Special Reducers/Adaptors
Golan supplies special reducers for individual projects.
- Reducers to match the inside diameter of Pexgol pipes to steel pipes or pipes made from other materials.
- Adaptors for Pexgol pipes with the same ID and different OD.
To order the Pexgol special reducers/adaptors, please consult Golan’s application engineer.
Spacers which are installed between Pexgol pipes and butterfly valves to allow the opening of the valve
Pexgol Instrument Tees & Water Flushing Ports
Pexgol Instrument tees & Water flushing ports for all Pexgol pipe sizes are available.
They are installed between two adjacent flanges.
The inlet is made of 316 stainless steel. Other corrosive resistant materials can be specified on request.
The inlet is available as 3⁄4" or 1⁄2" female thread. The inlet is available as 1", 3⁄4" or 1⁄2" male thread.
To order Pexgol special reducers/adaptors, please consult Golan’s application engineer.
Pexgol Single/Double Sided Orifice
Golan supplies this accessory according to the client design with one or two connecting points.
Flanged Couplers for Pexgol Pipes
Available in sizes from diameter 63 mm to 710 mm.
The couplers can be used for the full range of temperatures and pressures, the same as Pexgol pipes. Pexgol flanged couplers consist of either two halves or four quarters depending on the pipe size. The body of the coupling is made of Spheroidal cast iron GGG40 (ASTM A-536). The inner surface of the coupling has special stainless steel teeth.
These teeth penetrate into the pipe wall during tightening of the coupling and provide good anchoring onto the pipe, preventing the pipe from pulling out from the fitting. The flanged couplers are supplied with an integral gasket and bolts for connecting the two halves or four quarters.
The gasket seals between the coupler and the pipe, and also between the coupler and the opposite flange.
The gasket is designed so that the coupler does not come into contact with the liquid flowing through the pipe.
The standard gasket is made of EPDM; other materials are applied according to special order. The flange has oval holes designed to fit most international standards; see table 69.1.
Installing the coupler is simple and easy:
Place the gasket on the pipe.
Open the screws and apply anti seize lube.
Place the coupler around the pipe and tighten the screws equally. Recommended: use of electric rattle guns
For connecting two flanged couplers use Table 71.1 if needed.
A complete installation manual is available upon request.
Table No. 69.1: Compatibility with international flange standards
Table No. 70.1: General dimensions of flanged couplers and bolts for connecting 2 quarters of coupler
Table No. 71.1: Bolts for connecting 2 flanged couplings
Compatibility of Pexgol Flanges
Table 72.1 describes the compatibility of each flange. Useful dimensions are also presented in the table. The flanges were designed to be compatible with most existing flange standards. Therefore, most of the bolt holes are oval and slightly oversized.
Complete drawing of flanges according to any required standard are prepared on request. Flanges according to other flange standards can be supplied by special order. Split flanges of all flange standards are supplied by special order.
Table No. 72.1: Compatibility of Pexgol flanges
The fixpoint clamp (FPC) is made of steel with internal gripping teeth made of 316L stainless steel. The FPC is painted with a base paint that withstands welding.
The lower part of the clamp can be welded to the construction bridge (before installing the pipe) or it can be connected by screws. The distance between one adjacent pipe to the other is determined according to the width of the FPCs; see table 73.1.
Affix natural pipe bends with fixpoint clamps before and after each elbow. For pipe diameters of 280 mm and larger, support the natural pipe bends in the centre in addition to the two fix points noted.
Table No. 73.1: Dimension table of fixpoint clamps
Pexgol pipe behavior at high temperature
Pexgol pipes have a tendency to elongate considerably when exposed to sunlight due to a high thermal expansion coefficient which is typical for plastic pipes. With increasing temperatures, the elastic modulus of the pipe decreases so the developing stress is not high.
When placing Pexgol pipe over pipe bridges, the thermal expansion is reduced by the use of suitable fixtures so that the pipe will develop internal stresses which do not cause any damage. There is no need to use expansion joints!
Pexgol pipe behavior at low temperature
When the ambient temperature drops below 20°C, the tendency to axial contraction could create axial stresses in the pipe. These stresses are absorbed by the pipe without causing damage (stress relaxation).
Minimum service temperature is -50°C.
Determining the maximum distance between two guiding clamps (see page 102 & table 102.1)
Max. force at the fixpoint clamps
Determining the maximum force at the fixpoint clamp pipes in above-ground installations are subjected to temperature variations which induce axial thermal movements: contraction or elongation.
These axial thermal movements are partially balanced by external friction between the pipe and the construction.
If a pipe is restrained with fixpoints, they will tend to restrain these thermal movements. As a result, these fixpoints will be subjected to axial forces which are balanced by axial thermal stresses inside the pipe’s wall.
The axial thermal stresses can be calculated by the following formula:
- Sigma = E x A x ∆T where:
E is the relevant ( short term or long term) Modulus of Elasticity.
- A is the coefficient of Thermal expansion or contraction
- ∆T is the temperature difference.
The values of the Modulus of Elasticity and the values of the coefficient of Thermal expansion or contraction are temperature dependent and so are the values of the axial thermal stresses.
The highest values of the thermal stresses occur during the relatively short stage of temperature changes and therefore they involve the short term Modulus of Elasticity. These initial Short term thermal stresses in the pipe decrease with time due to Stress relaxation.
Theses Long term stresses are usually low and therefore they are of no concern for the Pexgol pipe itself.
However, the initial high forces are transmitted through the fixpoints to the metal construction and they can damage it.
Since the axial forces in the fixpoints and the metal construction are equal to the axial thermal forces in the pipe, it is easier to calculate directly the axial thermal forces in the pipe.
The axial thermal forces in the pipe can be calculated by multiplying the thermal stresses by the pipe cross section. It is recommended to design the metal construction based on the max. theoretical axial forces.
The values of max. theoretical axial forces are calculated assuming that the friction forces between the pipe and the construction are negligible.
The worst case scenario is when the pipe is installed in a certain ambient temperature T1 and then the temperature is going down to a lower temperature T2.
As the temperature is going down, the tendency of the pipe to contract is balanced by tensile forces in the fixpoints.
The following Table 73.1 presents the values of the initial Short term thermal stresses as a function of the design temperature.
Table No. 74.1: Initial short term thermal stresses vs design temperature
These values are valid for a temperature difference of 10°C.
The following calculation example illustrates the way to calculate the Axial forces in the fixpoints.
A Pexgol pipe OD 280mm Wall thickness 25.4 mm SDR 11 was installed in an ambient temperature of 40°C.
The design temperature in this case is 40 + 20 = 60°C
In winter the temperature drops down to -30°C. The design temperature in this case is -30°C
The axial forces in the fixpoints are calculated by adding the values of the thermal stresses for the temperature range between + 60°C to -30°C, and then multiply them by the cross section of the pipe.
The sum of the values of the thermal stresses from Table 74.1 is 7.72 MPa:
Sum of the values: 7.72
The cross section of the pipe can be easily calculated from the Formula: A = 3.14 x (D-T) x T
For OD 280 mm Wall thickness 25.4 mm the pipe cross section is 3.14 x 254.6 x 25.4 = 20,306 mm2
The axial forces in the fixpoints: 20,306 x 7.72 = 156762 N = 15.67 ton
Large side deflection might be expected in the event of a malfunction, but there is no risk of possible damage due to one pipe “leaning” on its neighbor or rubbing against it.
Guiding camps for Pexgol pipes
The Pexgol pipe’s tendency to “snake” is reduced by putting bars on both sides of the pipe to limit sideward deflection. Alternatively, using guiding clamps (GC), which are conventional clamps (FPC) without the internal gripping teeth, is recommended. The pipe can freely slide through in the axial direction but not sidewards.
Pullout protection of end couplings and other fittings
To ensure the pull-out resistance of certain fittings, do not lay the pipe perfectly straight, but rather with some surplus length (slack). In case of short pipes (up to about 10 meters), or in case of installations on pipe bridges (where it might be difficult to leave slack in the pipe), there should be a pull-out protection device such as a fixpoint clamp before and after every fitting.
This applies to some of the fittings; depending on the application design guidelines. If the pipe is installed in a an inclined or a vertical position (for example – in dewatering applications) and common fixpoint clamps cannot be used, the fitting should be protected by a floating fixpoint device such as a fixpoint bridge.
See table 75.1 and pages 58 & 85.