TPP Technical Data - Couplings 181015 - Thomas Pipe Products · 2019-08-20 · inevitably occur...

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Technical Data forCouplings

Glossary, Design and PerformanceGuideline

TechnicalData


Technical Data

Introduction

Copyright © 2015 by Thomas Pipe Products

Introduction

Overview

Angular Deflection

Setting Gap

Pressure Forces

Pipeline Design Extras

Installation

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- Glossary of Terms - Brief History of the Mechanical Coupling - Thomas Pipe Products Complete Range - Size - Working Pressure - Temperature - Suitability - Location - How it works

- Pipe Material - Pipe Outside Diameter - Diameter Measurement - Pipe Ovality - Pipe Tolerances - Pipe Coatings - Pipe Surface Finish - Working Pressure - Operating Temperature - Chemical Resistance - Corrosion, Site & Transport Protection - Spares

- Accommodation of Angular Deflection - Lateral Displacement - Ground Settlement - Long Radius Curves

- Pipe End Thrust & Pipe Restraint - Coupling Movement Under Pressure - Movement of Step Couplings due to Internal Pressure - Restrained Products - Restrained Adaptors & Dismantling Joints

- Anchored Couplings - Cathodic Protection - Center Registers - Inclined Pipelines - Shear Strength - Pipeline Expansion & Contraction - Pipe End Preparation

Glossary of TermsOD-Pipe Outside DiameterDN-Diameter Nominal = Nominal Diameter (ND) = Nominal Bore (NB)ID-Internal DiameterWP-Working Pressure = recommended operating pressureTP-Test Pressure. Traditionally 1.5 x WP for couplingsPN-Pressure Nominal = Nominal Pressure usually stated in bar. 1 bar = 0.1 MPa = 100 kPa = 100kN/m2PCD-Pitch Circle Diameter or Bolt Circle DiameteruPVC-Unplasticised Polyvinyl Chloride (Pipe)mPVC-Modified PolyVinyl Chloride (Pipe)oPVC-Orientated Polyvinyl Chloride (Pipe)HDPE-High Density Polyethylene PE100 (Pipe)MDPE-Medium Density Polyethylene PE80 (Pipe)LDPE-Low Density Polyethylene (Pipe)DI-Ductile Iron (Pipe)CI-Cast Iron (Pipe)GRP-Glass Reinforced Polyester (Pipe)GRE-Glass Reinforced Epoxy (Pipe)AC-Asbestos Cement (Pipe)FC-Fiberglass Cement (Pipe)EPDM-Ethylene Propylene Diene MonomerNBR-Nitrile Butadiene RubberVITON-Fluoroelastomer RubberDedicated Coupling-Suitable to fit on a single specified pipe ODWide Range/Wide Tolerance Coupling-Couplings with a wide working tolerance up to 23mmCOD-Constant Outside DiameterCID-Constant Inside DiameterMachined Pipe End-Certain pipe materials exhibit a machined end to provide a uniform specified diameter pipe end to connect the pipes, such as AC pipe.Pipe Barrel-The barrel of a pipe is the section between the two prepared pipe ends.FBE-Fusion Bonded Epoxy corrosion protection coatingISO-International Standards Organization

NoticeEvery effort has been made to ensure that the information contained in this document is accurate at the time of publishing. Thomas Pipe Products assumes no responsibility or liability for typographical errors or omissions or for any misinterpretation of the information within the document and reserves the right to change without notice. All information provided is intended as a guideline for the use of products manufactured and distributed by Thomas Pipe Products. Good engineering practice should always prevail and performance limits of the products should never be exceeded. No part of this documentation may be reproduced, in any form or by any means, electronic, hard copy or otherwise, without prior written permission of Thomas Pipe Products.

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Introduction


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How it WorksMost mechanical slip-on compression couplings operate on the same principle. The basic coupling configuration consists of a set of bolts with nuts and washers (1), two end rings (2), a center sleeve (3) and two tapered elastomeric rubber gaskets (4). The center sleeve is located between the rubber gaskets which are in turn housed inside the end rings.

1. Captivated ‘D’ Cup Bolt2. End Ring3. Center Sleeve or Center Barrel4. Tapered Rubber Gaskets

The operation of a mechanical coupling is simple. Thomas mechanical compression couplings use only three nut sizes - therefore only three size spanners are required to assemble all standard couplings: - 19mm Spanner for M12 Bolts and Nuts - 22mm Spanner for M14 Bolts and Nuts - 24mm Spanner for M16 Bolts and Nuts.

Once aligned correctly, the coupling is ready for tightening. When the nuts are tightened (1) the two end rings are pulled toward each other. Note the bolts have a captivated head, i.e. the ‘D’ cup mushroom head bolt locates into a ‘D’ shaped hole in the end ring, this locks the head of the bolt so that it does not spin when the nuts are tightened. The benefit of a captivated bolt head is that the installer does not need to use two spanners - as with an ordinary hex bolt head where a spanner is needed to hold the head of the bolt and another to turn the nut.

When the end rings are pulled toward each other the rubber is compressed in to the gap between the coupling sleeve (2) and the end ring resulting in a downward force on the pipe (3). The more the bolts are tightened the greater the compression force exerted on the rubber. At the specified torque ratings the coupling will provide a leak proof connection between two pipe ends.

Technical Data


Overview


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Constant Inside Diameter pipe or CID pipes have a constant inside diameter along the entire length of the pipe. However, the outside diameter can vary. These pipes often exhibit a machined end (1) that has a smaller diameter to the central barrel (2) of the pipe length. For example a DN350mm Class 18 AC pipe has a machined end of 396mm. The barrel of the pipe bulges outward as much as 5mm bigger in diameter than the machined end = 401mm. With CID pipes it is important to know the OD of the barrel of the pipe to ensure the use of a wide range Unifit coupling that can accommodate both the machined end and the larger diameter barrel. A dedicated coupling is unable to accommodate the machined end and the barrel of these pipes.

Pipe OvalityGenerally pipe ovality should fall within 0.75% of the specified pipe outside diameter. However on large diameter pipes even this can become a large amount of ovality. Wide range Unifit couplings accommodate ovality easier than dedicated couplings due to the thicker rubber seal and wider operating tolerance of the product. Often selective bolt tightening is used to provide a uniform gap between pipe and coupling. More severe pipe ovality, up to 1% of diameter, can be rectified by ‘jacking’ the pipe. Care should be taken not to damage the corrosion protection coating.

When considering connections where ovality is known it is wiser to consult our offices to recommend alternative products such as our G-Flex Install couplings that can accommodate larger amounts of ovality.

Pipe TolerancesAll couplings provide optimum performance when it is a tight fit on the pipe. Wide range Unifit products will similarly have higher working pressures at the top end of the working tolerance than at the bottom. Many wide range couplings offer a working tolerance that overlaps either the next size above or below. It is therefore prudent to select the wide range coupling where the pipe fits in toward the top end of the working tolerance.

Example, when joining a 315mm OD PVC pipe there are two standard stock Unifit couplings available:1. TC0300 (302-318mm) - Top of range on 315 PVC2. TC0300-2 (315-332mm) - Bottom of the range. Although both will work at 16bar working pressure, the TC0300 offers a far higher working pressure on 315mm OD PVC pipe.

Technical Data

Pipe MaterialAll popular rigid pipe materials can be joined with a product from the Thomas Pipe Products range. Most commonly used are the mechanical Unifit and Large Diameter Coupling products suitable for, but not limited to the following pipe materials: steel, stainless steel, ductile iron, PVC, HDPE, Glass Reinforced Polyester (GRP), concrete, clay and Asbestos Cement (AC).

The rigid materials with high strength characteristics such as steel, stainless steel and ductile iron can be joined using our standard fitting instructions. Lower strength more pliable pipe materials may require a reduction in bolt torque rating or a different product from our range.

GRP pipe can be damaged by excessive compression forces exerted on the pipe wall, longer coupling barrels to connect further from the pipe end and reduced bolt torque values are recommended. We generally recommend our G-Flex coupling with built in self-energizing rubber seal for GRP pipe as it offers negligible downward compression force on the pipe wall.

HDPE & oPVC pipe have a tendency to be effected by creep, expansion and contraction, due to thermal and pressure fluctuations. We offer a vast range of restrained and non-restrained coupling products for joining HDPE and oPVC pipe. Long barrel couplings are offered in order to take up any initial pipe movement experienced when an HDPE / oPVC pipeline is layed, buried and commissioned. If continuous expansion and contraction is experienced, an expansion bellows should be installed.

Please contact our technical sales staff to ensure the selection of the correct product for your application.

Pipe Outside DiameterWe manufacture products that can be specified to match pipe outside diameters from DN15mm to DN3000mm. Special products can be manufactured for non-standard pipe diameters. With the exception of our Internal Test Plug, all our products connect on the pipe outside diameter (OD). It is therefore imperative that the correct pipe OD is specified at the time of quotation and order.

Diameter MeasurementExperience has taught us that the most accurate method of measuring a pipe outside diameter is with the use of a Diameter Tape. Diameter Tapes wrap around the circumference of the pipe, thus eliminating the effects of ovality. Diameter tapes are available for purchase from our sales offices.


Overview


Technical Data


Angular Deflection


COUPLING DEFLECTION INCLINATION

DN (degree)

(mm)

Up to DN450 ± 6° 1 in 10

Over DN450 - DN600 ± 5° 1 in 12

Over DN600 - DN700 ± 4° 1 in 15

Over DN700 - DN1200 ± 3° 1 in 20

Over DN1200 - DN1800 ± 2° 1 in 30

Over DN1800 ± 1° 1 in 60

FLANGE ADAPTOR DEFLECTION INCLINATION

DN (degree)

(mm)

Up to DN450 ± 3° 1 in 20

Over DN450 - DN600 ± 2.5° 1 in 24

Over DN600 - DN700 ± 2° 1 in 30

Over DN700 - DN1200 ± 1.5° 1 in 40

Over DN1200 - DN1800 ± 1° 1 in 60

Over DN1800 ± 0.5° 1 in 120

X

COUPLING MINIMUM SPOOL

DN PIPE LENGTH L

(mm) (mm)

Up to DN450 Displacemnet Y x 10

Over DN450 - DN600 Displacemnet Y x 12




Over DN1800 Displacemnet Y x 60

SPOOL PIPE LENGTH

Technical Data


Angular Deflection


PIPE MAXIMUM

DN ANGULAR

(mm) DEFLECTION 3m 6m 9m 12m

Up to DN450 6° 29m 57m 86m 115m

Over DN450 - DN600 5° 34m 69m 103m 138m

Over DN600 - DN700 4° 43m 86m 129m 172m

Over DN700 - DN1200 3° 57m 115m 172m 229m

Over DN1200 - DN1800 2° 86m 172m 258m 344m

Over DN1800 1° 172m 344m 516m 688m

PIPE LENGTH

L

MINIMUM CURVE RADIUS

Technical Data

Ground SettlementWhere a pipe an underground structure, ground settlement may occur. This can be accommodated using two step couplings with a short spool pipe. In this case, pipe trenches are excavated below the pipe invert to allow for pipe bedding. If this is bedding is to be flexible (e.g. granular fill), some settlement will inevitably occur when the trench is backfilled. To minimize bending stresses in the pipe exiting the structure, a coupling should be installed as close as possible to the structure. The two couplings together allow the spool pipe to angulate (X) taking up the ground settlement (Y). The minimum length of spool pipe (L) is determined using the Spool Pipe Length table on the previous page. The structural strength of the pipe in bending may be considered.

Long Radius CurvesCouplings can be used to enable pipelines to be laid in long radius curves to follow geographic contours or avoid obstacles. This can be done without the use of specialized high cost bends and the associated necessary thrust blocks.

With reference to the figure above and using the equation below the radius of the curve can be calculated.

Radius R = L 2 sin ½ X

Where: R = Radius of curve L = Pipe length X = Angular deflection

Setting Gap



DN PRODUCT MAXIMUM

(mm) SLEEVE COUPLINGS FLANGE GAP

LENGTH (mm) G

(mm) (mm) (mm)

≤ 200 100 16 10 32

225 - 600 160 25 20 50

> 600 - 900 200 25 20 50

> 900 200 40 30 75

Long barrel ≥ 300 Ø dependant Ø dependant Ø dependant

RECOMMENDED GAP

SETTING GAPS

Technical Data

InstallationNOTE:Follow Installation InstructionsDo not encase in concreteLeave couplings exposed for pressure testing.

Coating Hanging RingNOTE:Products may be supplied with a small ring welded to the sleeve in order to assist with hanging during the coating process, this is not a lifting eye for a complete product.

Pressure Forces



Technical Data



Pressure Forces

Technical Data

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Pressure Forces

G-Flex Gripper

PolyGrip

Restrained Products

Couplings & Flange Adaptors

EvoGrip

Dism. Joint & Rest. FA

DN20-350mmCoupling products

63-315mmCouplings & Adaptors

110-160mmCoupling products

DN50-3000mmFlanged products

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Technical Data



Pressure Forces

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Technical Data

Anchored CouplingsThomas Couplings can be supplied with an Anchoring Cradle that can be bolted to a concrete plinth, structure, bridge or base. The cradle supports the coupling center barrel / sleeve when carrying a full pipe span (up to 10m) filled with water.

An anchored coupling provides an alternative method of supporting pipes above ground. Pipelines must remain directly above the cradle and remain relatively horizontal. Anchored above ground pipelines reduce installation costs and pipe installation time.

Anchored couplings are able to withstand the thrust forces associated with the maximum allowable angular deflection of the coupling.

Anchored couplings are generally supplied with center registers to prevent pipe creep.

Anchored couplings are not designed to withstand the axial thrust forces associated with internal pipeline pressure or external pressure forces and should therefore generally not be used in conjunction with restraining harnesses.

NOTE:An engineering study should be conducted to ascertain the suitability of anchored couplings when used with restraining harnesses.

This is to ensure the anchor points of the cradle are not responsible for preventing pipe movement or restraining against internal pipeline pressure thrusts. The anchor points of a cradle are designed to support the pipeline vertically above ground level.

A suitable plinth design must be considered in order to support the pipe and the weight of a 10m length of pipe filled with water.

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1 - Cathodic connection stud on opposing pipe ends2 - Cathodic connection stud on coupling end rings 3 - Cathodic connection stud on coupling sleeve

1 - Coupling End Ring2 - Coupling Bolts3 - Chemical Anchor Bolts4 - Anchor Cradle5 - Plinth

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Center registers are normally not necessary for buried couplings as the soil prevents coupling creep. However they may be necessary in wet clay or marshy soil conditions. Center registers may be useful in critical assembly conditions ensuring the correct location of the coupling over the pipe joint. They are not suitable for step couplings due to the internal thrust forces.

Center registers are available in electro-galvanized mild steel or stainless steel in the following sizes:

COUPLING PIN THREAD

DN DIAMETER

(mm) (mm) (mm)Up to 600 10 M12Above 600 14 M16

CENTER REGISTERS

Technical Data

Effects of External & Pipeline Vibration on a Mechanical CouplingExperience has taught us that extreme and regular vibration applied to a pipeline and / or the surrounding ground can result in the coupling bolts gradually working loose.

A case study in Kalk Bay, Cape Town, revealed that DN700mm M16 coupling bolts loosened rapidly with the regular passing of a train on a nearby railroad. Many couplings were backfilled, compacted and tarred beneath a roadway within 8m of a railroad. Each of these couplings were unearthed and re-torqued to prescribed levels on 3 occasions. Ultimately the solution lay in tightening the coupling bolts with the use of ‘LockTite’ and a ‘Nylock’ nut tightened behind the coupling nut. Therefore each bolt had two nuts tightened together with ‘LockTite’.

Torquing the nuts together, prevented any further loosening of couplings.

An additional case study in Limpopo Province South Africa revealed a very similar result. Several TC0150 couplings were installed on water lines feeding a Rock Crushing Plant Segregator on a Platinum mine. With extensive vibration the M12 coupling bolts repeatedly loosened over a period of several weeks. Two nuts were tightened on each coupling bolt with the use of ‘LockTite’ and the problem was resolved.

Center RegistersOwing to continuous pipe movement from pipeline operating vibrations, temperature expansion and contraction etc., couplings installed above ground tend to creep along the pipe. This is particularly evident on inclined pipelines. If left unchecked the coupling may creep off a pipe joint resulting in pipeline failure. The most economical means of preventing this is with a fixed or removable center register.

Fixed center registers are a series of pins welded on the internal center line of the coupling sleeve

Couplings with fixed center registers can not be slipped over a pipe end. Therefore, once installed, couplings with fixed center registers can not be slid back off a pipe joint allowing a single length of pipe to be removed from a pipeline.

A removable center register consists of a threaded pin that is tightened into a threaded hole in the center line of the coupling sleeve. The center register is inserted from the outside of the coupling. The pin extends through the coupling sleeve and interferes with the pipe wall. Therefore the center register must fit between the two pipe ends. Once a center register is removed, the coupling may be slid over the pipe end exposing the pipe joint. A single length of pipe can then be removed and replaced if necessary.




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Technical Data

PRODUCT PIPE MOVEMENT

(mm)

Coupling 10

Flange Adapter 5

End Cap 5

Half Coupling 5

EXPANSION & CONTRACTION

Installation



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Technical Data

In this case there was no failure, however, it was recommended that an additional coupling be installed several meters from the flange adaptor to reduce the angular deflection to within the recommended limits.

A common installation error occurs when the installer tightens all the bolts on one side of the coupling first before tightening the bolts on the other. This is often found in trenches where the bolts on the top of the coupling are tightened and the bolts on the bottom of the coupling are not. This results in uneven rubber compression that can result in leaks. It is important to ensure the fitting instructions are followed, tightening bolts in a diametrically opposite manner, several turns at a time.

When couplings are correctly installed it is plain and clear to see the parallel end rings of the coupling. Similarly the amount of bolt thread protruding beyoud the nut on all the bolts is the same. Clearly indicating a correct tightening procedure was followed (see below).

Effects of poor installationExperience has taught us that the vast majority of mechanical coupling failures are due to poor installation. Similar to many mechanical products, if pipe couplings are not installed correctly, there exists an increased risk of failure.

It is imperative that the installer adhere to the performance limits of the coupling. Characteristics such as angular deflection, setting gap and lateral displacement are important performance limits that determine long term safe operation of a mechanical coupling. Performance limits are specified within this document and the relevant marketing material for each of our product ranges. Aside from the adherence to performance limits, adherence to fitting instructions is also important, and good engineering practice.

Coupling fitting instructions are available for download from our website:


Poor installation such as the uneven tightening of coupling bolts results in an uneven distribution of the compressive forces on the rubber seal. In extreme cases, the rubber seal may not extrude evenly between the pipe outer surface and the coupling centre barrel inner surface. Thus, resulting in a leak.

Under pressure, rubber behaves similar to a viscous fluid. It will move from a place of high compression toward a place of lower compression. Uneven bolt tightening creates uneven compression loads exerted within the rubber seal. The movement of the rubber is hence due to the uneven tightening of the coupling bolts. Once the rubber has moved, and the pipeline has settled, it is common to find that coupling bolts appear loosened. The nuts themselves have not loosened or moved, it is only that the opposing force of the rubber seal that has abated. When the coupling is loosened and re-tightened according to the correct installation procedure it is found that the coupling works as it should.

The 355mm PVC PN16 PVC pipe connection below shows an angular deflection of 6°. This is double the allowable angular deflection of 3° for a DN350mm Flange Adaptor.

6°

Parallel End Rings

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TPP Technical Data - Couplings 181015 - Thomas Pipe Products · 2019-08-20 · inevitably occur...

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Transcript of TPP Technical Data - Couplings 181015 - Thomas Pipe Products · 2019-08-20 · inevitably occur...