Descripción caso de prueba de integración

Where bitumen lined pipes required with threaded and coupled joints, the thread shall have a taper thread on both the pipe and the coupling. The coupler shall be recessed in the centre to take the lining as shown in Figure 5.13.

Figure 5.13: Threaded and Coupled Joints Recessed for Bitumen Lining

(Ref: BS 534: 1990, page 12)

Mechanical joints are only permitted for cut pipe lengths, where internal cement mortar lining at joint is not possible and where movement of the pipeline is to be allowed for.

5.3.5 Fittings

Fittings are fabricated by welding together sections of steel pipe and are tailor-made which have been hydraulically tested before coating. Hence, they are considered as steel pipe specials. The end fittings produced are prepared to match those of the pipes to which they are to be joined. Steel fittings are much more costly because fabrication is labour intensive with the need to manually weld and apply cement mortar lining. Figure 5.14 shows the various ranges of fittings for steel pipe.

Figure 5.14: Various Ranges of Fittings for Steel Pipes

Long radius bend Short radius bend Gusseted bend

Plain end tee Sleeve joint tee Tee with flange

Concentric reducer Eccentric reducer Stub flange

5.3.6 Pipeline Hydraulic Design

Colebrook-White roughness coefficients (ks) recommended for hydraulic design of steel pipes for force main are as recommended in Table 5.7 below:

Table 5.7: Colebrook-White Roughness Coefficient (ks) for Steel Pipes

Mean velocity, V (m/s) Roughness Coefficient (ks,), mm

0.8 ≤V≤ 1.5 0.6

1.5 ≤V≤ 2.0 0.3

V≥ 2.0 0.15

5.3.7 Application of Pipes

The application of steel pipes for force main may subject to certain conditions and limitations as described in Section 3, Table 3.2 and Table 3.3.

Table 5.8 lists the advantages and disadvantages of the steel pipes for this application.

Table 5.8: Advantages and Disadvantages of Steel Pipes

Advantages Disadvantages

• More flexible than DI pipe.

• Polyethylene external coating makes it resistant to aggressive soils and is more reliable than PE sleeving used with DI pipe.

• Longer pipe lengths.

• Polyethylene internal coating is inert to chemical attack from hydrogen sulphide and is resistant to the maximum sulphuric acid concentrations that could be developed from septic sewage conditions.

• Less change in length with temperature variations compared with PE and uPVC.

• Hard, smooth surfaces resist scratches and impact damage.

• Better strength and safety. No corrosion, resulting in lasting durability.

• Thinner gauge material is used, resulting in lasting durability.

• Have a longer life-span, saving maintenance and replacement costs in the long term.

• If the PE internal coating is damaged to expose the steel, corrosion may result.

• Heavier than thermoplastic pipes.

• A range of fittings as required for sewer reticulation is not available.

• Careful checking for pinholes in the internal lining is required to ensure possible points of steel corrosion do not exist.

5.4 Glass-fibre Reinforced Plastics (GRP) Pipe

The design data and specifications of GRP pipes for force main are summarised in Table 5.9 below:

Table 5.9: Summary of GRP Pipe Design and Specifications for Force Main

Summary Filament Wound Pipe

Centrifugally Cast Pipe

Thermosetting resin or polyester resin Roving or woven fabrics of E-glass filaments Surface tissues

Additional material such as additives and colourants Thermosetting resin or polyester resin

Chopped strand mat of E-glass filaments Surface tissues

Aggregates and fillers

Additional material such as additives and colourants Standard Nominal Diameter 100mm to 1000mm

Standard Effective Length 3.0 and 6.0m

Jointing Method • Integral socket and spigot joint

• Loose collar joint

• Butt Joint

• Flange Joint

• DI coupling

a. Slip-on coupling

b. Stepped slip-on coupling c. Band coupling

d. Flange adapters e. Flange joints Classes

•

• Stiffness Classes (SN) Pressure Classes (PN)

Resin rich lining with superficial layers of C glass material

Standards Manufacture

Structural Pipeline Design Installation

Under special circumstances with prior approval from DGSS Approved

Suppliers/Manufacturers Refer to Table D1 and DGSS latest approval list

5.4.1 Manufacture

The material compositions and manufacturing processes of GRP pipe for force main are identical with the GFRP pipe applied for gravity system as described in Section 4.5.1.

5.4.2 Protective Coatings/Linings

The protective coatings and linings of GRP pipes for force main are generally same with those recommended for the GRP pipe applied for gravity system as described in Section 4.5.2.

5.4.3 Sizes/Classes

Nominal size (DN) of GRP pipes for force main is same with the nominal sizes for GRP pipes applied for gravity system as described in Section 4.5.3. However, the application of the GRP pipes for force main is limited for diameter up to 1000mm due to the higher pressure rating that need to be catered inside the pipe.

Pipe lengths of the GRP pipe for force main has the same value with those recommended for GRP pipe applied for gravity system as described in Section 4.5.3.

Classes of the GRP pipes for force main are defined by both pressure class and stiffness class as following:

1. Pressure – GRP pipe that classified for use under pressure is capable of withstanding internal hydrostatic pressure more than 0.5 bar. The pressure classes are referred as PN 12.5, PN 16 and PN 20 that corresponding to 12.5, 16 and 20 bar of working pressure. The pressure rating of the GRP pipe is not dependent on the wall thickness but the GRP composite through wall is the component that increases the pressure rating of the GRP pipe.

2. Stiffness – GRP pipe shall be classified according to their minimum initial specific stiffness.

This shall be referred to the preferred numbers (SN values) for nominal minimum initial stiffness in N/m² of SN 1250, 2500, 5000, 10000, 15000 and 20000. The ring bending stiffness is increased as the wall thickness of the GRP pipe is increased.

5.4.4 Joints

Jointing methods that are recommended for GRP pipes used in gravity system described in Section 4.5.4 are also can be applied for force main. The GRP pipes for force main is also compatible to be jointed with the application of DI couplings, as follows:

1. Slip-on coupling is designed for use with plain-ended pipes. It consists of a sleeve, at the ends of, which are wedge-shaped elastomeric gaskets and flanges held together by bolts as shown in Figure 5.15 below.

(Ref: BS 8010: Section 2.5: 1989, page 15) Figure 5.15: Typical slip-on

2. Stepped slip-on coupling is a special slip on couplings used to connect pipes of different