C ONCLUSIONES

machined in the spigot. Figure 5.4 shows the typical self-anchoring bolted mechanical joints of DI pipe that can be used for force main.

Figure 5.4: Typical Self -anchoring Bolted Mechanical Joints of DI Pipe for Force Main

(Ref: BS 8010: Section 2.1: 1987 Appendix A, page 21)

5. Slip-on couplings are designed for use with plain end pipes. The coupling consists of a sleeve, at the ends of, which are wedge-shaped rubber gaskets and flanges held together by bolts. The typical slip-on coupling for DI pipes is shown in Figure 5.5 below:

Figure 5.5: Typical Slip-on Coupling for DI Pipes

(Ref: BS 8010: Section 2.1: 1987 Appendix A, page 19)

6. Self-anchoring tie-bar joints have a special loose anchor ring placed behind the socket and a special anchor ring welded onto the outer surface of the spigot. Figure 5.6 shows the typical self-anchoring tie-bar joints used for DI pipes.

Figure 5.6: Typical Self-anchoring Tie-bar Joints for DI Pipes

(Ref: BS 8010: Section 2.1: 1987 Appendix A, page 20)

Sealing materials and jointing lubricant requirements of DI pipes for force main shall follow to that recommended for gravity system as stated in Section 4.4.4.

Allowable angular deflections of DI pipes for force main application shall meet the requirements recommended for DI pipes used for gravity system, as described in Section 4.4.4.

5.2.5 Fittings

The range of fittings for DI pipes applied for force main is basically same as the fittings used for gravity system except for the tapers.

Figure 5.5 shows the additional ranges of DI fittings that can be applied into the force main, other than those listed in Section 4.4.5.

Figure 5.7: Additional Ranges of DI Fittings for Force Main

Socket-socket flange scour tee Spigot-spigot flange scour tee

Socket-spigot-flange tee Spigot-spigot-flange tee

Non-thrust dismantling joint (Ref: Power and Water – Water Supply and

Sewerage Approved Products Manual/

www.powerwater.com.my)

Thrust dismantling joints

(Ref: Power and Water – Water Supply and Sewerage Approved Products Manual/

www.powerwater.com.my)

5.2.6 Pipeline Hydraulic Design

Typical roughness coefficient, ks values of Colebrook-White equation as recommended in MSIG Volume 3 given in Table 5.3 shall be referred to when determining discharge capacity of the DI pipes for force main.

Table 5.3: Colebrook-White Roughness Coefficient, ks for DI Pipes

Mean Velocity, V (m/s) Roughness, ks (mm)

0.8 ≤ V ≤ 1.5 0.6

1.5 ≤ V ≤ 2.0 0.3

V ≥ 2.0 0.15

5.2.7 Application of Pipe

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

Table 5.4 lists the advantages and disadvantages of the DI pipes for this application.

Table 5.4: Advantages and Disadvantages of DI Pipes for Force Main

Advantages Disadvantages

• Higher beam, ring and shear strength than plastic pipes

• Not affected by UV radiation.

• Slight change in length with temperature variations, unlike plastic pipes.

• High ring stiffness permits use with very shallow cover and up to unusually large superimposed loads unlike plastic pipes.

• High beam and shear strength permits use in ground subject to substantial differential settlement

• Not subject to damage from substantial impact loads making it suitable for rail, over dimensional highway and bridge crossings unlike unencased GFRP.

• High resistance to shock or impact due to improper handling, water hammer or unstable condition.

• Able to deform when stressed beyond yield point.

• Superior tensile strength to withstand severe loads and high internal pressure.

• More expensive than plastics pipe.

• Heavier than plastics. Mechanical lifting is required.

• External polyethylene (PE) sleeving required for buried application in corrosive soil conditions.

• Care is required to ensure sleeving completely wraps the pipe and is sealed.

PE sleeving is easily damaged.

• Where sleeving is damaged in certain aggressive soils (pH ≤5 and ≥9), corrosion will occur.

• Internally less corrosion resistant than VC and plastics.

• Less abrasion resistant than plastic pipes.

• Rougher bore than plastics thus require steeper grades or larger diameter pipes.

Slime adheres more readily to DI than plastics and is less easily washed off.

• Ductile iron is corroded by hydrogen sulphide and sulphuric acid produced in septic sewage conditions.

5.3 Steel Pipes

There are two types of steel pipe approved by DGSS that can be applied as force main pipeline system, which are mild steel and stainless steel.

The design data and specifications of mild steel pipes for force main are summarised in Table 5.5 below:

Table 5.5: Summary of Mild Steel Pipes Design and Specifications for Force Main

Summary

Material Carbon steel

Nominal Diameter (DN), mm DN 100 to 2200mm

Standard Length, m 6.0, 9.0 and 12.0 m. Longer lengths are available on special request

Classes

• •

• Operating Pressure

Conform to BS 534:1990

Varies with pipe diameter, wall thickness and material grade

Jointing Methods •

•

•

•

•

Butt-welded joint Sleeve joints for welding Slip-on type coupling Flange joint

Threaded and coupled joint Protective Coating

Coal tar enamel, bitumen enamel, asphalt enamel and glass fibre.

High alumina cement mortar, coal tar enamel, coal tar epoxy, sulphate resistant cement or bitumen.

Standards Manufacture

• Approval for use from the DGSS is required

• Pipe is allowed only for sizes 600mm and above

• Pipe protection linings and coatings are required.

• Permitted for inverted siphons (depressed sewers) and internal pump station pipework.

Approved

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

The design data and specifications of stainless steel pipes for force main are summarised in Table 5.6 below:

Table 5.6: Summary of Stainless Steel Pipes Design and Specifications for Force Main

Summary

Material Stainless steel

Nominal Diameter (DN), mm DN 21.34 to 273.05m

Standard Length, m Pipe length may be specified as long as transportable.

Classes

• •

• Operating Pressure

Conform to BS 3600: 1976

Varies with pipe diameter, wall thickness and material grade

Jointing Methods •

•

•

•

•

Butt-welded joint Sleeve joints for welding Slip-on type coupling Flange joint

Threaded and coupled joint Protective Coating

• Approval for use from the Director General is required

• Pipe is allowed only for sizes 600mm and above Approved

Manufacturers/Suppliers Refer to DGSS latest approval list in Table C1

5.3.1 Manufacture 5.3.1.1 Mild Steel

Material compositions for mild steel pipes is carbon steel that shall consist of structural or analysis grade steel comply with BS EN 10025: 1993 and BS 3601: 1987.

The most common manufacturing process that can be applied to produce all sizes of mild steel pipes is by using helical winding method as shown in Figure 5.8 below.

Figure 5.8: Typical Manufacturing Process of Mild Steel Pipes for Force Main

Helical Winding

Welding

Formation of Socket

A steel strip is helically winded and continuously welded to the adjacent windings

Socket is formed on the pipe end

Hydrostatic Testing X-ray Inspection Blasting and Priming

Coating Lining

Inspection Storage

The mild steel pipes can also be manufactured using other methods of manufacturing processes that is dependent on the sizes of the pipe, such as: