METHOD STATEMENT FOR DUCTILE IRON PIPE
1 CONSTRUCTION PROCEDURES
1.1 Preparation Work
1. The application of wayleave relaxation for the pipe will be submitted to relevant authority seeking approval (Authorities) prior to commencement of the pipe works.
2. Carry out the setting out of pipe route as specified in the construction drawing and within ROW, while setting out for pipe alignment will only be carried up upon approval of wayleave relaxation.
3. Areas where in to start permanent works shall be checked ensuring that they are ready for the said installation.
1.2 Trench Excavation
a) The trench shall be excavated by such method as allowed by relevant authority and project specification for proper installation.
b) Trench excavation shall be carried out by such methods and to such lines, dimensions and depths as per required in the specification and as shown in the construction drawing to allow for the proper construction of the works.
c) After identifying pipe crossing location, mark the alignment of pipe crossing and the alignment should approved by consultant and client.
d) Excavate along the pipe crossing trenches to the required depth and width.
e) Allowed to place excavated materials by the road-side. Excavated materials shall be carted away to a waiting lorry and transported to dump site if required.
f) Certain parts of the pipeline may be laid in ground with high water table, especially in areas adjacent to the streams, river crossings and ponds. Dewatering shall be carried out to ensure excavations and trenches dry for the pipeline installation work to be carried in a safe manner during the execution of the work.
g) The trench bottom should be place with approved sand and well compacted by small compactor.
h) Holes or pit for pipe bells should be provided at each joint but should be no larger than necessary for joint assembly.
i) Before jointing the pipe, the brick should placed pipe bottom and shall have 150mm spacing with bedding and bottom surface of the pipe.
1.3 Preparation for Pipe jointing
a) Before assembling the joint, the spigot of the pipe and interior of socket of the adjacent pipe shall both be thoroughly cleaned.
b) The gasket shall be wiped clean and flexed and then placed in the socket with bulb leading. The groove in the gasket must be located on the retaining bead in the socket, and the retaining heel of the gasket firmly bedded in its seat so that the heel of the gasket is not proud of the mouth of the pipe
c) To ensure the gasket fits evenly around the whole circumference, removing any bugles that prevent the proper entry of the spigot end
d) A thin film of lubricant is then applied to the inside surface of the gasket which will be in contact with the entering spigot. In addition, a thin film of lubricant should be applied to the outside surface of the spigot end.
e) The spigot of the pipe jointed must be aligned and entered carefully into the adjacent socket until it makes contact with the gasket. Final assembly of the joint is completed from this position.
1.4 Laying pipe
a) To deliver designated site numbers of Ductile iron pipe and handling properly at road shoulder to prevent any damage of pipe materials.
b) Cleaning the internal pipe cement lining, external bitumen wrapping and also both ends of the pipe with cloth.
c) Loading the pipe line into the trench by excavator or backhoe. The pipe should be lowered progressively into the trenches using width belt or sling. When the main is being laid downhill, for example, the pipes are occasionally laid with the bells facing uphill for ease of installation.
d) Dig a shallow bell hole in the trench bottom, lower the pipe and make up the joint. Slide the sling to the bell end and lift slightly to provide clearance to slide the encasement to the end. Small pipe can be pushed into the bell socket with a long bar. Large pipe requires additional power, such as a jack, lever puller, or backhoe.
e) After the pipe is lowered, it shall be laid in the line and level as specified in construction drawing.
f) Joint assembly is completed by forcing the spigot end of the entering pipe past the gasket, which is this compressed, until the first painted strip on the end of the pipe disappear and the second painted strip is approximately flushed with the socket face.
g) If joint is difficult to assemble, the spigot should be removed and rotated 90 degree before attempting to assemble a second time. If the joint is still difficult to assemble, the spigot should be removed and the gasket examined.
h) At times when pipe laying is not in progress, the open ends of the pipe should be closed with a watertight plug or other means approved by consultant or client. The plug should have a means of venting and, when practical, should remain in place until the trench is pumped dry. Air or water pressure in the pipeline must be released prior to removal of the plug. Care must be taken to prevent pipe flotation if the trench floods.
i) The pipes body shall sit on the brick with 2 meters interval.
j) After the new pipe line is completed, both ends capped with blank flange joint and ready to fill in water for Testing and Commissioning.
1.5 Pipe cutting
a) Where flexible joints are to be made, the cut ends must be trimmed with a file or grinder to remove the burr formed during cutting and a chamfer must be provided.
b) A Power Driven Abrasive Disc can be used and is suitable for all sizes. There is no need for adjustment to suit pipe size or to attach machinery to the pipe. The abrasive discs are fitted to suitable hand held power tools usually driven by compressed air or small internal combustion engines.
c) After cutting the pipe, check the cut end and where is found to be oval, locate and mark the major axis. Measure the length of the major axis. The ovality correction is required before jointing to ensure that the cut spigot must be chamfered.
1.6 Concrete Encasement
a) Once all the pipes jointed and laid on ground, the formwork shall be placed the both side of pipe with 150mm cover from the edge of the pipe.
b) All formworks support shall be fabricating accordingly to prevent any damage or lifted of formwork during concreting.
c) Once fabrication of formwork completed, invite client, consultant and main contractor to inspect the works before concreting.
d) Pour the concrete not more than 1-meter-high to prevent any segregation of the concrete upon approved by consultant.
e) Formwork shall be dismantling after get 7 days of compressive test result release and satisfactory by consultant.
f) Upon compressive test approved and dismantling formwork, backfill the entire area with the approved fill materials. Backfilling must follow procedure of embankment filling and its appropriate testing requirements.
1.7 Backfilling
a) Backfilling shall be use suitable materials or approved materials both side of concrete encasement until the subgrade level. The procedure of backfill including testing shall follow the specification requirements.
b) Fill materials shall be generally being placed in layer sand uniformly compacted by using plate/small compactor before the next layer is applied. Loose thickness of each layer shall not be greater than 300mm.
c) Special care shall be taken to properly compact backfill against the undersides of concrete encasement without disturbing or damaging the concrete encasement. Backfill shall be built up evenly on both sides of each concrete encasement along its entire length.
d) Backfilling shall not more than 300mm of cover has been placed and compacted.
Note: Testing and Commissioning of the pipe after all pipe crossing (both side carriageway) is completed. The testing will refer to the Testing and Commissioning Method Statement.
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