Tablas y gráficos

Low density polyethylene pipes shall be manufactured, tested etc. in accordance with BS.

Height density polyethylene pipes shall be manufactured tested etc., in accordance with BS 3284 and BS 3796.

Small diameters pipes shall be laid in the longest possible lengths without joints. Where joints are required these shall be butt welded using the heat fusion technique.

Pressure gauges shall be fixed on each main outside the pump house for reading the pressure in each main.

Isolation sluice valves shall be inserted in all the pumping mains just outside the pump house immediately on the downstream side of the pumping mains. Also recoil valves shall be fitted to the mains isolation sluice valves shall be provided each at one kilometer for all the mains, the diameter of all the valves are the same as that of the mains mentioned above. The diameter of washout valves shall be 100mm the washout shall be valved at their inner ends a small weep hole shall be drilled in the inverts of the washout pipes and their lower ends for drainage and the pipes nearest surrounded with one foot thickness of coarse gravel. The isolation valves shall be ½” tapped and drilled at each side of the wedge and fitted with ½” gunmetal ground plug ferrule cocks and extended to withstand the short distance of the ground surface with ½” galvanized iron pipes terminative with stop-cocks of ferrule ends for the purpose of taking pressure gauge readings. Conventional type cast iron surface box with locking lid shall be provided to the stop cocks and also to the isolation sluice valves air valves and washout valves together with a 100mm dia. pipe sleeve extending from the gland of the valves to within the surface box, the surface box shall be founded on concrete footings.

Necessary air valves shall be fitted to the mains, the first of which shall be located immediately downstream of the recoil valves hereinafter specified and thereafter at all ridges and other places as shown in drawings in the Appendix. The air valves shall be of 100mm dia. and be of the {double} kinetic type with isolating sluice valve or similar and shall be housed in water tight chambers formers formed in cement concrete work and which shall be fitted with suitable cast iron surface boxes with locking arrangement. Recoil valves as manufactured by Messrs. Glenfield. Kennedy Ltd. or similar shall be fitted to the mains. The recoil valves shall be housed in a chamber formed in concrete which shall be suitably floored and provided with manholes cover of adequate clear opening and shall be supported on a concrete stool. All valves shall be provided with tail pieces with anchoring to be built in the manhole thrust when the valve will be

closed under test pressure. Where the mains cross rivers or barrage, steel structures required on the existing weirs for this purpose and the contractor shall include in the Tender for the professional fees for the design and construction of such structures.

Where the mains cross canals and small distributor cannels meet within their alignments they shall be laid at such depth of cover as will provide a minimum of 15cm below the inverts of the distributaries and shall be graded to preclude any point where air may be trapped. The mains shall be square boxed with a minimum of thickness of 50cm of concrete of 1:2½:5 mixture at the distributor crossings and which shall be extended at a distance of 0.9m into each bank and likewise so at all road crossings. Necessary washout valves and air valves shall be fitted to the mains as shown on the drawings and other places where necessary with chambers. Where the mains cross big streams (more than 3.0m) steel structures required for this purpose and the contractor shall include in his tender the professional fees for the design and construction of such structure.

The contractor shall submit a design for approval before execution of the work. Where the mains cross roads and rail ways box culvert shall be required and shall include all cost in the total sum offender.

The work shall be executed according to the Regulations of state Organization of Roads and Bridges.

Where the mains cross Main River two No. of pipes used to be laid in the bed of the river. Thrust resisting joint type should be used to the crossing pipes. The distance between each pipe should be not less than 5m the contractor should supply all necessary valves and air valves and fittings.

Where to mains cross the canals and small distributory canals meet within their alignments they shall be laid at such a depth of cover as will provide a minimum of 15cm below the inverts of the distributaries and shall be graded to preclude any point where air may be trapped the means square boxed with a minimum thickness of 50cm of concrete of 1:2½:5 mixture at the distributory crossings and which shall be extended at a distance of 0.90m into each bank and likewise so at all road crossings. Necessary washout valves and air valves shall be fitted to the mains as shown on the drawings and other places where necessary with concrete chambers. Where the mains cross the main highway a box culvert required for each crossing and executed according to regulations of roads and bridges. As the target type water level indicator to all the elevated storage tanks will not be legible from the pump house, the Contractor shall supply and install an automatic alarm to each tank for the purpose of warning the operator when the tanks are full and the gloat valve in the tanks are closed.

ground storage tanks at site of waterworks will not be legible from the pump house, the Contractor shall supply and install an automatic alarm to each tank for the purpose of warning the operator when the tanks are full and the float valve in the tanks are closed. In principle the alarm shall be based on the increase in head which will build up in the pumping main to the storage tanks when the float valve closes, and flow in the main has ceased. A Bourdon type pressure gauge or gauges conforming to BSS 1780/1951 shall register the pressure increase and be arranged to sound an electric bell so that operator may stop the pumps. Water hammer protection of required for the pumping mains shall be ensured by cylindrical reservoir under pressure, vertically mounted, fed by electrical air compressor. The Contractor shall give with his offer full details of these protections, supported by calculations.

The Contractor should make arrangements for laying and supplying of all pipes, specials bends, air valves, washouts, fittings, etc. whatsoever required to complete the work in accordance with the Technical Specification.

Valve and penstock Actuators - Electrically Driven 1) General

Valve actuators shall be suitable for use on the nominal 3 phase power supply specified and shall incorporate motor integral reversing contractor starter, local control facilities and terminal for remote control and indication connections.