Herramientas / métodos

and printed. A printer for each fusion machine used on site shall be supplied to the S.O. for his sole use. An electronic data transfer unit suitable for use with the Butt and Electrofusion machines to transfer all joints data to a computer shall also be provided by the Contractor for the sole use of the S.O..

The full set of Automatic Butt Fusion welding machine shall comprise the following :

(a) Chassis and Clamps which are sufficiently robust to accurately align the pipe to be jointed and have insert rings to fit different pipe diameters up to 315mm nominal outer diameter.

(b) Hydraulic/Pneumatic Unit capable of actuating the clamp unit to provide adequate force and speed of operation for pipes diameter up to 315mm nominal outer diameter. The pressure required shall be automatically set and calculated by the control box.

(c) Trimming/Planning Tool capable of being mounted securely within the frame of the jointing machine, to prevent twist during trimming and planning to produce accurately matched planed surface.

(d) Electrically operated heating plate with temperature controller for a uniform temperature range of between 200 to 220 deg. C. The plate shall be uniformly coated with teflon having adequate release properties and fitted with an accurate temperature probe using a digital thermometer.

(e) Control Box designed to carry out the operations automatically for pipes diameter up to 315 nominal outer diameter with the following facilities :

(1) Automatic interlock of the entire joint cycle with correct heater temperature;

(2) Ambient temperature compensation at bead-up; nominal dwell time less than two seconds; constant monitoring of pipe slippage;

(3) Automatic monitoring of cooling cycle;

(4) Identification of real time; date; job and operator for every joint; (5) Pipe selection programme specific to material type; diameter and

SDR rating;

(6) Automatic recognition of dual pressure welding conditions for thick wall pipes;

(7) Complete data retrieval facility for all joints via a data printer or electronic transfer to comply with BS 5750:Part 1 4.9.2 on special processes;

(8) Audible alarm to alert operator at critical stages.

(f) Portable Generators of brushless alternator construction complete with voltage stability consistent with TIN-12 specification: alternator to be capable of providing a 10% overload facility. Generators to be rated to the appropriate fusion application and the equipment as specified by the manufacturer

The Butt Fusion jointing procedure shall be as follows :- (1) Cleaning of the trimming tool and the Heater plate.

The trimming tool shall be cleaned with water and lint free materials. The heater plate shall be cold when cleaned with soap and water and lint free materials. The heater plate shall be cleaned at the start of each working day by making a dummy joint. The joint shall be cut-off before actual jointing work is conducted.

(2) Trimming of pipe ends.

Before trimming, the pipe ends shall be wiped clean on both the inner and outer surfaces to remove mud or dust with a damp cloth. The pipe ends shall then be cut square to remove any embedded hard particles or stones using a universal or other approved PE pipe cutter. The pipe shall be dry prior to proceeding. The pipes shall then be positioned in the clamps with pipe makings aligned. This will assist in obtaining best match in diameter. The pipes clamps are then tightened to grip and reround the pipes. The pipe ends shall then be trimmed and planed with the trimming tool mounted onto the machine until continuous shavings are produced from each pipe end.

Bevel and clean outer and inner edges of loose shavings and check the pipe end for alignment. The pipe ends trimmed surface shall not be touched or handed to prevent contamination of the clean surfaces before fusion.

The pipe ends shall not have any visible gap when the ends are brought together. The maximum outside diameter mismatch of the pipe ends, measured by a depth gauge, shall not be more than 10% of the pipe wall thickness when the pipe ends are brought together for pipes up to 315 NOD. If the mismatch is greater, the pipe shall be realigned and replanned until permitted tolerance is obtained.

the automatic fusion cycle. All joints shall be assigned a number and shall be marked on the pipe by suitable marker approved by the S.O. and also recorded on drawings. A log book recording joints data shall be kept by the Contractor on site for the inspection of the S.O. or his representatives.

The full set of Automatic Electrofusion machine shall include the following; (1) Automatic Electrofusion Control Box capable of operating in a fully

automatic mode compatible with the integral heating elements of all electrofusion fittings for pipes up to 315mm nominal outer diameter used in this Contract. There shall be a complete data retrieval facility for all joints to be undertaken via a data printer or a data transfer unit.

(2) Potable Generator as specified for the automatic butt fusion machine. The generator shall be rated to the appropriate electrofusion application as specified by the manufacturers of the fittings.

(3) Universal main alignment and restraint clamps units with insert rings for pipe sizes up to 315mm nominal outer diameter, multi- functional for couplers, elbows and tees.

(4) Alignment and restraint underclamp bottom-loaded saddle kits and G- clamps for pipe sizes up to 315mm nominal outer diameter.

The Electrofusion jointing procedure shall be as follows:-

(1) Trimming of pipe ends square axis and any burrs removed. Check pipes and fittings for correct fit into couplers. If the pipes are found to be too oval to fit into couplers, the pipes shall be rerounded by on approved mechanical pipe rerounding tool or a straight length of suitable round pipe be fused onto the end before jointing.

(2) Clean pipe ends and prepare pipe ends with universal scraper or approved surface preparation tool capable of removing the oxidised surface of the pipe ends for length in excess of insertion depth. For tapping tees and saddles the general area in excess of the saddle base area shall be cleaned to the satisfaction of the S.O. The tool shall remove a layer 0.2 – 0.4mm thick from the outer surface preferably as a continuous strip of swarf over that length and round the pipe or for the full area of saddle base. Hand scrapers of the Harris type’ or equivalent are allowed for tapping tees and saddles.

The prepared area shall then be cleaned with acetone or other approved solvent. The prepared pipe surface shall not be handled or contaminated prior to welding.

(3) The electrofusion fittings or tapping tees shall be removed from packaging and degreased with acetone or other approved solvent prior to insertion to pipe ends or clamp onto pipe. The insertion depth is than marked by suitable marker by inserting the couplers/fittings up to the center stop.

(4) Using correct sized pipe clamps or saddle clamps, secure the pipe fittings. The alignment and gaps between the pipes and fittings shall be checked by depth gauges. The total gaps between the pipe outer diameter and fittings shall not exceed 2% of the pipes nominal outer diameter. The fittings shall be adjusted with suitable wedges, if required, to axially align the pipes centrally in the fittings.

Electrofusion shall then only be allowed to proceed after complying with the above checks.

(5) On completion, the melt indicators of the fusion fittings should appear. If there is no apparent movement of the melt indicators, the joint shall be cut out and a new joint be made.

(6) The joint shall be left in the clamps for the cooling time specified for the fittings or tapping tees.

(7) The main shall not be tap with the integral built-in cutter until the joints or saddles have been approved by the S.O.