METHOD STATEMENT PLUMBING WORK

Contents:

1. Objective
2.  Scope
3. References
4. Material
5. Material Procurement, Handling and Storage
6. Assembly
7. BUTT WELD PROCESS
8. Pressure Testing

1. Objective

This method statement provides information concerning the method of construction to ensure compliance with contract requirements, drawing, technical specification and quality control to provide a successful installation, testing, and commissioning of the Installation of HDPE Domestic Pipes.

• Scope

HAC shall complete installation of HDPE pipes, testing, witness testing at the site by the engineer, testing and commissioning of the A/G HDPE domestic work.

• References

• Contract Specifications.
• Material Submittal.
• Technical Literature for Manufacturer.
• Design Drawings.
• Shop Drawings.

• Material

• HDPE pipes (HEPEISH)-SDR17-PE100 as per approved one.
• Fittings are HDPE-PE100 Segmented  Fittings
• Joints are BUTT welding Joints

• Material Procurement, Handling and Storage

• Upon approval of the material and shop drawing submittals, Contractor shall survey the QTY including fittings as per approved shop drawing and purchase the material as per project schedule.
•   Upon delivery to site, all pipes and fittings shall be stored indoor, in a clean, dry and ventilated place.

• Assembly
• Before assembly, each pipes and fittings shall be examined from damages.
• Pipe inside surfaces shall be cleaned by rags or by purging air from an air compressor before assembly.
• HDPE piping shall be butt welded in accordance with the manufacturer’s instruction in conjunction with the project specification.
• HDPE piping shall be cut square using pipe cutter or fine toothed hand saw.
• Chamfer or deburr pipe using files or sand papers before jointing.
• HDPE pipes and fittings mating surfaces shall be clean and dry before welding.
• For Above Ground Piping:
• All piping shall be supported in such a manner to maintain its alignment and prevent from sagging.
• Suspended piping shall be supported with metallic hangers of sufficient strength at maximum 3 meters interval.
• Plumber’s strap, pipe clamps and brackets shall be used for suspended piping.
  
• BUTT WELD PROCESS
• Butt welding process is a hot-weld type of welding. However, there are technical limitations for both diameter and wall thickness in this kind of linking. Linking by this kind of welding is done from minimum 5 mm wall thickness to 100 mm wall thickness for 50 mm radius to 1600 mm radius.
• During the butt weld process, the pipe butt surfaces are heated by a hot plate until they reach the welding temperature. After the heater plate is removed, the pipe butt surfaces are linked under pressure.
• Equipment Used for Butt Weld, Clamps, Trimming unit, heating unit, Hydraulic unit.
• The following processes are carried out before butt welding:· 
• The temperature of heating unit plates must be checked. 10 minutes stand-by time is required for the heat to be dispersed homogeneously
• The hot plate surface must be cleaned before every process
• The pipes must be fixed vertically and horizontally in the welding machine
• The surfaces of the trimmed pipes to be welded must not be contaminated 
•  Carrying out the Butt Weld Process
•  The environment where the welding will be done must be protected against unfavorable weather conditions (moisture, dust, low temperature, etc). Precautions can be taken such as heating the welding area beforehand or blocking the wind, the welder must be well-trained.
• The pipes to be welded must have the same properties (same type of material, same pressure, same wall thickness).
• Hot plate temperature must be between 200-220oC. Temperature must be checked periodically.
• The pipe butt surfaces must be leaned against the hot plate under low pressure. Heating pressure is kept at P<0,02 N/mm level.
• Heating time is pipe wall thickness x 10 seconds. The thickness that is formed as a result of leaning between hot plate and pipe butt surface under P=0,15  N/mm2 pressure is called lip height.
• Changing time is the time elapsed while the pipe butt surfaces are removed away from hot plate after heating process is over. Without changing time, the hot pipe surfaces get cold and welding quality decreases.
• Linking time, pipe surfaces must be linked in a very short time after changing time is over. The pressure required is P=0,15 ± 0,01 N/mm2. Cooling time under pressure must be kept at the same level under linking pressure cooling time.  

  Table: Base values under 20^o ambient temperature 

• Pressure Testing
• Fill the pipeline with water; bleed off any trapped air.
• Subject the lowest element in the system to a test pressure that is 1.5 times the design pressure, and check for any leakage (i.e. 80 psi x1.5=120 psi).
• The test procedures consist of two steps; the initial expansion and the test phase. When test pressure is applied to a water filled pipe, the pipe expands. During the initial expansion of the pipe under test, sufficient make-up water must be added to the system at hourly intervals for 3 hours to maintain the test pressure. After about 4 hours, initial expansion should be complete and the actual test can start.
• When the test is to begin, the pipe is full of water and is subjected to a constant test pressure of 1.5 times the system design pressure. The test phase should not exceed 3 hours, after which time any water deficiency must be replaced and measured. Add and measure the amount of make-up water required to return to the test pressure and compare this to the maximum allowance in the table below.
• An alternate leakage test consists of maintaining the test pressure (described above) over a period of 4 hours and then dropping the pressure by 10 psi (0.69 MPa). If the pressure then remains within 5% of the target value for 1 hour, this indicates there is no leakage in the system.