High-density polyethene pipe for sewerage
1996 Edition

According to the standard, HDPE pipes are to be manufactured from resins conforming to IS 7328:1992, primarily using grades PEEWA-45-T-006 or alternatively PEEWA-45-T-012 with a melt flow rate (MFR) not exceeding 1.10 g/10 min. The MFR must lie between 0.20 and 1.10 g/10 min and be within ±30% of the resin’s MIFR. The material grades include PE 63, PE 80, and PE 100, each defined by their respective Minimum Required Strength (MRS) values to ensure adequate performance under specified pressure ratings.

The standard encompasses HDPE pipes with nominal diameters ranging from 63 mm up to 630 mm, including sizes such as 63, 75, 90, 110, 125, 140, 160, 180, 200, 225, 250, 280, 315, 355, 400, 450, 500, 560, and 630 mm. Pressure ratings covered span from 0.25 MPa (2.5 bar) to 1.0 MPa (10 bar). Additionally, larger diameters from 710 mm to 1000 mm with specified outside diameters and tolerances are addressed in amendments to the standard.

Minimum Required Strength (MRS) is defined as the lowest hydrostatic design stress the pipe material must withstand for a 50-year period at 20°C, expressed in megapascals (MPa). The standard specifies MRS values of 6.3 MPa for PE 63, 8.0 MPa for PE 80, and 10.0 MPa for PE 100. Verification is carried out via composite sample testing according to IS 2530:1963, including melt flow rate (MFR) measurements at 190°C under a 5 kg load, where MFR must remain between 0.4 and 1.1 g/10 min and within ±30% of the resin’s MIFR. A manufacturer’s certificate confirming compliance with the MRS requirement is mandatory.

Wall thickness is calculated based on maximum working pressure, nominal outside diameter, and allowable hydrostatic design stress, with formulas provided for minimum and maximum thickness limits. For pipes with diameters ≤355 mm, the maximum wall thickness is 1.1 times the minimum plus 0.2 mm; for diameters ≥400 mm, it is 1.15 times the minimum plus 0.2 mm, rounded to the nearest 0.1 mm or 1 mm as applicable. Dimensional tolerances on outside diameter vary with pipe size: for nominal diameters up to 75 mm, tolerance is the greater of 1.2 mm or 0.008 × DN + 1.0 mm; for DN between 75 and 250 mm, tolerance is 0.02 × DN; and for DN above 250 mm, it is 0.035 × DN, all rounded up to the nearest 0.1 mm. Ovality limits are also specified to control deviation from circularity.

The standard classifies HDPE pipe chemical resistance into three categories: 'S' for satisfactory suitability under pressure and non-pressure conditions, 'L' indicating limited suitability mostly for non-pressure applications, and 'NS' denoting not suitable. HDPE pipes exhibit strong resistance to substances like dilute and glacial acetic acid, aluminium chloride at various concentrations, and acrylic emulsions. However, they show limited or no resistance to chemicals such as acetaldehyde at higher concentrations, especially at elevated temperatures. Detailed chemical compatibility tables based on immersion tests at 20°C and 60°C guide appropriate selection for chemical exposure conditions.