Flexible PVC Pipes or Polymer Reinforced Thermoplastic Hoses for Suction and Delivery Lines of Agricultural Pumps - Specification
2003 Edition

IS 15265 mandates that hoses be made from flexible PVC or polymer reinforced thermoplastics suitable for agricultural pump suction and delivery lines. These hoses must exclude use with flammable or aromatic solvents and include polymer reinforcement for strength and flexibility. Construction requires passing bending tests in line with IS 12656, marking bending lengths based on the formula 1.6C + 2D (or a minimum of 200 mm), where C is twice the minimum bend radius and D is the hose diameter, with support on either side at least equal to the diameter. This ensures the hose's durability and performance in agricultural applications.

The standard defines nominal bore sizes ranging from 12.5 mm up to 315 mm. Internal diameters are measured with a vernier caliper to 0.05 mm precision, avoiding measurements within 24 hours post-manufacture. The internal diameter tolerance varies according to size, for example, ±0.75 mm for smaller bores and up to ±3.00 mm for larger sizes. Minimum burst pressures decrease with increasing bore sizes, typically from 0.5 MPa for smaller diameters to 0.2 MPa for the largest. Detailed tolerance bands for each nominal bore are specified in Table 1 of IS 15265.

The hydrostatic testing involves gradually increasing pressure within the hose at rates dependent on the nominal inside diameter, then holding proof pressure—defined as 50% of the minimum burst pressure—for 60 seconds while inspecting for leakage, cracks, or deformation. Tests are conducted at standard ambient temperature (27 ± 2°C) and optionally at elevated temperature (55 ± 2°C). The maximum working and burst pressures vary by hose size; for example, 0.7 MPa working pressure with 1.7 MPa burst pressure for 12.5–25 mm bore hoses, decreasing for larger sizes. Additionally, hoses undergo impulse testing at 120% of maximum working pressure for at least 10,000 cycles to verify endurance.

IS 15265 recommends using cast iron or plastic connectors of standard sizes for joining hoses. The hose end should be softened by immersing vertically in hot water at 70-80°C for 2 to 3 minutes without direct flame exposure. Immediately after heating, the softened hose end is pushed onto the hose nipple placed on a firm surface. The joint is then secured with an appropriate hose clamp to ensure a leak-proof and secure connection. This method facilitates easy assembly while maintaining hose integrity.

The standard requires hoses to undergo vacuum testing per Annex C, applying specific absolute pressures depending on the nominal bore—0.035 MPa for sizes up to 160 mm and 0.02 MPa for larger sizes—to assess resistance against collapse. Hoses must not exhibit collapse or fractures beyond one inside diameter length from the coupling; failures closer to the coupling necessitate retesting with a new sample. Reinforcement fracture testing involves placing split hose samples with polymer reinforcement over extension blocks (dimensions vary by nominal bore) and subjecting them to reverse bending for up to 336 hours (control) or 4 months (type test), ensuring no cracks develop. These tests confirm structural integrity and durability under vacuum and bending stresses.