Summarized Comparison of Cast Iron Double Flanged Pipes manufactured to Specification IS:1536 (Centrifugally Cast) and IS:7181 or IS:1537 (Hand Cast)
- The centrifugal casting process imparts to the screwed pipe barrel uniform sectional thickness, higher strength, high resistance to bursting and transverse stresses and ensures freedom form blow holes and homogeneity of structure.
- The Brinell Hardness which is a measure of Brittleness property of the pipe is favorable for Centrifugally Casted Pipes (Being less than 210 HB) where as it is up to 230 HB for hand Casted Pipes implying they are more prone to damage due to higher brittleness.
- In Sand Casted Pipes (IS:7181, IS:1537) the specified Tensile Strength is 150 MPa whereas in case of IS:1536, Modulus of Rupture is 390 MPa up to 300 mm dia and Tensile Strength is 180 to 200 MPa for higher sizes. Thus Centrifugally Casted Pipes are stronger than the Sand Casted Pipes.
- Hydrostatic Test Pressure, IS:1536 pipes can take higher pressures and the specified value is 35 Kg/cm2 for spun pipes whereas in case of sand casted pipes IS:7181, specified value is only 25 Kg/cm2 which may prove insufficient in case of Water Surge and Water Hammer. Thus Double Flange Pipe (IS:1536) will always be safer than the Sand Casted Pipe.
- The Centrifugally Casted barrel of IS:1536 Pipes have smooth inner surface and uniform cross section hence frictional losses are minimum resulting in more discharge over the same size of Sand Casted pipe, whose inner surface is much more rough. This results in lower pumping costs with Centrifugally Casted Pipes.
- In the manufacturing of D/F Pipes to IS:1536, CENTRIFUGALLY Machine Casted barrel pipe is used which has a dense and homogeneous structure with superior wear resistant qualities resulting in longer life of pipes. This has been proved beyond all doubts by a study conducted by IISCO (A Govt. of India Enterprise), that the life of 150 mm dia class ‘B’ Screwed Flange pipe is higher by 13% over Sand Casted pipe.
- It is well known that some stresses are developed in metal castings because of differential temperature of the metal during Casting and the Ambient Conditions of “Mould” etc. These stresses are relieved by annealing in case of Centrifugally Casted Pipes. There is no such provision in case of Sand Casted Pipes, which increases the hardness of these pipes and proness to brittle failure due to iMPact loads
- Sand Cast pipes are available in length of 9 ft. (2.75 mtrs) whereas our Screwed flange pipes are available in lengths up to 5.5 mtrs. Longer lengths (100%) longer means 50% of flange joints and fast laying of pipe. This results in saving of jointing and laying cost. Also the Sand Casted Pipes are available only in the length of 1.0 mtr. 2.0 mtr, 2.75 mtr fixed only. However, Screwed Flange Pipes can be supplied in varied lengths as per requirement & adjusting any desired set lengths, say of 27.250 mtr.
- Being machined on sophisticated machines, highest quality of pipe is ensured. Before tightening of flanges on the barrel a suitable epoxy resin is applied on the threads ensuring leak proof joints. The flanges once fixed to a pipe can never be UNSCREWED or taken out without breaking the Pipe of Flange. This is because after proper threading and applying Epoxy Resin, the Flanges are tightened on the pipes by TIGHTENING machines.
- The Screwed Flange pipes are lighter than the Sand Casted pipe, which means ease of handling, while raising and fixing the pipe for overhead thanks. In the Sand Casted Pipes, it is quite often that sand particles are impinged on the inner and outer surface of the pipe, which could not be cleaned out by hand fettling and cleaning using Wire brushes etc. While in case of Centrifugally Casted Barrel of Double Flange Pipes, SCOURING operation is performed to remove any particles on the inner surface. Hence the inner surface is much more cleaner and smooth for Centrifugally Casted Pipes.
- The cost factor for any Pipe shall be considered over the entire life time of the pipe & the related cost of maintenance, leakages, Pumping and Public Service. Here this Centrifugally Casted Screwed Flange Pipes definitely prove much more economical than the Sand Casted Pipes
