Koya & Company Construction Limited.

Mehdipatnam, Hyderabad, Telangana

This product is the best choice for applications like: Pressure water transmission and distribution mains (Pumping & Gravity) for water supply, Drainage, Lift Irrigation Schemes. Re-circulation and cooling water pipe lines. For plants like Thermal Power, Chemical, Cement, Fertilizer, Paper, Refineries etc. Pressure water lines. Gravity Sewer Systems. Conveying any liquid, not corrosive to concrete including sea water and sewage force main. The Design When transient loads such as surge or traffic are added to sustained loads, tensile stresses up to 30 kg/cm2 maximum may be permitted in concrete. It is usual to divide pipelines in steps of Internal Pressure and design pipe for each section taking advantage of economy to be gained by tailoring design to suit actual needs without reducing safety. Where local high pressures or heavy external loads occur, pipes in these places can be strengthened without affecting cost of the remainder of the pipeline. without affecting cost of the remainder of the pipeline. The following load components are taken into account. Mass of Pipe Mass of water in pipe Sustained Internal Pressure Surge Bedding and Backfill Construction traffic wheel loads Highway traffic wheel loads Best economy and safety are achieved when pipe is designed for realistic in-service pressures and loads. The alternative method of designing pipes for a factory test, based on working pressure plus an arbitrary factor without regard to surge, earth or traffic loads is sometimes inadequate for low pressure.The same method can be wasteful for high pressure pipelines. Following determination of wall thickness and prestressing the next step is to calculate factory test pressure which will stress pipe as severely as it will be stressed in service taking into account mass of pipe and water and support condition. If a pressure, test is required on pipes after installation the value may be similarly calculated. The required ring strength of pipe can be readily established because internal pressure and external load conditions of the pipeline are known. However, since loads causing longitudinal stresses are not known with certainty, it is assumed for design purposes that bedding is deficient and that pipe is a beam supported as its ends with backfill loads distributed evenly along the length of the pipe. This is conservative because installation specifications require bedding to be uniform along the length of pipe. Joint assembly design is related to clearances between joint surfaces, tolerance to pipe ends, rubber ring size, rubber hardness, creep of rubber on concrete.Blow-out resistance is produced for the most unfavorable combination of joint deflection and tolerance of pipe ends. The Manufacturing Process: The process of Manufacturing Pre-stressed Concrete (PSC) Pipes consists of the following steps: 1) Longitudinal Pre-stressing Longitudinal wires of specified diameter and length are placed between two end rings of the mould assembly, and stretched to the required tension. 2) Batching & Mixing of concrete Required quantity of aggregates, cement and water are mixed to produce high strength concrete. 3) Spinning Concrete is fed into the mould and is compacted by centrifugal spinning process to produce a high strength concrete core pipe. 4)Demoulding The tension in the longitudinal wires is released, making longitudinal pre-compression to the core pipe and then the core pipe is taken out of the mould. 5) Core Curing The core pipe is put in sprinkler yard until the concrete in the core pipe has attained adequate strength to withstand circumferential prestressing load. 6)Winding The core pipe is wrapped with high tensile wire at pre-determined pitch and tension to induce the desired pre-compression in the body of the core pipe. 7) Coating The steel wrapping is covered with a dense cement mortar coat by means of a brush coater developed by IHP. This coat creates and maintains a high alkaline environment around the prestressing wire and protects it from corrosion. 8)Curing The completed pipe is cured until it attains the desired strength. 9)Hydrostatic Testing Each and every pipe is subjected to hydrostatic pressure test in the factory before dispatch. Specials The necessary special fittings such as bends, tees and others supplied with the pipe are made of steel shells with a concrete lining and outer coating or corrosive resistant paint. The ends are fitted with rubber ring joints for connecting them to the concrete pipe.

These Steel Cylinder Concrete Pipes, have a very enviable position in the pressure ranges above 20kg/cm2 and sometimes, in special situations such as exposed pipeline, under-sea pipeline etc. Pipes are supplied with plain ends suitable for butt weld or slip-in-ends suitable for fillet welds. External protection to Steel Pipes is by cement rich mortar applied by brush coating process. Epoxy or bituminous coating is also offered. Our range covers : Diameters from 250 mm to 5000 mm. Length:- 6 to 7.5 meters. Choice of slip-in or butt joint. Special fittings such as bends, tapers, tees, adapters, saddle supports, expansion joints etc

The Pipe It is essentially a thin steel pipe cylinder; welded with thicker steel joint rings at the ends, hydraulically tested and centrifugally lined with cement mortar. The M.S bar / wire is helically wrapped on the cylinder with controlled tension ensuring intimate contact with cylinder and is then coated with cement mortar by high impaction process. This results in several performance advantages over conventional mortar gunited steel pipes and other metal pipes. Choice of Joints The joint rings are made of thicker steel plates. The field joint can be over lapping /sliding, butt welded or with confined rubber rings to suit requirement of the client. A joint is so designed that it will be water tight under all service conditions. Optimum Design The pipe is designed to resist internal hydrostatic pressure by steel cylinder and pre-tensioned helically wound rod. Hence, pipe can be custom designed by selecting steel-cylinder thickness, bar diameter and spacing .This flexibility in design can result in substantial saving. Structural Integrity Since rods are helically wrapped under tension , the structural integrity of these pipes is greatly enhanced because of the interlocking of steel elements of the pipe. This composite construction greatly increases rigidly of the pipe, beam strength and resistance to impact. Corrosion Resistance The cement mortar encasement maintains the steel elements in a highly alkaline environment (pH of 12.5 or greater) in which galvanic corrosion is permanently inhibited. Although, rarely required, supplemented protection can be provided for any unusual surrounding conditions. Stiffness Stiffness of pipe is the result of the keying action of the pre-tensioned rod wrap over steel cylinder and the coating. From the graph of pipe stiffness Vs. Diameter Vs. types of pipes, it is observed that these pipes are many times stiffer than steel pipes lined and coated with cement mortar, PVC & Ductile Iron Pipes. hence, less expensive bedding and side support during installation. This will result in added economy. Coefficient of Roughness The smooth surface of cement mortar lining provides value of Hazan Williams constant 'C' around 140 in the formula. Because cement mortar prevents corrosion of steel pipe, the water carrying capacity is not decreased with age of pipe. Diameter, Pressure & Length These pipes can be made from 250 mm to 1600 mm diameters for working pressure up to 25 Kg/cm2 . Length of each pipe shall be between 5 - 6 meter. Longer length pipes are also possible for large requirements.