It consists of a hydraulically tested steel cylinder with steel joint rings, centrifugally cast concrete core, high strength prestressing wire wrapped around the core and thereafter cement rich mortar coating.
Choice of Joint
The joint rings are made of thicker steel plates. The field joint can be over-lapping/sliding, butt welded or with confined rubber ring joint to suit the requirements of the client. a joint is so designed that it will be watertight under all service conditioned.
Pre-stressed concrete cylinder pipe makes optimum use of steel. The composite action of steel cylinder , concrete core and H T wire results substantial saving of the total steel in a steel pipe as used conventionally.
Interior joint space
For pipe smaller than 900mm. mortar
is placed at the bell ring so the inside recess is filled when the joints
are engaged. A swab pulled through the pipe smoothes any excess mortar.
On larger pipes the inside joint recess are filled with cement mortar and
finished smooth by a workman with a trowel.
Exterior joint space
The exterior joint space is grouted
by use of a wrapper strapped around the pipe and over the joint. The wet
cement mortar grout is poured at one side of the opening at the top of
the pipe until grout has advanced completely around the pipe.
Maintenance
Survey made by AWWA in USA identified
that there is hardly any maintenance required for PCCP pipelines.
External load strength
Conventional steel pipes can deflect
significantly under external loads as those are flexible pipes. Steel pipes
depend upon the soil on each side to resist horizontal deflection. To achieve
proper compaction special equipments, careful supervision by the contractor
and regular inspection by the owner is very much essential. This will result
in substantial additional laying cost compared to pre-stressed concrete
cylinder pipes which are more rigid.
Corrosion resistance
The cement mortar encasement maintains
steel elements in a highly alkaline environment (PH of 12.5 or greater)
in which galvanic corrosion is permanently inhibited. Although rarely required,
supplemental protection can be provided for any unusual surrounding conditions.
Resists damages in normal handling
The external mortar coating of prestressed
concrete cylinder pipe is rugged shield that protects the pipe from normal
damage during transportation, handling and installation whereas the fragile
corrosion barrier coatings of steel pipes are very sensitive to damage
during transportation, handling and installation.
The interior surface of a pre-stressed concrete cylinder pipe is very smooth and corrosion free. The highly alkaline concrete protects the interior surface and prevents internal corrosion which is customary with steel pipes. The coefficient of friction of these pipes is very low. This greatly reduces the cost of pumping compared to steel or ductile iron pipes which develop flow restricting problems from internal corrosion as time passes.
In most situations pre-stressed concrete cylinder pipes (PCCP) are substantially cheaper than conventional steel pipes with protective cement mortar lining and out coating as per I.S.1916 and ductile iron pipes with mortar lining and proper coating from outside.
Track record
These pipes have given excellent service for water supply and sewerage disposal for more than 55 years in the United States of America and Europe.
Diameter and Pressure
These pipes can be made from 400 mm
to 1500 mm diameter for working pressure up to 16 kg / cm2.
Bigger Diameter and higher pressure
pipes are also possible for large requirements. These pipes are manufactured
conforming to common European standard EN-642 or American Water Works Association
Standard AWWA C -301 or IS-784.