Unknown facts about steel and ductile pipes

All pipe materials are not equal. Many people think that there is not much difference between different pipe materials. The reason behind it would be that people do not take much interest or do not go in deep facts. There are some technical facts which differentiate steel pipes from ductile iron pipes. Here are some unknown and interesting facts about steel pipes and ductile iron pipes.

• Cost effectiveness

One perspective to look at both pipe materials is, cost. Cost plays a very significant role in choosing a pipe material. Steel pipelines often require cathodic protection system which involves higher design and installation cost. They require a life time monitoring and maintenance and hence increased cost. Cement-mortar lined ductile iron pipe has an inside diameter larger than nominal pipe size. However, steel pipe inside diameter is equal to nominal pipe size. Therefore, for a given flow, velocity will be greater in steel than in ductile iron pipe. Higher velocities means higher head losses and when this difference is taken into account, ductile iron pipe delivers significant savings through lower pipelines head losses.

• Back filling is easier in ductile iron pipe

Pipe material’s modulus of elasticity and the moment of inertia has a function called pipe stiffness. Ductile Iron pipe is a stiffer product than steel pipe because ductile Iron pipe design results in a thicker wall for a given set of parameters. Ductile Iron pipe is a stiffer product, hence, it relies less heavily on the sidefill soils to help support the external load. However, steel pipe requires more design with regard to laying conditions. Where the maximum standard modulus of soil reaction, E’, for Ductile Iron pipe is 700 psi per ANSI/AWWA C150/ A21.50, this is more nearly a minimum condition for steel pipe.

• Ductile iron pipelines adapt to field conditions in installation

Ductile Iron pipe has deflectable push-on and mechanical joints. This means that the ample deflection capabilities of the joints may be used to help reroute the pipe around existing underground obstructions, such as existing utilities. It provides more flexibility to the contractor than steel pipe can offer. It also eliminates the common need for special lengths of pipe to be manufactured and shipped.

• Difference in length

Ductile Iron pipe is furnished in 18 to 20 foot nominal laying length. On the other hand, steel pipe can be furnished in 20 foot length, however, is more commonly offered in 36 to 50 foot length. This exacerbates handling concerns.

There are plenty of advantages of Ductile Iron pipe. The conservative design approach gives the engineer an effective design that is easily accomplished while offering an impressive factor of safety.