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Introduction: What is Cast Iron?
Cast Iron pipe, which were mainly composed from gray cast iron, were crude pipes made from molds. The gray color from gray cast iron came as a result of graphitic microstructures (as a consequence of graphite being present in the mixture). Cast Iron pipes were commonly used up until the turn of the 20th century [1].
How it's made
There are three predominant ways that cast-iron is made. Horizontally cast, vertically cast, and centrifugally cast [2].
Casting Method | Details |
|---|
| Horizontally Cast | - One of the first methods of producing Cast Iron pipes
- The Horizontal Cast results in an uneven distribution of metal around the circumference
- The corwn of the pipe would collect slag that would make it weaker than the rest of the pipe [2]
|
| Vertically Cast | - A very common method of casting by the 1900's
- The Vertical Cast would result in all the slag collecting at the top, which could then simply be cut off
- The core of the pipe would often be off center, leading to one side of the pipe becoming thicker than the others [2]
|
| Centerfugally Cast | - The most commonly used method to make Cast Iron pipes
- Metal Molds:
- Metal molds would inject molten iron into the core which would then be uniformly distributed by the centrifugal force
- The pipe was removed from the mold once it cooled enough to hold its shape
- Often times, pipes would be annealed to eliminate stress and to inspect, measure, and test them before usage.
- Sand Molds:
- The Sand molding is similar to the Metal Molds, except how the sand molds are formed
- Method 1: A pipe was positioned inside a metal flask, then molding sand was rammed into the space.
- Method 2: Lining a heated flask, centrifugally, with measured amounts of thermosetting resin and sand
- They are also annealed like Metal Molds [2]
|
Cast Iron Pipes
Cast Iron is rated in eight classes, from A to H, based on pressure. Each of the incriments between the classes is 100 feet of head or ~43 psi. To check out the full specification for the pipe size and classes, navigate to the link below [3].
Cast Iron Pipe Fittings
|
|---|
| Cast Iron Pipe Fitting Examples [5] |
Advantages vs. Disadvantages
Advantages | Disadvantages |
|---|
- Has a thicker wall size than other pipes such as steel or ductile iron.
- Corrodes as fast as steel or ductile Iron
- A majority of the pipes made after 1950 were retrofitted or came with cement mortar lining [4]
| - There is little mechanical strength and no elastic properties
- A majority of the older pipes (before 1960) were not lined
- The manufacturing defects were something to keep in mind, like the variable wall thickness
- There was often no external protection to the pipes
- They were prone to corrosion when exposed to the elements [4]
|
Example Applications
For Cast Iron pipes specifically, they were mainly used as pressure pipes to transport water and sewage waste. The design of Cast Iron hasn't changed much since its high demand in the the 19th and 20th century and its no longer in demand as different solutions have come into place. [1]
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