Corrosion is a menace in operating and maintaining a Chemical Process Plant. Hence given a choice one would be tempted to dispense away with Steel all together as a material of construction for piping used in a Chemical Plant. Unfortunately it is not practical to undermine the usefulness of Steel in sustaining the Pressure and Temperature conditions normally foreseen in any Process Plant. That brings the concept of composite piping wherein an attempt is made to make use of the mechanical strength of Steel, at the same time to impart a high degree of corrosion resistance to the wetted surface of the component made of Steel.

Carbon Steel Piping internally lined with Rubber is a classic example of such composite piping. Due to the intimate bonding between Rubber and Steel during vulcanizing process, it provides one of the most practical solutions in dealing with chemically corrosive fluids within the limitations posed by the endurance of Rubber for the operating temperatures.

LINING MATERIAL:

Following are the commonly used Rubber varieties in the Chemical Plant in general

1.Natural Rubber

2.Butyl Rubber

3.Nitrile Rubber

4.EPDM

LINING PROCESS:

The Rubber Lining is a process of application of liner material (normally in the form of rubber sheets or extruded tubes) over the internal surface of the steel piping followed by vulcanizing at the required temperature to attain the desired degree of hardness.

The Lining Process generally consists of following steps

1. Inspection of Piping Items for verifying its fitness for the purpose. The aspects which need to be considered with respect to above, are the accessibility of the internal surface for application of lining and suitability of the internal contours for achieving a defect free lining.

Note: In order to provide reasonable access to the internal surface of the Piping for application of liner, necessitates that Piping profile is broken down into flanged spools/ fittings of predetermined dimensions.

2. Surface preparation in terms of removal of scale/ rust either by wire brushing or sand/ shot blasting.

3. Application of Rubber Solution/ lining material

4. Curing of Liner material (i.e. vulcanizing) at the required temperature either by employing hot water or steam. The vulcanizing of Rubber could also be done at ambient temperature by adding certain accelerators along with the filler materials used in the Rubber Stock.

5. Inspection of the lined surface for possible defects such as pin holes/ blisters etc.

6. Hydro testing of the lined components