Selecting and Purchasing Clad Piping
Internally clad piping offers several advantages over solid alloy piping in many corrosive applications. For example, carbon steel piping with type 316L SS clad lining will have the same expansion rate as solid carbon steel piping. This is a useful feature when a piping upgrade is required in an existing plant where the extra space needed to accommodate additional expansion required for solid SS piping is not available.
The cost advantage of clad piping over solid alloy piping ranges from 25% to 75% less capital cost. There are also some fabrication cost reductions possible in utilizing clad pipe. Induction bending clad carbon steel pipe with a stainless steel lining or a nickel alloy lining is much the same as induction bending unlined carbon steel pipe. Usually post bend heat treatment of the clad pipe bends is not required. Induction bends can be provided so that pipe spools may be fabricated with out the need for elbows as modern pipe bending can accommodate up to three changes in direction. There are fewer butt welds to make up.
The choice of the lining material: stainless steel, nickel alloy or other metal should be carefully done as the issue of butt welding lined pipe together or pipe to fitting or pipe to flange should be addressed. Secondly the minimum diameter of clad piping is usually NPS 3 or 4 (depending upon economics or practicalities), so compatibility with smaller diameter solid alloy pipe may have to be considered.
Few fabricators make clad flanges because of impracticalities. Clad blind flanges are possible but usually carbon or alloy steel flanges are weld overlayed in weld neck and blind types. Fittings are usually produced from clad pipe or clad plate. Delivery times of clad piping systems are often similar to that of clad pressure vessels: from 6 months to one year depending upon scope and complexity. Clad plate delivery alone may be 3 to 6 months. Explosion bond clad plate may be obtained in a shorter delivery time over roll clad plate, but, its cost may be 50% to 150% more than roll clad plate.
Some of the clad pipe manufacturers can produce complete piping spools. There are obvious cost and complexity savings in using this approach. In some project timelines piping design is not completed until the 90% stage of design is reached, so unless the clad piping design (including freezing designs) is made an early priority, delivery of clad piping may be an issue. An approach to accommodate clad piping procurement would be to designate each specific application of clad piping as a mechanical package that is designed “early” and procured “early”.