For every application, the right material has to be chosen. An example could be the construction of a corrosive, offshore oil platform. A case like this will require a material with high strength, as well with corrosion resistance, and a high service life. The material for such specialized cases is only part of the equation. The supplier is also important.

Duplex steel pipes are the material of choice for the modern, uncompromising engineer. Like most materials, even the best duplex steel pipes are the worst pipes when sourced from a bad supplier. The search for a reputable supplier of duplex pipes is as much a quality consideration as it is a procurement consideration.

Duplex steel (like most steels) is a two-phase microstructure, but is comprised of almost equal parts ferrite and austenite. This is, by no means, a marketing gimmick. This type of material has its advantages. Some of these advantages are:

Better yield strength than most of the austenitic grades like 304 or 316

Better resistance to stress corrosion cracking in chloride environments

Better weldability than most ferritic grades

Less nickel and hence better price stability

UNS S31803 (2205) and UNS S32750 (2507 Super Duplex) are the grades you’ll most commonly see.

Examining Duplex Pipe Suppliers

Good suppliers have many characteristics. The following are suggestions for supplier evaluation:

Mill Test Reports (MTRs) – Suppliers must provide certified reports. Be sure to ask, as some suppliers will claim to provide them but do not.

Third-party inspections – Potential suppliers must allow inspections of their facilities from verification agencies, such as Bureau Veritas, SGS, and TŰV.

International Certifications – As a minimum for critical applications, suppliers must have certifications for ISO 9001, PED, and NACE.

Pipe Range – Suppliers must have a range of pipe sizes and schedules, as well as supplies of seamless and Electric Resistance Welded (ERW) pipe.

Lead Time – Suppliers must be forthright with expected delivery times. Any delays are unacceptable.

Knowing which industries depend on duplex piping enables understanding of the importance of experience for duplex piping suppliers.

Oil and Gas – Subsea pipelines

Chemical Processing – Heat Exchangers

Power Generation – Flue Gas Desulfurization

Marine – Desalination and Seawater piping

Pulp and Paper – Bleaching Plant Equipment

All of these require piping that withstands chemical corrosion as well as extreme cycling of thermal and pressure.

Generally speaking, carbon steel piping will cost less than duplex steel piping. However, carbon steel piping has a higher cost of ownership than duplex steel piping because of its required maintenance and shorter service life. Longer service lives mean that it is often a better financial decision to source duplex steel piping from a reputable supplier than it is to source carbon steel piping.

This can be likened to the analogy of quality boots versus cheap boots. The cost for quality boots and cheap boots is the same, but cheap boots have a higher cost of ownership than quality boots.

Choose duplex steel piping for extreme conditions, high impact, or aggressive media. When sourcing duplex steel piping, choose a supplier that offers real certifications and traceability in addition to technical knowledge and not just a sales catalog.

Aesteiron Steels is an excellent option for sourcing a variety of duplex steel piping with certified, documented, and compliant piping, as they offer a variety of standard and super duplex steel piping.