Process Industry
Duplex, Super Duplex, and Liquor Service Flange Supply
A pulp mill is a chloride corrosion problem looking for somewhere to happen. Bleach plants, recovery boilers, and liquor cycles each demand specific material answers, with duplex 2205 and super duplex 2507 as the practical baseline.
Industry Overview
How Pulp & Paper Piping Actually Looks
Bleach plant piping is the most aggressive service in the mill. Chlorine dioxide, hypochlorite, and the chloride content of process water combine to eat stainless grades that would last decades elsewhere. Duplex 2205 and super duplex 2507 are mandatory, with the higher PREN of 2507 reserved for the worst stages.
The recovery cycle moves white liquor, green liquor, and black liquor through evaporators, recovery boilers, and the causticizing plant. Each stream has its own chemistry. Forged A105 carbon works in some service, while duplex shows up where chlorides and temperatures climb together.
Brown stock washing, screening, and stock prep round out the mill. We supply duplex and super duplex weld necks and blinds in the sizes and classes that bleach plant and liquor service actually use, rather than just the catalog standard. Forged construction dominates, with plate-cut showing up on lower pressure utility tie-ins.
Typical Flange Selections
What We Supply for Pulp & Paper
Duplex 2205 Weld Neck
ASME B16.5, Class 150 and 300
Bleach plant intermediate stages, brown stock
Super Duplex 2507 Weld Neck
ASME B16.5, Class 150 and 300
Chlorine dioxide stages and hot chloride service
316L Weld Neck
Class 150 and 300, F316L
Utility piping and lower aggression process
Carbon Weld Neck
A105, Class 150 to 600
White liquor, green liquor, and steam balance of plant
Blind Flanges
Duplex, super duplex, stainless, carbon
Vessel manways, evaporator nozzles, screen plant
Lap Joint with Stub End
Duplex stub with carbon backing
Cost control on long duplex piping runs
Material Selection
Common Materials and Why
Duplex 2205 (F51)
Standard bleach plant material. Pitting and crevice resistance well above 316L in chloride service.
Super Duplex 2507 (F53)
PREN above 40 for the hottest chloride stages where 2205 still pits.
ASTM A182 F316L
Lower aggression process streams and utility piping where duplex would be overspec.
ASTM A105
Forged carbon steel for white liquor, steam, and balance of plant where chemistry allows.
Industry Challenges
What Procurement Has to Solve
- 01
Stocking depth on duplex and super duplex flanges in the sizes mills actually use, not just commodity ranges.
- 02
Material confusion between 2205 and 2507 that has to be resolved with PMI at receiving.
- 03
Welding procedures on duplex that demand controlled heat input to preserve the phase balance.
- 04
Recovery boiler outage windows that compress delivery into days for high spec material.
Standards and Codes
Specifications We Quote To
Ready to Quote Pulp & Paper
Bleach plant and recovery cycle outages are our planning window. Send the duplex and super duplex list early.
PO Box 2889, Pearland TX 77588