Description
Supper Duplex Pipe Plate & Fittings Supplier in Singapore, Malaysia, Thailand, Philippines, Indonesia
Duplex Pipes
WHAT IS DUPLEX STAINLESS STEEL
Duplex Stainless Steel is characterized by its superior corrosion resistance, high mechanical strength and high resistance to stress corrosion cracking. This is made possible due to duplex stainless steel having an approximate 50% ferrite and 50% austenite microstructure. This allows them to combine the many benefits that are tied to both ferritic and austenitic stainless steels.
With almost double the mechanical strength of the common grades stainless steel (304 & 316), duplex has been picking up speed in terms of global usage due to the cost savings one might get due to the reduction of thickness requirements and as well as overall life cycle replacement cost savings due to its superior corrosion resistance. The corrosion resistance of these materials is commonly measured for comparison against their PREN number.
WHAT IS PREN
PREN refers to Pitting Resistance Equivalent Number, the higher the number, the better is the material’s pitting corrosion resistance. While not absolute, PREN provides a simple way to compare the various alloys and their ability to withstand pitting corrosion. Below are the standard formulas for the calculation of PREN, the second one being that for items with Tungsten content.
- PREN = %Cr + (3.3 x %Mo) + (16 x %N)
- PREN = %Cr + 3.3 x (%Mo + 0.5%W) + 16 x %N
While there are various sources of pitting corrosion, these usually looks like tiny little dots on the surface of the material. Duplexes have one of the highest ratings of pitting corrosion resistance under PREN
AVAILABLE SIZE RANGE
Here at HH Stainless, we carry a vast range of welded pipes with ready stock in Singapore:
DUPLEX UNS 31803 / UNS32205 SEAMLESS PIPE ASTM A790
Duplex S31803 / S32205 is the most commonly used grade of duplex. The most noticeable disparity between both grades is the presence of Nitrogen in S32205 which provides additional protection against corrosive elements. This is usually produced in dual specifications to meet the requirements for both specifications.
DUPLEX UNS 31803 / UNS32205 WELDED PIPE ASTM A928 CLASS 1
Similar to the ASTM A790 duplex pipe, this is the welded variant that we carry for our duplex pipes. There are 5 Classes to differentiate their processes ranging from Class 1 to 5, with 1 being the highest. Class 1 pipes are double welded by processes using filler metal in all passes and are radiographed completely upon completion. In comparison, a class 5 pipe is only spot radiographed.
SUPER DUPLEX UNS 32750 ASTM A790 SEAMLESS PIPE
Super Duplex has similar benefits as Duplex materials but only better. Comparing against Duplex, it has improved corrosion resistance, greater mechanical strength and stress corrosion cracking. Between the two grades of F53 and F55 super duplex, these are fairly similar except the addition of Tungsten and Copper in F55 but overall, both grades have a mixture of chemical compositions that work out to at least a PREN of 42.
