Technical Questions Library
Practical answers for industrial purchasers, maintenance teams and piping engineers.
16 technical answers
What is the difference between ASTM A106 Grade B and API 5L Grade B?
ASTM A106 Grade B is primarily a seamless carbon-steel pressure-pipe specification for high-temperature service. API 5L Grade B is a line-pipe grade for pipeline transportation systems and may be supplied in seamless or welded construction.
Read technical answer →Pipe FittingsWhat is the difference between ASTM A234 WPB and WPC fittings?
WPB and WPC are carbon-steel fitting grades under ASTM A234. WPC generally has higher specified tensile and yield strength than WPB, but selection must follow the piping material specification and design code.
Read technical answer →Pipe DimensionsWhat is the difference between SCH 40 and SCH 40S?
Schedule 40 belongs to the general steel-pipe dimensional series, while Schedule 40S belongs to the stainless-steel schedule series. Their wall thicknesses match in some smaller sizes but are not identical across every NPS.
Read technical answer →Stainless SteelWhat is the difference between SS 304L and SS 316L?
Both are low-carbon austenitic stainless steels. 316L contains molybdenum and normally provides better resistance to pitting and crevice corrosion in many chloride-bearing environments.
Read technical answer →Duplex SteelWhat is the difference between UNS S31803 and S32205 duplex steel?
Both belong to the duplex 2205 family. S32205 has tighter chemistry limits intended to assure alloying levels associated with 2205 corrosion and mechanical performance.
Read technical answer →FlangesWhat is the difference between WNRF and SORF flanges?
A WNRF flange has a tapered hub and is butt-welded to the pipe. A SORF flange slips over the pipe and is normally fillet-welded. Both descriptions include a raised-face sealing surface.
Read technical answer →FlangesAre ASME Class 150 and PN16 flanges interchangeable?
No. Class 150 and PN16 belong to different flange systems with different dimensions, drilling, ratings and material rules. They may appear similar in some sizes but are not generally interchangeable.
Read technical answer →PipesWhat is the difference between seamless and ERW pipe?
Seamless pipe is produced without a longitudinal weld seam. ERW pipe is formed from strip or coil and joined along a longitudinal seam by electric-resistance welding.
Read technical answer →FlangesWhat is the difference between ASTM A105 and ASTM A350 LF2?
ASTM A105 is a carbon-steel forging specification widely used for ambient and elevated-temperature pressure piping. ASTM A350 LF2 is a low-temperature carbon-steel forging grade with notch-toughness requirements.
Read technical answer →Alloy SteelWhat is the difference between ASTM A335 P11 and P22?
P11 is commonly associated with about 1.25Cr-0.5Mo alloy steel, while P22 is commonly associated with about 2.25Cr-1Mo. P22 is often selected for more demanding elevated-temperature service.
Read technical answer →FlangesWhat is the difference between RF and RTJ flange facing?
Raised Face uses a gasket compressed against raised sealing surfaces. Ring Type Joint uses a metallic ring seated in machined grooves, typically for higher-pressure or demanding service.
Read technical answer →InspectionWhat is the difference between EN 10204 3.1 and 3.2 certificates?
A 3.1 inspection certificate is validated by the manufacturer's authorised inspection representative independent of production. A 3.2 certificate additionally involves validation by the purchaser's authorised representative or an officially designated third-party inspector, as applicable.
Read technical answer →InspectionIs PMI the same as a laboratory chemical test?
No. PMI is a rapid identification method used to verify alloy family or key elements on material. A laboratory chemical analysis provides more complete quantitative composition using an agreed test method.
Read technical answer →Pipe FittingsWhat is the difference between ASME B16.9 and ASTM A403?
ASME B16.9 primarily defines dimensions, tolerances, ratings, testing and marking for factory-made wrought butt-weld fittings. ASTM A403 defines austenitic stainless-steel fitting materials and product classes.
Read technical answer →Duplex SteelWhat is the difference between Duplex 2205 and Super Duplex 2507?
Super Duplex 2507 has higher chromium, molybdenum and nitrogen alloying than Duplex 2205, giving higher strength and greater resistance to pitting in severe chloride environments.
Read technical answer →Pipe DimensionsWhat is the difference between NB/NPS and pipe outside diameter?
NB or NPS is a nominal pipe-size designation, not the measured outside diameter for most pipe sizes. The actual OD is fixed by the dimensional standard, while the wall thickness changes with schedule.
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