ASME SA688 TP304 stainless steel seamless U-bend tube for feedwater heaters

​​ASME SA688 TP304 stainless steel seamless U-bend tube for feedwater heaters is a high-performance heat exchange tube made from 18.0-20.0% chromium, 8.0-10.5% nickel, and ≤0.08% carbon austenitic stainless steel (TP304 grade) with a minimum yield strength of 205MPa and tensile strength of 515-790MPa, featuring seamless construction, U-bend geometry (radius typically 1.5-3.0 times tube diameter), and strict dimensional tolerances (outer diameter ±0.05mm, wall thickness ±0.03mm) to ensure reliable performance in feedwater heater systems operating at temperatures up to 300°C and pressures up to 10MPa, where corrosion resistance and thermal stability are critical.​

 

ASTM A688 U Bend Stainless Steel Tube Specifications

Straight length：max 30000 mm

Leg length：12000 mm, points of tangency of the bend to the leg end

Bending radius：max 1500 mm

Manufacturing method：TIG welding, Cold drawn

Finishes: Annealing Pickling (AP), Bright Annealed (BA)

Straight length equal to 2 x leg length + 3.1416 x R

Heat treatment shall be applied to the U-bend area plus approximately 6 in. [150 mm] of each leg beyond the tangent point of the U-bend after bending, if specified.

Chemical Composition

Grade		C	Mn	Si	P	S	Cr	Ni	N
304	min.	-	-	-	-	-	18.0	8.0	-
	max.	0.08	2.0	0.75	0.045	0.030	20.0	10.5	0.10
304L	min.	-	-	-	-	-	18.0	8.0	-
	max.	0.030	2.0	0.75	0.045	0.030	20.0	12.0	0.10
304H	min.	0.04	-	-	-0.045	-	18.0	8.0	-
	max.	0.10	2.0	0.75		0.030	20.0	10.5

Mechanical Properties

Grade	Tensile Strength (MPa) min	Yield Strength 0.2% Proof (MPa) min	Elongation (% in 50mm) min	Hardness
				Rockwell B (HR B) max	Brinell (HB) max
304	515	205	40	92	201
304L	485	170	40	92	201
304H	515	205	40	92	201
304H also has a requirement for a grain size of ASTM No 7 or coarser.

Physical Properties

Grade	Density (kg/m3)	Elastic Modulus (GPa)	Mean Coefficient of Thermal Expansion (μm/m/°C)			Thermal Conductivity (W/m.K)		Specific Heat 0-100°C (J/kg.K)	Electrical Resistivity (nΩ.m)
			0-100°C	0-315°C	0-538°C	at 100°C	at 500°C
304/L/H	8000	193	17.2	17.8	18.4	16.2	21.5	500	720

 

ASTM A688 U Bend Stainless Steel Tube Dimensional Tolerance

ASTM A688 U bend tube tolerance of outside should be accordance with specification A1016/M, the bent portion of U tubes for R =2 X D or greater, tolerance shall deviate from the nominal diameter prior to bending by more than 10 % if less than 2 X D is specified, tolerances could be greater, minimum wall thickness shall not exceed +20 % − 0, average wall thickness are 10 % of the nominal wall thickness, bent area wall tolerance shall not be less than value determined by the equation: 4RT/(4R+D).

Tube Leg Length Tolerance

Leg Length, Ft (M)	Plus Tolerance, In (Mm)
<= 20 (6)	1/8 (3.2)
>20(6), <=30(9)	5/32 (4.0)
>30 (9), <=40 (12.2)	3/16 (4.8)

Squareness Of Ends Tolerance

Tube OD, In, (Mm)	Tolerance, In, (Mm)
<=5.8 (15.9)	0.010 (0.25)
>5.8 (15.9), <=1 (25.4)	0.016 (0.4)

 

We offer ASTM A688 seamless and welded U bend stainless steel tube for feedwater heaters, Austenitic stainless steel and Ferritic stainless steels, surface condition in annealing and pickling, or bright annealed finishing, used in heat exchanger, boiler, condenser, heat transfer system.  If you have any project needs, please place an order.Email: info@gneestainless.com