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On April 25, 2025, we received a special order from an old customer – a batch of high-performance 904L weld neck & blind flanges. This is not just a deal, but another confirmation of the long-term trust and tacit understanding between us and our customers.

This customer has always been very demanding on product quality and material performance, and this time chose 904L flanges because of its excellent performance and extraordinary durability in extremely corrosive environments. We are well aware that these flanges will become an indispensable “connection point” in their key projects, carrying the safe transportation of fluids and the stable operation of equipment.

904L is a high alloy austenitic stainless steel, known for its excellent corrosion resistance, especially in dealing with strong acidic environments (such as sulfuric acid, phosphoric acid) and chloride corrosion (pitting, crevice corrosion and stress corrosion cracking). Therefore, 904L flanges are important components for connecting critical piping systems to ensure long-term stable operation under harsh conditions.

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Purchase List

ITEM	Description	Quanitity	Unit
1	BLIND FLANGE, DN200 RF, PN16 ASTM A182 F-904L. FORGED.EN 1092	4	EA
2	BLIND FLANGE,DN100 RF, PN10 ASTM A182 F-904L. FORGED. EN 1092	6	EA
3	BLIND FLANGE, DN80 RF, PN10 ASTM A182 F-904L, FORGED, EN 1092	2	EA
4	BLIND FLANGE, DN50 RF, PN10 ASTM A182 F-904L. FORGED. EN 1092	2	EA
5	WNRF, DN100 SCh 10S, PN10 ASTM A182 F-904L, FORGED, EN 1092	6	EA
6	WNRF, DN80 SCh 10S, PN10 ASTM A182 F-904L, FORGED, EN 1092	34	EA

Dimensional Inspection of 904L Flange

1. Outer Diameter
   Ensure overall compatibility: Verify that the flange can be properly installed within the reserved space in the piping system without interference from surrounding equipment or structures.
2. Thickness
   Ensure pressure resistance: Flange thickness is a critical factor in determining its pressure-bearing capacity. Sufficient thickness ensures the flange will not deform or crack under rated pressure, maintaining system sealing performance.
3. Sealing Face Diameter
   Ensure sealing integrity: This is one of the most critical inspection points. The sealing face diameter must precisely match the selected gasket size to ensure uniform compression under pressure and form an effective seal to prevent fluid leakage.
4. Bolt Circle Diameter (BCD)
   Ensure bolt hole alignment: This is a decisive factor for proper flange connection. An accurate bolt circle diameter ensures full alignment with the mating flange’s bolt holes, allowing bolts to pass through smoothly and be evenly stressed, avoiding damage from forced installation.
5. Number and Diameter of Bolt Holes
   Ensure connection strength: The number and diameter of bolt holes must meet the standard to ensure enough bolts are available to bear the stress at the flange connection and to apply uniform preload on the gasket.
6. Pipe End Outside Diameter
   Ensure match with pipe OD: This is the core objective. The outside diameter of the weld neck portion of the flange must closely match the pipe’s outside diameter to ensure proper alignment during welding, reduce misalignment, and achieve a high-quality weld joint.

Specification of Forged Steel Flange

Shape Type	Regular and Long Neck
Sealing Face	RF, FF, FTJ
Size Range	1/2″ – 48″/ DN15 – DN1200
Pressure Rating	Class 150, 300, 600, 900, 1500, 2500lb
Standard	ASME B16.5, ASME B16.47 Series A/B
Stainless Steel	ASTM A182 F304/304L/304H, 316/316L, 310S, 317,347,904L

ASTM A182 F904L Flange Chemical Composition

CHEMICAL	LIMITS	C	Mn	P	S	Si	Ni	Cr	Mo	N	Ti	Cu
ASTM A182 F904L  (N08904)	MIN						23	19	4			1
	MAX	0.02	2	0.04	0.03	1	28	23	5	0.1		2

ASTM A182 F904L Flange Mechanical Property

MATERIAL	T.S (MPA)	Y.S (MPA)	EL %
ASTM A182 F904L	490 min	215 min	35 min

PN16 Forged Flange Dimensions

Table 13 — Dimensions of PN 16 flanges
Dimensions in millimetres
DN	Mating dimensions					Outside diameter of neck	Bore diameters			Flange thickness				Chamfer	Collar thickness				Centre portion	Length						Neck diameters			Corner radii	Wall thickness (see 5.6.1)
	Outside diameter	Diameter of bolt circle	Diameter of bolt hole	Bolting
	D	K	L	Number	Size	A	B1	B2	B3	C1	C2	C3	C4	E	F				Gmax	H1	H2	H3	H4		H5	N1	N2	N3	R1	S
	Flange type
	01, 02, 04, 05, 11, 12, 13, 21					11      21 a      34 d 35 – 37	01 12 32	02	04	01 02 04	11 12 13	21	05	02 04	32 34 d	35	36	37	05	12 13	11 34 c,d	11 34 c,d	35	36	37	11 34 c, d	12 13	21	11 12 13 21, 34d	34 d	11, 35 to 37
10	90	60	14	4	M12	172	180	21	31	14	16	16	16	3	12	5	2	25		22	35	6	35	35	7	28	30	28	4	18	See Annex A
15	95	65	14	4	M12	213	220	25	35	14	16	16	16	3	12	5	2	25		22	38	6	38	38	7	32	35	32	4	20
20	105	75	14	4	M12	269	275	31	42	16	18	18	18	4	14	6	25	3		26	40	6	40	40	8	40	45	40	4	23
25	115	85	14	4	M12	337	345	38	49	16	18	18	18	4	14	7	25	3		28	40	6	40	40	10	46	52	50	4	26
32	140	100	18	4	M16	424	435	47	59	18	18	18	18	5	14	8	3	3		30	42	6	42	42	12	56	60	60	6	26
40	150	110	18	4	M16	483	495	53	67	18	18	18	18	5	14	8	3	3		32	45	7	45	45	15	64	70	70	6	26
50	165	125	18	4	M16	603	615	65	77	20	18	18	18	5	16	8	3	3		28	45	8	45	45	20	74	84	84	6	29
65	185	145	18	8b	M16	761	775	81	96	20	18	18	18	6	16	8	3	3	55	32	45	10	45	45	20	92	104	104	6	29
80	200	160	18	8	M16	889	905	94	108	20	20	20	20	6	16	10	3	3	70	34	50	10	50	50	25	105	118	120	6	32
100	220	180	18	8	M16	1,143	1,160	120	134	22	20	20	20	6	18	10	4	4	90	40	52	12	52	52	25	131	140	140	8	36
125	250	210	18	8	M16	1,397	1,415	145	162	22	22	22	22	6	18	10	4	4	115	44	55	12	55	55	25	156	168	170	8	40
150	285	240	22	8	M20	1,683	1,705	174	188	24	22	22	22	6	20	10	5	5	140	44	55	12	55	55	25	184	195	190	10	45
200	340	295	22	12	M20	2,191	2,215	226	240	26	24	24	24	6	20	11	6	6	190	44	62	16	62	62	30	235	246	246	10	63
250	405	355	26	12	M24	2,730	2,765	281	294	29	26	26	26	8	22	12	10		235	46	70	16	70	68		292	298	296	12	63
300	460	410	26	12	M24	3,239	3,275	333	348	32	28	28	28	8	24	14	10		285	46	78	16	78	68		344	350	350	12	71
350	520	470	26	16	M24	3,556	3,595	365	400	35	30	30	30	8	26	18	10		330	57	82	16	82	68		390	400	410	12	80

Applications of 904L Weld Neck & Blind Flanges

Sulfuric acid treatment and production

Seawater and brine treatment

Marine engineering and offshore platforms

Desalination plants

Coastal power plants

Pollution control equipment

Flue gas desulfurization (FGD) systems

Chemical and petrochemical industries:

Pharmaceutical industry

Food and beverage industry

Pulp and paper industry

11 6 月, 2025