Bulb Flat

Bulb flat is a structural profile with a flat web and rounded bulb edge. The optimized cross-section improves stiffness, load distribution and welding efficiency, making it a widely used stiffener in structural engineering.

Commonly used in shipbuilding structures, offshore platforms, bridges and heavy steel frameworks where high strength and fabrication efficiency are required. Chalco supplies bulb flat sections in carbon steel, aluminum and stainless steel for marine and structural projects worldwide.

• Size range: width 60–430 mm · thickness 4–20 mm
• Standard lengths: 6 m · 9 m · 12 m · cut-to-length supply
• Tolerance: thickness ±0.3 mm · width ±0.5 mm
• Typical sections: HP80×6 · HP100×8 · HP160×9 · HP220×10
• Processing: drilling · punching · bending · grooving · angle cutting
• Certification: ISO · DNV · ABS · CCS · LR classification approval

Structural Advantages of Bulb Flat

Bulb flat sections are widely used as structural stiffeners in shipbuilding and heavy engineering because their asymmetric cross-section provides high stiffness with efficient material usage. Compared with conventional flat bars or angle sections, bulb flats offer improved structural performance and fabrication efficiency.

• High stiffness-to-weight efficiency: the bulb edge increases section modulus and buckling resistance while maintaining relatively low weight.
• Efficient stiffening profile: widely used as longitudinal and transverse stiffeners in ship hull structures, decks and bulkheads.
• Improved welding performance: the flat web allows simple welding to plates and structural members during ship fabrication.
• Structural stability: the bulb geometry helps distribute stress and improves resistance to deformation in large welded structures.
• Reduced fabrication complexity: bulb flat sections simplify stiffener installation compared with angle or built-up structural profiles.
• Proven marine structural solution: widely adopted in shipbuilding, offshore platforms and large steel structures worldwide.

Bulb Flat Applications

Bulb flat profiles are widely used as structural stiffeners in shipbuilding, bridge engineering, offshore structures, and heavy industrial frameworks. Their unique cross-section provides excellent stiffness, efficient load distribution, and convenient welding performance, making them suitable for large structural assemblies requiring high strength and reliable fabrication.

Bulb Flat for Shipbuilding

Application: hull frames, deck stiffeners, bulkheads and keel reinforcement structures

Material: marine carbon steel (Grade A, AH36, DH36) and aluminum alloys such as 5083

Structural value: bulb edge improves buckling resistance and welding efficiency for ship structures

Bulb Flat for Bridge Structures

Application: bridge decks, beam webs and structural reinforcement components

Material: structural carbon steel profiles designed for heavy load-bearing applications

Engineering value: efficient cross-section improves structural stability and reduces steel consumption

Bulb flat profiles are also used in offshore platforms as structural stiffeners, wind turbine tower internal support systems, and port or coastal infrastructure where corrosion resistance and structural stability are required.

If you are selecting bulb flat sections for shipbuilding, bridge engineering or other structural projects, our engineering team can help recommend suitable materials, dimensions and supply specifications according to your project requirements.

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Bulb Flat Dimensions and Weight Chart (HP60–HP430)

Bulb flat sections are available in a wide range of standard marine sizes, typically ranging from HP60 to HP430, and are widely used in shipbuilding and structural engineering. The following tables show typical dimensional parameters and weight references for commonly used carbon steel and aluminum bulb flat profiles. Custom sizes and lengths can also be produced according to project requirements.

Typical Carbon Steel Bulb Flat Sizes (HP60–HP430)
Size	Unit Weight 12m+ (kg)	b (mm)	t (mm)	c (mm)	r (mm)	Section (cm²)	Surface Area (m²/m)	Ixx (cm⁴)	Wxx (cm³)
60 x 4	35,33	60	4	13	3,5	3,58	0,146	12,2	3,2
60 x 5	41,26	60	5	13	3,5	4,18	0,148	14,4	3,89
60 x 6	47,31	60	6	13	3,5	4,78	0,150	16,4	4,55
80 x 5	53,36	80	5	14	4	5,41	0,189	33,87	6,91
80 x 6	61,23	80	6	14	4	6,21	0,191	38,7	8,1
80 x 7	69,21	80	7	14	4	7,00	0,194	43,3	9,24
100 x 6	76,47	100	6	15,5	4,5	7,74	0,235	76,8	12,7
100 x 7	86,27	100	7	15,5	4,5	8,74	0,236	85,3	14,5
100 x 8	96,32	100	8	15,5	4,5	9,74	0,238	94,3	16,3
120 x 6	91,96	120	6	17	5	9,32	0,276	133	18,5
120 x 7	103,82	120	7	17	5	10,52	0,278	149	21
120 x 8	115,68	120	8	17	5	11,72	0,280	165	23,6
140 x 7	122,21	140	7	19	5,5	12,43	0,320	241	29
140 x 8	135,52	140	8	19	5,5	13,83	0,322	266	32,5
140 x 9	150,04	140	9	19	5,5	15,20	0,324	291	36
140 x 10	165,77	140	10	19	5,5	16,63	0,326	315	39,5
160 x 7	143,99	160	7	22	6	14,60	0,365	373	38,6
160 x 8	159,72	160	8	22	6	16,20	0,367	411	43,3
160 x 9	176,66	160	9	22	6	17,80	0,369	449	47,9
180 x 8	186,34	180	8	25	7	18,86	0,411	609	55,9
180 x 9	204,29	180	9	25	7	20,66	0,413	664	61,8
180 x 10	221,43	180	10	25	7	22,46	0,415	717	67,7
180 x 11	239,58	180	11	25	7	24,26	0,417	770	73,5
200 x 9	232,32	200	9	28	8	23,66	0,457	942	77,7
200 x 10	252,89	200	10	28	8	25,66	0,459	1017	85,1
200 x 11	273,46	200	11	28	8	27,66	0,461	1091	92,3
200 x 11,5	283,14	200	11,5	28	8	28,60	0,462	1126	96,2
200 x 12	291,61	200	12	28	8	29,66	0,463	1164	99,5
220 x 10	286,77	220	10	31	9	29,00	0,503	1396	105
220 x 11	308,55	220	11	31	9	31,20	0,506	1496	114
220 x 11,5	319,44	220	11,5	31	9	32,30	0,506	1550	118
220 x 12	329,12	220	12	31	9	33,40	0,507	1595	122
240 x 10	319,44	240	10	34	10	32,49	0,547	1865	126
240 x 11	344,85	240	11	34	10	34,89	0,549	1997	137
240 x 12	369,05	240	12	34	10	37,29	0,551	2127	148
260 x 10	355,74	260	10	37	11	36,11	0,591	2434	150
260 x 11	381,15	260	11	37	11	38,71	0,593	2605	163
260 x 12	407,77	260	12	37	11	41,31	0,596	2774	175
280 x 11	422,29	280	11	40	12	42,68	0,637	3333	191
280 x 12	448,91	280	12	40	12	45,48	0,639	3647	206
280 x 13	476,74	280	13	40	12	48,28	0,641	3757	221
300 x 11	462,22	300	11	43	13	46,78	0,681	4192	222
300 x 12	491,26	300	12	43	13	49,79	0,683	4459	239
300 x 13	522,72	300	13	43	13	52,79	0,685	4722	256
320 x 12	534,82	320	12	46	14	54,25	0,728	5525	275
320 x 13	566,28	320	13	46	14	57,45	0,730	5849	294
320 x 14	598,95	320	14	46	14	60,85	0,732	6168	313
340 x 12	581,28	340	12	49	15	58,84	0,772	6757	313
340 x 13	612,26	340	13	49	15	62,24	0,774	7152	335
340 x 14	648,56	340	14	49	15	65,54	0,776	7540	357
370 x 13	687,28	370	13	53,3	16,5	69,70	0,840	9469	402
370 x 14	723,58	370	14	53,3	16,5	73,40	0,842	9980	429
370 x 15	761,09	370	15	53,3	16,5	77,10	0,844	10483	456
400 x 14	804,65	400	14	58	18	81,48	0,908	12924	507
400 x 15	844,34	400	15	58	18	85,48	0,910	13573	538
400 x 16	883,30	400	16	58	18	89,48	0,912	14211	568

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Aluminum Bulb Flat Size Reference
Thickness T1 (mm)	Width W1 (mm)	Thickness T2 (mm)	Width W2 (mm)	Length L (mm)
4.0	45	8	11.5	6000
5.0	50	8	12	6000
5.0	60	11	15	6000
6.0	85	15	20	6000
6.0	95	20	12	6000
4.5	50	—	14	6000
5.4	98.7	—	19	6000
5.6	76.2	—	19	6000
6.0	127	—	19	6000

Bulb Flat Inventory and Section Availability

• Stock availability: commonly used marine bulb flat sections available for fast delivery
• Standard marine sections: HP80 – HP430 profiles widely used in shipbuilding structures
• Length options: 6 m · 9 m · 12 m fixed length supply
• Custom production: special dimensions and project-based orders supported

Chalco maintains stable supply of commonly used bulb flat sections for shipbuilding and structural projects. Standard marine sizes are available for fast delivery, and customized dimensions or fixed-length supply can also be arranged according to project requirements.

Bulb Flat Technical Specifications and Tolerances

The following technical specifications define the dimensional accuracy, straightness control, and surface quality requirements for Chalco bulb flat sections used in shipbuilding and structural applications.

Straightness – bow and camber

Straightness tolerance of bulb flat bars measured along the full length according to EN10067.

Flatness tolerance

Web flatness: h ≤ 0.003 × b; Bulb heel flatness: n ≤ 2.0 mm

Bulb head dimensional tolerances

Web edge dimensional tolerances

Twist tolerance

Permissible twist per meter length.

Surface condition

Surface quality complies with EN10163-3:2004, subclass 3, class C.

If you need detailed bulb flat specifications, engineering drawings or assistance in selecting the appropriate section size for your structural project, our technical team can provide professional support and material recommendations.

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Materials for Bulb Flat Profiles

Bulb flat profiles can be manufactured from different materials depending on structural strength, corrosion resistance and weight requirements. Chalco supplies bulb flat sections in aluminum alloy, carbon steel and stainless steel to support shipbuilding, bridge engineering and other structural applications.

Aluminum Bulb Flat

Application: lightweight ship structures, transportation equipment and industrial frameworks

Alloys: 6061 · 6082 · 5083 · 5754

Features: lightweight · corrosion resistant · excellent weldability

Carbon Steel Bulb Flat

Application: ship hull structures, heavy steel frameworks and bridge stiffeners

Grades: Grade A · AH36 · DH36 · EH36

Standards: ASTM A131 · EN10025 · GB712

Stainless Steel Bulb Flat

Application: marine facilities, petrochemical structures and corrosive environments

Grades: 304 · 316 · 316L

Features: corrosion resistant · durable · hygienic surface

If you are selecting bulb flat profiles for shipbuilding, bridge engineering or structural fabrication projects, our team can help recommend suitable materials, grades and supply specifications based on your design and project requirements.

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Chalco Bulb Flat Manufacturing Capability

Chalco provides integrated manufacturing and processing services for bulb flat profiles used in shipbuilding and structural engineering projects. From raw material supply to precision processing and customized delivery, we support project-based production for global shipyards and engineering contractors.

Production Capability

• Stable supply of aluminum, carbon steel and stainless steel bulb flat profiles
• Standard marine sections available from HP80 to HP430
• Flexible production for fixed-length supply such as 6m, 9m and 12m
• Production according to ASTM, EN, GB and marine classification standards

Processing Services

• Cut-to-length processing and section customization
• Drilling, slotting and structural connection preparation
• Bending and forming for structural installation requirements
• Surface treatments including blasting, galvanizing and coating
• Welding preparation and fabrication support for structural assemblies

Our integrated manufacturing and processing capabilities help shipyards and structural contractors simplify fabrication, maintain dimensional accuracy and ensure reliable delivery for large-scale structural projects worldwide.

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Chalco also provides other marine supporting materials

Chalco manufactures and supplies a wide range of bulb flats, flat bars and other shipbuilding structural products: the diversity of a factory, the flexibility of a dealer!

Plate

Flat/Square Bars

Equal / Unequal Angle

Half-round Bars

Round Bars

Pipes

Corrugated Plates

Beams

Inverted Angles

Frequently Asked Questions (FAQs)

Q: What materials are available for bulb flat profiles?

A: Bulb flat sections can be supplied in carbon steel, aluminum alloy and stainless steel depending on structural strength, corrosion resistance and weight requirements.

Q: What standards do bulb flat profiles comply with?

A: Common standards include EN 10067, ASTM A131, GB/T 9945 and other marine structural specifications depending on the material and project requirements.

Q: What are the common sizes of bulb flat sections?

A: Standard marine sections typically range from HP80 to HP430, with thickness generally between 4 mm and 20 mm depending on the profile specification.

Q: Do you support customized dimensions or processing?

A: Yes. Custom lengths, special dimensions and secondary processing such as drilling, cutting and bending can be arranged according to project drawings.

Q: Can bulb flat profiles be supplied with classification society certification?

A: Yes. Materials can be supplied with certifications from major classification societies such as DNV, ABS, LR, CCS and BV depending on project requirements.