Compact Flanges | NORSOK L-005 / ISO 27509 Compact Flanged Connections (CFC)

The NORSOK L-005  Compact Flange is a high-integrity piping connector designed specifically for the rigorous demands of the Norwegian offshore industry. It offers a significant weight reduction of up to 80% compared to traditional ASME B16.5 flanges while ensuring zero-leakage performance in high-pressure environments.

Compact flanges are high-integrity forged flange connection systems designed for high-pressure, high-temperature and subsea applications where leak-free performance and reduced weight are critical.

Manufactured according to:

• NORSOK STANDARD L-005 COMPACT FLANGE
• ISO 27509

compact flanges provide:

• superior sealing performance
• reduced size and weight
• improved fatigue resistance
• enhanced operational safety

Compared with conventional ASME flanges, compact flanges offer:

• significantly lower weight
• smaller outside diameter
• improved sealing reliability
• reduced bolt load requirements

We are a professional manufacturer and exporter of:

• NORSOK Compact Flanges
• ISO 27509 Compact Flanges
• Compact Weld Neck Flanges
• Compact Blind Flanges
• Compact Hub Connectors in China.

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What is a Compact Flange?

A compact flange is a high-performance flange connection system developed for:

• high-pressure piping systems
• offshore platforms
• subsea applications
• critical process systems

Unlike conventional ASME flanges, compact flanges use:

• metal-to-metal sealing
• compact geometry
• optimized bolt preload

to achieve:

• zero leakage performance
• improved fatigue resistance
• smaller flange dimensions

Compact flanges are particularly suitable for:

• offshore oil & gas systems
• subsea manifolds
• high vibration service
• critical sealing applications

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NORSOK L-005 Standard

NORSOK L-005 is the Norwegian standard covering:

• compact flange connections
• high-integrity piping systems
• offshore piping applications

The standard defines:

• flange dimensions
• seal ring design
• bolt requirements
• gasket geometry
• pressure ratings
• inspection requirements

NORSOK compact flanges are extensively used in:

• North Sea offshore projects
• subsea production systems
• FPSO piping systems

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ISO 27509 Standard

ISO 27509 is the international standard for:

• compact flange connections
• high-pressure flange systems
• offshore and subsea piping

ISO 27509 harmonizes compact flange requirements for global oil & gas projects.

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Advantages of Compact Flanges

Reduced Weight

Compact flanges can reduce:

• flange weight
• piping system weight
• offshore structural loads

Weight reduction may exceed:

• 50% compared with ASME flanges

Improved Sealing Performance

Compact flange systems use:

• metal-to-metal sealing
• self-energized sealing mechanism

to achieve:

• high-integrity sealing
• low leakage risk

Smaller Dimensions

Compact flanges have:

• reduced outside diameter
• shorter installation length

allowing:

• easier installation
• space saving

Improved Fatigue Resistance

Ideal for:

• offshore platforms
• subsea systems
• dynamic piping systems

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Compact Flange Specifications

Specification	Details
Standard	NORSOK L-005 / ISO 27509
Product Type	Compact Flange
Material	Carbon Steel / Stainless Steel / Alloy Steel
Design	High Integrity Metal Seal
Connection Type	Compact Hub Connection
Service	High Pressure / Offshore / Subsea

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Available Types of Compact Flanges

Compact Weld Neck Flange

Used for:

• high-pressure pipelines
• subsea piping systems

Compact Blind Flange

Used for:

• pipeline isolation
• pressure sealing

Compact Connector Flange

Used in:

• subsea equipment
• offshore manifold systems

Compact Hub Flange

Designed for:

• critical piping systems
• fatigue-sensitive service

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Compact Flange Materials

Compact flanges are commonly manufactured from:

• ASME A694: F42 / F52 / F60 / F65 / F70ASTM A350: LF2 Classes 1 an 2 / LF1 to LF9

  ASTM A105

  NORSOK M-630 

  API A182 : F316 / 316L / F304 / 304L

  API A182 : F51 / F53 / F55 / F22 / F5 / F9 / F11 / F91

  ASME IX / DNV-OS-F101 : Corrosion Resistance Overlay (Cladded)

Material selection depends on:

• pressure rating
• operating temperature
• corrosion environment

 

DN	NPS	DW3 [mm]	HW3 [mm]	HW5 [mm]	BCD [mm]	A [mm]	B [mm]	NUMBER OF HOLES	DIAM. [inch]
15	1/2″	93	20	51	67,3	21,3	15,8-11,7	4	1/2″
20	3/4″	98	20	53	72,7	26,7	21,0-15,6	4	1/2″
25	1″	105	20	56	79,4	33,4	27,9-20,7	4	1/2″
40	1 1/2″	121	23	64	95,3	48,3	42,8-34,0	8	1/2″
50	2″	136	23	60	110	60,3	54,8-42,8	8	1/2″
65	2 1/2″	149	26	66	123,1	73,0	66,9-59,0	12	1/2″
80	3″	161	25	61	134,9	88,9	82,8-73,7	12	1/2″
100	4″	203	31	70	171,7	114,3	108,2-97,2	12	5/8″
125	5″	230	35	78	198,6	141,3	134,5-122,2	12	5/8″
150	6″	258	36	75	226,8	168,3	154,1-146,4	12	5/8″
200	8″	312	43	87	280,4	219,1	206,4-193,7	20	5/8″
250	10″	382	53	102	344,8	273,1	260,4-242,9	20	3/4″
300	12″	450	60	108	407,7	323,9	307,1-288,9	20	7/8″
350	14″	482	64	113	439,2	355,6	339,8-317,5	24	7/8″
400	16″	547	73	122	499	406,4	387,3-363,5	24	1″
450	18″	614	80	131	560,1	457,2	438,1-409,5	24	1-1/8″
500	20″	664	86	139	610,6	508,0	482,6-455,6	28	1-1/8″
550	22″	730	94	149	670,7	558,8	533,4-501,6	24	1-1/4″
600	24″	785	100	158	725,6	609,6	584,2-547,7	28	1-1/4″
650	26″	835	105	166	775,6	660,4	632,0-604,4	32	1-1/4″
700	28″	900	112	176	835,2	711,2	679,4-655,2	32	1-3/8″
800	32″	1016	126	195	945,7	812,8	777,8-752,8	32	1-1/2″
850	34″	1081	133	205	1004,8	863,6	828,6-799,6	32	1-5/8″
900	36″	1134	145	214	1058,4	914,4	876,3-842,4	32	1-5/8″
950	38″	1196	147	223	1115	965,2	925,2-893,2	32	1-3/4″
1000	40″	1251	153	232	1169,6	1016,0	976,0-936,0	36	1-3/4″
1050	42″	1312	165	241	1225,2	1066,8	1022,4-986,8	32	1-7/8″
1100	44″	1365	170	249	1278,5	1117,6	1073,2-1027,6	36	1-7/8″
1150	46″	1438	174	262	1345,9	1168,4	1124,0-1078,4	36	2″
1200	48″	1490	189	270	1397,4	1219,2	1169,2-1129,2	36	2″

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Compact Flange Face Design

Compact flanges use:

• metal-to-metal sealing faces
• compact seal rings

The sealing mechanism provides:

• high gasket seating stress
• improved sealing integrity
• reduced leakage probability

Unlike conventional flanges, compact flanges rely less on:

• gasket compression alone

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Compact Flange vs ASME B16.5 Flange

Property	Compact Flange	ASME Flange
Weight	Lower	Higher
Outside Diameter	Smaller	Larger
Sealing Performance	Superior	Standard
Fatigue Resistance	Excellent	Moderate
Offshore Use	Ideal	Common
Bolt Load	Lower	Higher

Compact flanges are increasingly preferred for:

• offshore platforms
• subsea systems
• critical piping applications

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Pressure and Temperature Performance

Compact flanges are designed for:

• high-pressure service
• high-temperature service
• cyclic loading conditions

Suitable applications include:

• subsea production systems
• HPHT pipelines
• offshore manifolds

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Manufacturing Process of Compact Flanges

Typical manufacturing process includes:

• open die forging
• heat treatment
• CNC machining
• groove machining
• seal face machining
• dimensional inspection

Strict quality control ensures:

• flange flatness
• sealing surface accuracy
• dimensional consistency

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Heat Treatment of Compact Flanges

Depending on material grade, compact flanges may be supplied in:

• normalized condition
• quenched and tempered condition
• solution annealed condition

Heat treatment improves:

• toughness
• strength
• fatigue resistance

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Inspection and Testing

Compact flanges may undergo:

• chemical composition analysis
• mechanical testing
• hardness testing
• ultrasonic testing (UT)
• magnetic particle testing (MT)
• dye penetrant testing (PT)
• dimensional inspection

Optional inspection includes:

• PMI testing
• third-party inspection
• subsea project qualification

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NACE MR0175 Compliance

Compact flanges can be manufactured according to:

• NACE MR0175
• ISO 15156
• NACE MR0103

Additional sour service requirements may include:

• hardness control
• HIC testing
• SSC resistance testing

NACE compliant compact flanges are widely used in:

• sour gas systems
• offshore production systems
• subsea oil & gas facilities

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Surface Protection Options

Compact flanges can be supplied with:

• anti-rust oil
• phosphating
• zinc coating
• offshore protective coatings

Surface protection depends on:

• transportation conditions
• offshore storage requirements
• project specifications

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Applications of Compact Flanges

Offshore Oil & Gas Platforms

Used in:

• topside piping
• process systems
• manifold piping

Subsea Production Systems

Applied in:

• subsea manifolds
• subsea trees
• subsea jumpers

FPSO Systems

Suitable for:

• compact piping layouts
• weight-sensitive applications

LNG & Petrochemical Plants

Used in:

• high-pressure process piping
• critical sealing systems

Compact flanges are ideal for:

• limited-space installations
• fatigue-critical applications
• high-integrity sealing systems

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Why Use Compact Flanges in Offshore Projects?

Compact flanges provide:

• lower offshore structural weight
• reduced installation space
• superior leak prevention
• lower maintenance requirements

These advantages significantly reduce:

• offshore installation cost
• lifecycle maintenance cost
• operational risk

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Frequently Asked Questions

What is a compact flange?

A compact flange is a high-integrity flange connection system designed for offshore and high-pressure piping applications.

What is NORSOK L-005?

NORSOK L-005 is the Norwegian standard for compact flange connections used in offshore oil & gas systems.

What is ISO 27509?

ISO 27509 is the international standard covering compact flange systems for high-pressure piping.

Why are compact flanges used offshore?

Compact flanges reduce:

• weight
• installation space
• leakage risk

making them ideal for offshore systems.

Are compact flanges better than ASME flanges?

For offshore and high-pressure applications, compact flanges generally provide:

• better sealing
• lower weight
• improved fatigue resistance

Can compact flanges meet NACE MR0175 requirements?

Yes. Compact flanges can be manufactured for sour service applications according to NACE MR0175.

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Related Products

• ASTM A694 F60 Flange
• ASTM A694 F65 Flange