Flange Bolt

1. Industrial Context of Flange Bolts

Flange bolts are critical structural fastening elements developed to improve load distribution, joint stability, and assembly efficiency in engineered bolted joints. Unlike conventional hex bolts requiring separate washers, flange bolts integrate a washer-like bearing surface directly beneath the head.

Across modern industrial sectors, flange bolts are widely adopted where:

• High clamp load stability is required
• Vibrational loosening risk exists
• Assembly speed and repeatability are essential
• Controlled bearing pressure must be maintained

Primary Industrial Adoption

Industry	Functional Role
Structural Steel Construction	Beam-to-column secondary connections
Oil & Gas	Equipment skid mounting, pipe supports
Power Generation	Turbine housings, generators
Petrochemical Plants	Pumps, valves, flange assemblies
LNG & Offshore	Corrosion-resistant structural joints
Automotive & Heavy Equipment	Chassis and engine assemblies
Railways	Bogie structures, track assemblies
Shipbuilding	Deck fittings, machinery bases

Within EPC project environments, flange bolts reduce installation variability while improving torque transfer efficiency — a major advantage during large-scale installations.

SM Fasteners manufactures flange bolts aligned with international compliance frameworks suitable for global procurement environments.

2. Technical Definition

A Flange Bolt is defined as:

A hexagonal head bolt incorporating an integral circular flange designed to distribute clamping load over a wider surface area while eliminating the need for a separate washer.

Key Structural Elements

1. Hexagonal driving head
2. Integral flange bearing surface
3. Shank (partial or full thread)
4. External thread form
5. Fillet transition radius

The flange increases the effective bearing diameter, reducing localized compressive stress.

3. Functional Role in Bolted Joints

Flange bolts perform three simultaneous mechanical functions:

3.1 Clamping Function

Generates preload to compress joint members.

3.2 Load Distribution

Flange spreads compressive forces, minimizing:

• Surface indentation
• Coating damage
• Joint relaxation

3.3 Anti-Loosening Assistance

Serrated flange variants increase friction resistance.

4. Load Mechanics & Force Behaviour

A bolted joint behaves as a preloaded spring system.

Fundamental Relationship

$$F = \frac{T}{K \times D}$$

Where:

Symbol	Meaning
F	Preload force
T	Applied torque
K	Nut factor
D	Nominal diameter

Load Path Concept

External loads are shared between:

• Bolt tensile elasticity
• Joint compression stiffness

Proper preload ensures external loads do not separate joint members.

Load Conditions Acting on Flange Bolts

Load Type	Engineering Effect
Tensile	Bolt elongation
Shear	Joint slip risk
Dynamic	Fatigue initiation
Thermal	Differential expansion
Vibratory	Self-loosening tendency

5. Torque–Tension Relationship

Only a small percentage of tightening torque produces preload.

Energy Distribution	Typical Percentage
Thread friction	40%
Bearing friction	50%
Useful preload	10%

The integral flange increases bearing stability, improving torque repeatability.

6. Joint Design Principles

6.1 Preload Requirement

Preload must exceed expected service loads.

Recommended:$$Preload = 70\%-75\% \text{ of proof load}$$

6.2 Flange Bearing Pressure

$$P = \frac{F}{A}$$

Where:

• P = Bearing pressure
• A = Flange contact area

Larger flange diameter reduces substrate stress.

6.3 Thread Engagement Rule

Minimum engagement:

Material	Engagement
Steel	1 × diameter
Aluminum	1.5 × diameter
Cast Iron	1.25 × diameter

6.4 Joint Stiffness Ratio

Ideal joint design ensures:$$K_{joint} > K_{bolt}$$

Meaning joint compression dominates load absorption.

7. Failure Mechanisms in Flange Bolted Joints

Fatigue Failure

Occurs from fluctuating tensile stress due to insufficient preload.

Shear Failure

Develops when frictional resistance is lost.

Hydrogen Embrittlement

Risk in high-strength coated bolts (>1000 MPa).

Stress Corrosion Cracking

Common in chloride and sour gas environments.

Embedment Relaxation

Reduced preload caused by surface flattening.

SM Fasteners controls these risks through:

• Controlled heat treatment
• Verified coating processes
• ISO 9001 traceability systems

8. Flange Bolt vs Conventional Hex Bolt

Parameter	Hex Bolt	Flange Bolt
Washer Required	Yes	No
Load Distribution	Localized	Wide
Assembly Speed	Moderate	Faster
Torque Stability	Lower	Higher
Vibration Resistance	Moderate	Improved

9. Engineering Advantages in EPC Projects

• Reduced component count
• Lower installation error probability
• Improved torque accuracy
• Reduced maintenance intervention
• Better coating protection

10. Functional Selection Criteria

Engineers select flange bolts based on:

Parameter	Consideration
Load magnitude	Tensile vs shear
Environment	Corrosive, offshore
Temperature	Material expansion
Accessibility	Installation tools
Inspection requirements	Traceability
Maintenance interval	Anti-loosening needs

11. Role in High-Reliability Systems

Flange bolts are frequently specified where failure consequences are high:

• Rotating equipment bases
• Pressure system supports
• Offshore modules
• Structural vibration zones

SM Fasteners integrates certified manufacturing, advanced materials, and inspection control to meet such reliability requirements.

12. Product Types and Variants of Flange Bolts

Flange bolts are engineered in multiple configurations to meet differing mechanical, installation, and environmental performance requirements. Selection must consider load transfer characteristics, joint surface condition, and operational reliability.

12.1 Standard Hex Flange Bolt (Plain Flange)

Description:
Hex head bolt with smooth integral washer flange.

Characteristics

• Uniform load distribution
• Compatible with coated surfaces
• Reduced surface galling risk
• Controlled torque repeatability

Typical Uses

• Structural assemblies
• Machinery mounting
• Pump and compressor housings
• Steel fabrication

12.2 Serrated Flange bolt

Description:
Flange underside incorporates radial serrations acting as a locking mechanism.

Mechanical Function

• Increases friction coefficient
• Resists rotational loosening
• Eliminates lock washer requirement

Engineering Consideration
Not recommended where:

• Surface coatings must remain intact
• Soft materials are clamped

Applications

• Automotive chassis
• Vibratory equipment
• Rail assemblies

12.3 Heavy Hex Flange Bolt

Designed for:

• High preload joints
• Structural steel connections
• Elevated clamp loads

Features:

• Larger head height
• Increased wrenching area
• Higher torque capability

12.4 Metric Flange Bolt (ISO Series)

Widely used internationally.

Advantages:

• Standardized pitch systems
• Global interchangeability
• EPC procurement compatibility

12.5 Inch Series Flange Bolt (UNC / UNF)

Used primarily in:

• Oil & Gas legacy equipment
• American-designed machinery
• Offshore installations

12.6 Partially Threaded Flange Bolt

Purpose:

• Shear load transfer through shank
• Reduced stress concentration

Recommended for:

• Structural joints
• Dynamic loading environments

12.7 Fully Threaded Flange Bolt

Used where:

• Adjustable grip length required
• Thin joint stack-up exists

12.8 PEEK Flange Bolts (High-Performance Polymer)

SM Fasteners manufactures advanced PEEK flange fasteners for specialized environments.

Advantages

Property	Performance
Electrical insulation	Excellent
Chemical resistance	Outstanding
Weight reduction	High
Non-magnetic	Yes
Temperature capability	Up to 260°C

Applications

• Semiconductor equipment
• Chemical plants
• Medical systems
• Offshore instrumentation

13. Dimensional Logic and Geometry

The geometry of flange bolts directly affects preload accuracy, bearing stress, and fatigue life.

Key Dimensional Parameters

Symbol	Description
d	Nominal diameter
P	Thread pitch
k	Head height
s	Across flats
dc	Flange diameter
r	Under-head fillet radius
b	Thread length

Engineering Geometry Principles

13.1 Flange Diameter Selection

Typical design rule:$$dc = 1.7d \text{ to } 2.2d$$

Provides optimal pressure distribution.

13.2 Under-Head Radius Importance

Prevents stress concentration at transition zone — a common fatigue initiation location.

13.3 Grip Length Optimization

$$Grip\ Length = Total\ Joint\ Thickness$$

Threads should ideally remain outside shear plane.

14. Standard Dimensional Specification Table

(Representative ISO Metric Flange Bolt Dimensions)

| Size | Pitch (mm) | Head AF (mm) | Head Height k (mm) | Flange Dia dc (mm) | Std Length Range (mm) |
|—|—|—|—|—|
| M5 | 0.8 | 8 | 3.5 | 11 | 10–40 |
| M6 | 1.0 | 10 | 4.0 | 13.5 | 10–60 |
| M8 | 1.25 | 13 | 5.3 | 17 | 12–80 |
| M10 | 1.5 | 15 | 6.4 | 21 | 16–100 |
| M12 | 1.75 | 18 | 7.5 | 25 | 20–150 |
| M16 | 2.0 | 24 | 10 | 33 | 25–200 |
| M20 | 2.5 | 30 | 12.5 | 41 | 30–300 |
| M24 | 3.0 | 36 | 15 | 50 | 40–300 |

Dimensions manufactured by SM Fasteners are verified through calibrated inspection equipment under ISO 9001 quality systems.

15. Thread Standards & Tolerances

Global projects require compatibility across multiple threading systems.

Thread Systems Supported

Thread System	Standard	Typical Usage
Metric Coarse	ISO 261 / ISO 965	Global EPC projects
Metric Fine	ISO 261	Automotive & precision
UNC	ASME B1.1	Oil & Gas equipment
UNF	ASME B1.1	High fatigue joints
BSW	BS 84	Legacy British equipment
BSF	BS 84	Fine thread applications

Thread Tolerance Classes

System	External Thread
Metric	6g
Precision Metric	4g6g
UNC/UNF	Class 2A
High Precision	Class 3A

Thread rolling preferred over cutting due to:

• Improved fatigue strength
• Work-hardened grain flow
• Reduced notch effect

16. Applicable International Standards

Flange bolts must comply with recognized global specifications for interchangeability and inspection acceptance.

ISO Standards

Standard	Description
ISO 4162	Hexagon flange bolts
ISO 4014	Partially threaded bolts
ISO 4017	Fully threaded bolts
ISO 898-1	Mechanical properties
ISO 3506	Stainless fasteners

DIN Standards

DIN Standard	Application
DIN 6921	Hex flange bolts
DIN EN ISO 10642	Structural compatibility
DIN 267	Coating requirements

ASTM Standards

ASTM	Description
ASTM A307	Carbon steel bolts
ASTM A325	Structural bolts
ASTM A193	Alloy steel pressure service
ASTM F568M	Metric mechanical properties
ASTM A453	High-temperature bolting

British Standards (BS)

BS Standard	Application
BS 3692	Metric bolts
BS EN 14399	Structural assemblies
BS 4190	General engineering bolts

17. Property Class System (Metric)

Mechanical performance classification:

Property Class	Yield Strength MPa	Tensile Strength MPa
5.8	400	500
8.8	640	800
10.9	940	1040
12.9	1100	1220

Higher class → higher preload capability.

18. Proof Load & Tensile Strength Table (Representative)

Size	Property Class	Proof Load (kN)	Ultimate Tensile (kN)
M8	8.8	18	23
M10	8.8	29	36
M12	8.8	42	52
M16	8.8	78	98
M20	10.9	140	174
M24	10.9	202	252

Values verified during mechanical testing aligned with ISO 898-1 requirements.

19. Interchangeability Considerations

Critical factors during international procurement:

• Thread compatibility
• Head clearance
• Flange diameter interference
• Tool access requirements
• Surface finish compatibility

SM Fasteners supports EPC buyers with cross-standard dimensional verification and custom engineering solutions when replacement bolts must match legacy equipment.

20. Engineering Selection Matrix — Flange Bolt Type

Requirement	Recommended Variant
High vibration	Serrated flange
Structural loading	Heavy hex flange
Corrosive environment	Stainless/Duplex
Electrical isolation	PEEK flange bolt
High temperature	Alloy steel
Maintenance-critical	Plain flange

21. Design Integration with Modern Assemblies

Flange bolts simplify assemblies by:

• Eliminating washers
• Reducing inventory complexity
• Improving torque repeatability
• Increasing assembly speed
• Enhancing automated production compatibility

These advantages make flange bolts standard components in globally engineered systems supplied by SM Fasteners.

22. Material Engineering Philosophy for Flange Bolts

Material selection is the most critical engineering decision governing flange bolt performance. The chosen alloy must simultaneously satisfy:

• Mechanical strength requirements
• Corrosion resistance
• Temperature stability
• Fatigue resistance
• Environmental compatibility
• Compliance with international project specifications

SM Fasteners manufactures flange bolts across a full industrial metallurgy spectrum, enabling EPC procurement teams to standardize sourcing under a single ISO 9001 certified quality system.

23. Industrial Material Range

23.1 Carbon Steel Flange Bolts

Primary application material for structural and general engineering assemblies.

Typical Grades

• ASTM A307
• ISO Property Class 4.6 / 5.8 / 8.8
• EN 10269 carbon steels

Advantages

• Cost efficiency
• High availability
• Good machinability
• Suitable for coated systems

Limitations

• Requires corrosion protection
• Limited high-temperature capability

23.2 Alloy Steel Flange Bolts

Designed for high strength and elevated temperature service.

Typical Standards

• ASTM A193 B7
• ASTM A193 B16
• ISO Property Class 10.9 / 12.9

Applications

• Pressure vessels
• Refinery piping supports
• Turbine equipment
• LNG modules

23.3 Stainless Steel Flange Bolts

Provide corrosion resistance without coating dependency.

Grade	Equivalent	Characteristics
A2-70	SS304	General corrosion resistance
A4-80	SS316	Marine & chloride resistance
321	Stabilized SS	High temperature
904L	High alloy	Acid resistance

23.4 Duplex & Super Duplex Stainless Steel

Used in aggressive offshore environments.

Grade	Standard	Key Benefit
Duplex 2205	UNS S32205	High strength + corrosion resistance
Super Duplex 2507	UNS S32750	Seawater resistance
Zeron 100	Super Duplex	Extreme offshore duty

Compliant with NACE MR0175 / ISO 15156 for sour service applications.

23.5 Nickel Alloy Flange Bolts

Manufactured for severe chemical and high-temperature applications.

Alloy	Typical Environment
Inconel 625	Offshore, high temp
Inconel 718	Aerospace & turbines
Monel 400	Seawater
Hastelloy C276	Acid processing
Incoloy 825	Chemical plants
SMO 254	Chloride-rich seawater

23.6 PEEK Flange Bolts (Advanced Polymer Engineering)

SM Fasteners manufactures PEEK flange bolts for specialized industrial systems.

Key Engineering Properties

Property	Value
Continuous Temperature	260°C
Density	1.3 g/cm³
Chemical Resistance	Excellent
Electrical Conductivity	Insulating
Magnetic Response	None

Applications

• Semiconductor manufacturing
• Chemical dosing systems
• Medical instrumentation
• Offshore electronic enclosures

24. Material Comparison Table

Material	UTS (MPa)	Yield (MPa)	Corrosion Resistance	Temp Limit	Relative Cost	Typical Use
Carbon Steel	500–800	300–640	Low	300°C	Low	Structural
Alloy Steel	900–1200	700–1000	Moderate	550°C	Medium	Pressure systems
SS304	700	450	Good	400°C	Medium	General industry
SS316	800	600	Very Good	450°C	Medium	Marine
Duplex 2205	800	550	Excellent	300°C	High	Offshore
Super Duplex	900	650	Outstanding	300°C	Very High	Seawater
Inconel 625	1000+	700	Exceptional	980°C	Premium	LNG/Turbines
PEEK	—	—	Chemical resistant	260°C	High	Electrical isolation

25. Corrosion Resistance vs Environment

Environment	Recommended Material
Atmospheric Industrial	Zinc coated carbon steel
Marine	SS316 / Duplex
Seawater immersion	Super Duplex / Monel
Acidic chemical plant	Hastelloy
H₂S / Sour service	Duplex / Alloy steel (NACE compliant)
High temperature oxidation	Inconel
Chemical dosing	PEEK

26. Mechanical Properties by Grade

Property Class	Hardness (HRC)	Yield MPa	Tensile MPa	Elongation
5.8	16–20	400	500	20%
8.8	22–32	640	800	12%
10.9	32–39	940	1040	9%
12.9	39–44	1100	1220	8%

Hardness limits are tightly controlled to avoid hydrogen embrittlement risks.

27. Heat Treatment Processes

Heat treatment determines final mechanical behavior of flange bolts.

27.1 Normalizing

• Grain refinement
• Uniform structure formation

27.2 Quenching

Process:

1. Austenitizing
2. Rapid cooling
3. Martensite formation

Purpose:

• Strength enhancement

27.3 Tempering

Reduces brittleness while maintaining strength.

Critical for:

• Property Class 8.8+
• ASTM A193 B7 bolts

27.4 Solution Annealing (Stainless Steel)

• Dissolves carbides
• Restores corrosion resistance

27.5 Age Hardening (Nickel Alloys)

Applied to:

• Inconel 718
• Precipitation-strengthened alloys

Heat Treatment Control Parameters

Parameter	Control Method
Furnace uniformity	Calibrated thermocouples
Cooling rate	Controlled quench media
Hardness verification	Rockwell testing
Batch traceability	Heat number tracking

SM Fasteners integrates full heat treatment traceability linked to EN 10204 certification.

28. Manufacturing Workflow — End-to-End Process

Step 1 — Raw Material Verification

• Mill Test Certificate (MTC)
• Chemical composition check
• PMI verification for alloys

Step 2 — Cutting & Preparation

• Bar stock cutting
• Automated length control

Step 3 — Hot Forging / Cold Heading

Process	Advantage
Cold heading	High production accuracy
Hot forging	Large diameter bolts

Forging aligns grain flow improving fatigue strength.

Step 4 — Flange Formation

Integrated die forging creates:

• Uniform flange thickness
• Controlled bearing face

Step 5 — Thread Formation

Thread Rolling (Preferred)

• Improves fatigue resistance
• Work hardening
• Smooth surface finish

Thread Cutting

Used for:

• Large diameters
• Exotic alloys

Step 6 — Heat Treatment

Performed under controlled furnace conditions ensuring mechanical compliance.

Step 7 — Surface Preparation

• Shot blasting
• Pickling
• Passivation (stainless steel)

Step 8 — Coating / Surface Engineering

29. Surface Finish & Coating Technologies

Surface engineering extends service life.

Common Industrial Coatings

Coating	Thickness	Corrosion Protection	Temp Limit
Zinc Plating	8–12 µm	Moderate	120°C
Hot Dip Galvanizing	45–85 µm	Excellent	450°C
Mechanical Galvanizing	Uniform	Good	300°C
Dacromet / Geomet	Thin film	Very High	300°C
PTFE / Xylan	Low friction	Chemical resistant	260°C
Black Oxide	Minimal	Low	150°C
Passivation	Stainless only	Enhances CR	High

30. Surface Finish Comparison Table

Finish	Corrosion Life	Friction Stability	Hydrogen Embrittlement Risk	Typical Industry
Zinc Electroplate	Medium	Good	Possible	Construction
HDG	High	Moderate	Low	Infrastructure
Dacromet	Very High	Excellent	Very Low	Automotive
PTFE Coating	High	Excellent	None	Chemical
Passivated SS	Excellent	Stable	None	Offshore

31. Hydrogen Embrittlement Control

Critical for high-strength flange bolts.

SM Fasteners applies:

• Baking after plating
• Controlled hardness limits
• Certified coating vendors
• Process validation records

32. Manufacturing Traceability System

Each production batch includes:

• Heat number traceability
• Production lot identification
• Heat treatment records
• Mechanical test linkage
• Inspection documentation

All maintained under ISO 9001 quality management systems audited under UKAF accreditation.

33. Engineering Impact of Manufacturing Choices

Manufacturing Factor	Engineering Outcome
Forged head	Increased fatigue life
Rolled threads	Higher tensile performance
Controlled tempering	Reduced brittleness
Proper coating	Extended service life
Accurate flange geometry	Stable preload

34. Procurement Advantages from SM Fasteners

• Multi-material capability under one manufacturer
• Custom flange geometry development
• PEEK and exotic alloy manufacturing
• EPC documentation readiness
• Consistent batch traceability

35. Inspection & Quality Control Philosophy

Flange bolts used in industrial systems are classified as safety-critical mechanical components. Their acceptance depends not only on dimensional compliance but also on verified metallurgical integrity, mechanical performance, and full traceability.

SM Fasteners operates under an ISO 9001 certified quality management system audited under UKAF accreditation, ensuring compliance with global EPC inspection and procurement protocols.

Quality assurance integrates:

• Incoming material verification
• In-process manufacturing inspection
• Mechanical validation testing
• Final inspection and documentation release

36. Incoming Raw Material Inspection

Every production batch begins with verification of raw material integrity.

Incoming Inspection Controls

Inspection Activity	Method
Mill Test Certificate Review	EN 10204 3.1
Chemical Composition	Spectrometer analysis
Positive Material Identification (PMI)	XRF / OES
Surface defect inspection	Visual & magnetic
Heat number allocation	Traceability marking

Material traceability is maintained from steel mill to final dispatch.

37. In-Process Dimensional Inspection

Critical flange bolt geometry is monitored during production.

Controlled Parameters

• Head dimensions
• Flange diameter
• Thread pitch accuracy
• Thread concentricity
• Under-head fillet radius
• Straightness and runout

Inspection tools include:

• Digital micrometers
• Go/No-Go thread gauges
• Optical profile measurement
• Coordinate measuring instruments

38. Mechanical Testing Requirements

Performed according to ISO 898-1, ASTM, and DIN requirements.

Test	Purpose
Tensile Test	Ultimate strength verification
Proof Load Test	Elastic limit confirmation
Hardness Test	Heat treatment validation
Wedge Test	Head integrity
Impact Test (if specified)	Low-temperature service
Elongation	Ductility confirmation

39. Non-Destructive Testing (NDT)

Used for critical or high-value fasteners.

Method	Detection Capability
Magnetic Particle Inspection	Surface cracks
Ultrasonic Testing	Internal defects
Dye Penetrant	Micro surface flaws
Eddy Current	Thread defects

40. Coating Inspection

Surface engineering quality significantly influences corrosion life.

Inspection includes:

• Coating thickness measurement
• Adhesion testing
• Salt spray testing (ASTM B117)
• Hydrogen embrittlement verification

41. Documentation & Certification Package

SM Fasteners supplies full documentation required by EPC contractors and third-party inspectors.

Standard Documentation

Document	Standard
Mill Test Certificate	EN 10204 3.1 / 3.2
Heat Treatment Report	Furnace traceability
Dimensional Inspection Report	ISO compliance
Mechanical Test Report	ISO / ASTM
Coating Certificate	Process validation
Certificate of Conformity	ISO 9001 system
PMI Report (when required)	Alloy verification

42. Failure Prevention & Reliability Assurance

Major Failure Modes

Failure Mode	Preventive Control
Fatigue failure	Correct preload
Shear failure	Proper grip design
Hydrogen embrittlement	Controlled plating
Stress corrosion cracking	Material selection
Galling	Lubrication or coating
Joint relaxation	Correct flange bearing

SM Fasteners integrates engineering review during procurement stages to prevent mismatch between bolt design and operating environment.

43. Industrial Application Mapping

Construction & Structural Steel

• Secondary structural joints
• Equipment platforms
• Steel fabrication assemblies

Oil & Gas — Upstream / Midstream / Downstream

• Pipe supports
• Compressor bases
• Valve mounting
• Offshore modules

Power Generation

• Turbine casings
• Generator housings
• Boiler auxiliary equipment

Petrochemical & Chemical Processing

• Pumps
• Heat exchangers
• Reactor assemblies

LNG & Offshore Installations

• Corrosion-resistant assemblies
• Marine structural equipment

Automotive & Heavy Equipment

• Chassis mounting
• Engine brackets
• Suspension systems

Railways & Infrastructure

• Track structures
• Bridge fittings
• Signaling equipment

Shipbuilding & Marine Engineering

• Deck equipment
• Machinery fastening
• Corrosion-prone assemblies

PEEK Flange Bolt Applications

• Electrical isolation joints
• Instrumentation panels
• Chemical dosing systems
• Semiconductor production lines

44. Export Capability & Global Supply Readiness

SM Fasteners supports international EPC procurement programs with structured export logistics.

Industrial Packaging

Packaging Method	Purpose
VCI Packaging	Corrosion prevention
Thread Protectors	Damage avoidance
Heat-sealed bags	Moisture control
Batch labeling	Traceability

Export Crating

• ISPM-15 compliant wooden crates
• Fumigated export pallets
• Shock-resistant packing
• Containerized bulk shipment capability

Global Documentation Support

• Packing List
• Commercial Invoice
• Certificate of Origin
• Material Traceability Records
• Third-Party Inspection Approval
• Customs compliance documentation

45. Tightening Torque Chart

(Lubricated Condition — Typical Engineering Reference)

Size	Grade 8.8 (Nm)	Grade 10.9 (Nm)	Grade 12.9 (Nm)
M6	10	14	17
M8	25	36	43
M10	49	70	84
M12	85	120	145
M16	210	300	355
M20	410	580	690
M24	710	1000	1200

Torque values depend on lubrication coefficient and coating type.

46. Preload Calculation — Worked Engineering Example

Formula

$$F = \frac{T}{K \times D}$$

Where:

• T = Torque applied
• K = Nut factor (≈0.18 lubricated)
• D = Bolt diameter

Example — M16 Flange Bolt

Given:

• Torque = 300 Nm
• Diameter = 16 mm = 0.016 m
• Nut factor = 0.18

$$F = \frac{300}{0.18 \times 0.016}$$

$$F = 104,166 \text{ N } \approx 104 kN$$

This preload ensures sufficient clamp force for structural reliability.

47. Thread Standards & Tolerance Table

Thread Type	Pitch Example	Tolerance	Application
Metric Coarse	M16×2	6g	Global EPC
Metric Fine	M16×1.5	6g	Dynamic loading
UNC	5/8-11	2A	Oil & Gas
UNF	5/8-18	2A	Fatigue resistant
BSW	5/8″	Medium	Legacy equipment
BSF	Fine	Precision	British systems

48. Surface Finish Performance Comparison

Coating	Corrosion Life	Friction	Reusability	Industry
Zinc Plated	Medium	Stable	Moderate	Construction
HDG	High	Higher friction	Limited	Infrastructure
Dacromet	Very High	Excellent	High	Automotive
PTFE	Chemical resistant	Very Low	High	Chemical
Passivated Stainless	Excellent	Stable	High	Offshore

49. Weight Chart — Flange Bolts

(Approximate Values — aligned with SM Fasteners manufacturing data)

Size	Length (mm)	Weight/Pc (kg)	Weight/100 pcs (kg)
M8	25	0.020	2.0
M10	30	0.040	4.0
M12	40	0.075	7.5
M16	50	0.160	16
M20	60	0.300	30
M24	70	0.520	52

Weight data supports project estimation, logistics planning, and structural load calculations.

50. Proof Load & Tensile Strength Reference Table

Size	Grade	Proof Load (kN)	Ultimate Tensile (kN)
M12	8.8	42	52
M16	8.8	78	98
M20	10.9	140	174
M24	10.9	202	252
M24	12.9	230	290

51. Engineering Selection Checklist

Before specifying flange bolts, engineers should confirm:

• Required preload
• Joint material hardness
• Environmental exposure
• Temperature range
• Required inspection level
• Coating compatibility
• Standard compliance
• Documentation requirement

SM Fasteners supports customized engineering consultation aligned with EPC specifications.

52. Integration into ISO 9001 Manufacturing System

SM Fasteners quality integration includes:

• Documented procedures
• Calibration control
• Process validation
• Risk-based manufacturing planning
• Continuous improvement monitoring
• UKAF audited certification framework

53. SM Fasteners — Engineering Manufacturing Capability

SM Fasteners positions flange bolts as engineered components rather than commodity hardware by providing:

• Multi-standard manufacturing (ISO / ASTM / DIN / BS)
• Advanced metallurgy capability including Duplex, Nickel alloys, and PEEK
• Precision forging and thread rolling
• Complete inspection traceability
• Global export packaging and logistics support
• Custom fastener engineering solutions

FINAL ENGINEERING SUMMARY

Flange bolts represent an optimized fastening solution combining:

• Improved load distribution
• Enhanced preload stability
• Reduced assembly complexity
• Increased vibration resistance
• Reliable performance across demanding industrial environments

Through certified quality systems, advanced materials capability, and full compliance with international standards, SM Fasteners demonstrates global readiness to supply flange bolts suitable for structural, mechanical, offshore, petrochemical, and high-reliability engineering applications.