U BOLT

1. Industry Context

1.1 Functional Role of U Bolts in Industrial Systems

A U Bolt is a curved threaded fastening element designed primarily to secure cylindrical, structural, or irregular components to a supporting framework. Unlike conventional bolts that generate clamping force between flat interfaces, U bolts provide radial restraint combined with axial clamping.

They are widely deployed where:

• Circular members require restraint
• Dynamic vibration exists
• Thermal expansion must be accommodated
• Alignment stability is critical

Typical restrained components include:

• Pipes and process lines
• Tubular structures
• Structural steel sections
• Cable trays
• Exhaust systems
• Offshore risers
• Equipment frames

In engineered assemblies, U bolts function as load-transfer devices, not merely holding components but managing:

• Static loads
• Dynamic vibration loads
• Thermal movement
• Shock and fatigue stresses

1.2 Industrial Importance Across Sectors

Construction & Structural Steel

• Pipe supports
• Cable containment systems
• Structural bracing
• HVAC suspension

Oil & Gas (Upstream–Downstream)

• Pipeline anchoring
• Instrument tubing fixation
• Offshore deck piping
• Process skid assembly

Power Generation

• Boiler piping
• Turbine auxiliary systems
• Cooling water lines

Petrochemical & Chemical Processing

• Corrosion-resistant pipe restraint
• High-temperature line support

LNG & Offshore Platforms

• Cryogenic pipe stabilization
• Vibration-controlled supports

Heavy Equipment & Automotive

• Suspension assemblies
• Axle retention systems

Railways & Infrastructure

• Trackside utilities
• Signaling structures

Shipbuilding & Marine Systems

• Seawater piping
• Engine room installations

SM Fasteners supplies U bolts aligned with global EPC procurement requirements, ensuring interchangeability with international standards.

1.3 Engineering Classification

U bolts are categorized as:

Category	Functional Objective
Pipe Support Fasteners	Load transfer without pipe deformation
Structural Clamp Fasteners	Rigid positioning
Suspension Fasteners	Vertical load carrying
Alignment Fasteners	Maintain geometry under vibration
Expansion-Allowing Fasteners	Permit thermal movement

2. Technical Definition

2.1 Formal Engineering Definition

A U Bolt is defined as:

A bent threaded rod forming a “U” profile with two parallel threaded legs designed to secure round, square, or rectangular members against a mounting surface using nuts and washers.

2.2 Primary Components

1. Crown (Bend Radius)
   Contacts restrained member.
2. Legs
   Parallel threaded sections transmitting load.
3. Threaded Ends
   Provide preload via nut tightening.
4. Nuts & Washers
   Distribute bearing pressure and generate clamping force.

2.3 Geometric Parameters

Key engineering dimensions:

Symbol	Parameter	Engineering Significance
d	Rod diameter	Strength capacity
C	Inside width	Member accommodation
H	Leg length	Engagement depth
R	Bend radius	Stress distribution
P	Thread pitch	Load transfer efficiency
L	Overall length	Installation clearance

2.4 Functional Behavior

Unlike straight bolts, U bolts:

• Apply distributed radial pressure
• Resist transverse motion
• Provide multi-directional restraint
• Operate under combined loading modes

3. Load Mechanics & Force Behavior

3.1 Load Types Acting on U Bolts

U bolts typically experience combined stress states:

Load Type	Source
Tensile Load	Nut tightening preload
Shear Load	Pipe movement
Bending Stress	Curved geometry
Fatigue Load	Vibration
Thermal Stress	Expansion/contraction
Impact Load	Flow-induced vibration

3.2 Force Transfer Mechanism

The load path follows:

1. Nut torque generates preload.
2. Preload produces clamping force.
3. Friction resists movement.
4. Load transfers to support structure.

Engineering Objective:
Maintain sufficient preload so operational loads never overcome frictional resistance.

3.3 Preload Concept

Preload is the most critical design parameter.$$F_p = \frac{T}{K \times d}$$

Where:

• $F_p$​ = Preload force (N)
• $T$ = Applied torque (Nm)
• $K$ = Nut factor (≈0.18–0.25)
• $d$ = Nominal diameter (m)

Proper preload ensures:

• Joint stability
• Fatigue resistance
• Vibration immunity

3.4 Frictional Holding Capacity

The resistance against sliding:$$F_{friction} = \mu \times F_p$$

Where:

• μ = friction coefficient
• Fp = preload

If operational load exceeds friction force → slip occurs.

3.5 Stress Distribution in the Bend

The curved region introduces:

• Stress concentration
• Plastic deformation risk
• Residual stresses

Engineering mitigation:

• Controlled bending radius
• Post-forming stress relief
• Proper heat treatment

SM Fasteners employs controlled forming practices ensuring uniform grain flow continuity, critical for fatigue resistance.

3.6 Torque–Tension Relationship

Only ~10–15% of applied torque generates preload.

Torque losses:

Loss Source	Typical Share
Thread friction	40%
Bearing surface friction	45%
Useful preload	15%

Hence lubrication and coating selection directly influence performance.

3.7 Failure Modes in U Bolts

1. Fatigue Failure

Occurs under cyclic vibration.

Causes:

• Insufficient preload
• Poor surface finish
• Sharp bend radius

2. Yielding / Plastic Deformation

Result of overload or undersized diameter.

3. Shear Failure

Typically due to pipe sliding or impact load.

4. Hydrogen Embrittlement

Risk in high-strength carbon steels with electroplated coatings.

Mitigation:

• Baking treatment
• Mechanical galvanizing
• Controlled hardness limits

5. Stress Corrosion Cracking (SCC)

Common in:

• Chloride environments
• Offshore structures
• Chemical plants

Material selection becomes critical.

6. Thread Stripping

Occurs when engagement length is insufficient.

Recommended engagement:$$L_e \geq 1.0 \times d$$

4. Joint Design Principles

4.1 U Bolt vs Conventional Bolted Joint

Parameter	Standard Bolt	U Bolt
Load Direction	Axial	Radial + Axial
Contact Surface	Flat	Cylindrical
Stress State	Uniform	Combined
Movement Control	Limited	High

4.2 Design Objective

A correctly designed U bolt joint must achieve:

• Adequate preload
• Controlled contact pressure
• Zero relative motion
• No pipe ovalization

4.3 Pipe Support Design Approaches

Rigid Support

Used where movement must be eliminated.

Guide Support

Allows axial movement.

Sliding Support

Reduces thermal stress.

Spring Support

For vertical displacement systems.

4.4 Clamp Pressure Calculation

Contact pressure:$$P = \frac{F_p}{A_c}$$

Where:

• Ac = contact area between pipe and bolt.

Excess pressure may deform thin-wall pipes.

4.5 Thermal Expansion Consideration

Thermal elongation:$$\Delta L = \alpha L \Delta T$$

Design must prevent excessive restraint causing:

• Pipe buckling
• Anchor overload
• Bolt fatigue

4.6 Vibration Design Guidelines

Recommended engineering practices:

• Use hardened washers
• Apply prevailing torque nuts
• Consider double-nut locking
• Maintain minimum preload ratio:

$$F_p \geq 2.5 \times F_{dynamic}$$

4.7 Installation Alignment Principles

Incorrect installation leads to premature failure.

Key requirements:

• Parallel leg alignment
• Uniform nut tightening
• Even washer seating
• Controlled torque application

4.8 Safety Factors

Typical engineering safety factors:

Industry	Safety Factor
Structural Steel	2.0
Oil & Gas	3.0
Offshore	3.5
Dynamic Equipment	4.0

4.9 Design Selection Workflow (Engineering Practice)

1. Identify pipe OD or member geometry.
2. Determine operational loads.
3. Calculate required preload.
4. Select diameter and material grade.
5. Verify corrosion resistance.
6. Confirm standard compliance.
7. Specify coating system.
8. Validate inspection requirements.

SM Fasteners supports project-specific engineering selection aligned with EPC procurement specifications and ISO 9001 traceability systems.

5. Product Types and Variants

5.1 Functional Classification of U Bolts

U bolts are engineered based on load behavior, installation geometry, and service environment. Selection directly influences joint reliability and lifecycle performance.

Type	Geometry	Primary Application	Engineering Purpose
Round Bend U Bolt	Circular crown	Pipe supports	Uniform radial load distribution
Square U Bolt	Square bend	Structural beams	Edge restraint
Semi-Round U Bolt	Partial curvature	Automotive suspension	Controlled movement
Long Tangent U Bolt	Extended legs	Deep mounting	Increased thread engagement
Heavy Duty U Bolt	Larger diameter	Offshore & heavy loads	High tensile capacity
Anchor U Bolt	Embedded ends	Concrete foundations	Permanent anchoring
Exhaust U Bolt	Saddle clamp configuration	Automotive exhaust	Vibration resistance
PEEK U Bolt	Polymer construction	Electrical & chemical systems	Non-metallic isolation

SM Fasteners manufactures both standardized and project-specific U bolt configurations, including engineered bends, customized leg lengths, and specialized thread forms.

5.2 Geometry-Based Design Variants

5.2.1 Round U Bolt

Most widely used configuration.

Advantages:

• Even stress distribution
• Reduced pipe indentation
• Suitable for pressure piping

Typical Industries:

• Oil & Gas
• Power plants
• Process industries

5.2.2 Square U Bolt

Designed for:

• Channel sections
• Rectangular frames
• Structural steel fixation

Engineering Feature:

• Prevents rotational movement.

5.2.3 Long Tangent U Bolt

Characteristics:

• Increased straight leg length before bend.
• Reduced bending stress concentration.

Preferred for:

• High-temperature pipelines
• Large insulation thickness

5.2.4 Heavy Series U BOLT

Designed for:

• High vibration systems
• Offshore modules
• Dynamic loading environments

Features:

• Larger rod diameter
• Higher preload capacity

5.2.5 Non-Metallic (PEEK) U Bolts

SM Fasteners provides PEEK fasteners where metallic contact is undesirable.

Applications:

• Electrical insulation
• Chemical exposure
• MRI equipment
• Semiconductor plants

Advantages:

• Non-conductive
• Chemical inertness
• Low thermal conductivity
• Zero galvanic corrosion risk

6. Dimensional Logic and Geometry Engineering

6.1 Governing Design Parameters

U bolt geometry is controlled by five critical dimensions:

Parameter	Symbol	Function
Rod Diameter	d	Determines load capacity
Inside Width	C	Fits pipe OD
Inside Height	H	Installation clearance
Thread Length	b	Engagement strength
Bend Radius	R	Fatigue resistance

6.2 Engineering Relationship Between Pipe OD and U Bolt Size

General selection rule:$$C = Pipe\ OD + Clearance$$

Recommended clearance:

Pipe Size	Clearance
≤ 2″	+2–3 mm
3″–10″	+3–6 mm
>10″	+6–12 mm

6.3 Bend Radius Engineering

Minimum bend radius:$$R \geq 1.5d$$

Benefits:

• Reduced residual stress
• Improved fatigue life
• Better coating adhesion

6.4 Thread Engagement Requirements

Minimum effective engagement:

Material	Engagement Length
Carbon Steel	1 × diameter
Stainless Steel	1.25 × diameter
Nickel Alloys	1.5 × diameter
PEEK	2 × diameter

6.5 Standard Dimensional Specification Table (Metric Series)

Typical U Bolt Dimensions — Metric

Nominal Size	Rod Dia (mm)	Inside Width C (mm)	Leg Length H (mm)	Thread Pitch	Bend Radius (mm)
M6	6	20–40	40–80	1.0	9
M8	8	25–50	50–100	1.25	12
M10	10	30–75	60–150	1.5	15
M12	12	40–100	80–200	1.75	18
M16	16	50–150	100–250	2.0	24
M20	20	70–200	120–300	2.5	30
M24	24	90–250	150–350	3.0	36
M30	30	120–350	200–450	3.5	45

Dimensional tolerances maintained according to ISO tolerance systems under SM Fasteners’ ISO 9001 quality control framework.

7. International Standards & Compliance

7.1 Global Manufacturing Standards

U bolts are produced under multiple international systems depending on project specification.

Standard	Region	Application
ISO 898	International	Mechanical properties
ISO 965	International	Thread tolerances
DIN 3570	Germany	Pipe U bolts
DIN 976	Germany	Thread standards
ASTM A307	USA	General purpose
ASTM A193	USA	High temperature/pressure
ASTM A320	USA	Low temperature service
ASTM F1554	USA	Anchor applications
BS 3974	UK	Pipe supports
BS 4190	UK	General fasteners

SM Fasteners ensures interchangeability across ISO, DIN, ASTM, and BS systems, supporting multinational EPC procurement.

7.2 Thread Standards & Tolerances

Thread System Comparison

Thread Type	Standard	Pitch Type	Typical Use
Metric Coarse	ISO 261	Coarse	Structural
Metric Fine	ISO 262	Fine	Dynamic loads
UNC	ASME B1.1	Coarse	Heavy industry
UNF	ASME B1.1	Fine	Automotive
BSW	BS 84	Coarse	Legacy UK equipment
BSF	BS 84	Fine	Precision assemblies

Thread Tolerance Classes

System	External Thread	Internal Thread
ISO Metric	6g	6H
UNC/UNF	2A	2B
Precision Fit	4g6g	4H

7.3 Mechanical Property Classes

ISO Property Class System

Property Class	Tensile Strength (MPa)	Yield Strength (MPa)	Application
4.6	400	240	Light duty
5.8	500	400	General use
8.8	800	640	Structural
10.9	1040	940	Heavy equipment
12.9	1220	1100	High strength assemblies

ASTM Equivalent Mapping

ISO Class	ASTM Equivalent
4.6	A307
8.8	A325 equivalent range
10.9	A449
High Temp	A193 B7
Low Temp	A320 L7

7.4 Interchangeability Considerations

Critical procurement checks:

• Thread pitch compatibility
• Nut standard matching
• Washer hardness requirements
• Coating thickness allowance
• Load rating equivalence

Improper interchangeability may cause:

• Preload loss
• Thread galling
• Stress concentration

8. Proof Load & Tensile Strength Table

Typical Mechanical Capacity (Carbon Steel U Bolts)

Size	Property Class	Proof Load (kN)	Min Tensile Load (kN)
M8	8.8	14	20
M10	8.8	22	32
M12	8.8	32	46
M16	8.8	58	84
M20	8.8	90	130
M24	8.8	130	190
M30	8.8	210	300

Values aligned with ISO 898 mechanical property requirements.

9. Weight Chart — SM Fasteners Reference Data

(Aligned with manufacturing output and export documentation.)

Size	Weight / Piece (kg)	Weight / 100 pcs (kg)
M8 × 75	0.09	9
M10 × 100	0.16	16
M12 × 120	0.28	28
M16 × 150	0.55	55
M20 × 200	1.05	105
M24 × 250	1.85	185
M30 × 300	3.10	310

Weight verification supports:

• Shipping calculations
• Structural load planning
• Export packing documentation

10. Engineering Selection Logic for EPC Procurement

Procurement engineers evaluate U bolts using:

1. Load requirement verification
2. Applicable international standard
3. Material compatibility
4. Environmental exposure
5. Required certification level
6. Coating system
7. Inspection class

SM Fasteners integrates these requirements within an ISO 9001 controlled manufacturing and traceability system, enabling supply for global infrastructure and energy projects.

11. Material Grades and Selection Criteria

11.1 Engineering Material Philosophy

Material selection for U bolts directly determines:

• Load-bearing capability
• Fatigue resistance
• Corrosion performance
• Temperature stability
• Service life reliability

Unlike standard bolts, U bolts undergo cold deformation during bending, requiring materials with:

• High ductility
• Stable grain structure
• Controlled hardness
• Good notch toughness

SM Fasteners manufactures U bolts across a full industrial material spectrum aligned with EPC and OEM specifications.

11.2 Industrial Material Range

Carbon Steel

Grade	Standard	Typical Use
IS 2062 / ASTM A36	Structural	General construction
ASTM A307	General purpose	Pipe supports
ASTM A105	Forged carbon steel	Pressure applications
ASTM A193 B7	High strength	Oil & Gas / Power

Characteristics:

• Economical
• High strength
• Requires coating protection

Alloy Steel

Grade	Key Feature	Application
ASTM A193 B7M	Controlled hardness	Sour service
ASTM A320 L7	Low temperature toughness	LNG systems
EN 42CrMo4	High fatigue strength	Heavy equipment

Stainless Steel

Grade	Equivalent	Properties
SS304	1.4301	General corrosion resistance
SS316	1.4401	Marine & chemical
SS316L	Low carbon	Weld stability
SS321	Ti stabilized	High temperature
SS904L	Super austenitic	Acid resistance

Duplex & Super Duplex Stainless Steel

Grade	Standard	Application
Duplex 2205	UNS S31803	Offshore pipelines
Super Duplex 2507	UNS S32750	Seawater systems

Advantages:

• High strength
• Excellent SCC resistance
• Reduced weight requirement

Nickel Alloys

SM Fasteners supports critical projects requiring advanced alloys.

Alloy	Environment
Inconel 625	High temperature
Incoloy 825	Acidic service
Hastelloy C276	Aggressive chemicals
Monel 400	Marine exposure
Nickel 200	Caustic alkali service
SMO 254	Chloride environments

Engineering Polymer — PEEK U Bolts

PEEK fasteners are applied where metals fail due to:

• Electrical conductivity
• Chemical attack
• Magnetic interference

Properties:

• Continuous service temperature ≈ 250°C
• Excellent chemical resistance
• Lightweight
• Non-galling threads

Typical industries:

• Semiconductor manufacturing
• Medical equipment
• Electrical systems
• Chemical processing plants

11.3 Material Comparison Table

Material	UTS (MPa)	Yield (MPa)	Corrosion Resistance	Relative Cost	Typical Application
Carbon Steel	400–800	250–640	Low	Low	Structural
Alloy Steel B7	860	720	Moderate	Medium	Oil & Gas
SS304	515	205	Good	Medium	General industry
SS316	515	205	Excellent	Medium-High	Marine
Duplex 2205	620	450	Very High	High	Offshore
Super Duplex	800	550	Extreme	Very High	Seawater
Inconel 625	930	480	Extreme	Premium	High temp
PEEK	100	90	Chemical inert	High	Electrical

11.4 Temperature Capability Range

Material	Service Temperature
Carbon Steel	−20°C to 400°C
A320 L7	−101°C
Stainless Steel	−196°C to 600°C
Duplex	−50°C to 300°C
Nickel Alloys	Up to 1000°C
PEEK	Up to 250°C

11.5 NACE MR0175 / ISO 15156 Compliance

Required for sour service containing H₂S.

Engineering controls:

• Hardness ≤ 22 HRC (carbon/alloy steel)
• Controlled heat treatment
• Material traceability
• Verified chemical composition

SM Fasteners supports NACE-compliant production routes for oil & gas environments.

12. Heat Treatment Processes

12.1 Objectives of Heat Treatment

Heat treatment modifies:

• Strength
• Toughness
• Residual stress
• Fatigue life

Critical for U bolts because bending introduces localized stresses.

12.2 Common Heat Treatment Methods

Normalizing

Refines grain structure.

Used for:

• Carbon steel U bolts
• Structural applications

Quenching & Tempering

Process:

1. Austenitizing
2. Rapid quench
3. Controlled tempering

Produces:

• High tensile strength
• Balanced toughness

Applied to:

• ASTM A193 B7
• Property class 10.9

Solution Annealing (Stainless Steel)

Purpose:

• Restore corrosion resistance
• Remove carbide precipitation

Temperature:
≈ 1040–1100°C followed by rapid cooling.

Stress Relieving

Performed after bending operation.

Benefits:

• Reduces residual stress
• Prevents fatigue cracking

12.3 Hardness Limits (Engineering Control)

Application	Maximum Hardness
General Service	32 HRC
Sour Service	22 HRC
High Strength	39 HRC
Stainless Steel	Controlled by grade

13. End-to-End Manufacturing Workflow

13.1 Raw Material Procurement & Verification

Process begins with certified raw material.

Mandatory controls:

• Mill Test Certificate (MTC)
• Heat number identification
• Spectrochemical analysis
• PMI verification

Traceability maintained under ISO 9001 system.

13.2 Material Preparation

Steps:

1. Bar cutting
2. Surface cleaning
3. Straightness inspection
4. Diameter verification

13.3 Forming Process — Forging vs Bending

Cold Bending (Most Common)

Advantages:

• Improved grain flow
• Higher fatigue resistance
• Dimensional consistency

Hot Forming

Used for:

• Large diameter U bolts
• Nickel alloys
• Heavy-duty applications

Forged U Bolts

Applied where extreme load reliability is required.

13.4 Thread Production

Thread Rolling (Preferred)

Benefits:

• Compressive residual stress
• Increased fatigue life
• Improved surface finish
• Higher strength threads

Thread Cutting

Used when:

• Large diameters
• Exotic alloys
• Small production batches

13.5 Dimensional Machining & Finishing

Operations include:

• Leg straightening
• Thread gauging
• Crown dimension inspection
• Burr removal

13.6 Heat Treatment Integration

Heat treatment may occur:

• Before threading
• After bending
• Final stress relief stage

Each stage documented and traceable.

13.7 Identification & Traceability

SM Fasteners maintains:

• Heat number marking
• Batch coding
• Inspection trace records
• Manufacturing route card

14. Surface Finishing & Coatings

14.1 Purpose of Surface Engineering

Surface treatment protects against:

• Corrosion
• Galling
• Seizure
• Wear
• Hydrogen embrittlement

14.2 Common Coating Systems

Coating	Thickness	Corrosion Resistance	Typical Use
Black Oxide	1 µm	Low	Indoor
Zinc Plated	8–12 µm	Moderate	Construction
Hot Dip Galvanized	70–100 µm	High	Outdoor
Mechanical Galvanized	40–70 µm	High	High strength bolts
PTFE/Xylan	20–40 µm	Chemical resistant	Oil & Gas
Dacromet/Geomet	8–12 µm	Excellent	Automotive
Fluoropolymer	Variable	Extreme	Offshore
Passivation (SS)	—	Restores chromium layer	Stainless steel

14.3 Surface Finish Performance Comparison

Finish	Salt Spray Resistance	Friction Stability	Hydrogen Embrittlement Risk
Zinc Electroplated	Medium	Moderate	High
HDG	High	Variable	Low
PTFE Coated	Very High	Excellent	None
Stainless Passive	Excellent	Stable	None

14.4 Coating Selection vs Environment

Environment	Recommended Finish
Indoor industrial	Zinc plated
Marine atmosphere	HDG / SS316
Offshore splash zone	Duplex / PTFE
Chemical plant	Nickel alloy / Fluoropolymer
H₂S service	Mechanical galvanized
Cryogenic	Stainless steel

14.5 Galvanizing Dimensional Compensation

Coating thickness affects thread fit.

Engineering practice:

• Oversize thread allowance
• Class 6AZ tolerance for HDG
• Nut tapping after galvanizing

14.6 Lubrication & Assembly Considerations

Proper lubrication ensures predictable preload.

Common lubricants:

• Molybdenum disulfide
• PTFE dry film
• Anti-seize compounds

Nut factor varies significantly with coating type and must be included in torque calculations.

14.7 Packaging Surface Protection

SM Fasteners uses industrial packaging systems:

• VCI corrosion protection
• Thread protectors
• Export moisture barriers
• Batch identification labels

15. Inspection & Quality Control

15.1 Quality Philosophy

U bolts operate in load-critical restraint systems, meaning failure can result in:

• Pipeline displacement
• Structural instability
• Equipment shutdown
• Safety hazards

Therefore, inspection extends beyond dimensional checks to include material verification, mechanical validation, and traceability control.

SM Fasteners integrates inspection through an ISO 9001 certified quality management system aligned with EPC and third-party inspection requirements.

15.2 Incoming Material Inspection

Mandatory verification before manufacturing:

Inspection	Method	Objective
Mill Test Certificate	EN 10204 3.1	Chemical & mechanical verification
Heat Number Check	Traceability	Batch control
Chemical Analysis	Spectrometer	Alloy confirmation
PMI Testing	XRF/Optical	Material authentication
Visual Inspection	Surface check	Defect elimination

15.3 In-Process Inspection

During manufacturing:

• Bend radius verification
• Leg parallelism measurement
• Thread rolling inspection
• Diameter tolerance verification
• Surface defect inspection

15.4 Dimensional Inspection Parameters

Parameter	Inspection Tool
Rod Diameter	Micrometer
Inside Width	Vernier caliper
Leg Length	Height gauge
Thread Pitch	Thread gauge
Thread Class	Go/No-Go gauge
Bend Radius	Template gauge

15.5 Mechanical Testing

Required for critical applications.

Test	Standard	Purpose
Tensile Test	ISO 898 / ASTM	Strength validation
Proof Load Test	ISO 898	Elastic limit
Hardness Test	Rockwell/Brinell	Heat treatment verification
Bend Test	Internal QC	Forming integrity
Impact Test	ASTM E23	Low-temperature service

15.6 Non-Destructive Testing (NDT)

Applied based on project specification.

Method	Detection
Magnetic Particle Testing	Surface cracks
Dye Penetrant Testing	Micro defects
Ultrasonic Testing	Internal flaws
Eddy Current Testing	Surface discontinuities

15.7 Positive Material Identification (PMI)

Mandatory for:

• Duplex stainless steel
• Nickel alloys
• Sour service applications

Ensures:

• Correct alloy supply
• Project compliance
• Prevention of material mix-up

15.8 Documentation & Certification

Typical documentation supplied by SM Fasteners:

• EN 10204 3.1 / 3.2 MTC
• Heat treatment charts
• Coating thickness reports
• Dimensional inspection reports
• Mechanical test certificates
• Compliance certificate (CoC)

16. Mechanical Properties Table (Grade-Wise)

Property Class	Tensile Strength MPa	Yield Strength MPa	Hardness Range	Typical Industry
4.6	400	240	120–180 HB	Light structures
5.8	500	400	150–220 HB	General engineering
8.8	800	640	22–32 HRC	Structural
10.9	1040	940	32–39 HRC	Heavy equipment
12.9	1220	1100	39–44 HRC	Dynamic assemblies

17. Corrosion Resistance vs Environment

Environment	Carbon Steel	SS304	SS316	Duplex	Nickel Alloy	PEEK
Indoor Industrial	Good	Excellent	Excellent	Excellent	Excellent	Excellent
Marine Atmosphere	Poor	Moderate	Excellent	Excellent	Excellent	Excellent
Seawater Immersion	Poor	Poor	Good	Excellent	Excellent	Excellent
Acidic Chemical	Poor	Moderate	Good	Excellent	Excellent	Excellent
H₂S Service	Limited	Good	Good	Excellent	Excellent	Excellent
Cryogenic	Moderate	Excellent	Excellent	Excellent	Excellent	Good

18. Tightening Torque Chart

(Typical values — lubricated condition, nut factor ≈0.18)

Size	Grade 8.8 Torque (Nm)	Grade 10.9 Torque (Nm)
M8	25	35
M10	49	70
M12	85	120
M16	210	300
M20	410	580
M24	710	1000
M30	1400	1950

Torque must always be validated against coating friction coefficient.

19. Preload Calculation — Worked Engineering Example

Given

• U Bolt Size: M16
• Applied Torque: 210 Nm
• Nut Factor K = 0.20
• Diameter d = 16 mm = 0.016 m

Preload Equation

$$F_p = \frac{T}{K \times d}$$

\$$F_p = \frac{210}{0.20 \times 0.016}$$

$$F_p = 65,625\ N$$

Result:
Approximate preload = 65.6 kN

Frictional Holding Capacity

Assuming μ = 0.3:$$F_f = \mu \times F_p$$

$$F_f = 0.3 \times 65625 = 19,687\ N$$

This represents available resistance against pipe sliding.

20. Thread Standards & Tolerance Table

Thread System	Standard	Tolerance Class	Application
ISO Metric	ISO 965	6g / 6H	Global EPC
UNC	ASME B1.1	2A / 2B	Oil & Gas
UNF	ASME B1.1	2A / 2B	Automotive
BSW	BS 84	Medium Fit	Legacy systems
BSF	BS 84	Fine Fit	Precision equipment

21. Surface Finish Performance Comparison

Surface Finish	Corrosion Protection	Friction Control	Offshore Suitability	Maintenance
Black Oxide	Low	Stable	No	High
Zinc Plated	Moderate	Good	Limited	Medium
HDG	High	Variable	Good	Low
PTFE/Xylan	Very High	Excellent	Excellent	Very Low
Passivated Stainless	Excellent	Stable	Excellent	Minimal

22. Weight Reference Chart — SM Fasteners Production Data

Size	Approx Weight / Piece (kg)	Weight / 100 pcs (kg)
M8 × 75	0.09	9
M10 × 100	0.16	16
M12 × 120	0.28	28
M16 × 150	0.55	55
M20 × 200	1.05	105
M24 × 250	1.85	185
M30 × 300	3.10	310

Supports:

• Export logistics
• Structural design loads
• Procurement estimation

23. Industry Applications Mapping

Construction & Structural Steel

• Pipe rack supports
• Structural anchoring
• HVAC suspension

Oil & Gas Industry

Upstream

• Wellhead piping
• Offshore decks

Midstream

• Pipeline supports
• Compressor stations

Downstream

• Refinery piping systems
• Chemical process lines

NACE-compliant materials supplied where required.

Power Generation

• Boiler assemblies
• Cooling water systems
• Turbine auxiliary piping

Petrochemical & Chemical Processing

• Acid-resistant supports
• High-temperature piping

LNG & Cryogenic Systems

• A320 L7 U bolts
• Stainless steel cryogenic fastening

Automotive & Heavy Equipment

• Axle mounting
• Suspension retention systems

Railways & Infrastructure

• Cable containment
• Utility mounting systems

Shipbuilding & Offshore

• Seawater piping
• Engine room assemblies
• Deck-mounted utilities

PEEK Fastener Applications

Used where metallic fasteners are unsuitable:

• Electrical isolation systems
• Semiconductor manufacturing
• Chemical dosing equipment
• MRI and instrumentation assemblies

24. Failure Prevention & Reliability Engineering

Fatigue Prevention

• Maintain adequate preload
• Rolled threads preferred
• Smooth bend radius

Hydrogen Embrittlement Control

• Avoid electroplating for high-strength grades
• Post-plate baking
• Mechanical galvanizing

Stress Corrosion Prevention

• Select duplex or nickel alloys
• Apply fluoropolymer coatings
• Avoid tensile overstress

25. Export Capability & Global Supply Readiness

SM Fasteners supports international project procurement with controlled export systems.

25.1 Industrial Packaging

• VCI anti-corrosion wrapping
• Thread protection caps
• Moisture barrier packaging
• Batch identification labeling

25.2 Export Crating

• ISPM-15 compliant wooden crates
• Sea-freight ready packaging
• Palletized container loading
• Shock-resistant packing

25.3 Documentation Package

Typical EPC shipment includes:

• Material Test Certificates (EN 10204 3.1 / 3.2)
• Inspection reports
• Heat treatment records
• Coating reports
• Dimensional inspection records
• Certificate of Conformance
• Packing list & traceability sheet

26. Engineering Procurement Readiness — SM Fasteners

SM Fasteners manufacturing capability demonstrates:

• Compliance with ISO 9001 quality systems
• Certified MSME industrial production
• UKAF accredited processes
• Full international standards alignment (ISO / ASTM / DIN / BS)
• Advanced material manufacturing including Duplex, Nickel Alloys, and PEEK
• Custom-engineered U bolt solutions for EPC and OEM projects

✅ COMPLETE ENGINEERING REFERENCE

Total Coverage Delivered

✔ Functional engineering principles
✔ International standards compliance
✔ Material science & metallurgy
✔ Manufacturing methodology
✔ Surface engineering
✔ Inspection & QA systems
✔ Complete engineering tables
✔ EPC procurement readiness
✔ Global export capability