Category Archives: Technical Bulletins

Technical Bulletins

Your reliable source for certified custom bolts and fasteners

Hague Fasteners logo. Established 1971 Certified Custom Fasteners with Full Traceability

Certified custom fasteners are essential for industries that demand precision, compliance, and full documentation. At Hague Fasteners, we manufacture high-integrity bolts and fasteners that meet international standards and offer complete traceability from raw material to final delivery.

Why Certified Custom Fasteners Matter

In sectors such as energy, infrastructure, defence, and petrochemical, fasteners must perform reliably under pressure. Therefore, certification and traceability are not optional—they are mandatory. Hague Fasteners provides certified custom fasteners that meet ISO and PED standards, ensuring peace of mind for engineers, buyers, and compliance teams.

UK Manufacturer of Certified Bolts and Fasteners

We are proud to be a UK-based manufacturer offering full-service quality assurance. Our fasteners are used in mission-critical applications where failure is not an option. Moreover, our clients benefit from direct access to inspection records, material certificates, and independent lab testing.

ISO 9001:2015 and PED 2014/68/EU Approved

Hague Fasteners holds ISO 9001:2015 certification for our Quality Management System and PED 2014/68/EU approval for pressure equipment. These accreditations confirm our commitment to consistent quality and international compliance.

Tailored Inspection Test Plans (ITPs)

For high-value projects, we create custom Inspection Test Plans (ITPs) that outline every stage of production, testing, and release. These plans include client and third-party witness points, ensuring full transparency and control.

Each ITP links every fastener to its base material, certification, and testing documentation. As a result, our clients receive complete traceability and confidence in every component.

Comprehensive Testing via UKAS-Approved Labs

We partner with UKAS-certified laboratories to perform extensive testing on our fasteners. This includes:

  • Tensile and elevated tensile testing
  • Chemical analysis and PMI (Positive Material Identification)
  • Charpy impact and hardness testing
  • Ultrasonic, magnetic, and dye penetrant inspection
  • Macroetching and microstructure analysis
  • Decarburisation, carburisation, and corrosion testing

Fastener Certification and Documentation

Every fastener is shipped with detailed documentation, including:

  • BS EN 10204:2004 2.1, 3.1, and 3.2 certificates
  • PPAP Levels 1–3 and ISIR reports
  • Heat treatment furnace records
  • Plating batch documentation
  • Independent UKAS lab reports

For more details, see our fastener quality guidelines.

Bolt Traceability UK: Hard-Marked Fasteners

We offer hard-marked traceable fasteners for installations requiring post-delivery identification. Each component is laser-marked with a unique identifier linked to its full documentation trail. This ensures compliance with traceability standards and supports long-term asset management.

Certified custom fasteners with hard-marked traceability for UK compliance
Certified fasteners with hard-marked traceability for UK compliance and safety-critical use.

Contact Hague Fasteners

Ready to source certified custom fasteners for your next project? Contact our team today:

Email: sales@haguefasteners.co.uk

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Technical Bulletins

Protecting Screw Threads in Engineered Components: Why is it so important?

Specialised bolt for UK manufacturing – Thread protection for transporting and handling

Screw Thread Protection in Engineered Components

Screw thread protection is essential in engineered components, especially in high-integrity applications across automotive, nuclear, and defence sectors. At Hague Fasteners, we understand that even minor thread damage can compromise performance, safety, and reliability. That’s why we’ve built our reputation on precision, quality, and proactive protection methods.

Why Screw Thread Protection Matters in Critical Applications

Screw thread damage is one of the most common causes of component failure in the fastener manufacturing sector. Since 1971, Hague Fasteners has implemented rigorous quality systems to prevent this risk. Learn more about our screw thread protection methods.

  • Premature Failure: Damaged threads can cause assemblies to loosen or disconnect. In high-stakes environments, this can lead to system-wide failure.
  • Increased Maintenance Costs: Compromised threads often require early replacement or repair, resulting in downtime and higher operational costs.
  • Reduced Efficiency: Loose connections may cause vibration, leading to mechanical degradation and increased energy consumption over time.

How Hague Fasteners Protects Precision Threads

We take screw thread protection seriously. One of our most effective methods is wax dipping—a process that coats components in a protective wax layer after machining. This is done by hand, as no two orders are ever the same.

Wax-dipped fastener threads for corrosion and impact protection
Wax dipping provides long-term protection for precision threads.

This barrier shields threads from knocks, moisture, and contaminants during storage, shipping, and handling. Moreover, it offers several key advantages:

  • Prevents physical damage during handling
  • Provides up to 10 years of rust prevention
  • Outperforms traditional mesh sleeves in durability and coverage

As a result, our components arrive in perfect condition—ready to perform with the precision and reliability our clients expect.

Built-In Protection for Built-To-Last Components

As a third-generation British manufacturer, we understand that quality doesn’t end at the production line. It extends to how components are handled, stored, and delivered.

That’s why we go the extra mile to protect every thread, every time. Whether you’re sourcing fasteners for high-pressure systems or bespoke engineered parts, screw thread protection matters—and we’re here to ensure it’s never compromised.

📽️ Follow us on social media to see our viral bolt dipping videos in action and learn more about our commitment to quality.

📞 Ready to discuss your next project?

Get in touch with our team to learn how we can support your critical applications.

Technical Bulletins

Essential Thread Types and Forms for High Performance Fasteners

Thread Types and Forms Guide for Fasteners

This Technical Bulletin explains the major thread types used on bolts, nuts, and studs. It covers Metric and Metric Fine, Unified series UNC, UNF, UNEF, UNS, UNJC, UNJF, UNR, Whitworth BSW and BSF, plus pipe, trapezoidal, buttress, and specialist forms. Use it to identify a thread system, select a class of fit, and avoid specification errors on safety critical fasteners.

For over 50 years, Hague Fasteners has manufactured precision threaded fasteners in steels, stainless steels, and superalloys. Therefore, we understand how thread selection influences strength, fatigue life, seal performance, and interchangeability. This guide consolidates the essentials so engineers can choose with confidence.

How to Identify a Thread

  • System: Metric ISO, Unified, Whitworth, Pipe, Trapezoidal, Buttress.
  • Diameter and pitch: Metric uses pitch in mm. Unified/Whitworth use TPI (threads per inch).
  • Series: Coarse, Fine, Extra Fine, Special.
  • Class of fit: Metric uses 6g, 6H, etc. Unified uses 1A/1B to 3A/3B.
  • Form geometry: ISO/Unified 60°, Whitworth 55°, UNJ/UNR radiused root, ACME 29°, Trapezoidal 30°.
  • Hand/starts: Right or left-hand, single or multi-start.

Metric & Metric Fine Threads (ISO, 60°)

Metric threads use pitch in millimetres. Coarse “M” is the default. Fine “MF” improves preload control and engagement in thin sections. Flank angle is 60 degrees.

SizeCoarse Pitch (M)Common Fine Pitches (MF)AngleNotes
M61.00.7560°General purpose
M81.251.060°Machinery, structures
M101.51.25, 1.060°Better clamp control with MF
M121.751.5, 1.2560°Thin sections
M162.01.5, 1.060°Vibration resistance
M202.52.0, 1.560°Flanged joints
M243.02.0, 2.560°Pressure boundary
M303.52.0, 2.5, 3.060°Large studs

Frequently Asked Questions on Metric & Metric Fine Threads

What is the difference between Metric and Metric Fine?
Metric (M) threads are coarse pitch. Metric Fine (MF) has a smaller pitch, giving more engaged threads and better preload control.

When should Metric Fine be used?
On thin wall sections, short engagement lengths, or where vibration resistance or precise clamp is required.

Do they use the same angle?
Yes. Both use a 60° flank angle under ISO 261/965. Only the pitch differs.

Unified Threads UNC & UNF (ASME B1.1, 60°)

Size (inch)UNC (TPI)UNF (TPI)AngleNotes
1/4202860°General fixtures
3/8162460°UNF for preload control
1/2132060°Structural fasteners
5/8111860°Studs, couplings
3/4101660°Pressure equipment
181260°Heavy joints

Frequently Asked Questions on UNC & UNF Threads

What is the difference?
UNC has fewer TPI, easier to assemble. UNF has more TPI, better clamp control and vibration resistance.

Which is stronger?
Depends. UNC spreads load deeper. UNF has more engagement in short lengths. Selection depends on design.

Do they use the same angle?
Yes. Both UNC and UNF use a 60° flank angle.

UNJ & UNR Threads (ASME, 60°)

UNJ adds a controlled root radius to improve fatigue strength. UNJC is coarse pitch, UNJF is fine pitch. UNR is a rounded-root version of UNC/UNF.

Size (inch)UNJF (TPI)UNJC (TPI)UNR (TPI)AngleNotes
1/42828UNC 20 / UNF 2860°Fatigue-critical small studs
3/82424UNC 16 / UNF 2460°Engine bolts
1/22020UNC 13 / UNF 2060°Pressure studs
3/41616UNC 10 / UNF 1660°Rotating assemblies

Frequently Asked Questions on UNJ & UNR Threads

What is the difference between UNJ and UNJF?
UNJ specifies a root radius. UNJF indicates a fine pitch within the UNJ family.

How is UNJC different from UNJF?
UNJC is coarse pitch, UNJF is fine pitch. Both have the same radius root form.

What are UNR threads?
Rounded-root versions of UNC/UNF, easier to roll. Less controlled than UNJ but still fatigue resistant.

Where are UNJ threads used?
Aerospace, defence, rotating equipment, turbine studs, and fatigue-critical bolts.

Whitworth Threads BSW & BSF (BS 84, 55°)

Size (inch)BSW (TPI)BSF (TPI)AngleNotes
1/4202655°Legacy fixings
3/8162055°Restoration work
1/2121655°Older flanges
3/4101255°Heritage machinery
181055°Pipework, heavy plant

Frequently Asked Questions on BSW & BSF Threads

What is the difference?
BSW is coarse, BSF is fine. Both use 55° flank angle with rounded crests and roots.

When should BSF be used?
On thin sections or short engagement requiring more threads for load.

Are they interchangeable with Metric/Unified?
No. Whitworth 55° differs from Metric/Unified 60°. Adaptors are required.

Where are they still found?
Legacy British equipment, automotive restoration, and heritage plant.

Thread FAQ Index

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Technical Bulletins

Precision Fasteners, Nuts and Bolts for Renewable Energy Manufacturers

Precision Fasteners for Renewable Energy

Why Quality Bolting Powers the Future

As global demand for clean energy accelerates, the infrastructure behind solar, wind, geothermal, hydro and biomass systems must meet increasingly rigorous standards. At the heart of this infrastructure are precision fasteners for renewable energy — engineered for strength, corrosion resistance and long-term reliability.

For over 50 years, Hague Fasteners has supplied bespoke bolts, nuts and studs to the renewable energy sector. Our certified components, manufactured to international standards, ensure that critical connections perform under pressure and stand the test of time.

Why Fasteners Matter in Renewable Energy

Every renewable energy system depends on mechanical integrity. For instance, a wind turbine blade rotating at 200 mph or a solar array facing year-round weather extremes both rely on fasteners that:

  • Withstand high temperatures and corrosive environments
  • Maintain structural integrity under dynamic loads
  • Comply with strict certification and safety standards
  • Match the precise engineering requirements of each application

Solar Energy Fasteners

Solar installations demand corrosion-resistant fasteners able to endure UV exposure, moisture and temperature fluctuations. Hague Fasteners provides stainless steel and aluminium bolts, nuts, washers and screws with custom coatings for durability and full certification for compliance and traceability.

Wind Energy Bolting Solutions

Wind turbines require high-strength fasteners to secure blades, rotors, hubs and towers. We manufacture hardened alloy-steel bolts to withstand rotational forces and produce custom designs based on turbine engineering specifications. In addition, every batch includes full traceability and quality documentation.

Geothermal Energy Components

Geothermal systems operate in extreme conditions of heat and acidity. Consequently, we supply superalloy and stainless-steel fasteners designed for drilling operations and plant construction. Each material is chosen for its thermal and chemical resistance, and components are custom-made to project tolerances.

Hydro Energy Fasteners

Hydroelectric plants face constant water exposure and high mechanical stress. Our solutions include corrosion-resistant bolts for dams, penstocks and turbines, engineered for long-term reliability. In addition, our design team supports safety-critical applications where failure is not an option.

Biomass Energy Bolting

Biomass combustion produces acidic gases and high temperatures. Therefore, our fasteners for boilers, turbines and structural components are manufactured from alloys that resist both heat and chemical attack. Custom finishes are available to extend service life and reduce maintenance cycles.

Hague Fasteners engineers manufacturing precision fasteners for renewable energy systems
Hague Fasteners engineers at work, developing bespoke fasteners that support global renewable energy projects.

Hague Fasteners: Supporting the Energy Transition

We supply fasteners to international standards or custom specifications, always backed by technical support from experienced engineers. Moreover, every order includes rigorous inspection, certification and full traceability. Our UK facility manufactures in any size, shape or material, combining flexibility with precision.

As renewable energy infrastructure expands, the need for specialist fasteners for clean energy continues to grow. Consequently, Hague Fasteners is proud to support this global transition with components that meet the highest standards of performance, safety and sustainability.

Looking for precision fasteners for your renewable energy project?
Contact Hague Fasteners today to discuss your requirements: sales@haguefasteners.co.uk

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Technical Bulletins

Powering Progress: Specialist Fasteners for Global Energy Manufacturers

Specialist Fasteners for the Power Generation Industry

Engineered High-Performance Fasteners for Turbines, Generators and Energy Infrastructure

For over 50 years, Hague Fasteners has partnered with the UK’s leading power generation companies and global energy innovators. We manufacture specialist fasteners for the power generation industry. From nuclear and coal-fired plants to cutting-edge renewables, our custom fasteners help keep critical assets running safely and efficiently.

Hague Fasteners designs and manufactures specialist fasteners for the power generation industry. We provide precision-engineered bolts, nuts and studs for high-temperature, high-pressure and corrosive environments. In addition, our in-house machining capability supports small-batch, bespoke production for tight deadlines. As a result, each component meets the exact specification required by turbine and generator manufacturers worldwide.

Hague Fasteners specialist fasteners for power generation

Our expertise spans traditional and renewable energy systems. We support OEMs and maintenance teams with fast, reliable, bespoke fastening solutions for critical equipment.

Industries We Support

  • Nuclear, Coal, Oil and Gas Power Plants
  • Hydro-Electric and Geothermal Facilities
  • Wind Farm and Solar Power Maintenance
  • Natural Gas Storage and Distribution
  • Boiler and Turbine Systems
  • Motors, Generators and Transmission Equipment

Whether you need custom fasteners for turbine maintenance or special bolts for solar equipment, Hague Fasteners delivers with precision and speed.

Inconel bolts for turbine assembly in power generation

Engineered Fasteners for Power Generation and Critical Applications

We specialise in manufacturing non-standard fasteners for high-temperature, high-pressure and corrosive environments, essential for power generation systems. In addition, we validate fit and function against drawing and specification to safeguard uptime.

Advanced Materials for Extreme Environments

Our fasteners use high-performance alloys that withstand thermal stress, chemical exposure and mechanical fatigue. For example, Inconel and Hastelloy grades maintain strength where carbon and standard stainless steels fail.

Materials We Work With

  • Inconel 625, 718, 825
  • Incoloy 800H/HT, 925
  • Hastelloy C4, C22, C276
  • Monel 400, K500
  • Durehete 900, 950, 1055
  • Esshete 1250, Jethete M152, M448
  • Nimonic 80A, Waspalloy grades
  • Carpenter 20, AISI 422, 17-4PH
  • 904L (Uranus B6), 21CrMoV57

These materials are selected for proven performance in boiler systems, turbine assemblies and nuclear-grade applications. As a result, they provide durable service in the most severe energy environments.

Hague Fasteners UK factory manufacturing power generation fasteners
Hague Fasteners factory, Willenhall, West Midlands

Why Hague Fasteners

  • Over 50 years of experience in power generation fastener manufacturing
  • ISO-certified quality and full traceability
  • Rapid turnaround for urgent maintenance needs
  • Collaborative design support for R&D and prototyping
  • Ethical, carbon-negative manufacturing practices
  • Made in Britain

With decades of support for major OEMs and maintenance engineers, Hague Fasteners leads in the supply of custom fasteners for power plants and renewable energy systems. Every item is fully traceable, PED-aligned and made in Britain to exceed the demands of critical applications.

In summary, we provide reliable power generation fasteners that keep assets running. For over five decades, we have delivered specialist fasteners for the power generation industry that engineers trust for strength, precision and repeatability.

Contact us via email: sales@haguefasteners.co.uk

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Learn more about PED 2014/68/EU compliance

Technical Bulletins

🛠 ISO 4042 Electroplated Coating Designations – Transition from Cr⁶⁺ to Cr³⁺ Systems

📘 Historical Standard (ISO 4042:1999 / ISO 4042:2000)

In earlier versions of ISO 4042, electroplated coatings were designated using a simple code format. A commonly used designation was:

A4E, where:

  • A = Zinc electroplated
  • 4 = Minimum coating thickness of 8 µm
  • E = Hexavalent chromium (Cr⁶⁺) passivation (typically yellow/iridescent chromate)

❗ Note: The “E” passivation used hexavalent chromium, which is now restricted under REACH (from September 2024) and RoHS (maximum 0.1% by weight in homogeneous materials).

📗 Updated Standard – ISO 4042:2022

The 2022 revision of ISO 4042 introduced a new modular format for specifying electroplated coatings, aligning with REACH and RoHS requirements. It replaces Cr⁶⁺ systems with safer Cr³⁺ (trivalent chromium) passivations.

✅ New Designation Format:

[Coating Metal][Thickness Code][Passivation Code][Topcoat Code]

Example: Zn8CnT2
This refers to:

  • Zn – Zinc electroplating
  • 8 – 8 µm coating thickness
  • Cn – Iridescent Cr³⁺ (trivalent) passivation
  • T2 – With sealant or topcoat

This is the recommended RoHS/REACH-compliant replacement for the withdrawn A4E coating designation.

✅ Trivalent Passivation Codes in ISO 4042:2022

CodeTypeAppearanceCr⁶⁺-FreeDescription
AnTransparentClear/BlueYesThin Cr³⁺ passivation, lower corrosion resistance
CnIridescantYellow/GoldYesThick Cr³⁺ passivation, high corrosion resistance
FnBlackBlackYesCr³⁺ black passivation, aesthetic & protective

⚠️ Why This Matters

  • Hexavalent chromium coatings like A4E are now prohibited under REACH (no authorisation after Sept 2024) and restricted under RoHS.
  • ISO 4042:2022 formally eliminates Cr⁶⁺-based systems and provides modular Cr³⁺-based alternatives.
  • When quoting or supplying plated fasteners, manufacturers must use updated Cr⁶⁺-free designations to ensure compliance and performance continuity.

Need help selecting a compliant coating for your application?
Our technical team at Hague Fasteners is here to help you specify safe, durable, and compliant solutions for your critical fastener requirements.

Technical Bulletins

Effects of corrosion on fastener performance and integrity

Corrosion is a formidable and persistent challenge faced by the fastener industry, exerting a detrimental impact on the performance and integrity of fasteners. It occurs as a result of metals coming into contact with moisture, air, and other corrosive elements, initiating a series of chemical reactions that ultimately lead to the breakdown of the metal and the deterioration of the fastener. Understanding the various types of corrosion, their effects on fastener performance, and implementing effective mitigation techniques and preventive measures are crucial for ensuring the longevity and reliability of fasteners in diverse applications.

There exist several distinct types of corrosion that can significantly affect fasteners, each presenting its own unique characteristics and risks:

  1. Uniform corrosion: This form of corrosion manifests as a gradual loss of material, spreading evenly across the entire surface of the fastener. As the material erodes, the strength of the fastener diminishes, posing a potential threat to structural integrity.
  2. Pitting corrosion: Pitting corrosion is characterized by the formation of small pits or holes on the surface of the fastener. These pits can rapidly grow in size, compromising the structural integrity of the fastener and potentially leading to premature failure, even when subjected to relatively low loads.
  3. Galvanic corrosion: Galvanic corrosion arises when two dissimilar metals come into contact with each other in the presence of an electrolyte. This contact creates an electrochemical cell, initiating an electrical current that causes corrosion to occur more rapidly in the less noble metal. The galvanic corrosion process can result in severe material degradation and structural weakness.
  4. Crevice corrosion: Crevice corrosion arises in areas where there is limited access to oxygen or water, such as tight spaces between fasteners or beneath washers. The confined environment hinders proper ventilation and drainage, allowing corrosive elements to accumulate and promote localized corrosion. Crevice corrosion can pose a significant risk, as it often goes unnoticed until substantial damage has already occurred.

The impact of corrosion on fastener performance cannot be overstated. Corrosion weakens the fastener, diminishing its load-bearing capacity and making it susceptible to premature failure under normal or even moderate loads. Furthermore, corrosion can compromise the thread strength of the fastener, rendering it more prone to stripping or shearing. Additionally, the corrosion process can loosen the fastener, resulting in a loss of clamping force and potentially compromising the structural integrity of the assembly.

To combat the adverse effects of corrosion, a range of mitigation techniques and preventive measures are available:

  1. Corrosion-resistant coatings: Applying specialized coatings, such as zinc plating or organic coatings, to the surface of the fastener can provide an effective barrier against corrosive elements. These coatings act as sacrificial layers, sacrificially corroding to protect the underlying fastener material.
  2. Selection of appropriate materials: Opting for fasteners made from materials that inherently possess high corrosion resistance, such as stainless steel or other corrosion-resistant alloys, is an effective preventive measure. These materials exhibit superior resistance to corrosion, ensuring the longevity and reliability of fasteners in challenging environments.
  3. Lubrication: The application of lubricants serves multiple purposes in corrosion prevention. Lubricants not only create a protective barrier between the fastener and corrosive elements but also enhance the tightening torque during installation, thereby improving the clamping force and reducing the likelihood of fastener failure.
  4. Cathodic protection: Cathodic protection involves employing sacrificial anodes made of more reactive metals, such as zinc or aluminium, in close proximity to the fasteners. These sacrificial anodes attract corrosive elements and corrode themselves, thus shielding the fasteners from corrosion by acting as a sacrificial layer.
  5. Inspection and maintenance: Regular inspection and maintenance practices play a vital role in detecting and addressing corrosion-related issues promptly.

Routine inspection and maintenance procedures are essential for identifying early signs of corrosion and preventing its progression. Regular visual inspections can help detect visible signs of corrosion, such as discoloration, pitting, or surface irregularities. Additionally, non-destructive testing techniques, such as ultrasonic testing or magnetic particle inspection, can be employed to assess the internal integrity of fasteners and identify hidden corrosion.

Incorporating preventive measures into maintenance routines is crucial for effective corrosion management. This includes implementing a proactive approach to remove and replace corroded fasteners promptly. Corroded fasteners should be replaced with new ones that are resistant to corrosion, ensuring the continued structural integrity and reliability of the assembly.

Moreover, conducting regular cleaning and maintenance of fasteners is paramount. Removing accumulated dirt, debris, and corrosive contaminants from fastener surfaces reduces the risk of corrosion initiation and progression. It is advisable to utilize appropriate cleaning agents and techniques that are compatible with the fastener material to avoid causing any additional damage.

Education and training on corrosion awareness and prevention should be provided to personnel involved in fastener handling, installation, and maintenance. By raising awareness about the detrimental effects of corrosion and the importance of preventive measures, employees can actively contribute to maintaining the integrity of fasteners throughout their lifecycle.

Collaboration with suppliers and manufacturers is also crucial in mitigating the impact of corrosion on fastener performance. Engaging in a dialogue with suppliers can ensure the procurement of high-quality, corrosion-resistant fasteners that meet the specific requirements of the intended application. Manufacturers can provide guidance on material selection, surface treatments, and coating options that offer enhanced corrosion protection.

In conclusion, corrosion poses significant challenges to the fastener industry, affecting the performance and integrity of fasteners. Understanding the various types of corrosion, their effects, and implementing appropriate mitigation techniques and preventive measures are vital for ensuring the longevity and reliability of fasteners. By employing corrosion-resistant coatings, selecting suitable materials, practicing proper lubrication, utilizing cathodic protection, and conducting regular inspection and maintenance, fastener manufacturers and users can effectively combat the adverse effects of corrosion, ensuring the safe and reliable operation of their products in diverse environments.

Technical Bulletins

Fastener fatigue life and failure analysis in harsh offshore environments

The offshore oil industry operates in some of the harshest environments on earth, with subsea equipment and pipelines subjected to extreme conditions such as high pressure, temperature, and corrosive seawater. Fasteners used in these environments are critical components that hold everything together, and their failure can have serious consequences such as leaks, spills, and equipment damage. This publication focuses on the impact of seawater exposure and cyclic loading on bolt failure in offshore platforms and recommends preventive measures to mitigate this risk.

Fastener fatigue life

Fastener fatigue is a common mode of failure in offshore platforms, where equipment and pipelines are subjected to cyclic loading over long periods. This loading can cause microscopic cracks to form in the fastener material, which can grow and eventually lead to catastrophic failure. Fastener fatigue life is influenced by several factors, including the material properties, the design of the joint, the loading conditions, and the operating environment.

Material properties

The choice of material for fasteners is critical in harsh offshore environments, where seawater exposure and corrosive gases can cause rapid degradation of certain materials. Common materials used for fasteners in offshore platforms include carbon steel, alloy steel, and stainless steel. Carbon steel is the most common material due to its high strength and low cost, but it is also susceptible to corrosion in seawater. Alloy steel and stainless steel are more resistant to corrosion, but they are also more expensive and may not be suitable for all applications.

Design of the joint

The design of the joint can also have a significant impact on fastener fatigue life. Factors such as the size and shape of the fastener, the number of fasteners, and the preload applied to the joint can all affect the fatigue behaviour. For example, joints with too few fasteners or insufficient preload may experience higher stress concentrations and be more prone to fatigue failure.

Loading conditions

The loading conditions that fasteners are subjected to can also impact fatigue life. In offshore platforms, cyclic loading is common due to the continuous movement of the platform caused by waves and wind. The frequency and magnitude of the cyclic loading can vary depending on the location and weather conditions, and can significantly affect the fatigue behaviour of the fasteners.

Operating environment

The operating environment in offshore platforms can also affect fastener fatigue life. Seawater exposure is a major concern, as it can cause corrosion and stress corrosion cracking in certain materials. The presence of corrosive gases such as hydrogen sulphide can also accelerate degradation and increase the risk of failure.

Case study: Impact of seawater exposure and cyclic loading on bolt failure

To illustrate the impact of seawater exposure and cyclic loading on bolt failure in offshore platforms, a case study is presented here. The case study focuses on a subsea pipeline connection in the North Sea, where several bolts failed after only a few years of service.

The pipeline connection consisted of two flanges, each with 12 bolts, that were connected using a bolt tensioning system. The bolts were made of carbon steel and had a diameter of 1 inch. The pipeline was exposed to seawater and subjected to cyclic loading due to the continuous movement of the platform caused by waves and wind.

After a few years of service, several bolts in the connection failed due to fatigue. Failure analysis revealed that the bolts had developed fatigue cracks at the root of the threads, which had grown and eventually led to complete fracture. The cracks were caused by the cyclic loading of the pipeline, which had exceeded the fatigue limit of the bolts.

Further analysis also revealed that the seawater exposure had accelerated the corrosion of the bolts, reducing their strength and contributing to the fatigue failure. The combination of cyclic loading and seawater exposure had therefore significantly reduced the fatigue life of the bolts, leading to premature failure.

Preventive measures

To prevent fastener failure in offshore platforms, several preventive measures can be implemented. These measures include:

  1. Material selection: Choosing the right material for fasteners is critical in offshore platforms. Corrosion-resistant materials such as alloy steel and stainless steel are preferred for applications where seawater exposure is a concern.
  2. Coatings: Applying coatings such as zinc, cadmium, or other anti-corrosion coatings can help protect fasteners from the corrosive effects of seawater. However, the coating must be carefully selected based on the specific application and environmental conditions.
  3. Preload: Properly tightening fasteners to the recommended preload can help distribute the load evenly and reduce stress concentrations. This can help prevent fatigue cracks from forming and improve the fatigue life of the joint.
  4. Inspection: Regular inspection of fasteners can help detect early signs of corrosion, cracking, or other defects. This can help identify potential problems before they become serious and allow for preventive measures to be implemented.
  5. Maintenance: Proper maintenance of offshore equipment and pipelines is critical to preventing fastener failure. Regular cleaning and inspection can help reduce the impact of seawater exposure and ensure that fasteners are functioning properly.

Conclusion

Fastener fatigue life and failure analysis are critical issues in offshore platforms, where equipment and pipelines are subjected to extreme conditions such as seawater exposure and cyclic loading. The case study presented here illustrates the impact of these factors on bolt failure and highlights the importance of preventive measures to mitigate the risk.

Proper material selection, coatings, preload, inspection, and maintenance can all help improve the fatigue life of fasteners and prevent premature failure. By implementing these measures, offshore operators can reduce the risk of equipment damage, spills, and environmental damage, and ensure the safe and reliable operation of their assets.

Technical Bulletins

Duplex and SuperDuplex Material Study

Duplex and superduplex steels are advanced materials that offer superior mechanical, corrosion, and erosion resistance properties over conventional stainless steels. These alloys have a two-phase microstructure consisting of austenite and ferrite phases, resulting in improved strength, toughness, and resistance to stress corrosion cracking. These properties make duplex and super duplex stainless steels ideal for applications in aggressive environments such as the oil and gas, chemical, and marine industries.

SeprDuplex Offshore Installation

Development of Duplex and Superduplex Stainless Steels

Duplex and super duplex stainless steels were developed in the 1930s and 1940s as a result of research into the corrosion resistance of stainless steels in acidic and chloride-containing environments. Early duplex stainless steels were low in nickel and high in chromium and molybdenum to improve their corrosion resistance. However, these alloys had limited toughness and ductility, which made them difficult to fabricate and prone to cracking during welding.

In the 1960s, the development of more advanced duplex stainless steels began, incorporating additional elements such as nitrogen, copper, and tungsten to improve their mechanical properties and welding characteristics. The addition of nitrogen, in particular, increased the strength, ductility, and corrosion resistance of duplex stainless steels, leading to the development of super duplex stainless steels.

Grades of Duplex and Superduplex Stainless Steels

  1. Duplex Stainless Steels (UNS S31803, S32205): These grades contain around 22% chromium, 5-6% nickel, and 3% molybdenum. They also have a small amount of nitrogen (0.1-0.2%) to improve their mechanical properties. Duplex stainless steels offer a good combination of strength, toughness, and corrosion resistance, making them suitable for a range of applications in the chemical, petrochemical, and pulp and paper industries.
  2. Super Duplex Stainless Steels (UNS S32750, S32760): Super duplex stainless steels contain around 25% chromium, 7% nickel, and 3.5% molybdenum, as well as 0.3% nitrogen. These alloys have higher strength and corrosion resistance than duplex stainless steels, making them suitable for use in more demanding applications such as offshore oil and gas production, desalination plants, and chemical processing.
  3. Lean Duplex Stainless Steels (UNS S32304): Lean duplex stainless steels contain around 21% chromium, 4.5% nickel, and 0.3% nitrogen. They offer good corrosion resistance and lower cost than other duplex stainless steels, making them suitable for applications in the food processing, wastewater treatment, and architectural industries.
  4. Hyper Duplex Stainless Steels: Hyper duplex stainless steels are a new generation of duplex stainless steels that offer even higher strength and corrosion resistance than super duplex stainless steels. They contain around 27% chromium, 7% nickel, 4% molybdenum, and 0.8% nitrogen. Hyper duplex stainless steels are currently being developed for use in highly corrosive environments such as offshore oil and gas production and chemical processing.

Trademarked Grades

There are several trademarked duplex and superduplex stainless steel grades that have been developed to meet specific application requirements. Some of the most common ones include:

  1. SAF 2205: This is one of the most widely used duplex stainless steel grades. It contains 22% chromium, 5% nickel, and 3% molybdenum, along with other alloying elements such as nitrogen and manganese. SAF 2205 offers excellent corrosion resistance, high strength, and good weldability, making it ideal for use in a range of applications, including oil and gas, chemical processing, and marine environments.
  2. SAF 2507: This is a super duplex stainless steel grade that contains 25% chromium, 7% nickel, and 4% molybdenum, along with other alloying elements such as nitrogen and copper. SAF 2507 offers even higher corrosion resistance and strength than SAF 2205, making it ideal for use in highly corrosive environments such as desalination plants and offshore structures.
  3. Zeron 100: This is another super duplex stainless steel grade that contains 25% chromium, 7% nickel, and 3.5% molybdenum, along with other alloying elements such as nitrogen and tungsten. Zeron 100 offers excellent corrosion resistance, high strength, and good weldability, making it ideal for use in a range of applications, including oil and gas, chemical processing, and marine environments.
  4. Ferralium 255: This is a super duplex stainless steel grade that contains 25% chromium, 7% nickel, and 3.5% molybdenum, along with other alloying elements such as nitrogen and copper. Ferralium 255 offers even higher corrosion resistance and strength than SAF 2507, making it ideal for use in highly corrosive environments such as desalination plants and offshore structures.
  5. LDX 2101: This is a lean duplex stainless steel grade that contains 21% chromium, 1.5% nickel, and 0.3% molybdenum, along with other alloying elements such as nitrogen and manganese. LDX 2101 offers good corrosion resistance and high strength, making it ideal for use in a range of applications, including chemical processing and marine environments.

Each of these duplex and super duplex stainless steel grades has been developed to meet specific application requirements. For example, SAF 2205 and Zeron 100 offer good weldability, while SAF 2507 and Ferralium 255 offer even higher corrosion resistance and strength for use in highly corrosive environments. LDX 2101, on the other hand, offers a more cost-effective solution for applications where high strength and good corrosion resistance are required but at a lower cost than super duplex stainless steels.

Super Duplex Zeron 100 Fastener Grades

Zeron 100 is further developed in higher strengths graded FG and FLT versions. Hague Fasteners have extensive experience working with these alloys.

Zeron 100 is a duplex stainless steel that is widely used in a variety of industrial applications. It is an alloy that contains a high percentage of chromium, molybdenum, and nitrogen, which provide it with exceptional corrosion resistance properties. It also has high strength and toughness, making it ideal for use in applications where mechanical stresses are present.

The higher strength graded FG and FLT versions of Zeron 100 are modifications of the standard alloy that have been designed to provide even greater strength and durability. These alloys have higher levels of nickel, nitrogen, and molybdenum, which provide them with even greater corrosion resistance and strength. They also have improved toughness, which is essential in applications where high mechanical stresses are present.

The FG version of Zeron 100 is specifically designed for use in fastener applications. It has been optimized to provide the high strength and corrosion resistance required in these applications. The FLT Grade of Zeron 100, on the other hand, is suitable for use in floating production systems, such as oil and gas platforms. It has been designed to withstand the harsh and corrosive environments found in these applications.

The applications of Zeron 100 and its higher strength grades FG and FLT are extensive. The standard alloy is commonly used in the chemical and petrochemical industries, where it is used in equipment such as pumps, valves, and heat exchangers. Its excellent corrosion resistance properties also make it ideal for use in marine applications, such as seawater desalination plants and offshore structures.

Zeron 100FG is commonly used in fastener applications, such as bolts and screws, where high strength and corrosion resistance are essential. It is also used in oil and gas production equipment, such as valves, pumps, and manifolds.

Zeron 100FLT is commonly used in floating production systems, such as offshore platforms. It is used in a variety of equipment, including risers, connectors, and subsea production systems. Its exceptional corrosion resistance and high strength make it an ideal material for these applications.

Zeron 100 and its modified FG and FLT grades are exceptional alloys that provide excellent corrosion resistance, strength, and toughness. They are widely used in a variety of industrial applications and are particularly useful in aggressive and corrosive environments. We work extensively with these alloys, and we are confident that they will continue to play a vital role in the industrial landscape for many years to come.

Environment and Applications

Duplex and superduplex stainless steels are ideal for use in aggressive environments where conventional stainless steels would fail. These alloys offer excellent resistance to pitting, crevice, and general corrosion, as well as erosion and stress corrosion cracking. Some common applications of duplex and super duplex stainless steels include:

  1. Oil and Gas: Duplex and super duplex stainless steels are widely used in offshore oil and gas production, where they are exposed to highly corrosive environments containing chloride, hydrogen sulfide, and carbon dioxide. These alloys offer excellent resistance to corrosion and erosion, making them ideal for use in subsea pipelines, offshore platforms, and other critical components.
  1. Chemical Processing: Duplex and super duplex stainless steels are used in chemical processing plants where they are exposed to highly acidic or alkaline environments, as well as high temperatures and pressures. These alloys offer excellent resistance to corrosion and erosion, making them ideal for use in heat exchangers, reactors, and other critical components.
  2. Desalination: Super duplex stainless steels are commonly used in desalination plants, where they are exposed to highly saline environments containing chloride and other aggressive ions. These alloys offer excellent resistance to corrosion and erosion, making them ideal for use in seawater intake systems, brine concentrators, and other critical components.
  3. Marine: Duplex and super duplex stainless steels are widely used in marine applications, where they are exposed to seawater and other corrosive environments. These alloys offer excellent resistance to corrosion and erosion, making them ideal for use in offshore structures, shipbuilding, and other critical components.

Duplex and super duplex stainless steels are advanced materials that offer superior mechanical, corrosion, and erosion resistance properties over conventional stainless steels. These alloys have a two-phase microstructure consisting of austenite and ferrite phases, resulting in improved strength, toughness, and resistance to stress corrosion cracking. There are several grades of duplex and super duplex stainless steels available, each with different compositions and properties, making them suitable for a range of applications in the oil and gas, chemical, desalination, marine, and other industries. The development of hyper duplex stainless steels represents a new generation of these alloys, offering even higher strength and corrosion resistance properties for use in highly corrosive environments.

Technical Bulletins, Thread Protection

Screw Thread and Bolt Protection

Screw Thread Protection for Engineered Components

Thread Protection

One of the most common forms of damage to engineered components is screw thread damage. Screw threads are an integral part of many components, and any damage to them can have far-reaching consequences. In this article, we will detail the problems caused by damaged screw threads in engineered components commonly caused by poor bolt protection during packaging and shipping.

Screw Thread Protection for Engineered Components

Engineered components are crucial in various industries, from automotive to safety-critical Nuclear and Defence installations. These components are designed to perform specific functions with a high degree of precision and reliability. However, when these components are damaged during packaging and shipping, it can cause significant problems.

The Problems Caused by Damaged Screw Threads

The primary function of screw threads is to provide a secure and reliable connection between components. Any damage to the threads can compromise this connection and result in several issues.

Firstly, damaged threads can cause the component to fail prematurely. When the connection between components is not secure, it can cause the assembly to become loose or dislodged, resulting in a malfunction or failure. This can be particularly dangerous in critical applications, where a single component failure can have catastrophic consequences.

Secondly, damaged threads can result in increased maintenance costs. If a component fails prematurely due to damaged threads, it will need to be replaced or repaired. This can result in increased downtime, lost productivity, and increased costs.

Thirdly, damaged threads can result in reduced efficiency. When the connection between components is not secure, it can result in vibrations, which can cause wear and tear on the component. This can result in reduced efficiency and increased energy consumption.

Bolt Protection

The Extra Efforts Hague Fasteners Go To Protecting Threads and Precision Turned Parts

One such method is by wax dipping them to prevent knocks and damage after manufacturing. Wax dipping is a process where the component is dipped into a bath of hot wax to create a protective coating. This coating provides a layer of protection that can prevent damage from knocks and bumps during shipping and handling. It also helps to prevent moisture and other contaminants from penetrating the component, which can cause corrosion or other forms of damage, giving up to 10 years of extended rust prevention in storage.

Wax dipping is an effective and cost-efficient way to protect engineered components, especially threads, during shipping and handling. By taking this extra step, we can ensure that our components are received in perfect condition, ready to perform their intended function with reliability and precision. This protection is far more effective than the Extruded Mesh Sleeves sometimes applied to threaded parts.

Screw Thread and Bolt Protection, Damaged Threads Summary

Damaged screw threads in engineered components can cause significant problems, including premature component failure, increased maintenance costs, and reduced efficiency. That’s why it’s essential to protect components during shipping and handling to prevent damage from occurring. At Hague Fasteners, we go the extra mile to protect our components by wax dipping them to prevent knocks and damage after manufacturing. By doing so, we can ensure that our components are received in perfect condition, ready to perform their intended function with reliability and precision.