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bolt securing

On site, offshore, under pressure


First published in Bolted #1 2016.

Customer: Heat Solutions on Site BV (HSOS)
Location: 207 km east of Aberdeen
Assignment: Bolt tensioning/piping pressure testing
End customer: Offshore oil platform
Product used: Boltight bolt tensioner

Dutch company Heat Solutions on Site BV (HSOS) is a leading service provider in the metal sector. Their services include heat treatment, machining on site, flange management and leak sealing.

Among its many assignments, HSOS is often brought in to undertake bolt tensioning and pressure testing of piping on offshore platforms, where leaks could potentially lead to disasters.

Customers have been very satisfied with the results, with no leaks being recorded. One example is Talisman Energy UK, which subcontracted HSOS when constructing a new 9,500-tonne oil platform off Aberdeen, Scotland. While not performing the pressure testing itself this time, HSOS provided all calculations and Boltight 1,500-bar series bolt tensioners for the project.

“The Boltight equipment is high-quality and easy to use with easy retraction,” says Marcus Sutton, Flange Management, HSOS. “The Boltight staff are fast and efficient, and they offer lots of engineering support. They don’t just sell you a product; they sell you a solution. And if they haven’t got it, they will engineer it for you.”

“Offering a greater field of solutions”

13 July 2016

Text: Nic Townsend

photo: Sam Lee


First published in Bolted #1 2016.

FACTS: Fred Heaton
Role: Founder and Managing Director of Boltight.

Background: Started his career with GKN Bolt & Nuts at the age of 15. After ten years with GKN, he founded Hydratight Ltd in 1975, which he sold to T&N in 1979. He remained Managing Director of Hydratight for 17 years before becoming New Business Director for the T&N General Products Group. After T&N was acquired by the automotive company Federal Mogul he left and started his own management consultancy company, which would later become Boltight.

For Fred Heaton, what started out as a hobby in 1999 quickly grew into a thriving business specialising in hydraulic bolt tensioners. Now Boltight has been acquired by the Nord-Lock Group, in a move that is set to strengthen both companies.

What does Boltight do?
“As the name suggests, we provide tools for tightening bolts. Bolted joints do not always receive sufficient attention at the design phase, which can lead to tightening problems later, and we are here to provide a solution.

“Most of our customers are in the oil and gas, offshore, power generation and heavy engineering industries. Around 50 per cent of the time, we can provide a solution using standard tools, while the other 50 per cent will require tools designed and manufactured by us to meet the customer’s needs. We use a 3D CAD system to model the customer’s problem and our solution.”

What are Boltight’s strengths?
“We are fast to respond, quick to deliver and have many years of experience solving customers’ bolting problems. We keep every tool we’ve ever designed stored in our 3D modelling system, which we can use as references whenever we’re faced with a new problem.”

What will Boltight bring to the Nord-Lock Group?
“Being able to draw on our product range will mean the Nord-Lock Group can offer a greater field of solutions. No one tightening solution fits all applications, so it’s important to have a number of different products, other than just mechanical. Some customers will want a hydraulic solution, and Boltight has a whole range.”

What will the Nord-Lock Group bring to Boltight?
“We have good products and good engineers, but we are a small company and not particularly strong when it comes to sales and marketing. We have built up a distribution network and 95 per cent of our products are exported from the UK but we’ve only really scratched the surface of the available market. With Nord-Lock sales & marketing resources, we can reach out to new markets and applications, and we expect to see good growth. For example, we tend to sell to large one-off projects, but with the Nord-Lock network, we can now start to supply to original equipment manufacturers as well.”

Is the Nord-Lock Group a good fit for Boltight?
“Yes, Nord-Lock has a clear strategy and sees this as a long term investment. They are not just buying and selling companies – they expect long-term value and want to see Boltight grow.”

The Experts: Can I use an additional locking system?


First published in Bolted #2 2011.

Q:  Can I use an additional locking system with Nord-Lock washers?

A:  It is recommended to use only standard fasteners (nuts and bolts) with Nord-Lock washers. Other specialised locking systems, including prevailing nuts and adhesives, are not advisable and would not add any benefits to the joints.

Theoretically, it is possible to use prevailing nuts and adhesives together with Nord-lock washers, but they will increase the thread friction when tightening the joint. When tightening, less of the torque can be converted into useful clamp load because the torque must overcome the additional friction. Also, increased thread friction raises the risk of torsional stress in the bolt and may lead to unexpected bolt failures. Additionally, these systems will add more cost to the joint.

Nord-Lock is a reliable, engineered system and there is no need to use any additional locking systems. The superior quality guarantees excellent tightening control and the joint is exceptionally secure.

The prevailing nut category includes a multitude of fasteners. Nylon insert nuts, metal insert nuts, flex top expanding nuts and distorted thread nuts are just some of the products that are available. These products add friction to the bolted joint and are more costly than a standard nut.

Adhesives are a little different but can cause the same problems. Some existing adhesives are thread lockers, joint sealants and thread sealants. In addition to adding undesirable friction to the bolted joint, the option of using a thread lubricant is also eliminated. A good lubricant is recommended in order to reduce friction, further minimise clamp load deviation and protect against corrosion.

To optimise your joints it is re­commended to use lubricated standard fasteners together with Nord-Lock washers which will result in a secure joint, predictable preload and low deviation.


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First published in Bolted #1 2016.

The Myth: A small thread pitch reduces fatigue life due to the notch effect.

The Truth: A general statement is, as so often, not possible in this case since various parameters interact. In the literature there are partially contradictory statements. Heinrich Wiegand et al have conducted comprehensive studies on the influence of thread pitches. Dia­gram (a) shows the influence of thread pitches on bolt fatigue life.

Different property classes result in different characteristics. The fatigue life of high-strength 12.9-class bolts decreases with increased thread fineness, caused by the increasing notch effect. With decreasing strength and increasing ductility this effect is not visible anymore.

For bolts of property class 8.8, a decrease in fatigue life can also be seen. A larger cross-section of the fine thread will compensate for the decreasing fatigue life. The tolerable load amplitude (diagram b) is practically continuous.

There are more factors that influence the thread pitch than those mentioned. These include, for example, the displacement of the force application point, the root radius, the notch depth, the distribution of load force at the thread pitch and the notch sensitivity of the bolt material.

Health & Safety: Shared expertise increases safety

15 June 2016

Text: David Nikel

photo: Terry Vine/Getty images


First published in Bolted #1 2016.

Each year objects dropped from height damage equipment, disrupt operations and cause a number of injuries – in the worst case fatal ones. To counteract this, the work group DROPS (Dropped Objects Prevention Scheme) was started in the late 1990s.

Oil and gas operators, major engineering and drilling contractors, inspection specialists, industry bodies and suppliers come together in DROPS to share and discuss best practice. The organisation produces publications and offers resources such as training to its members.

“While the collaboration of all the key players is not so unusual in the oil and gas industry, our single-issue focus is unique and means we can be very effective at what we do,” says Greg Reid from Silver­dot Ltd, who administers the activities of DROPS.

With over 200 member organisations, interest in DROPS continues to grow. “When DROPS started it was solely focused on the drilling sector within the oil and gas industry,” Reid says. “Today, we are a truly global organisation that covers all aspects of the industry. In fact, we are attracting attention from mining and construction companies, as they see the benefits of industry-wide collaboration.”

The Nord-Lock expertise in bolted connections is showcased in the third revision of Reliable Securing, which highlights the company’s washers as a recommended solution for mechanical and structural connections where maintaining the clamping force is critical.

“Nord-Lock has been a very active member of DROPS for around ten years,” explains Reid. “Our organisation can only be successful if all our members bring a collaborative attitude to the table. Nord-Lock are always free and open with their advice, offering unbiased expertise that doesn’t have their own interests at heart.”

For more information:

Nord-Lock Group uses Siemens NX CAE to develop cutting edge technologies

NX simulation solutions help Nord-Lock Group solve complex joint-related problems

At the global Technical Center in Lyon, France, the Nord-Lock Group sets out to help customers worldwide conduct tests and checks. The lab is equipped with advanced technologies, measuring instruments and test equipment. To remain at the forefront of expertise and build on our technical know-how, the Technical Center has chosen to use the NX™ software and NX™ Nastran® software from product lifecycle management (PLM) specialist Siemens PLM Software for simulation purposes.

NX CAE is mainly used for advanced non-linear calculations to analyze stress states, deformations and movements in joints. The solution was naturally selected for precision, performance and reliability of its NX Nastran solver, its integrated management of CAD data, and its openness. The digital solution is also used as an alternative to physical testing.

The results from using the simulation solutions are positive, they helped gain insights to the bolted joint phenomena, determine likely causes of joint failures in different scenarios, and reduce reliance on physical testing.

Read the complete article (in English) here: NX simulation solutions help Nord-Lock Group solve complex joint-related problems

New innovations to solve difficult shaft coupling bolting problems

innovative bolting solution for shaft coupling

The white paper “New innovations to solve difficult shaft coupling bolting problems” is written by Stephen J. Bussalacchi, Product Manager of Superbolt Division, Nord-Lock Group.



Demanding bolting applications in the hydro industry, such as shaft couplings, have typically required the use of fitted or interference fit bolts for proper torque transfer. However, these bolts require large and expensive tools for tightening, precision machining and extreme tolerances/surface finishes. These extreme machining requirements also apply to the mating coupling bores. Assembly may require further mechanical adjustments and disassembly is often time consuming and cumbersome. Additional concerns with these methods include worker safety, stuck bolting, and failures as a result of fatigue. This paper will examine a possible means to overcome these bolting challenges and achieve a bolted connection that is pre-loaded safely, cost effectively, and with as little downtime as possible. One such system is a radial fit ‘expansion bolt’ that utilizes split expanding sleeves and low input torque multi-jackbolt tensioners to achieve a true radial pre-load into the coupling bores as well as high axial clamping of the split line. Shaft coupling flanges are a critical component of hydro turbines all over the world. Utilizing the latest procedures and tools to achieve a secure bolted joint is essential to ensure many years of safe operations.


To receive the full white paper, please submit the form below. This white paper is currently only available in English.

► Request for paper: “New innovations to solve difficult shaft coupling bolting problems”





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Safely securing connections in structural steel

Securing bolting connections on structural steel

From the Empire State Building in New York to the Eiffel Tower in Paris and Burj Khalifa in Dubai, steel has been used in some of the world’s most famous landmarks and is used everywhere around us, in buildings, bridges, highways or other civil engineering projects.

Steel is one of the most commonly used materials in commercial and industrial building construction as it provides high design flexibility, durability, and low long term maintenance costs. Since steel has higher strength than concrete, it allows for bigger and more slender constructions. It is also much lighter compared to frameworks made of concrete. Using steel frames is also time efficient since pillars, beams and other constructions elements can be delivered to the construction site ready to install. This, in turn, gives great savings potential.

Connecting structural steel

In the past, riveting was a common way to connect structural steel. Today, bolting and welding are the primary connection methods. Both methods have their advantages and constraints. A general practice is that welding is done at an earlier stage, in a workshop, where it can be executed in a controlled environment and then larger frameworks can be assembled by bolts at the construction site.

Performing welding at a construction site, however, may lead to uneven joint quality and is often very costly. It requires specialist skills and equipment, and is sensitive to the surrounding environment since uneven heating and cooling members may distort, which can result in additional stresses.

With bolting it is possible to assemble structural steelwork parts quickly and cost-effectively. It is also easier to get the steel parts fitted and adjusted during assembly on site. Unlike welding, bolting is less susceptible to poor weather conditions and has less inspection requirements.

Steel construction elements are safety critical and need to ensure that the final result is strong and durable. Connections in such structures must comply with strict quality requirements and standards for the design (the Eurocodes) and fabrication (EN 1090-2) of structural steelwork. This means that both welding and bolting have regulations to follow according to Eurocode 3.

Securing preloaded bolting connections

Bolted connections can be commonly divided into preloaded and non-preloaded structural bolting assemblies. As recommended in EN 14399, preloaded bolts are almost always used on bridges. These bolts are specially designed to withstand vibration and dynamic loads, and also recommended when slip between joining parts is to be avoided. In buildings, preloaded bolts may be utilized where oversized or slotted holes are used to increase tolerances during assembly.

For preloaded bolted steel connections there are two different bolting systems developed and standardized in Europe (EN 14399): HV-sets (in accordance to EN 14399-4 and EN 14399-8) and HR-sets (in accordance to EN 14399-3 and EN 14399-7). Both systems are similar and consist of bolts, pre-lubricated nuts and washers. The radius under the bolt head is a particular characteristic for those bolt sets. It is larger than for normal standard bolts in order to decrease the notch effect.

The manufacturer of these bolt sets provides the customer with tightening guidelines that must be followed according to the European regulations. In spite of this practice, it is known that the bolts may still loosen due to dynamic loads and require time-consuming and costly retightening.
Using standard locking washers would be the easiest solution to cope with loosening of bolted joints or to decrease retightening frequency. For structural steel parts using HV/HR-sets this is, however, not the case. The radius under the bolt head makes the use of common locking methods with HV/HR bolt sets impossible.

It is not only impossible design-wise but also from a legal perspective since regulations in Eurocode only allow dedicated washers according to EN14399 for these types of bolt sets.

The Nord-Lock Group has developed a locking washer specially designed to fit the HV/HR sets. Each Steel Construction (SC) washer pair has chamfers on the inner diameter to ensure an optimal contact surface between the bolt and the washer. Nord-Lock wedge-locking technology secures the bolt with tension instead of friction preventing the bolt from rotating loose. The washer is CE approved to be used together with HV bolt sets.