Aztec Bolting celebrates 25 years of business with a new headquarters. Company president Larry Garza cuts the ribbon on the new facility while League City Mayor Tim Paulissen, to the right, hold the ribbon. City Chamber Member Shari Ferguson stands to the side of the mayor.

After completing a recent expansion to the headquarters in League City, Texas, with a new office facility and state-of-the-art calibration lab, Aztec is focused on demonstrating a commitment to remain a cornerstone in the torque and tension business. The facilities will allow for employee growth, expansion of outreach, and maintaining an extensive supply of inventory.

Another aspect of growth for Aztec is the pending accreditation of  ISO 17025 for the new calibration lab. ISO includes the tightest of technical requirements and reliability standards. It also ensures a commitment to streamline managerial focus of continued quality, consistency in techniques, and clear communication with customers.

Aztec Bolting Services consists of tooling sales, rentals, in-house calibration labs, industrial tool repairs, and qualified field services for all torque and tension requirements. The company represents several fine-standing manufacturers and suppliers providing the highest quality products and services that include Enerpac, Norbar, Skidmore, Stahwille, and others.

Aztec Bolting Services Inc.
www.bolting.com

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Aztec Bolting hydraulic bolting products for wind turbines.

One particular bolt design has an indicator cap on its head. If the cap turns easily by hand, the bolt is under tensioned. When difficult to turn by hand, the bolt is at its proper tension, a value set during manufacturing. Another design places a visual indicator in the bolt head. When the indicator is out of position, the bolt is under or over tensioned. The feature makes checking for tension a brief visual task.

Why torque control is a questionable way to achieve consistent pretension in structural bolts comes down to friction or what’s known as the k-factor. This is the relationship between the torque applied to a fastener assembly and the actual tension produced in the bolt. A short form of the relationship is:

Tension = Torque/kd

where: k = k-factor, and d = diameter

K-factors can range from 0.10 to more than 0.20 and vary from lot to lot, from bolt to bolt within a lot, and as a consequence of storage and lubrication. Also, consider the variability of the torque tool. Manufacturers of tension indicators say it is likely that when using torque control to govern bolt tension that actual bolt tensions will vary ±40% or more.

A preassembled pair of washers provides a structural, self-locking fastener that prevents bolted joints from loosening by shock or vibration in high-stress applications. The device consists of two preassembled (glued for easier handling) washer-shaped pieces. Each has an inclined cam on one side and a series of ridges on the other. On installation, the cam sides are mated and placed between nut and joint material. Under vibration, the nut tries to rotate loose but, because the angle of the cams is greater than the pitch angle of the bolt thread, the interlocking cams and the nonslip ridges of the washer work together to create a jam which prevents loosening. The washer pair can also be used on bolts in either blind-holes or through-holes. In blind-holes, the washer pair is placed under the bolt head, while through-hole applications use the washers beneath a nut.

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One particular bolt design has an indicator cap on its head. Until the cap turns by hand with difficulty, the bolt is under tensioned. The device works by drilling out part of the bolt center and installing a tension indicator link to the cap. When tensioned, the bolt elongates, tightening the link and preventing the cap from rotating under finger pressure. Another design places a visual indicator in the bolt head. When the indicator is out of position, the bolt is under or over tensioned. The feature makes checking for tension a brief visual task.

Why torque control is a questionable way to achieve consistent pretension in structural bolts comes down to friction or what’s known as the k-factor. This is the relationship between the torque applied to a fastener assembly and the actual tension produced in the bolt.

The short form of the relationship is:

Tension = Torque/kd

where: k = k-factor, and d = diameter.

K-factors vary from lot to lot, from bolt to bolt within a lot, and as a consequence of handling, storage, and lubrication. K-factors can range from 0.10 to over 0.20. Also, consider the variability of the torque tool. Manufacturers of tension indicators say it is likely that when using torque control to govern bolt tension that actual bolt tensions will vary ±40% or more.

A preassembled pair of washers provides a structural, self-locking fastener that prevents bolted joints from loosening by shock or vibration in high-stress applications. The device consists of two preassembled (glued for easier handling) washer-shaped pieces. Each has an inclined cam on one side and a series of ridges on the other. On installation, the cam sides are mated and placed between nut and joint material. Under vibration, the nut tries to rotate loose but, because the angle of the cams is greater than the pitch angle of the bolt thread, the interlocking cams and the non-slip ridges of the washer work together to create a jam which prevents loosening. The washer pair can also be used on bolts in either blind-holes or through-holes. In blind-holes, the washer pair is placed under the bolt head, while through-hole applications use the washers beneath a nut.

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The enhanced corrosion-protected anchor is one version of large diameter rock or soil anchors installed around the perimeter of a turbine foundation. The anchors require less excavation and a substantial reduction in the amount of poured concrete versus traditional reinforced concrete in spread footing foundations. Williams has designed other rock and soil anchors in various size and strengths such as 150-ksi grade bars or 270 ksi multi-stranded tendons.

All successful wind projects begin with strong foundations. Larger wind turbines naturally call for taller towers and larger foundations that consume enormous amounts of concrete and rebar. To handle variations in wind turbines, the current state of practice includes spread-footing foundations, “tensionless” pier foundations, and hybrid foundations that use rock anchors and micropiles to resist overturning turbines and compressive loads. A brief review of foundation designs shows the advantage of the hybrid foundation.

Spread-footing foundations are most common. Large gravity concrete pads, hexagonal in shape, use about 400 to 500 cubic yards of concrete and a truckload of rebar. The load transfer from the tower is accomplished with high capacity, post-tensioned threaded bars connected to an embedment plate near the foundation bottom. Bars are sleeved through the foundation to transfer loads generated by the turbine from the tower base all the way down to the embedment ring in the foundation bottom. Enginneers traditionally specify a preload for the anchor bolts that is higher than the tower service loads, thus eliminating fatigue and impact factors. Post-tension bars use clever cold-rolled “knuckle” threads, which are more durable than regular NC (National Course) threaded bars necessary for ease of tower installation.

Hybrid foundations are one way to reduce concrete and rebar, and are becoming more common. In them, a shorter (shallower) and smaller diameter concrete “cap” is constructed with blockouts – recessed holes – to allow drilling through the constructed

foundation. Contractors then drill a small, about 8-in. diameter, hole to a depth dictated by geotechnical reports (typically 30 to 40 ft), place an anchor in the hole, and completely fill it with a grout-a neat cement. Anchor features include a no-bond zone (also called a Free Stressing Zone) at the upper 10 ft of the anchor, so the load transfers deep into the ground. Good practice requires a load test on every anchor, as well as an extended “creep” test, one that evaluates the anchor movement over time, on a sampling of the production anchors. The anchors are then locked off at loads higher than anticipated service loads.

Long ground-anchor bolts, 40 ft in some cases, allow using smaller diameter and shallower foundations for wind turbines.

As turbine and tower technologies change, so must foundations. What was common 10 years ago is no longer the standard, and a decade from now the foundations on wind farms will continue to evolve to meet higher loads and stricter design standards. WPE

By: Tom Bird, Vice President, Western Division of Williams Form Engineering Corp.

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The pins use a 2¼ coil cross-section to make them self-retaining pins that compress when installed into a host component. The company says they are the only pins with uniform strength and flexibility after insertion.

The company suggests those seeking a custom fastener might be interested in the its Optimal Application Engineering program. This is a five step procedure for designing and delivering the fastener more useful than one off the shelf. Step one, with the client, defines product performance, assembly, and commercial objectives. This includes gathering sample components, the drawings of the individual components, and assembly-level drawings. This stage also defines commercial objectives such as a target product cost, product packaging and labeling, and delivery requirements.

Step two calls for a comprehensive engineering evaluation after gathering product, assembly, and manufacturing objectives. Spirol says its application engineers can help find a best solution for the particular application.

In step three, the company provides a formal technical and commercial proposal, including prototypes for evaluation in the client assembly. The proposal will detail other products considered for the application, and why the recommended part is the best design.

Step four: When installation equipment is involved, Spirol can design a fixture to hold and align components during insertion. The company also builds, tests, installs, and certifies the machine, and educates operators and maintenance personnel.

Dowel bushings and spring dowels, other company products, can maintain alignment and are used to locate components with respect to each other. These roll-formed, hollow alignment dowels have lead-in chamfers that facilitate insertion into the holes of both mating components.

In step five, the company plans production to meet client-delivery requirements and will ship certified products anywhere in the world. Spirol says it provides a formal technical and commercial proposal, including prototypes for evaluation in an assembly. The proposal will detail other products that were considered for the application, and ultimately why the recommended part is the optimum solution. The brochure is available at the URL below.

Spirol International Corp.
http://www.spirol.com/library/main_catalogs/SPIROL_Corporate_Brochure_us.pdf

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The ferrule-tightening adaptor can be swapped for ProCut, a device which makes clean tube cuts even in heavy wall stainless steel fast and efficient. A ProBend head for the same motor body lets operators set needed bend angles for automatic bending, or use a touch button to set bends to any needed position by observation.

SSP
www.mysspusa.com

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Thomas & Betts
Meyer Steel Structures
www.meyersteelstructures.com

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The wind industry recognizes the importance of proper bolt tension. The acknowledgement will challenge some of the industry’s torque-tightening practices as it matures and adopts more sophisticated technology to improve reliability and reduce maintenance costs.

To start, let’s review current practices. For instance, bolts on turbines are often tightened in one of two ways: either by torque or by hydraulic tension tightening.

Torque is a rotational force applied to a lever and multiplied by its distance from the centre of the tightening end (fulcrum). Torque, measured in Nm or lbs-ft, rotates a bolt head or nut to tighten and stretch the bolt so it clamps two surfaces together. Hydraulic torque wrenches allow the operator to control the torque applied and are extensively used to tighten wind-turbine bolting.

One design for a tell-tale bolt comes from UK-based James Walker’s RotaBolt. A simple mechanism inside the bolt provides an indicator of the real load or tension. RotaBolt fasteners are guaranteed to consistently indicate within ±5% of the specified load regardless of environmental influences.

Although simple to use, the technique suffers from inaccuracy due to inconsistent friction. Even on lubricated threads and nuts, the level of friction is uncontrollable. This means there is a critical lack of tension control that can lead to bolt failure, and ultimately compromise joint integrity.

Hydraulic tension tightening is also used to tighten large diameter bolts on wind-turbine structures. A hydraulic ‘jack’ pulls the bolt axially. When the bolt is stretched by a specified amount, the nut inside the tensioner rises off the flange creating a gap between flange faces. The gap is closed by tightening the nut. Releasing the hydraulic pressure transfers tension to the bolt and flange.

If you can turn the indicator cap, the bolt is not tensioned.

The drawback here is that tension loss occurs when releasing the hydraulic pressure. It’s an effect called “load transfer relaxation.” To compensate for the loss, the hydraulic pressure originally applied is increased a bit, a “hydraulic overload value”. However, the amount of load-transfer relaxation is not accurately predicted and so varies from one bolt to another. Consequently, hydraulic tensioners are unable to control or measure the tension achieved for each bolt. The device is also unable to provide an in-service reliability check.

One way around the shortcomings of both tightening methods is with a bolt that indicates when its specified load or tension has been reached during tightening. The RotaBolt can be used in either torque or tension tightening. When this bolt is tightened, the cap locks at exactly the right amount of preload in the bolt. This allows for more control during tightening while ensuring that an OEM’s design criteria is met independent of the tightening system. It also allows checking the bolt’s status in service (if a cap on the bolt does not turn, it’s still tight) something traditional bolt retightening checks are unable to do.

Accuracy is not affected by friction, as in torque control, nor by load transfer errors, as in hydraulic tensioners. This bolt-tension solution can ensure joint integrity on wind turbines. Joint integrity, in turn, allows for greater reliability and the more efficient production of renewable energy.

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Brennan products are stocked at full-service distribution centers in: Atlanta, Cleveland, Dallas, Los Angeles, Seattle, Toronto and Shanghai.

A supplier of hydraulic fittings and adapters offer a line of double ferrule instrumentation-grade tube fittings that are interchangeable, intermixable, an traceably stamped.

Brennan Industries Inc. says its double-ferrule, instrumentation-grade fittings feature interchangeable nut and ferrule sets, which enables the installer to use one tube fitting manufacturer’s nut and ferrule sets within the body of another manufacturer. The tube fitting line also has intermixable components that work with those of several other manufacturers. The design characteristics are comparable in form, function and fit allowing for intermixability between the designs. All components of the tube fittings are Brennan stamped and all packaging has traceable codes printed on the box for easy reference. Each fitting is packaged in its own pouch and thread-protector to keep the fitting clean from contaminants.

“Brennan’s instrumentation fittings offer convenience with hassle free interchangeability and intermixability features. Identifying markings found on the packaging and individual parts make it easy to identify what product you are working with,” says Bill Jarrell, vice president of sales and marketing.

Supplying a wide range of industries throughout the world, Brennan offers more than 20,000 standard and special products in sizes ranging from 1/8″ to 2-1/2″. These include pipe and straight-thread fittings, O-ring face-seal fittings, 37° flare tube fittings, bite-type fittings, DIN fittings, international fittings and conversion adapters. Most products are available in carbon steel, stainless steel and brass, and meet or exceed J.I.C., S.A.E. and other specifications.

Brennan Industries Inc. www.brennaninc.com

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Many companies make the same mistake every year assuming their torque tools are accurate and in working order. They also assume factory torque charts are correct and a certified gauge ensures tool accuracy. It’s a hazardous assumption because calibrated power tools frequently are not performing as expected.

Although there are other ways of establishing the tension on a bolt, torque is used most often. Such tools include hydraulic and electric torque wrenches, torque multipliers, and manual wrenches. After the required yearly calibration, tool owners usually get a certificate detailing the particulars which also verifies the quality of the equipment.

Technicians with mobile calibration equipment say they can calibrate all makes and models of torque wrenches up to 25,000 ft-lb. The computer, just behind the Mobil- Cal technician, lets him sign into the company’s online system, identify the tools that need calibration, and follow the step-by-step ISO procedures for the task.

Certificates are also needed after turbine assembly. For instance, during mechanical-completion inspections, inspectors with OEMs must work through punch lists. The OEM inspector will look for training records and calibration sheets for the tools used. Also, internal quality reviews conducted by companies will need to see the calibration sheets. What’s more, companies go through a process to become ISO certified and having a documented calibration process is part of ISO procedures.

Most technicians keep the calibration forms handy in a three-ring binder–kept…somewhere. If proof of certification cannot be produced, the technician may be forbidden to use the tool on the job site until it is. That could be a problem for the technician who may have to resort to a manual tool for the day, and accept a significant loss of productivity.

Engineers at Alltite Total Bolting Solutions may have an answer to the problem in an online service that tracks tools, their calibration, and certification. One goal is to get rid of the easily lost certification forms and make them more readily accessible.

The MobileCal sample calibration report lists the values measured and calculated for a hydraulic torque wrench.

For example, the Customer Portal-Calibration chart lists all the tools in a particular facility. “This could be a single wind farm, a region, or all the tools that need calibration for a particular company,” says Alltite CEO Tom Smith (alltite.net). He adds that the program was devised with two sides in mind. On the calibration technician’s side, data and procedures assist with calibrating torque tools step-by-step to ISO standards 6789 and 17025.

Clients, says Smith, see and manage all their calibrations through the online portal. A user name and password lets customers access the data. Customers search by their calibration ID, printed on a sticker placed on their tool at the last calibration. Users might also search by calibration-due date, or the tool and equipment type. Smith says the program can be customized for particular needs.

Benefits are that the company’s quality-control person would see the entire fleet of tools to make sure they are compliant. The paperless system lets users get away from chasing the sheet of paper that usually comes with calibrations.

An alternative method at some large companies is to send equipment to its lab where it’s calibrated and sent back with a folded sheet of paper or calibration certificate. But the wind industry is so wide spread, says Smith, a technician could be in Pennsylvania one week and Minnesota the next. “If he’s hunting down this piece of paper, he’s losing time and money. With this system he can log into the portal, find the tool in question, pull up the certification in standard or metric units, and print or download it. It’s also viewable on smart phones.

The Expires column on the Calibrations and Search page of Alltite’s TorqueWare customer portal tells which tool in the fleet is next up for calibration.

The calibration reports show measured and calculated values, such as the torque to pressure ratio, as-found readings, as-left readings (after adjustments), serial number of the wrench, and more. “Another plus is it provides a quality program for an entire organization,” says Smith. “With the online system, it drives consistency across all business units and eliminates variance by having a single quality program. Without something like it, a company with 15 different sites could have 15 different vendors and possibly gaps in their quality program. This program wraps all calibration, certifications, and documentation into a single point which give clarity and consistency to the organization.

The portal also gives an inventory list so companies can allocate their resources. For instance, one site may have half of a company’s torque equipment, when in fact it’s more needed elsewhere. Smith says he’s yet to find a company that can track all its tools, and is 100% accurate. A frequent discovery, for example, is that more than 65% of clicker torque wrenches don’t meet OEM specifications.

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