Selecting tool tethers and lanyards for working up-tower

Maintaining a wind turbine often means working at heights exceeding 300 feet. Although a tool falling from any height is a problem, in the case of wind-power maintenance, an object falling several hundred feet endangers everything and everyone below. It is a site safety issue. A large, free-falling tool, such as a torque wrench, could kill someone. If it hits a blade or lands on a pump or bearing, the falling tool will do significant damage and cost a company in productivity, workmen’s compensation claims, medical bills, and equipment repairs.

Tool tethers are the best way to protect employees, their tools, and the work site. When the tool, employee, and application are correctly mated, working aloft becomes easier and more efficient. The safety engineer’s goal in correct Description: tethering procedures is to make sure the tool, application, and recoil-retraction force are in balance. When the tool is extended for use, only minimal force should be necessary so as not to cause worker fatigue or, in the reverse, a ”kick” when retracted. A tool is correctly tethered when its storage or use minimizes the dangers of entanglement, fatigue, and annoyance, and maximizes worker satisfaction and output.

A new safety engineer may ask: How do I know which type of tether to use in each application? There are at least three: retractable tool tether, coiled, or lanyard. That engineer may also wonder: Should the tether be attached to the worker or anchored to the structure? Do you need a quick release device to safely change out tools?

It can seem overwhelming, but when a tether is correctly matched with a tool, worker, and application, the work is safer, easier, and more efficient. Conversely, a poorly matched tether can become a safety hazard. The safety engineer’s challenge is to provide a tether that is user-friendly and appropriate for the work environment. The following overview describes a few tool and instrument-tethering options.

 

One size does not fit all
With such a high risk to workers’ safety, it’s unfortunate that little has been published on the subject of tethering equipment and tethering safety techniques. Many safety professionals are unaware of the available options. And most companies that sell safety equipment or personal fall-arrest systems fill their product line by importing a basic tether in two or three sizes. When tool tethers are ordered without specifications beyond the weight of the tool, chances are good the tether may not be appropriate.

In reality, safety engineers have thousands of choices from U.S. manufacturers specializing in tool, gear, and instrument tethers. Tethering systems can be specified for a variety of applications in a broad range of industries. Each application has its own set of criteria, such as standing up to saltwater, chlorine exposure, and high temperatures, or special mounting or attachment needs. Manufacturers like Hammerhead Industries Inc. and Snap-on Tool’s (snapon.com ), with its Tools-at-Height program, are addressing the importance of selecting a proper tether.

An appropriate lanyard and tether for each application
The objective of tethering is to secure tools to prevent injury and damage. But there are factors that may impact the safety of the worker using the tether or lanyard. An improperly mated tool and lanyard can inherently lead to lower productivity and exposure to injury. When the tethering device limits mobility, recoils too fast, or exerts too much resistance on extension, it can often backlash on workers. The general result is fatigue, annoyance, and often non-compliance in lanyard use.

The correct design philosophy is to provide a lanyard that has a low-stretch force. This helps eliminate or reduce user fatigue when it is at full extension and providing the proper amount of recoil. This is accomplished by sewing the elastic material inside the webbing during manufacturing instead of assembling it after the fact. In this manner, the elastic provides optimum retraction tension and low stretch force.

Tethers heavier tools to a structure–not a person
Tethering heavy tools, (generally over 5 lb) to a person is a significant safety concern. Instead, safety engineers should consider using anchor tethers. Anchored tethering transfers the shock load from by a dropped tool to the structure and not that worker. For heavier tools (over 10 lb), structure anchoring should be mandatory.

For tools less than 2 lb
Picture a worker using several small tools, say an electrician using screw drivers, pliers, and an amp meter. These tools and working conditions are poor choices for coil tethers or lanyards. But they are ideal for a retractable tether that safely permits attaching multiple tools to the worker with almost no risk of entanglement or snagging. Tool and gear retractable-tethering devices offer hundred’s of combinations of mounting systems, line technology, and shock-absorbing capabilities.

Quick-release fittings for several tools on a tether
Change the tool not the tether. A single-tool lanyard is sufficient when one tool is the only thing tethered. But what do you do when you have multiple tools to tether? It’s a common scenario. There are many options for worker safety in multi-tool tethering situations. Quick-Connect tethers offer easy tool change-out and are available in a large selection.

The ratings
Unfortunately, there are none. Tool-tether ratings have not been established or standardized by either the tethering or safety industries. There are no universal specifications governing tool tethers as there are with fall-protection devices. As such, the safety engineer has no real basis for choosing proper tethers and thus arbitrarily makes a selection based on tool weight. Without additional specs, the safety engineer maybe creating a potentially dangerous situation.

Of greater concern is how some suppliers arbitrarily rate their lanyards so they meet customer’s requests. For example, when a safety engineer requests a tether for a 3-lb tool, the distributor may offer to send one rated for up to 15 lbs, for a higher safety margin. Although both supplier and buyer have good intentions, they may be setting up a potentially hazardous situation. For instance, using a tether rated for a much heavier tool will not operate effectively because its stretch and recoil are considerably out of scale for the lighter tool. The more serious problem is when a worker, assuming a lanyard is rated for 15 lbs, thinks he can connect a 15-lb tool to his tool belt. That’s a bad idea. The 15-lb tool, at a full-drop length, will generate in excess of 250 lbs of shock load, more than enough to knock a worker off his perch. A personal fall-protection device may not further protect that person. Safety engineers should explore practical tool tethering solutions with reputable manufacturers.

Make the employee your partner in tethering
For a successful tool and instrument tethering-safety program, employees and safety engineers must partner. A properly tethered tool or instrument makes work more efficient. It simplifies every repair, maintenance, or manufacturing project by keeping workers’ tools handy and accessible. Tethers that correctly complement the tool, worker, and application are conductive to advocates rather than antagonists.

John Salentine
Vice President
Hammerhead Industries
www.gearkeeper.com
www.gearkeeperblog.com/#

WPE

Tower bolting technology improved with interlocking cam fasteners

Greg White
Vice President
DISC-LOCK International
Culver City, Calif.
www.disc-lock.com

 

 

Wind-turbine towers appear to be rising to new heights–literally. As blade lengths increase to capture more wind energy, towers must also reach higher to accommodate the longer blades.

Increased tower dimensions also translate into elevated levels of vibration and stress on tower fasteners, which can lead to loosening and bolted-joint failure. However, fastener failure can be eliminated with a locking washer.

The working principle behind the device is simple: It consists of two washer-shaped pieces that are preassembled (glued pairs), and have inclined cams on one side with a series of radial ridges on the other. On installation, the two cam sides are mated together and placed between the nut and joint material. Under vibration, the nut attempts to rotate loose. But because the cam angle is greater than the bolt-thread-pitch angle, the interlocking cams and non-slip ridges of the washer work together. The resulting jamming effect prevents loosening and further locks the assembly, thereby maintaining joint integrity. The result: a vibration proof fastening system.

The locking washers also offer a fastening system that combines a heavy hex nut and tension-control bolt. Tension-control bolts are replacing conventional high-strength, friction-grip bolts and swaged-collar rivets because they are quick and easy to install with a lightweight electric shear wrench. Guaranteed tension and a visual inspection eliminates the likelihood of operator error and ensures engineers that connections are tightened in accordance with specifications. This bolting system is easily removed and can be reused. Other types of secure bolts are not reusable because they must be burned or cut off for removal, thus destroying the bolt.

The electrically powered shear wrench is lighter than hydraulic wrenches, a distinct advantage when considering tower height and precarious installations. This translates to a one-man operation that trims installation cost. The DISC-LOCK shear wrench uses an outer socket to engage the nut, while an inner socket engages the bolt. The two sockets rotate in opposite directions allowing the nut to turn while the bolt remains stationary. This counter-force operation transfers no torque to the operator, thereby reducing fatigue that can cause carpal tunnel syndrome.

Other interlocking cam fasteners from the company can help maintain bolted-joint integrity on wind farms. These include hex-head bolts for use in blind-hole applications and locking nuts that can be installed with standard tools. Forces that induce other lock nuts to loosen cause locking cam nuts to tighten.

WPE

Engineering a taller tower

Placing wind turbines at greater hub heights puts them in stronger, steadier wind which improves their performance. Wind speed at just one more meter per second can pay off big. Turbine performance becomes a critical consideration as units with larger rotors and greater power outputs enter the market. Taller conventional steel towers, however, are too heavy and too large to transport and erect easily. To make conventional towers more impractical are conventional foundations. They take a lot of prep work and concrete.

One way around the challenges of tall towers is to start with a wide-diameter concrete base. The large diameter provides improved stability by spreading tower weight over a larger area, thereby avoiding large and deep (2 to 3m in some cases) concrete foundations.   An added benefit is the ground-level space available for ground-mounted electrical and other turbine support equipment. Tindall Corp., a manufacturer of precast concrete, has given the concrete-tower base some thought. “The final design of the Atlas CTB (Concrete Tower Base) has features that will optimize existing steel-tower technology and place the focus on height,” says Tindall spokesman for Atlas, Chris Palumbo. “For instance, the Atlas CTB’s large-diameter base uses a shallow-ring foundation that can reduce material by 60 to 70%.  Initially, precast concrete sections are positioned against each other to form a cone shaped bottom section that provides the stability necessary to extend hub heights above 100 meters. The 50-ton, 26-m long sections transport by truck or rail.

After assembling the tapered base, a circular concrete section fits like a collar atop the base. All concrete sections are held together with post-tensioning tendons that loop through the circular sections and around an arched shelf of each taper section. Once the tendons are properly tensioned, the entire structure performs as a unit. A conventional steel tower then bolts to the top of the 31-m tall concrete base. Palumbo says hub heights to 130 m and higher are possible for utility scale turbines.

The final tower has a foundation of about 18-m diameter and one-meter thick. Germanischer Lloyd recently issued a certification report for the Atlas CTB. Palumbo says the company plans to have a prototype installed at Tindall’s Atlanta, Georgia manufacturing facility by summer. Watch an animated construction of an Atlas CTB at: tinyurl.com/atlasctb.

WPA

Reducing uncertainty with a third-party warranty

AWEA Off-Shore Wind Expo – The Buzz from Day 1

After successfully launching numerous onshore projects, the U.S. wind industry is looking into utilizing its offshore energy potential. But issues with money, politics, transportation, and other schematics, this is easier said than done. “It’s taking its time,” as Sara Mallo of Rotor Clip puts it. The company has been part of the offshore industry in Europe and says the market is catching on slowly in the U.S. as well.

Some companies are already looking ahead, sharing their thoughts and plans at the AWEA 2010 North American Offshore Wind Conference in Atlantic City. For one, Gamesa will launch their G11X, a 5-MW offshore turbine in 2013,  a progression of their G10X onshore turbine.

REpower is also planning to lunch their MM100, 1.8-MW offshore turbine exclusively for the North American market. The company also shows off their 6M offshore turbine of 6.15-MW.

The offshore wind market is not exclusive to turbine manufactures, many of the attendees and exhibitors’ interests lie within the component manufacturers, turn-key energy consultants, site selection tool providers, and federal, state, and local economic and energy development departments.

The buzz is there’s a great opportunity for offshore wind development, even though it is yet to reach its infancy. By this time next year, while the turbines off the coast of Cape Cod or in the freshwaters of Lake Erie begin to generate energy, offshore projects should be in development throughout North America.

Better blade lets 1.5-MW turbines deliver 5% more power

LM Wind Power’s LM 42.1 GloBlade 1 will extend the life cycle of the 1.5-MW segment by offering a design that provides annual energy production and requires no mechanical upgrading of the current platform. The blade is a way of meeting expectations for high performing rotors. By using its know-how in aerodynamics and structural design, the company developed a more cost effective blade for the 1.5-MW segment, ensuring the end user up to 5% more power generation from an existing platform.

“The market trend has been to move up in the MW range, however this presents many technical challenges and the need for customers to develop and invest in new equipment. The current 1.5-MW industry standard blades are 34, 37.5, and 40.3-m long with only the latter sold in any real volume now. This underlines the end user requirement to generate more power from an existing platform, and there are many manufacturers who offer these products. This lets OEMs sell a tested designs that offers higher electricity revenues,” says Ian Telford, VP Sales & Marketing.

Manufacturability was a key design requirement. This means that the GloBlade can be produced in most LM factories. “We expect the new blade will gradually replace the existing 37.3 and 40.3m blades. A next step is to extend the concept to create several platforms also fitting larger wind turbine types. The blade will be in full-scale production in China and North America in 2010 and in other regions in 2011 depending on demand,” says Telford. The company says that based on its projections, more than 50% of its blade sales in 2012 will be from products it does not currently sell.

The first GloBlade will be spinning on turbines in the second quarter of 2010. In China and America, about two out of three turbines installed are within this segment.

Bronto Skylift unveils 90m aerial platform

The 90m working height Bronto S-90 HLA is able to drive directly to a turbine and, in a matter of minutes, be fully operational. These capabilities result in faster, safer and more accurate inspection and maintenance of turbine exteriors and blades at a lower cost than other methods currently in use.

The Bronto S-90 HLA machines have been used in Europe for years and have been time-tested in tough conditions. When elevated, they can withstand wind speeds up to 12m/s (25 mph) and they can lift up to 45kg (1000 lbs) of men and materials in an 8 X 3, fully enclosed platform to a 90m (295 ft) maximum working height. Maximum horizontal outreach is 33m (108 ft). Mounted on a 6-axle chassis, the Bronto S-90 HLA machines can navigate most terrain and reach remote tower locations.

With advanced outrigger controls and one-button automatic leveling of the outriggers, from the time the Bronto aerials are driven onto the site they can be positioned, set-up and elevated to the overhead area in 15 to 20 minutes or less.

Encoders Give Turbine Controls More Data

To improve the efficiency of large turbines, many operators have turned to a rather small, 58-mm dia. absolute encoder from Denmark’s Leine&Linde. The Model 500 series of Incremental and absolute encoders provide speed and positioning  feedback to controls in nacelles. Siemens wind turbines, for example, use a pulse encoder on each rotor blade and one to track where the turbine is pointing. The main control system uses position information to optimize generator speed.
Heidenhain Corp
heidenhain.com