Thursday, July 31, 2008

Bucket trucks or "Cherry Pickers" fall under OSHA standard guidelines for safety

Bucket trucks are used for a number of industries and can be seen along roadsides every day. For example, have you ever driven down the road and watched as the local telephone or utilities company rides in a bucket to the top of a pole to fix something? If so, then you have seen a bucket truck. This is exactly what a bucket truck is used for - lifting and lowering workers to places too tall for ladders.

These trucks are sold in a number of sizes and shapes, each to help make work easier. While the bucket truck is used for many different purposes, the most common is power linemen. By using this type of equipment, they can complete their work in a comfortable, safe, and efficient manner, primarily where steel or concrete poles are used.

The design of the bucket truck includes a storage bin that is perfect for holding tools and material needed by the worker. In addition, some bucket trucks are designed with a single or double-arm boom or a hydraulic outrigger jack, which provides extra stability. You will also find some designs that are powered by the actual truck engine while others are operated with an auxiliary engine that is mounted on the back section of the truck.

Just remember that while the bucket truck is easy to operate and can make the job much easier to complete, this is still a large piece of equipment that needs to be handled properly. When the manufacturer’s operation is followed, the worker will experience a smooth, safe ride while keeping maintenance to a minimum.

Bucket trucks fall under OSHA standard guidelines, which must be adhered to for safety. Some of the requirements for using a bucket truck under these rules include:

  • The truck should be used to elevate employees to any job site located above ground.
  • The bucket truck can be constructed of wood, fiberglass, metal, or reinforced plastic.
  • Bucket trucks may be modified for use other than the intended use but only if approval to the modification is received in writing by the manufacturer or equal authority.
  • For bucket trucks to be used near electrical power lines, strict requirements must be followed, which includes keeping to a specific distance, de-energizing procedures, only qualified employees using the truck, grounding any overhead lines, and so on.
  • The brakes must be set
  • Bucket trucks should never be driven while employees are still in the bucket
  • Controls must be clearly and visibly marked and defined by function
  • Controls should be tested every day prior to the bucket truck being used
  • Load and distribution should always be checked to make sure they fall within the manufacturer’s recommendations
  • Any employee operating the bucket truck must wear appropriate protective gear at all times to include safety goggles, safety boots, a hard hat, gloves, etc. to protect from falling objects
  • The employee must keep his feel planted firmly on the floor of the bucket at all times
  • The lower controls should not be operated without the permission of the employee in the bucket expect in the case of an emergency

These are just a few of the many rules that fall under OSHA guidelines to ensure top safety when using a bucket truck. However, when employees are trained and the truck used the proper way, this piece of equipment can provide years of support in the workplace. Just remember, this is a large truck and if not handled according to the manufacturer’s recommendations and OSHA guidelines, injury or worse could occur.

Therefore, while a bucket truck can save tremendous time and effort, it definitely needs to be respected for the powerful machine that it is. For the business owner, the key to safety is training. You can obtain a number of excellent tapes for drivers and bucket truck operators to watch through OSHA or directly from the truck manufacturer

Friday, July 18, 2008

Telehandler Popularity Increases Concerns of Safe Operation

Could Telehandlers Be the New Skid-Steer Loader?
Published 07/10/2008 on

Double-digit sales growth fueled by versatility that is attracting new owners has drawn a rush of marketers and compact machines Stability Triangle Determines if Telehandlers Tip

There are many facets to safe operation, but keeping them upright is key to keeping them productive In the late 1990s, OSHA required that telehandler operators be trained, but didn't specify what that training should include. Mike Popovich, training director at JLG, uses an all-encompassing five-step approach to teaching accident avoidance that asks five important questions:

Five Steps
Walk-around inspection — Is the unit safe, visually?
Worksite assessment — Is the worksite safe to operate in?
Function test — Is the unit safe, functionally?
Proper operation — Am I operating safely?
Proper shutdown — Is the unit in a safe place and shut down properly?
At the center of this regulation, and the five steps, is a machine that stands on a triangular footprint and lifts heavy weights to impressive heights. Of course, there are other dangers, but the key objective is to keep the telehandler upright.

The two front wheels and the rear-axle pivot point form a telehandler's triangular base. The rear wheels are not part of the base because the rear axle typically oscillates. As long as the machine's center of gravity (the point in three dimensions around which the machine's weight is balanced) remains oriented inside this stability triangle, the telehandler remains upright.

Adding a load to the forks while the boom is down moves the center of gravity forward and down. Raising the load will move the center of gravity up and to the rear, while at the same time causing the stability triangle to shrink. The higher you lift a load, the less margin for error you have because the stability triangle becomes smaller.

A small stability triangle leaves less room for the center of gravity to wander left or right if the frame is not perfectly level. Imagine the center of gravity as a plumb bob hanging from the boom. You'll always find the center of gravity somewhere on a perfectly vertical line between a point on the boom and the center of the Earth. If the frame's not level, the center of gravity will not be oriented over the machine's centerline. But the stability triangle is always aligned with the telehandler centerline.

With the boom raised and extended (the stability triangle very small), the frame only has to be slightly out of level to make the center of gravity drift to either side of the triangle. The laws of physics are as certain as gravity. The moment the machine's center of gravity moves beyond the boundaries of the stability triangle, the telehandler begins to tip.

At any jobsite, there are things affecting the stability of a telehandler other than where you put the boom. You may be on a 1-degree side slope, in a 5-mile-per-hour wind. There may be a little ice under your wheels, and one tire a little low on air pressure. If the machine goes over, there may be no single cause. It was a combination of factors that are all things you can catch and correct or avoid if you do all of the Five Steps.

A safe lift starts well before putting the boom in motion, or even before the operator assesses the site for hazards. Most of today's telehandlers are designed with a quick-attach coupler at the end of the boom. Before installing an attachment, be sure it's approved by the telehandler manufacturer and that its specific capacity chart is in the operator's station.

"It's an OSHA violation to run a machine if the proper load chart for that particular combination of machine and attachment isn't in the machine," Popovich says.

Make sure forks haven't been tampered with. Other than block forks, all forks should be used in matched pairs. Block forks are used in matched sets.

"Putting on and taking off attachments is critical," adds Marty Turek, curriculum developer/instructor, Operating Engineers Local 150. "You have to make sure it's secure."

The maximum capacity of a telehandler-and-attachment combination will be the lightest of these: capacity stamped on the attachment identification plate, the fork capacities stamped on the side of each fork (fork capacity is multiplied by the number of forks on the attachment, not to exceed the maximum on the attachment ID plate), maximum capacity indicated on the proper load chart, or the load rating of the telehandler.

Referring operators to the capacity chart can be easier said than done on many jobsites because the weight of the load is not always known. Construction sites require a lot of general lifting that obviously doesn't approach a telehandler's limits, though — miscellaneous materials and tools that need to be unloaded and kept out of the way. As long as the telehandler is properly equipped and maintained, the operator assesses the site for hazards and makes these lifts carefully, work can continue without knowing the exact weight of each load.

"But every experienced operator knows when they're about to lift something that's going to test a machine's limits," Popovich says. "The key is to find out how much loads weigh."

Truckers can be a reasonable source of information, as can project supervisors, and sometimes the subcontractor or crew chief that will be working with whatever's on the pallet. If general inquiry fails, though, there are few options for determining the safe boundaries for a lift.

Equipment manufacturers can't recommend picking up the load and extending the boom forward until you feel the rear wheels getting light. It is intentionally destabilizing the machine. It's not likely to result in immediately recognizable damage, but the practice is discouraged because if the machine tips forward and lands on the pallet, it can damage the load and accelerate boom wear.

But by extending the load to the point where it reaches the machine's stability limit, you can use the load chart to estimate its weight. Find the boom angle on the chart on the following page and follow it out to the zone matching the boom extension. The load weighs more than the weight limit printed in that load zone.

Handle this estimate with extreme caution. You've exceeded the safety factors built into the load chart, so the margin for error becomes very slight. Don't plan a lift at the furthest reaches of the stability range using this estimate, and observe stability-enhancing procedures dealing with frame level, tire pressure, load center and the like meticulously.

"Whenever you test the limits of the load chart you should do a test pick without a load on the forks — position the telehandler as you plan for the actual lift and run the forks up to where you plan to place the load," Popovich says. By noting the boom extension and boom angle at the extreme point of the lift, this exercise confirms the vertical height from ground level where the load is to be placed, and the horizontal distance from the front tires to where the load will be placed.

On the capacity chart, find the horizontal line for the height of the lift and follow it over to where it intersects the line for the distance. The point where the two lines meet should fall within a load zone marked on the chart. If it doesn't, the machine and attachment can't complete this lift. The weight indicated in the zone where the height and distance lines intersect is the maximum capacity for this lift. If the two lines meet on a boundary between zones, use the lighter of the two weights for this lift's limit.

Check the boom-extension and boom-angle limits of this load zone on the capacity chart. When the load is in the air, no matter what happens, do not exceed those boom-extension and angle limits or the machine will tip.

All of the loads shown on capacity charts are assigned with the assumption that the machine is on firm ground with the frame level; forks positioned evenly on the carriage; load centered on the forks; proper size tires properly inflated, and the telehandler in good operating condition. Failing to comply with any of these conditions could tip the machine over.

Once you've determined that the lift is within the telehandler's and attachment's capabilities, it's time to set up the machine. Never engage a load or lift a load more than four feet above ground unless the telehandler is level.

"One of the things we always emphasize in our training classes is, when you get ready to place a load: Park Brake; Neutral; Level," Popovich says. "We drill it into people just like that."

Stop the machine on a stable surface in the best place to lift and place the load, set the parking brake and shift the transmission into neutral. Before raising the boom, check the level indicator to see if the frame needs to be leveled from side to side. Many telehandlers have hydraulically tilting main frames that allow you to compensate for uneven terrain. Some have outriggers. Set the boom in the "carry" position — forks less than four feet off the ground — and level the machine. The machine should be ready to make the lift.

Never use the leveling system (sometimes called "frame sway") or outriggers to level the telehandler after the load is more than four feet off the ground. After the load is in the air, if you discover that the telehandler is not level, bring the load back down before leveling the frame.

"We instruct operators not to use the frame sway to position the load with the boom elevated," Popovich says.

The higher up you go, the closer the sides of the stability triangle are — you don't have to go very far to move the center of gravity outside the triangle. If you use the frame sway with a load high in the air, the boom only has to move a couple of degrees right or left and the machine may tip over.

If the telehandler isn't level when you reach the limits of the frame-leveling system, don't attempt the lift until the problem is solved. Reposition the telehandler on more-level ground, or have the surface where it is standing leveled.

Always lift the load slowly, watching closely for changes in the footing or other conditions that could cause the frame to shift out of level. Don't move the machine once the load is more than four feet off the ground. Placing a load at height requires a careful combination of multiple functions — boom down, boom out, while holding the forks level.

"One of the most important things to remember is to maintain constant engine rpm so the hydraulic flow remains the same," says Turek, from the Operating Engineers. "People in tense situations often want to let off the throttle, but the change in engine speed slows down the hydraulic flow, which changes what the levers do. You want to run at a high rpm all the time so the hydraulic performance is predictable, and feather the controls to control the lift."

Machines with the carriage-transfer feature, which slides the entire boom forward hydraulically, simplify the procedure. But the machine's load capacity is derated for any carriage position forward of the rear-most position.

Turek says most of Local 150's telehandler operators take the OSHA 10-hour safety awareness training and learn a lot about their job from the section on scaffolding. He recommends that program or any of OSHA's scaffolding-specific programs to all telehandler operators. Once the lift is complete, the boom should be retracted and lowered to the carry position before the telehandler is moved.

Telehandlers are designed to handle rough terrain, but that doesn't mean they can be driven without regard for the terrain. Risk of tipping or load loss is much greater when traveling on slopes. If you must drive on a slope, keep the load low and proceed slowly, with great care. Before you get on the slope, downshift to a lower gear and four-wheel drive. Engine braking will help control the telehandler's speed. Avoid turning on a slope, but if you must turn, make the turn as wide as possible and use extreme caution.

Never drive across excessively steep slopes under any circumstances. Ascend and descend slopes with the heavy end of the telehandler pointing up the incline. When there's no load on the forks, the counterweighted rear of the machine is the heavy end, so you should back up slopes. When the telehandler is loaded, the front of the machine is the heavy end, so you should back down slopes

Operator training becomes very important on a mixed jobsite — with rear-pivot machines and coordinated-steering machines on the same jobsite where everyone is allowed to run all the equipment. Someone accustomed to operating a coordinated-steer machine jumps on a rear-pivot machine. One really significant difference between the way those two machines operate has to do with what part of the machine extends outside the turning radius.

The load or the forks cut the widest swath in a tight turn on a four-wheel-steer machine. But on the rear-pivot machine, it's the counterweight or the outermost rear wheel that's at the edge of the turning radius. In either case, the operator has to look in the direction of travel to be sure the path is clear. But in cases where the operator is using a machine with rear-pivot steering, it's especially important to be aware of the counterweight.

The things an operator does to ensure safe telehandler use don't take a lot of time. Accidents tend to happen when people neglect basic safety requirements in the name of speed.

Regardless of brand (or equipment) safety training is priority.

Case IH ProHarvest safety training for custom harvesters draws 500+
Friday, July 18, 2008 on

Case IH photo-More than 500 custom harvesters recently attended the 24th annual Case IH ProHarvest kickoff, held at the Great Plains Technical College in Frederick, OK.

Every spring, just before the wheat harvest begins along the border of southern Oklahoma and northern Texas, Dan Renaud picks a date to host the Case IH Pro Harvest kickoff in Frederick, OK. The kickoff is a half-day combine safety training program for custom harvesting crews. And the date changes every year, depending on the weather and the wheat crop.

What doesn’t change is the location: the Great Plains Technical College in Frederick. “This is our 16th year at Great Plains Technical Center, and the 24th year of the ProHarvest support program,” says Renaud, the Case IH Combine Specialist who organizes the ProHarvest kickoff. “We show up at the college and Jim Smith, [Agricultural & Mechanization Technology Instructor], opens his doors to us for a few days.”

Meanwhile, Bill Blankenship, who heads the local FFA Chapter, rounds up a posse of FFA volunteers. Together with Box Implement, the host Case IH dealer in Frederick, they plan and serve the Case IH-sponsored free breakfast to every custom harvester who comes to the kickoff. Just like the date of the kickoff, total attendance also depends on the weather. If the wheat is not quite ready or Mother Nature provides rain that means more attendees.

This year, more than 500 custom cutter crew members showed up for the breakfast and Case IH combine safety training over two days (the same program is repeated on day two). “This was our largest crowd in many years, and the more the merrier,” Renaud explains. “We don’t care what color combine you run. This is non-denominational training. Everyone’s welcome.”

Getting the attention of young crew members

Renaud says the goal of the ProHarvest kickoff is simple: Get the custom harvester crew members, many of whom are 18 to 23 years old, thinking about safety before they start the season. “Young guys this age think they’re invincible, so we review safety procedures, show them safety videos, and photos – some gory, some not – to remind them that accidents happen,” he adds. “We want to wake them up, raise the awareness of combine safety and get them started on the right foot.

Thursday, July 17, 2008

Safety in Automation (Part 3 of 3) Safety Switches

Safety Switch Technology With Sensaguard
Safety in Automation: New Products

The new Allen-Bradley SensaGuard family of RFID-coded, non-contact switches from Rockwell Automation includes a high safety rating, flexible design, extended diagnostics and RFID coding, while improving safety and reducing troubleshooting time and machine wiring costs.

The switches are Category 4/SIL 3 rated per EN954-1, TÜV functional safety-approved to IEC61508. Unlike lower rated switches, SensaGuard will shutdown a machine if a failure occurs before there is a demand on the safety device — which improves machine operator safety. They are especially suited for machines where multiple access doors must be monitored up to a Safety Category 4/SIL 3.

Safety Guard Switching Unit

Omron Scientific Technologies has introduced new G9SX-GS safety guard switching units. External outputs enable status indication of two safety input devices. Auxiliary outputs enable monitoring of safety inputs, safety outputs and errors, and detailed LED status indicators provide system diagnostic tools.

Additionally, logical AND connections help facilitate complicated applications in combination with other G9SX series units. Each G9SX-GS unit supports unique auto switching and manual switching functions.

Auto switching ensures safety and productivity in applications with coordinated operations by monitoring a machine or robot, plus the operator, to make certain neither enters the coordinated area at the same time. Manual switching is for applications that require limited machine access for operations such as maintenance and cleaning.

Safe Relays For Process Applications

Phoenix Contact now offers safe relay modules, approved to SIL3/IEC 61508, designed specifically for process applications. Optimized turn-on behavior eliminates high start-up current that a control system might interpret as a short circuit. The safe relays provide two channels of redundant normally open contacts and one normally closed status contact that can switch up to 250V ac/6 A in a 22.5-mm housing.

These compact safety relays are used to electrically isolate field applications from the control system or to adjust the voltage or power. In addition to being used in conjunction with safety-oriented control systems, these relays form an integral part of the safety chain for electrical and electronic applications in process technology and mechanical engineering.

Safe Camera System For 3-D Control and Monitoring

SafetyEYE is a camera system for three-dimensional safety monitoring from Pilz Automation, developed in conjunction with DaimlerChrysler. The system places a customized, three-dimensional protective cocoon around a danger zone with a single system. It is designed to replace a multitude of two-dimensional sensors currently in use today. The system offers functions for control and monitoring and allows detection zones to be configured flexibly and quickly on a PC.

More than just a sensor, SafetyEYE is the basis for a technology that safely detects objects in a three-dimensional zone and alters a robot or a machine's movement to prevent accidents. It is suitable for a wide range of applications from manufacturing operations, to the tire and packaging industries, to high-bay racking systems and automatic car parks. The system can also provide uninterrupted object monitoring and access guarding.

Safe Motion™ Technology With Safety-On-Board

Bosch Rexroth's IndraDrive with Safety-On-Board features Safe Motion™ technology integrated directly in the drive, including the latest international standards for safe stopping and safe motion.

These capabilities are available on a common platform that functions as a servo drive or frequency converter. The system has reaction times up to 400 times faster than conventional solutions that use contactors to produce a safe stop.

Because the Safety-On-Board technology is integrated directly into the drive, motion controllers, regardless of manufacturer, are able to leverage the technology. The drive has enough I/O for the safeguarding logic needed to interface to safety gates, panel switches and interlock switches. The machine builder only needs to learn one safety solution for an application and the machine is pre-certified, so the OEM doesn't have to worry about the safety certification process.

Powerlink Safety

The ACOPOS drive system from B&R Automation uses POWERLINK Safety to enable functions such as safe limited speed directly over the network. Wiring these safety-related signals to the drive is eliminated and the information is collected from its source via safe digital inputs and outputs. It is distributed to corresponding sensors, actuators or drive via the SafeLOGIC central processing unit.

Safety in the drive system comprises the following functions according to Category 3, EN 954-1: uncontrolled and controlled stops, safe stop and safe operation halt, safe limited step measurement and safe limited absolute position, safe limited speed and safe rotational direction. Functions like safe restart inhibit or safe output for the motor holding brake are integral parts of the system.

Safety Relay For Motion In Hazardous Areas

The new Allen-Bradley MSR (Minotaur™ Safety Relay) 57 speed monitoring safety relay from Rockwell Automation is designed to allow personnel to enter hazardous areas while motion is present. The MSR57 will be available later this year.

The device supports numerous input devices such as E-stops and light curtains, allowing switches and interlock switches to stop the motion, put the machine into safe speed and monitor personnel in the hazardous area during safe speed conditions. The MSR57 can be configured and monitored via Drive Explorer or an HMI device. During configuration, the user can set a variety of parameters to specific requirements for their application including type of input devices, door locking and monitoring, enabling switches and a maintenance (safe speed) mode. One example is that the MSR57 can unlock doors automatically when zero speed is detected.

Safety At Work E-Stop Safety Switches

Pepperl+Fuchs has introduced a new family of emergency stop switches with integrated Safety at Work (SaW) functionality. These intelligent switches are powered by the AS-Interface network and offer fast, error-free installation in field or panel-mount applications. Field and panel-mount models are available in high-intensity, wide-angle illuminated versions, as well as non-illuminated versions, to suit any e-stop application requirement.

Illuminated models are lit with a high-intensity LED to eliminate the need for auxiliary power, while reducing the number of required leads to two. For added flexibility, the LED is not activated by the button but is controlled by a PLC, which allows users to solve even the most unusual applications. Non-illuminate e-stops provide safe operation at a lower price point than illuminated models.

Field-mountable versions eliminate all wiring to save time and eliminate the possibility of incorrectly wiring the e-stop switch and feature an M12 connector that works in conjunction with flat-to-round cable adapters to reduce installation time to less than 60 sec.

Wednesday, July 16, 2008

Construction industry forms safety group

The New York City Construction Industry Safety Council will establish a tower crane maintenance database that contractors will be able to consult before renting equipment.

July 01. 2008 2:32PM Daniel Massey

Buck Ennis

In the wake of two deadly crane accidents since March, the city’s construction industry on Tuesday announced the formation of an independent organization to promote safety on work sites across the five boroughs.

The 17-member New York City Construction Industry Safety Council will be made up of the city’s largest contractors, the Building and Construction Trades Council of New York, the Real Estate Board of New York and many of the trade associations that represent the construction industry. The council will bring industry leaders together for the first time to share safety procedures and expertise.

"Development cannot take place at the expense of public safety, and it’s going to take the industry’s cooperation to make construction sites safer," acting building commissioner Robert Limandri said in a statement. "The formation of the NYC Construction Industry Safety Council is a step toward that end, and I look forward to real results that raise the safety standards on job sites.”

The new group will be funded by its members, who, so far, have raised $500,000 to get it off the ground.

“We recognize that construction safety isn’t just a story because there was an accident,” said Steven Spinola, president of REBNY. “This is a long-term commitment to safety.”

The creation of the council comes as the city’s Buildings Department is preparing to propose a new series of crane safety regulations that will focus on maintenance and repair records. The City Council is also considering comprehensive construction-safety legislation.

The safety council’s first task will be to establish a tower crane maintenance database that contractors will be able to consult before renting equipment.

“Many of you have heard of the Car Fax system where you can go online and find out the maintenance information on any used car you’re going to buy,” said Louis Coletti, president and chief executive of the Building Trades Employers’ Association. “The concept is the same: a crane system to be able to get up-to-date information on cranes as they are delivered from site to site.”

The group will also research safety practices being used across the country and around the world and urge governmental agencies to adopt safety standards that all contractors should follow. For the first time, the group will bring contractors together to share safety information with each other.

"It used to be that our safety plan is a proprietary plan, my competitors’ safety plans are proprietary plans,” said Daniel Tishman, president and CEO of Tishman Construction Corp. “We’re now prepared to share best practices with each other relative to safety. Safety plans should not be a marketing advantage.”

Safety in Automation (Part 2 of 3) Networking Safety

Networking Safety
Flexibility is a key benefit of implementing Safety at Work technology

With safety in the spotlight, advocates for networked safety have hardwired safety system technologies clearly in the crosshairs. They argue that safety relays, auxiliary contacts and redundant cable runs are all part of systems that deliver poor diagnostics, high setup complexity and create time-consuming installations.

But according to Helge Hornis, Ph.D., manager of Intelligent Systems for Pepperl+Fuchs, the key to acceptance of the technology is helping engineers understand how networking safety provides flexibility in terms of expanding the safety system, implementing multiple safety zones and improving diagnostics.

“The basics of flexibility mean that when you need to have another device (safe or non-safe) in your system, you simply run a spur from anywhere on the network in that new direction and put the new device on the network,” says Hornis. He says the networks provide diagnostics that are not only better than what was before, but also completely impossible.

“How do you detect a contact that is intermittent? In the past, you simply didn't. The flexibility the system gives the engineer, in terms of uptime and what they can do with the machine, goes way up,” he says.

Pepperl+Fuchs has developed safe systems using the AS-Interface Safety at Work networking technology for about five years. Hornis says the possibility of expanding the safety system in minutes is just one of the many advantages the technology brings to the plant floor.

Other advantages include a wiring reduction compared to hardwired solutions while maintaining Category 4 safety and detailed diagnostics down to the contact level without a single inch of additional wire. Multiple safety zones, dependent and independent, can be implemented with no additional wiring and systems have the ability to capture nuisance shutdowns due to faulty safety contacts or wiring connections at the safety device level.

Hornis says even though networked safety solutions have been around almost 10 years, some engineers still question if they are legally allowed to use networked safety and if it is actually safe. “There is too little understanding of the basics of network safety and how it can be safe if it doesn't use four wires,” says Hornis.

When Europe moved to allow networked safety under certain very stringent conditions, still forbidden in the U.S. at the time, it was clear machine builders that wanted to sell into Europe would need to be able to address these requirements. But once a machine is designed that utilizes a modern technology, why build one for the U.S. market which is really very primitive and doesn't give users the abilities of a machine sold in Japan or Europe?

“There is a strong trend toward safe systems and we have been selling these products for about five years,” says Hornis. “We're going through a major upgrade cycle now, where what we have learned over the years from customer input and requirements is resulting in new products and technologies.”

One example is remote safety relay technology that will be available by the end of the year. This new capability will allow systems that run on AS Interface, when there is a need to shutdown a motion safety somewhere else and no original plan to do that, to utilize a safety-rated output module (Category 4, SIL-3 and performance level “e”) in the field to expand the network.

The overall impact of safety networking is continuing to expand, as well. At the end of 2007, the total number of safety installations worldwide based on AS Interface alone totaled 50,000. The number of safety modules or safety inputs in the field totaled more than 350,000 units, numbers Hornis thinks makes Safety at Work the number one solution in terms of customer adoption rate.

Part 3 Continues...

Tuesday, July 15, 2008

Safety in Automation (Part 1 of 3) Creating opportunities for safe technologies

Motion Control and Automation

Safety in Automation

The spotlight on safety is creating opportunities for safe technologies

Safety technologies are benefiting from the surge of interest in machine safety, even though it is being propelled in large part by external forces, marketplace issues and regulations. But achieving higher levels of safe motion is also a good thing for OEM machinery builders and users because the end result extends beyond human safety, to material assets and reduced probability of machine failures.

This special section takes a look at solutions for safety in automation. The focus on safety is effectively providing an impetus for the adoption of technologies and products that ultimately will be the basis of new generations of safer machines.

Focus on Feedback Redundancy
Safety-related position measuring systems rely on pure digital, dual feedback

Redundant systems are critical to the goal of functional safety which minimizes and reduces the risks that can occur during normal or impaired operation of machinery. So, a fundamental requirement for axes of motion in safety-oriented applications is redundant position information to perform corresponding safety functions.

“A key requirement for safety is built-in redundancy,” says Tom Wyatt, national sales and product manager for Heidenhain. “To achieve safer machines, it has always been a requirement for feedback suppliers to come up with effective dual feedback systems for redundancy.”

Heidenhain has made a major ongoing commitment to safety-related position measuring systems using its EnDat 2.2 pure serial data interface. Drive encoders have achieved safety approvals with control category SIL-2 (in accordance with IEC 61508 or performance level “d” of ISO 13849). A linear scale product already available with the interface is in the process of gaining safety approvals from the various governing bodies and their goal is to get all products switched over.

“What we have done is taken a rotary encoder, along with a linear scale perspective as well, and built two encoders into one,” says Wyatt. He says, on the rotary encoder side, there are two independent scanning methods and pure serial communications, as well. The requirement on the driver control side is a dual processor system, so when a data packet is sent there are two independent data packets one right after the other on the same line from two independent measuring systems built into the encoder.

“You can imagine with a machine tool, that if something happens with a drive axis, there is always a runaway situation where damage can happen,” says Wyatt. “The combination of sensors and feedback systems prohibits runaway situations and puts the system in safety stop if something is missing. If the two data packets that come back from the encoder suddenly don't match or one is missing, immediately within microseconds the system is shut down.”

In the past two years since the initial approval of this position measuring technology by BGIA in Europe, the equivalent of the Occupational Safety and Health Administration in the U.S., the focus has been on safe machines to meet European machine tool standards. He says the concept is now being looked at for all types of automation applications.

A key area for growth is the robotics industry because of the need for the work envelope for robots to be safe and the ability it provides for manufacturers to save space on the manufacturing floor by placing robots into tighter spots. But there is also interest in packaging for applications such as palletizing, all driven by the spotlight on European machine tool standards and the increased general focus on the need for safety approvals.

Wyatt says the technology has established itself but there are still certain levels to fulfill. The technology already achieved SIL-2 which is probability of failures and Category 3 which pertains to machine tool safety. But the whole idea is to reduce the probability of failure and along with that comes both higher levels of material safety and, of course, human safety.

“We continue to see safety as a rising issue down the road and safety is a big issue with high-end interfaces,” says Wyatt. “The probability of failure is really the only place you can improve and we are currently at 10-8 and 10-7 for SIL-2. The probability of failure is already next to nothing, but the next step is improving on that even though you can only go so far.”

Part 2 continues...