Pneumatics

To ensure optimum machine safety, design engineers need a solid understanding of the Machinery Directive 2006/42/EC and how to comply with required safety levels. 

A safety exhaust valve when incorporated into an air preparation system, lets the user safely and reliably shut off the pneumatic energy, stopping compressed air-flow to the machine and allowing downstream pressure to exhaust. 

Installing a pneumatic safety exhaust valve is a simple and cost-effective way to achieve machine safety and to comply with the directive.

Here are four things to consider for your application:

To eliminate the danger of residual energy making its way into the machine, select a solution which offers a series-parallel flow design, such as Parker’s P33 valve. This permits higher exhaust flow capability and ensures low residual pressure during a fault. 

Essentially, the two valve elements are arranged such that air from inlet to outlet must pass through both valves in series, but the flow path from outlet to exhaust is in parallel.

Cross-flow technology ensures that both valve elements (redundant design) must shift to supply air downstream and, if either valve element is out of position with the other, downstream air will dump to exhaust in parallel.

Monitoring detects faults or failures in control systems, and checks for short-circuit faults. The monitoring portion of a safety system must check if both sides of the safety valve shift together every time by monitoring the condition of pressure-operated sensors. These sensors are hardwired into the controls and monitored by the external control system.

This is generally done with most safety relays and safety PLCs. The use of sophisticated controls and monitoring ensures sensors are not bypassed and faults are detected so the valve functions as intended. 

Statistical component life (B10d) is key to any safety component. When designing a safety system according to ISO 13849-1, each component in the system needs a B10d or a mean time to dangerous failure (MTTFd). 

Engineers use a B10d value, along with the number of operations (nop) to determine the MTTFd of the component for the application:

MTTFd = B10d/nop.

Valves that use electromechanical components for monitoring are usually limited by the life of the circuit boards or mechanical wear parts.

Using solid-state electronic pressure sensors for monitoring greatly improves the B10d numbers as there are no mechanical wear components. 

The required Performance Level (PLr) should be determined by a risk assessment. Once a PLr is determined, application statistical component life (MTTFd), controls architecture (Category), diagnostic coverage (DC), and consideration of common-cause failures (CCF) can be used to determine the system PL. The system PL must equal or exceed the Performance Level. 

For applications where the severity of injury and level of exposure to the hazard are high, the percentage of diagnostic coverage of the monitoring system must be high as well. Depending on the safety relays or safety PLCs used, the system can achieve a High-Performance Level, up to PL e and Safe Integrity Level to SIL 3.

If a risk assessment demands a safety rating of PLc or higher, a redundant safety exhaust valve is a simple-to-implement and cost-effective way to attain the required safety level.

Our white paper Selecting & Integrating Pneumatic Safety Exhaust Valves provides more in-depth support with the correct specification and integration of safety exhaust valves.

Article contributed by Linda Caron, global product manager for Factory Automation, Pneumatic Division.

With the ever-increasing complexity of modern pneumatic components, it becomes crucial to know what to look for and what is best suited to your system. Choosing and maintaining system components wisely, right through from compressors to workstations, can help save the expense of unplanned downtime or costly rebuilds. Conversely, a few wrong choices can lead to everything from wasted energy to system failures. To avoid these pitfalls, here are some simple steps to take when looking to maximise the performance of your company’s all-important pneumatic components.

Just like carrying out maintenance tests and oil changes on a vehicle, pneumatic systems also require regular upkeep to prevent more serious issues down the line. In compressed air systems, it is important to ensure that lubricators are not left to run dry; filters are cleaned; and all contaminants such as rust, metal shavings, water, and unwanted oils are removed.

Predictive maintenance is about being proactive, rather than reactive, to avoid component failures, and it is often the work of sensors (available for almost every factory component) that alert you to potential problems. A flow sensor that fits in-line with a Filter Regulator Lubricator (FRL) unit are able to identify blocked filters, while continuous position sensors can be an indicator over time to the wear to which cylinders are exposed.

Making sure that a system is compliant with current standards is also critical to avoid costly downtime and equipment overhaul. The recently-updated standard known as DIN ISO 8573-1 governs filtration levels. Defined down to the micrometre, it identifies the solids, water and oil that should be separated out to maintain a well-functioning system.

Similar to checking system compliance, carrying out a risk assessment and consulting an administrative body that serves those involved in workplace health and safety are important procedures to help minimize the risk of workplace injuries. Bringing in light curtains, interlocks, machine guarding or safety exhaust products to block or prevent hazards can be impactful measures in this regard.

Right from the start of the specification process, selection of accurately sized equipment saves money and valuable energy, which oversizing wastes. As alternatives to oversizing and waste, consider implementing pressure boosters that allow the flow from a compressor to the largest workpiece, and pneumatic zoning on manifolds that can be used to mix pressures. The simple step of locking regulators prevents workers from adjusting a system’s overall pressure to supply more air to individual workstations which ultimately could damage a sealing system, waste energy, or even cause physical harm.

Updates in terms of the connectivity of the factory floor are worth considering as well. Low-cost Ethernet connections are more frequently replacing hardwired solutions and associated trunks of cables to provide network-based connectivity across a facility. IO-Link connectivity, to run field-level devices back to the IO-Link master, provides further opportunity for savings in time, wiring, component cost and troubleshooting. Additionally, many of today’s advanced network nodes are able to supply prognostic data for predictive maintenance and in-built sensors to check for shorts, over current, cycle counting, thermal management, among other things.

If you would like to discover out more about Parker’s range of pneumatic components, please click here.

Article contributed by Linda Caron, global product manager for Factory Automation, Pneumatic Division.

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The demand for aluminium has been on a relentless growth track, driven by the needs of many and diverse industries in established and rapidly developing regions of the world. The introduction of point feeding in the aluminium processing and production industry back in the 1970s helped provide a welcome improvement in equipment and pot life as well as reducing maintenance costs and downtime.

An additional important benefit has been a significant advancement in the controllability of alumina feeding. A regular repeatable small alumina dose is critical to the control of reduction pots, providing the operator with control over the pot, optimising its performance and reducing generation of global warming gases.

Controlling alumina feeding enables the cells to run at an optimum level and prevents the build-up of undissolved alumina in the bath, leading to a “mucky” pot. Point feeding the pot correctly requires the feed hole in the crust to be open at the time of alumina discharge. 

The quest for open feeder holes has led to crust breaker technology advancements and the introduction of bath sensing systems. The bath sensing system controls the operation of a pneumatic crust breaker cylinder to break the crust and retract as soon as the contact with the bath is detected. The decision to pursue advanced crust breaker technology was based on the compressed air consumption and its associated costs. Generally, over 80 percent of compressed air consumption is for breaker/feeder devices. Thus, it important to target performance improvements by adopting an evolutionary crust breaker technology on pot lines.

Crust breaker technology has evolved and improved, and this along with data driven process control enhancements have helped maximise the benefits of point feeding. In simple terms, pneumatic cylinders are used to break the crust. The fact that the crust to penetrate may vary from strong to weak, or indeed may not have formed at all, raised the need for intelligent crust breaking (ICB) technology developed by Parker.

The operating principle in ICB differs from that of a standard actuator with the air supply being fed to the piston via flow restrictions to reduce the air feed to the actual driving sides of the piston. The resultant effect of the air restrictions is that low piston loads are applied to more than 90 percent of crust breaker strokes – effectively apply the force required as opposed to a repeated high force.

The ICB has served the industry well, but additional gains are possible if, rather than sensing the ICB end of stroke, the ICB reverses on contact with the bath - Parker’s Bath Sensing Modules (BSMs) enable this. A signal to the Pot Control System from the BSM indicates that the ICB has sensed the liquid bath. The sensing of the bath effectively means that there is an open hole in the crust and that alumina can be properly fed. 

Parker’s electronic BSM is able to operate in the harsh environments of a pot room in magnetic fields and at high temperatures. BSMs currently installed have proven to be 100 percent reliable with zero defects over a five-year period. The units are optimised for ease of deployment and use and are plug-and-play with a ‚self-teach’ routine, tuning the modules internal electronic component parameters to suit environmental and pot conditions.

If you would like to find out more about Parker's Intelligent Crust Breaking cylinder and Bath Sensing Technology contact us. 

Article contributed by:

Madhu Gaste, application manager, global primary aluminium smelters, Parker Pneumatic Division Europe.

Alex Moerel, senior electronic engineer, Parker Pneumatic Division Europe.

Goran Kling, gobal marketing manager, primary aluminium, Parker Pneumatic Division Europe

Soumen Mitra, business development manager, Parker India

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The popularity of air motors is on the rise as a result of their many advantages. However, not all pneumatic motors are made the same, so choosing the right one for your application can prove the difference between project success and failure. For the purposes of this blog post we will focus on vane-type air motors as they are more suitable for regular operating cycles, where speeds of no more than 10,000 rpm are required.

To provide an example of the differences between air motors currently available on the market, consider the following. Across modern industry, oil and oil mist are avoided wherever possible to ensure a clean work environment and comply with H&S regulations. With this thought in mind, you should select an air motor from a manufacturer that actively avoids using components which require lubrication. The P1V series from Parker, for example, is equipped with vanes for intermittent lubrication-free operation at power below 1000 watts, which is the most common application of air motors.

For those of you working on food-grade projects and other hygienic/high cleanliness applications, check that external components are made from stainless steel. In our P1V-S range, for example, the air motor and planetary reduction gear are built into a polished stainless steel housing. Moreover, the output shaft, which is also made of polished stainless steel, is sealed by a fluorocarbon (FKM) rubber seal. Note that this design means the motors can be deployed under water to a depth of around 8 metres. These drive solutions are particularly suitable for use in industrial agitators and mixers, as used in the paint, food and pharmaceutical industries.

Once the physical aspects have been decided, you can set about calculating the required power of the air motor. Many factors come into play here, including direction of rotation, air pressure working range, air class quality and, principally, expected torque and speed under load. 

Basic power can be calculated using an established formula: P = M x n / 9550. Here, P is power output in kW, M is nominal torque in Nm, and n is nominal speed in rpm. As a tip, you should always select a motor which is slightly too fast and powerful, then regulate its speed by throttling the flow and torque by reducing the pressure to achieve the optimum working point. Also, ensure that the pressure supplied to the inlet port of the motor is correct, so it can work at maximum capacity. If the valve supplying a large motor is too small or the supply line is underspecified, you might find that the pressure at the inlet port is so low that the motor cannot function. 

Further factors determining the selection of an air motor include the position in which it will be used. Also, will standard or spring-loaded vanes be required? Spring loaded vanes are selected to ensure they remain pressed against the cylinder when the motor stops, and when working at low speeds. 

Will you require an integrated brake? If so, it’s worth noting that brake motors must only ever be supplied with unlubricated air, otherwise there is a risk of oil from the supply air getting into the brake unit, resulting in poor brake performance or no braking effect whatsoever. 

Watch in this video Parker’s latest range of air motors and the benefits they can bring to your project.

Any engineers who are involved in machine building as part of their core activities will know all about the EU Machinery Directive 2006/42/EC. Most will have stood in front of a newly built machine performing a risk assessment, trying to pick out potential danger points.

Of course, in identifying any safety risks, one must subsequently design them out or guard against them accordingly. Indeed, the Machinery Directive mandates the keeping of a technical file to show what risk avoidance was implemented to create a safer machine.

Although the directive does not mandate the use of safety-rated products, it clearly differentiates standard components used in a safety application from those built and intended as safety-rated products. The latter are classified separately and subjected to more rigorous requirements, testing and performance expectations.

The directive states that common sense strategies be employed on machinery, such as the use of e-stop buttons and the removal of air in pneumatically operated machines to protect from unexpected movement (where safe to do so). 

Some manufacturers specialise in the development of safety-rated components for pneumatic applications. Here at Parker, for example, we have recently developed the P33 safety exhaust valve series, which meets the needs of the Machinery Directive to remove air from machines during either an e-stop or a faulted condition.

When incorporated into an air preparation system, a safety exhaust valve lets you safely and reliably shut-off the pneumatic energy, stopping the flow of compressed air to the machine and allowing downstream pressure to exhaust.

The P33 valve is designed for two-channel control architectures and is externally monitored. Moreover, the valve has a patented fail-safe design that is suitable for use in applications up to Cat 4 PL e. External monitoring gives greater control at the safety device for an application, a feature that also reduces machine complexity with regard to valve start-up or reset functions.

For those seeking further assurances, the P33 ticks all the major criteria associated with specifying a safety exhaust valve, namely: fast exhaust time to faulted condition; fast switching time; utilising series-parallel flow so that both valve elements (redundant design) shift to supply air downstream; high B10 value (life expectancy in switching cycles); and comprehensive monitoring capability to achieve the highest level of diagnostic coverage.

Installing a pneumatic safety exhaust valve, such as the P33, is a simple and cost-effective way to achieve machine safety and comply with the directive. After all, safety allows no room for error. Knowing that products exist which incorporate the needs of the directive and provide an enhanced level of certified safety, brings peace of mind to machinery designers and engineers responsible for enhanced and integrated safety - be safe, not sorry.

If you would like to find out more about Parker’s P33 series of safety exhaust valves and the benefits they can bring to your machine-building projects, please download and read the white paper Selecting & Integrating Pneumatic Safety Exhaust Valves. 

Learn more

Article contributed by Linda Caron, global product manager for Factory Automation, Pneumatic Division.

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In every manufacturing industry, machine safety is always a top priority. When operating in Europe, utilizing machinery and components with CE certification is the best way to ensure the reliability of the equipment that benefits both production and the operators who use the equipment. 

What is the Machinery Directive?
First published in 1989, the Machinery Directive was designed to provide freedom of movement across Europe for machinery and safety of workers in an effort to reduce injuries. 

In 2009, the Machinery Directive 2006/42/EC became law in Europe, and its primary role is to ensure common safety levels of machinery placed on the market and put into service. 

Today this directive lays down the foundation and regulatory basis for the harmonization of Essential Health and Safety requirements (EHSR) in the field of machinery. It is unified with CE requirements and covers almost 21 distinct EN Standards to guide machine builders on safety requirements and has worked to harmonize with other safety organizations. Ultimately becoming the foremost authority on where to go to design a safe piece of equipment globally.

Directive qualities
A unique quality of the Machinery Directive is its broad coverage for machinery design. The standards start at concept of design or designing out risk. The directive mandates a technical file be kept on the machine to show its inception and what risk avoidance was implemented to create a safer machine. 

Guidance is provided to the machinery builder in the form of EN standards which mandate a risk assessment be conducted on machinery. Finally, the directive includes information on disposal at end of life of machinery. While broad, the directives do a great job of ensuring safety is addressed at every level and even account for “unintended use of machinery” at the design stage.

Safety
Another interesting note is given that one of the primary purposes of the Machinery Directive is to ensure common safety, the directive does not mandate the use of safety rated products. It does clearly differentiate standard components used in a safety application versus those products built and intended as safety rated products.

Safety rated products are classified separately and are subjected to more rigorous requirements, testing and expectations for performance. 

The directive does state that common sense strategies be employed on machinery such as the use of e-stop buttons, the removal of air in a machine to protect from unexpected movement (where safe to do so) and the addition of technical measures where risk cannot be designed out. Additionally, to meet enhanced safety levels on machinery, redundancy and monitoring must be included in the controls of the machine EN ISO 13849-1 as well as validation of the system EN ISO 13849-2.

Some manufacturers offer safety rated components, such as Parker’s P33 series of safety exhaust valves, which meet the needs of the directive to remove air from machinery during either an e-stop or a faulted condition on the machine. 

Knowing that products now exist which incorporate the needs of the directive and provide an enhanced level of certified safety can bring peace of mind to machinery designers and the engineers responsible for enhanced and integrated safety on machine. 

If you would like to find out more about Parker’s P33 series of safety exhaust valves and the benefits they can bring to your machine-building projects, please download our white paper What You Need to Know About Safety Exhaust Valves.

Article contributed by Linda Caron, global product manager for Factory Automation, Pneumatic Division.

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