Worker health and safety in plastics compounding

Plastics Additives & Compounding looks at some of the top worker health and safety issues in the plastics compounding industry - hazardous materials handling, ergonomics, machinery safety, and noise control – and summarizes some of the keys to success.

Keeping workers healthy and safe does not happen by chance – careful management processes, preventive action, and commitment throughout the organization are needed. Safety management includes conducting risk assessments, installing engineering controls, establishing procedures, and auditing. Much effort goes into keeping up with changes in regulations – from implementing REACH to complying with electrical safety standards and combustible dust handling requirements, for example. International compounding companies maintain high standards of worker and environmental health and safety globally; each facility follows company standards that meet or exceed local requirements. These issues can be broken down into a number of key areas.

Hazardous materials handling

Additives used in the compounding process, as with any chemical, require careful handling. In fact, handling these additives and encapsulating them in a resin pellet is one of the primary services compounders offer to their plastics processing customers. Good management processes include carefully evaluating raw materials and implementing controls such as containment, safe handling procedures and use of appropriate personal protective equipment.

Product safety
The primary tool for communicating health and safety information about raw materials is the material safety datasheets (MSDS). Compounders may ask additive suppliers for additional information, not listed on the MSDS, which is used to ensure safe handling of the additive within the compounding plant as well as to communicate health and safety information to the compounder’s customers. “Part of what we sell to our customers is a high standard of compliance with regulations, and appropriate documentation,” says Heinz Seeberg, global ESHA product safety and systems management director for the Masterbatches Division of Clariant International Ltd. David Yopak, director of regulatory affairs at Teknor Apex Company, adds: “One must evaluate raw materials in terms of their suitability for use in specific product offerings. For example, for FDA applications, all raw materials must have FDA approval. Never underestimate the liability of using the wrong raw material.”

Dust explosion risk reduction
Compounding includes handling materials that create combustible dust, which under certain conditions of dust in the air could explode if ignited. Dust explosion risk analysis must take the entire system into consideration – including any silos, storage bins, feeders, and filtering systems, notes K-Tron. “It is essential to classify potential hazards effectively, through assessment of probability and severity, and to engineer protective measures into the process. We help large and small manufacturers manage these complex challenges,” says Dean Hamel, head of EHS services for the Americas at Ciba Expert Services. Good housekeeping and dust containment and extraction systems are the first line of defence in mitigating explosion risk. In addition, equipment is designed to meet either U.S. NEC (National Electrical Code) standards or the requirements in the European ATEX Directive regarding equipment and protective systems intended for use in potentially explosive atmospheres. Packaging can be designed to mitigate the risks of an electrostatic discharge occurring around powder handling systems. “Unless the packaging is actually used in the manner intended, however, the protectiveness is greatly reduced. For example, it’s critical that bags of product received in Type C FIBCs [flexible intermediate bulk containers] be bonded and grounded. In other cases, operators must wear static dissipative shoes or be physically grounded,” explains Mr. Hamel. He notes that the U.S. Chemical Safety Board and the U.S. Occupational Safety & Health Administration (OSHA) are paying close attention to dust explosion hazards. In 2007, OSHA initiated a National Emphasis Programme, which requires OSHA offices to inspect combustible dust hazards.

Dust and volatiles control
In addition to explosion risk, dust in the air creates potential for inhalation of hazardous materials and poses a health risk. Particulate levels in inhaled air are strictly regulated by government organizations such as OSHA and the United Kingdom’s Health and Safety Executive (HSE); dust collection systems are commonly used to ensure a safe working environment. Also, during extrusion, additives may produce volatiles that are vented from the extruder. Fume extraction hoods must be used for some additives, as described in the MSDS.
Where possible, compounders try to reduce operator contact with additives. For large additive quantities, some compounders have designed closed, mechanical systems for unloading FIBCs or supersacks directly into additive hoppers. Additive suppliers work with customers to deliver in packages that fit their systems. Low-dusting or no-dusting additive forms available from various additive suppliers are also welcomed by compounders as an aid to reducing dust levels. Coarser grinds and compacted forms have less dust than powders but are still somewhat friable, while extruded additive pellets produce much less dust, notes Keith Hughes, global marketing manager for thermoplastics at Chemtura. While compounders use low-dusting forms where possible, they continue to use granular or powdered forms to obtain required dispersion with some additives such as pigments. Additive feeders are designed to separate hazardous materials from the environment and the operator, notes supplier K-Tron. Additive feeders may have closed filters on top, from which dust can be cleaned with an air jet and put back into the feeder, or feeders can connect to central dust collection systems.
Extraction equipment can be used to catch dust from the process, from a controlled environment such as a downflow booth used for bulk bag emptying, or at the point where dust or fumes are emitting from the process using flexible arms or controlled vacuum systems, explains equipment supplier Flextraction Ltd. Dust collection systems must have adequate capture velocities at the pick-up points, properly designed duct velocity to transfer captured dust, and properly selected filter media, adds Joseph Anderson, senior applications engineer at Donaldson Co., Inc., manufacturer of Donaldson Torit dust collection systems.

Nanoparticles

Carbon nanotubes (CNT) are a large family of materials, each with different characteristics such as particle size and shape that may affect toxicity. Each product must be carefully characterized and tested depending on its characteristics and use patterns, notes Jacques Ragot, product stewardship manager for Bayer Material Science (BMS), which produces Baytubes CNT. Researchers have identified inhalative exposure to CNT as a main health issue. Test methods are still being developed, and much research on the safety of CNT is ongoing.
Currently the important point for compounders is to control and limit exposure, says Dr. Ragot. In Germany, the German Chemical Industry Association (VCI) and the Federal Institute for Occupational Safety and Health (BAuA) recently published guidance for handling nanomaterials. Bayer’s handling code is in line with these recommendations, says Dr. Ragot, noting that for compounders, the MSDS gives advice on safe handling, such as appropriate ventilation and personal protective equipment, for a particular CNT product. He adds that Baytubes are sold as large, stable agglomerates, which lowers their inhalation risk, and that toxicological testing to date has shown no adverse effects.

Manual handling

Because custom compounding is a labour-intensive process, protecting workers from injury during manual handling of materials is always one of the top health and safety issues for custom compounders. Ergonomics, or human factors engineering, seeks to minimize operator fatigue, discomfort, or injury by adapting the work environment to the workers’ needs. Material transfer is automated where possible and aids such as mechanical lifts are used, but it is difficult to eliminate manual handling. At SABIC Innovative Plastics’ LNP Business, cross-functional ergonomic teams at each manufacturing site identify issues and solutions customized to their specific needs, says Tom Ficca, global EHS leader for the business.

Machinery safety

Government regulations in Europe and North America require that operators be protected from moving parts of machinery. For example, a feeder with a vertical agitator must be designed so that an operator cannot reach in while the agitator is moving, notes Otto Rothlin, K-Tron’s global business development manager for the plastics and chemical industries. He explains that quick-release connections must be equipped with an automatic shut-off switch, while machinery parts that require a tool to open must be opened by trained personnel following appropriate safety procedures. ‘Lock-out and tag-out’ procedures, which electrically isolate a piece of equipment before maintenance, are commonly used in the industry. “We require a double layer of protection - both a lock-out procedure and an automatic shut-off switch if a critical piece of machine guarding is removed,” says Clariant’s Seeberg, noting that his engineers work with machinery companies to make safety modifications if needed or will do their own retrofits. Safety evaluations must be an integral part of new machinery design and installation, agree safety directors.

Noise control

The compounding plant is a noisy environment in which operators must work. Where possible, compounding companies use engineering controls to reduce noise. Engineers use sound-deadening insulation around noisy machinery, replace machinery with lower-noise versions, or try to improve the system designs. For example, Mr. Seeberg says, vacuum systems to remove water from strands are much quieter than air-blowing systems. Noise level is a key feature considered when purchasing new equipment, says Mr. Ficca. Beyond engineering controls, companies rely on personal protective equipment and operator training in the importance and use of hearing protection.

Keys to success in maintaining worker health and safety

A key to a safe operation is ‘behavioural safety’ – safety awareness and safety as a priority at all levels, from the operator to the site manager, says Mr. Seeberg. He explains: “Workers will notice if their site manager or supervisor is only concerned with output or is also concerned with safety.” Before safety training can be effective, top management must show a clear commitment that is transferred down the line, says Bruno Schmaeling, managing director of BSI, a Swiss-based behavioural safety consultancy. “We ask – do managers communicate the value of safety and stop dangerous behaviour on the spot when they see it?” explains Mr. Schmaeling, noting that sometimes they need to train supervisors in how to communicate safety issues. Ampacet’s corporate goals have a safety component, and individual employees also have yearly safety goals, says Denise Holl, Ampacet’s global director of safety and environment. Mr. Ficca adds: “The key to making management systems work is employee engagement and buy-in. Some of the ways we gain buy-in are employee involvement on safety committees, asking employees for input on specific problems, and a wellness programme that incorporates personal and workplace health.”
Compounding companies agree that training is key. “Training must include all levels - everyone from the new shop floor employee who has never worked in the plastic processing industry before, to the new compounding chemist straight out of college. Each requires a significant amount of training before they can be allowed on the factory floor,” says Mr. Yopak. John Vamosi, quality and EH&S manager at A. Schulman adds: “Training helps make safety a priority and a daily activity. We’re raising the education level of managers as well as making sure operators understand policies.” At Ampacet, safety coordinators at each worksite have completed a three year training course from the National Safety Council.
In addition to training, successful companies share best practices across manufacturing sites. For example, Clariant’s environmental, safety, and health global management system includes a database used for communicating its global rules and procedures, audit information, and any incidents and resulting fixes, says Mr. Seeberg. Ampacet’s global auditing programme ensures that every location is following the strictest safety procedure available, whether it is based on a regulation from an individual country or an internal procedure. “We seek continuous improvement. We learn from experiences and apply this knowledge to all our locations,” adds Ms. Holl.

Contacts:
A. Schulman; www.aschulman.com
Ampacet; www.ampacet.com
Bayer Material Science; www.bayermaterialscience.com/www.baytubes.com
BSI; www.ibs-schmaeling.de
Chemtura Corporation; www.chemtura.com
Ciba Corporation; www.ciba.com/expertservices
Clariant Masterbatches; www.clariant.com
Donaldson Torit; www.donaldsontorit.com
Flextraction; www.flextraction.co.uk
K-Tron Process Group; www.ktron.com
SABIC Innovative Plastics LNP Business; www.sabic-ip.com
Teknor Apex Company; www.teknorapex.com