Product Inspection: The Safety of Workers
While consumer safety and protection is of paramount importance when manufacturing consumable goods, the safety of those working on the production lines must also be taken firmly into consideration. There are legal and moral responsibilities to protect workers which go beyond safety for the sake of compliance. It is safety for the protection of people first and foremost. John Uber, Product Management Leader at Mettler-Toledo and Chair of the ANSI B155 (Safety Requirements for Packaging and Processing Machinery) 2016 Revision Committee, answers a series of questions to highlight the importance of getting the equipment design process right first time.
Q: As a customer looking to purchase PI equipment, what are the key factors to consider before purchase and installation from a worker safety perspective?
A: The first thing you need to have is a risk assessment from your intended supplier. It is essential to assess the risk for the complete machine. This risk assessment determines the level of safety circuit required for the system. The methods to validate that safety circuit, and verify periodically, must also be provided to the user. It is important to remember that the risk assessment by the supplier is design-based, and should be the starting point for the user’s task-based risk assessment.
The real challenge is to strike a balance between having a machine which can be operated and having one which is properly guarded to prevent access to hazards. That is a balance that everybody has to work hard to achieve. One area that presents a significant challenge – where we as a supplier are a part of extensive communication with the user – is integration. There are many things to consider. Are you transferring product on to or off of the inspection device? Are you rejecting packages? How are you accumulating packages? How are you addressing the non-mechanical areas, such as electrical energy, communications and signals, safeguarding and safety circuits? All of these questions should be answered and addressed at the design stage, and reviewed at each stage of the order process.
Q: What are the most common risks faced in a manufacturing environment with regard to equipment safety?
A: The most common are electrical – there is more concern about electrical energy than any other area, as it is potentially the most severe. These areas are well guarded. There are established protocols for accessing hazard areas and well-defined standards on how to design out or guard against the perceived hazards. To take an example, in the US in particular there is industry awareness with regard to things like arc-flash – where they consider the potential energy that could be delivered from an interaction with a high-voltage source and how much damage it could cause to a person. If voltage values are considered to be potentially harmful, then technical personnel are required to wear protective equipment, such as face-shields, gloves, and cotton-only clothing.
Reject areas also present risks. They operate intermittently and without warning, so those are designed to minimise the severity of potential injury. Crush areas and draw-in positions are examined to make sure there are no finger traps. The rejector blades/contact areas, for example, are never more than 6mm from the surface of the belt, so that if the finger was to engage the gap between the conveyor belt and the pusher plate it is difficult to get the finger trapped underneath. Gaps between rejector plates and fixed supports are also examined. There is a gap of 25mm or 50mm between the back of the pusher plate and the support structure. The 25mm gap is larger than a finger would be for a small plate, and 50mm gap is larger than a hand when larger plates are used.
Transfers are also often overlooked. In Product Inspection, transfers, as a performance standpoint, are critical. This is particularly the case with checkweighing, where you need a smooth transition to stabilise the package for weighing. Stability of the package is something that you want with every form of inspection, as the more stable the package, the more reliable the inspection. Where transfer is connected to safety we have motor control over our system, but we do not have control of the machines upstream and downstream from our machine. Someone has to have an overall view of the interactions between machines. In the EU, the Machinery Directive makes the obligation clear. The user, or the user’s integrator, has responsibility for the safety of the various areas of integration, and for the safety of the “assembly of machinery”.
Q: Are there any concerns that arise with regard to MT equipment – x-ray for example?
A: The level of x-ray emission and exposure is lower than that which you would typically experience in an airport. Regardless, there are regulatory requirements which state you must provide guarding and safety notifications appropriate for the level of risk. You must also initially validate the systems for radiological safety, and periodically verify that the safety measures are effective. The guarding has to be of a certain material; gaps are tightly controlled. There are techniques used such as curtains, to allow packages to pass through while still providing protection to the user. Leak testing is also very important. Workers can be genuinely scared of x-ray radiation, therefore it is important to reassure them that their surroundings are safe and free from harmful levels of radiation.
Q: Can you explain the design process from a worker safety perspective?
A: There are four key stages to the safe-design process. The first emphasis – the priority for achieving an acceptable level of risk – is to design out the hazards. The second is to guard against those hazards that cannot be entirely removed. Third, you must advise or notify operators with regard to hazards and risk via labelling. And finally, you must train and instruct effectively. That is the progression to follow in order to design a machine with ‘an acceptable level of risk’. We use this phrase, as the term safe is often used too freely. Machines, regardless of their function, should never be described as 100% safe. Suppliers strive to reach a level of acceptable risk, and this should be reviewed openly with the user. That can mean gap control between guards, or maintaining certain operating parameters. For instance, if you have a system which has been designed where you do not want the pusher plate to go over the edges of the conveyor, you design it with an air cylinder which only has a certain length of stroke, as opposed to trying to control it with the pneumatic supply. It is mechanically constrained so that it cannot create a more hazardous condition. Having the awareness to naturally build these features into a machine is the way Mettler-Toledo thinks and works.
Design and risk assessment should be concurrent. There is little point waiting until a machine is at the installation stage to run a risk assessment. By then it is very difficult to make changes if necessary. The assessment must be carried out parallel to the design process. This reiterates the point that the first stage is to design-out the hazards. Consider the potential hazards during the design and you will have a much lower-risk machine.
Another aspect of designing-out the hazards relates to hygienic design. You cannot put a guard on a microbe, so if you have a hazard relating to liquid pooling for example, this has to be designed out before a machine is put into production. There is a minimal risk to the workers here, more to the consumer, but loss of brand reputation through microbiological or cross-contamination could lead to plant closures. If that happens there is no worker safety issue at all – but of course that is very far from the ideal scenario.
Q: What should customers expect from suppliers in terms of highlighting and safeguarding against potential risks?
A: On an application basis, suppliers should explain to the user the following: how the machine is designed, what safeguards are present and what residual risks are transferred to the user. That is the risk assessment essentially – which should be the basis of a conversation between the user and the supplier.
On a larger perspective, companies from the supplier and user side should be encouraged to collaborate and work in industry groups. Participation in industry standards leads to the development of soundly structured best practice guidelines. Industry groups such as ANSI and ISPE are good examples. These interactions at the very top level set the tone and establish best practices for how to communicate with customers to make sure that a) the supplier provides all the necessary information, and b) the user has that information to apply when they integrate the system into the line.
Q: Do you offer training to ensure machines are operated safely by workers once installed?
A: We will train customers on the hazards that are present in our system, because that is what we know, and what we can practically control. The bigger side of ensuring adequate training is for the user to conduct a task-based risk assessment knowing how their operators are going to use the equipment. Their frequency of interaction positions, where they are accessing different parts of the system – these are variables that we do not control. We can train on the hazards that are identified in a design-based risk assessment, and the user will complement that with training that is task based.
From an integration perspective, safeguards at machine interfaces should be provided by those who have control of the design in those interface areas, and have knowledge of hazards that may be present or may be introduced through the assembly of machinery. To assist the user in this important task, Mettler-Toledo Product Inspection provides safety and interface information to allow the responsible persons to plan and execute the safe integration in an efficient manner.
About Mettler-Toledo Product Inspection
Mettler-Toledo Safeline is the world’s leading supplier of metal detection and x-ray inspection solutions for the food and pharmaceutical industries. Together with Garvens Checkweighing, CI-Vision and Pharmacontrol Electronic GmbH (PCE), Mettler-Toledo Safeline forms the Product Inspection division of Mettler-Toledo.
Mettler-Toledo develops, produces and markets precision instruments worldwide. The company is one of the largest suppliers of weighing and quality control systems in the world, whose products are used in laboratories as well as industrial processing and food retailing applications. Renowned producers of all conceivable everyday products rely on Mettler-Toledo’s technology as an important aid to delivering consistent product quality and innovative developments. These producers reap the benefits of the company’s global presence and sales and service network.
Mettler-Toledo’s corporate philosophy centres around high-quality standard and tailored solutions. The company forms a true partnership with its customers providing support during the selection of appropriate systems and working together to develop unique solutions which increase process efficiency, reduce overall manufacturing costs and improve competitiveness.
For general information on Mettler-Toledo Product Inspection, visit: http://www.mt.com/piLeave a reply →