Trapped key interlocks vs light curtains in the food industry

In all industries it is important to balance the demand for safety with the need for fast access to machinery. The latter is vital in the food industry, for several reasons:

  1. The need to easily and hygienically clean the production environment.
  2. The impact on downtime of repetitively cleaning electronic systems.
  3. The requirement to clean all guards and accessories in the immediate location of the food area.

When protecting workers from the dangers of food processing equipment, both light curtains and trapped key interlocks can provide ways to control risk.

Light curtains offer such benefits as:

  1. Immediate access to production areas.
  2. A reduced need for guarding, which in turn reduces the time needed to clean a production area.
  3. Levels of protection ranging from full-body to finger, depending on the light curtain selected.
  4. When programmed appropriately, allowing raw materials to be passed into the production environment without halting processes.

The advantages of trapped key interlocks include:

  1. The ability to isolate the dangerous area until food machinery is made safe through timed or motion-sensing control.
  2. Higher life expectancy thanks to their mechanical (as opposed to electrical) design.
  3. Putting the operator in the hazardous area in full control of restarting the machine through the use of full-bodied interlocks and personnel keys.
  4. Resisting wash-down environments for extended periods due to their mechanical design.


Although light curtains can detect personnel crossing into a full-body zone, they are unable to determine if anybody remains in the danger zone when the machine restarts

The clear difference between light curtains and trapped key interlocks is most obvious in relation to full-body access. Although light curtains can detect personnel crossing into a full-body zone, they are unable to determine if anybody remains in the danger zone when the machine restarts. This can lead to a dangerous situation if workers are hidden from sight behind equipment.

Trapped key interlocks are able to protect workers while they are in the danger zone through the use of a personnel key. When the operator is in the danger zone, the key is retained with them. This means that the machine cannot be restarted until the personnel key is returned to its original position. If multiple personnel are required to enter the danger zone, several keys can be provided to allow access – the machinery cannot be re-started until all access keys are returned to the exchange point.

In summary

Ensuring that the best solution is applied will depend on:

  • Understanding the hygiene regime requirements for each application.
  • Assessing who needs access to these areas, why and how often.
  • Evaluating access requirements: full- or part-body?
  • Conducting a risk assessment to understand the specific risk around the machinery or equipment.
  • Remembering to assess risk both pre- and post-implementation of a solution.

By: David Hughes, Sales Director, Castell Safety International Ltd.

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How figure symbol trapped key interlocks improve efficiency in the food industry

After safety, the most important area of focus in the food industry is the efficiency of a production line. Ensuring that deliveries meet the demanding schedules set out by retailers is key to maintaining and growing market share for food producers in every market.

Figure symbol trapped key interlocks are designed to be faster and easier to clean, making them practical for the food industry.

It is widely understood that trapped key interlocks, by enforcing procedures, ensure that workers remain protected across a manufacturing site. From raw material receipt through the manufacturing process to the despatch of goods, trapped key interlocks ensure that potential accidents are designed out of each process. In many cases trapped key interlocks, and figure symbol interlocks in particular, can also have a very positive impact on efficiency and overall equipment effectiveness. They achieve this in a number of ways.

1)    Reducing downtime caused by hygienic processes

Being mechanical in design, trapped key interlocks do not suffer from the water-induced electrical faults that can see alternative technologies fail in just a few months.

2)    Reducing downtime during unscheduled interventions

Machine guarding refitted under the pressure of a manufacturing plan which has not allowed for an unplanned stoppage can be unreliable. This can cause issues where guards are incorrectly placed and misaligned sensors will not allow the machine to restart, extending downtime. Through key transfer, trapped key interlocks enable faster restart as it is immediately clear which guard has and hasn’t been refitted.

3)    Avoiding damaged sensors

In a fast-paced manufacturing environment, damaged safety sensors can introduce delays and the potential for hazardous operation. Trapped key interlocks’ robust design enables them to operate safely for many years and they often outlast the design life of the equipment they are fitted to.

4)    Reducing the need for hygiene

Washing down machinery in the food industry after operation is an expensive and time-consuming overhead. Any opportunity to reduce this cost improves overall profitability. Figure symbol trapped key interlocks are designed to be faster and easier to clean. Typical lock mechanisms suffer from plugging where food and debris enter the lock, reducing the performance of the mechanism. Unlike a conventional key and lock mechanism, figure symbol interlocks are designed so that the coded key operates with the like-coded lock surface, rather than engaging into the typical internal tumbler mechanism. Figure symbol locks remove this unwanted feature, making them more practical for the food industry.

5)    Improving operator efficiency

Figure symbol trapped key interlocks improve operator efficiency in multi-language and temporary worker environments by introducing a coding system, which is easy to identify, and preventing shortcuts and operator error.

By: David Hughes, Sales Director, Castell Safety International Ltd.

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Food manufacturer improves warehouse safety with Salvo™

Greencore installs drive-away prevention system at four UK sites

Leading convenience foods manufacturer Greencore has installed Castell’s drive-away prevention system Salvo™ at four UK sites. The interlocking device is providing loading bay safety at Greencore’s Kiveton, Warrington, Wisbech and Park Royal facilities.

Greencore has installed Castell’s drive-away prevention system Salvo™ at four UK sites

Part of the risk assessment process identified a potential for a drive-away from the loading bays. Although Greencore had systems and procedures in place to prevent this type of occurrence, the company investigated several potential safety systems to negate the risk, before deciding that Salvo™ was the right choice.

“Castell gave us the most competitive price and their product was the best suited to the task in hand,” said Simon Chamings, safety, health and environment officer at Greencore Kiveton. “Since installing Salvo™ we’ve had absolutely no problems whatsoever.”

Dave Massey, Greencore Kiveton’s transportation shift manager and a former HGV driver, was unequivocal in his verdict: “In terms of loading bay safety, it’s the best thing I’ve ever seen.”

The shunter fits a Salvo™ Susie lock to a trailer’s exposed emergency airline, which immobilises the trailer and releases a key from the end of the Susie. The shunter then inserts the key into the SCP+ control panel unit next to the bay door. Turning the key powers up the bay, and illuminates a green beacon inside the warehouse and a red one in the yard. While the bay door is open, the key remains trapped in the SCP+ and therefore the trailer cannot be moved. When loading or unloading has been completed, the process is reversed.

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The top five ways trapped key interlocks protect workers in the food industry

Trapped key interlocks provide fast, safe and reliable access to machinery, prevent shortcuts and enforce procedures. This is achieved through the transfer of keys as the process is stopped or started. The repetitive wash-down procedures common to the food industry can affect the reliability of electrical safety devices, but the rugged, mechanical nature of trapped key systems makes them particularly suited to food processing applications. Here are the five most popular areas in which mechanical interlocks safeguard workers in the food industry.

1) Palletisers, blenders and mixers

These machines present the same risk – that personnel can be exposed to danger without being immediately visible to others – but for different reasons. In the case of palletisers, the large size of the segregated area, the equipment within it and the full pallet itself make it easy for an operator standing outside the machine guarding to miss a colleague’s presence inside. Blenders and mixers, on the other hand, present an impenetrable metal wall at ground-level to external workers.

Electronic methods of detection are sometimes unable to ascertain if individuals remain within a hazardous area. But trapped key interlocks, through the use of a personnel key, and lockout / tagout procedures can ensure that all operators and engineers are safe prior to the machine running. The operator retains the personnel key the whole time they are in the protected area, putting them in control of the machine start-up. Until this key is returned to its original position, there is no way to restart the machine.

2) Clean-in-place

The nature of the chemicals used in clean-in-place operations means that any product contamination is extremely hazardous to human health. It is therefore imperative that the correct procedure is followed and completed prior to food production starting. Trapped key interlocks force workers to follow a strict process, without them deliberately skipping or inadvertently missing steps.

3) Product filtration valves

Maintaining and replacing filters in food processing pipework while product flow is present carries two risks. First, removing filters can lead to loss of product and high clean-up costs. Second, operators can be exposed to high-pressure and / or high-temperature product. Interlocking product flow and access to filters ensures that access can only be gained when product flow has ceased i.e. when the valve is closed.

4) Dosing

Ensuring the correct dosage of ingredients or additives is administered at the right time can prevent product being spoiled or wrongly formulated, and money being lost. Companies that interlock dosing valves maintain product consistency. Ingredients and additives can only be introduced in the correct order and individual steps cannot be missed or ignored.

5) Ovens and chillers

The risk when maintaining ovens and chillers is that the temperature may not have returned to a safe enough level to allow prolonged exposure by maintenance and operation teams. Having a robust method to guarantee enough time has elapsed before access can be granted means that personnel remain safe while in the danger zone. The access key to the hazardous area is only released once sufficient time has passed to allow the temperature to return to a safe level. The provision of a personnel key that is kept by workers while they are exposed to danger inside the equipment means that they remain in control of the process.

By: David Hughes, Sales Director, Castell Safety International Ltd.

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Castell hosts 2013 channel partner forum

Event helps ensure customers worldwide get latest technical advice

As part of its global sales growth strategy, Castell Safety International recently hosted a forum for its network of international distribution, or channel, partners.

Castell hosts its 2013 Channel Partner Forum

The event saw channel partners receive training in the principles of trapped key interlocking, undertake a manufacturing facility tour and attend presentations focused on Castell’s new product development, vertical market strategy and emerging applications.

Castell’s channel partners help ensure that customers receive expert technical advice, market- and application-specific knowledge, customs brokerage and timely delivery in a large number of countries around the world. The company’s network of partners spans over 20 countries on four continents and includes qualified technical sales engineers who speak more than a dozen languages in total.

Castell sales director David Hughes added: “This event has been a great opportunity to educate our channel partners on our vertical market strategy and help them become experts in our key markets of energy, industrial, manufacturing and transport.”

Channel partners gave presentations on their own markets and Castell success stories, which encouraged discussions on new opportunities across the distribution network. Perry De Brujn, of TSA Safety Group, the exclusive distributor for Castell in the Netherlands and Belgium, commented: “The channel partner presentations greatly enhanced my awareness of the huge range of applications which can be safeguarded using Castell products.”

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Safety interlocking manufacturer appoints new distributor in West Africa

Wined Resources will distribute full Castell Safety International product range

British safety interlocking manufacturer Castell Safety International has agreed a new distribution partnership with Wined Resources, a prominent specialist distributor of safety equipment in Nigeria. The new partnership marks the first time Castell products have been made available through a distributor in West Africa.

A Nigerian company, Wined Resources is based in Warri, a hub of West Africa’s oil and gas industry, and has affiliations with multinational companies. Wined Resources will deliver a full range of distributor services including on-site sales visits, order processing, customs clearance and delivery, and after-sales support.

Castell sales director David Hughes commented: “Nigeria is a growing market for Castell and we are proud to partner with Wined Resources, an organisation with over 20 years’ experience serving the Nigerian business community, and with deep knowledge and expertise in several key industries. Their skilled technical sales team will be able to quickly help customers wanting to buy our products.”

Edwin O. Ezeocha, Wined Resources managing director, added: “Castell’s safety products are well known for their high quality and reliability, and will be an excellent complement to our existing safety product range. We see the potential for a vast range of safety applications across numerous industries in Nigeria.”

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Castell launches new spring-loaded interlock

KSP more efficient than traditional bolt interlocks

Castell has launched a new spring-loaded lock, the KSP, to increase efficiency in traditional bolt interlock applications.

Spring-loaded bolt interlock

The KSP is a spring-loaded version of the Castell K lock, and uses an internal spring to automatically extend the lock’s bolt to its fullest extent when circumstances permit. The key-operated mechanical interlock is suitable for the safe locking of simple actuating mechanisms.

The KSP is generally used at the start of a process and traps a key while equipment is running. When the equipment is switched to a safe state and the aperture in the actuating mechanism is aligned, the spring-loaded bolt automatically extends and is locked in position. This represents an advantage over existing bolt locks as the operation happens immediately and without the need for human intervention.

Once the equipment is in the safe state, the key is released and can be used to gain access or start a separate process. The key must be inserted and turned, retracting the bolt, to allow the actuating lever to be moved again.

Paul Marks, Castell’s technical director, said: “We were already using a spring-loaded lock within our product range and realised that the same device could deliver significant benefits elsewhere for our customers. We view the KSP as an important addition to our existing K bolt interlock range.”

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How trapped key interlocks can ensure the long-term safety of electrostatic precipitators

The hazards of electrostatic precipitators in power generation are well known. High-voltage current, confined spaces and the respiratory risk of fly ash all put workers in potential danger. These issues are compounded by infrequent access and harsh environmental conditions.

This is why selecting a trapped key safety system that provides protection for many years is an important factor in safeguarding power station workers.

Factors to consider when choosing a system include:

•    the product’s ability to withstand hot and cold climates
•    outdoor use
•    the impact of fly ash

This means the type of key (heavy- or light-duty), the material (brass or stainless steel) and the location of the interlocks are crucial to determining long-term usability.

This is only part of the story, though. To perform reliably over many years, interlocking systems need to be maintained and should be serviced as part of a shutdown regime. Simple preventative maintenance steps, such as using graphite powder rather than grease, have a huge impact on longevity.

Regular functionality testing of locks can also prolong a trapped key safety system’s life. This ensures the system is fully operational, saving time and money during a planned or unplanned outage. If locks are only used during an outage and they fail, it can take time to repair or replace them.

Should a failed lock prevent a power station from being brought back online, the financial penalties incurred could be severe. For this reason, it is best practice to regularly check and maintain locks between outages.

With the right maintenance plan, system selection and material choice, a trapped key interlocking system can provide 30-40 years’ service on an electrostatic precipitator, in even the harshest locations.

By: David Hughes, Sales Director, Castell Safety International Ltd.

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NSK improves loading bay safety at Netherlands warehouse

Castell’s Salvo™ also protecting staff at UK facility

NSK, one of the world’s leading manufacturers of industrial and automotive components, has chosen Castell’s drive-away prevention system Salvo™ to protect staff at its warehouse in Tilburg, Netherlands.

NSK warehouse, Netherlands, Salvo, loading bay safety, Castell

NSK’s huge facility distributes more than 4,000 pallets a month across the whole of Europe and North Africa. Customers include Ford, Volkswagen, Siemens and Bosch.

Salvo™ has been installed on 12 loading bays, while NSK has also bought four Salvo™ Club steering wheel locks to safeguard deliveries made by rigid vehicles. There have been no reported health and safety incidents since Salvo™ was commissioned at the Tilburg site.

Having reversed their vehicle onto the relevant loading bay, drivers install the Salvo™ SGL lock on the exposed emergency airline coupling, releasing a trapped key. This key is then inserted and turned in the Salvo™ Control Panel (SCP+) on the outside of the bay. An amber beacon illuminates on the inside to indicate that the loading bay is now safe and ready to use. The loader opens the door, trapping the key in the SCP+ outside. While the door remains raised and the key trapped in the control panel, the trailer cannot be moved.

NSK has also installed Salvo™ at its distribution centre in Newark, UK.

The Health & Safety Executive booklet ‘Warehousing and storage: A guide to health and safety’ recommends interlocks as a safe system of work to combat drive-aways. Salvo™ also features as an example of a safe system of work in the Freight Transport Association’s ‘Loading dock safety guide’, produced in conjunction with the Institution of Occupational Safety & Health.

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Castell’s new range of padlocks now even safer

Improved differ code delivers higher level of complexity

Castell has launched an enhanced version of its Iso-Lok padlock range. The new range features a more complex differ code system, increasing the overall safety level offered to customers.


Castell’s tracking system already ensures that each padlock supplied to a site is unique. This removes the issue of keys fitting multiple padlocks and therefore reduces risk in lockout / tagout procedures. The company’s enhanced range of padlocks now takes the separation of differ codes one stage further.

“The quality of the Iso-Lok range is very important to our client base,” said David Hughes, Castell’s sales director. “By increasing the integrity of our padlocks we have effectively increased the safety of the Iso-Lok range.

This product improvement – coupled with our ability to track differ codes, paint and engrave padlocks – delivers substantial value to our customers.”

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