Castell launches new heavy-duty access interlocks to protect workers in heavy industries

AI-HD and AIE-HD withstand high potential loads and high frequency of use

Castell has launched heavy-duty access interlocks for use in industries such as waste and recycling, aggregates, steel and chemical processing. The AI-HD and AIE-HD have been designed to deliver robust performance where there are high potential loads and a high frequency of use.

The AI-HD and AIE-HD interlocks will deliver years of performance in the harshest environments

The risks to personnel safety in harsh environments can be increased due to the heavy wear placed on safety components. The UK’s HSE recently reported that the construction industry in particular, while accounting for only around five per cent of Britain’s employees, still accounted for 31 per cent of fatal injuries to employees and 10 per cent of reported major or specified injuries.

Recognising these issues, Castell examined how it could develop its durable AI and AIE access interlocks to deliver enhanced products that would meet the day-to-day operational cycles encountered in heavy industry.

The AI-HD and AIE-HD will deliver years of performance in the harshest environments. The products use a heavy-duty stainless steel support mechanism, designed to take up to 1.5 times the load of current access interlocks, which reinforces the locking action. The design also provides additional protection for applications with high levels of vibration, such as mixers and shredders.

Elisa Hunt, Castell’s marketing manager, commented: “Castell has always been synonymous with high-performing products in harsh environments and the new HD access range takes this to a new level. Taking feedback from our customers in the cement mixing, tanker loading and waste and recycling industries has enabled us to develop a product that offers new levels of safety performance.”

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How trapped key safety systems make cement mixing more efficient

Concrete production is big business in the UK, with around 1,000 ready-mix sites and a large number of facilities producing precast concrete structures. In these environments fast, safe access to the mixer is important as set concrete can easily cause blockages if not regularly washed down.

Fast, safe access to the mixer is important as set concrete can easily cause blockages if not regularly washed down

The World Business Council for Sustainable Development’s ‘Health and safety in the cement industry: Examples of good practice’ recommends that when access to hazardous areas is required during normal operation, interlocking guards should be considered the number one safety option. Regulation 11 of the HSE’s ‘Provision and use of work equipment regulations 1998 (PUWER 98) (ACOP 2008)’ suggests fitting interlocked guards to protect operators from the dangerous parts of machinery.

There are three main ways trapped key interlocking systems can provide an efficient safety solution for the cement mixing industry:

  1. Trapped key interlocks ensure operators follow a strict procedure.
  2. Isolation of the power supply can be coupled with a motion-monitoring device which grants access to the mixer as soon as safely possible. In contrast to fixed-time delay systems, which can overcompensate rundown times for lighter loads, a motion-sensing system reduces downtime for equipment with variable rundown speeds.
  3. Trapped key interlocks are highly durable, have a longer product life and require less maintenance than alternative safety systems. As a result, the machinery to which they are fitted suffers less downtime and so overall plant utilization is increased.

The robust mechanical nature of the locks and keys is well suited to the harsh environment of a concrete plant, as well as being resistant to regular wash downs.

By: James Seel, Marketing Assistant, Castell Safety International Ltd.

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Castell supplies safety interlocks to Tianwan Nuclear Power Plant

FS interlocks and key exchange boxes provided for Phase II project

Castell is to supply interlocking systems to the Tianwan Nuclear Power Plant Phase II project under construction in Lianyungang, Jiangsu province, China. Tianwan is the nuclear power plant with the highest unit capacity in China. To date, it is the largest joint technical and economic project undertaken by China and Russia.

Tianwan Nuclear Power Plant Phase II project in Lianyungang, China, uses Castell safety interlocking products to ensure the safety of maintenance staff

Castell will provide multiple sets of mini FS industrial safety interlocks and key exchange boxes for the China National Nuclear Corporation construction project. These devices prevent the busbar earthing switch from connecting during maintenance on high-voltage switchgear, thereby guaranteeing the safety of maintenance staff.

Since 2010, Castell has provided customised safety interlocking devices for six successive nuclear power projects in China. Project supporter ABB China recommended Castell to the China National Nuclear Corporation as part of this latest Power Plant Phase II project.

Christy Zhang, Castell senior sales manager for the China region, said: “Once again, Castell has retained the trust of its Chinese nuclear power industry clients. The company continues to establish its products’ leading edge within the high-end field of nuclear power.”

The unit capacity for the Tianwan Nuclear Power Plant’s Units 3 and 4, which are currently under Phase II construction, will be one million kilowatts. Units 3 and 4 are expected to be put into commercial operation in February and December 2018 respectively.

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Two ways trapped key interlocks can help to achieve Target Zero in the quarrying industry

The HSE describes quarrying as “one of the most dangerous industries to work in”. Nearly 3,500 UK workers have suffered an injury reportable to the HSE since 2000, a figure that includes 29 fatalities.

Trapped-key interlocks are particularly suited to the quarrying and aggregates industries

Between 2000 and 2010, the Hard Target initiative led to a reduction in RIDDOR-reportable injuries in quarries by 76%. The initiative involved collaboration between the HSE, trade associations and industry representatives. These three groups make up the membership of the Quarries National Joint Advisory Committee (QNJAC).

At Hillhead 2010, Judith Hackett, Chair of the HSE, congratulated the industry on the improvement in safety Hard Target had achieved, and introduced Target Zero, a continuation of the drive to reduce injuries in the quarrying sector.

Target Zero is the industry’s pledge to reduce injuries by a further 15% year-on-year from 2010 until 2015. All the major players in the quarrying industry have pledged their allegiance to Target Zero, implementing their own internal strategies to achieve the target reduction in injuries and improvement in safety. These efforts have led to a reduction in the lost-time injury frequency rate (LTIFR) reported by the principal quarrying companies in recent years. LTIFR is the main internal indicator of the performance of these firms against their own zero harm targets.

The HSE’s Approved Code of Practice and guidance document ‘Health and safety at quarries – Quarries Regulations 1999’ recommends that interlocks should be included in any risk inspection scheme. Trapped-key interlocks are particularly suited to the quarrying and aggregates industries for two main reasons:



The quarrying sector has a fatality rate 12 times higher than the all-industry average. Any safety solution must be robust and durable, as the harsh working environment places severe demands on both operators and machinery. Trapped key interlocks are resistant to wash-down and cleaning regimes. Figure symbol interlocks are particularly beneficial as, unlike tumbler mechanism locks, their normal operation won’t be compromised by plugged dirt or other substances.


Regular maintenance is required to keep machinery functional, but each round of maintenance introduces a safety risk as access to dangerous parts of machinery is sometimes required. The desire to minimise downtime means the maintenance process needs to be as safe and efficient as possible. Trapped-key technology ensures that the correct procedure is followed every time, improving safety and maximising productivity.

By: James Seel,  Marketing Assistant, Castell Safety International Ltd.

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Seven reasons to choose safety interlocks for MV and LV switchgear systems

The risks surrounding the operation of electrical switchgear systems are defined in detail and mitigating these is an important aspect of any health and safety policy. As set out by regulatory bodies like the HSE, in publications such as Electrical Switchgear Safety (INDG373), there are a number of important factors to consider. These are well documented and include:

  • Providing the correct training;
  • Ensuring regular maintenance;
  • Ensuring staff know the rules and their responsibilities;
  • Carrying out regular risk assessments and acting on their findings.

Each switchgear system will have its own set of operational and maintenance requirements, and it is important these are taken into consideration before implementing a safety solution.

The use of trapped key technology to ensure the safe operation of electrical switchgear systems has been established since the early 1920s. There are two principal issues that interlocking provides a solution for: the correct operation of switchgear equipment – reducing the possibility of arc flash – and the provision of safe access during maintenance.

Trapped key interlocks offer seven distinct advantages when used to safeguard MV and LV switchgear systems:

  1. They prevent personnel from accessing live terminals and cabinets.
  2. They protect equipment by ensuring it can only be operated safely.
  3. They can be operated by less skilled personnel, reducing training costs.
  4. They can reduce unintended outages caused by incorrect operation.
  5. They perform in harsh environments.
  6. They deliver a solution that satisfies the higher global MV standard IEC/EN 62271-200, defined as ‘accessible and interlocked’ as opposed to ‘accessible by procedure’.
  7. They allow the integration of LV and MV switchgear systems, different manufacturers’ equipment, and subsystem elements such as breakers and transformers.

Each switchgear system will have its own set of operational and maintenance requirements, and it is important these are taken into consideration before implementing a safety solution. In general, trapped key interlocks are highly flexible and provide integrated and retrofit solutions across a wide range of manufacturers’ equipment.

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

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Plant maintenance and safety interlocks – myths and facts

In a recent article entitled “Unsafe Maintenance”, Judith Hackitt, chair of the UK’s Health and Safety Executive, examined some of the reasons why so many serious accidents and even fatalities continue to occur within processes related to the maintenance of machinery and equipment.

Trapped key interlocks ensure that machinery is maintained in a safe and efficient manner

Judith identified several common attitudes, concerns or faults which can ultimately lead to the safety of maintenance workers being compromised:

  • Time pressure – while machinery is stopped, money is being lost.
  • A focus on addressing everyday risks such as slips and trips, rather than mitigating the potential risks involved in machine maintenance.
  • A failure to plan maintenance activities or consider the best and safest ways to carry them out.
  • A perception that safety equipment will slow down production.
  • An absence of basic safety equipment, such as lockout / tagout and “Castell key arrangements”, which prevent access to running machinery and accidental start-up during maintenance activities.
  • A lack of the necessary ability to safely maintain equipment.


Trapped key interlocks can address all of these issues. It would be helpful to challenge some of the common industry misconceptions and separate fact from fiction.

“Mechanical trapped key interlocks slow down production; sensor-type safety solutions are much faster and just as safe.”

MYTH – A well designed safety interlocking system will work in harmony with existing manufacturing processes.

 “A well designed trapped key interlock can ensure the highest levels of safety integrity.”

FACT – The secret to a good safety system is a comprehensive risk assessment and understanding of the maintenance requirements. Trapped key technology will enforce these procedures.

 “I have to choose between implementing a trapped key system or a lockout / tagout system.”

MYTH – Trapped key interlocks and lockout / tagout can be combined to deliver an integrated safety system that covers planned and unplanned maintenance intervention.

 “Trapped key interlocks are expensive and inflexible.”

MYTH – With a wide installed base, trapped key interlocks have a long heritage of flexibility across heavy and light manufacturing operations. They are often found in excellent working condition even after decades of use, providing years of cost-effective safety.

“Interlocks are complicated and confusing.”

MYTH – Being process-driven, trapped key interlocks are easy to use, regardless of language or technical expertise.


Allied to thorough risk assessments and clear method statements, trapped key interlocks ensure that machinery is maintained in a safe and efficient manner by:

  • Dramatically reducing process risks and enforcing routines.
  • Isolating a machine’s power supply before work can begin.
  • Creating a robust process in areas where noise and communication could be an issue.
  • Performing in harsh and difficult manufacturing environments.

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

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Castell provides safety interlocks to Zambia’s largest power station

ZESCO chooses British firm as partner for Kariba North Bank extension project

Industrial safety specialist Castell has provided several K Locks and key exchanges boxes to the Kariba hydropower station North Bank extension project in Zambia.

Castell’s interlocks, installed in Zambia’s Kariba hydropower station more than 50 years ago, are still performing well today.

Photo caption: Castell’s interlocks, installed in Zambia’s Kariba hydropower station more than 50 years ago, are still performing well today.

In the early 1960s, Castell provided interlocks to the power station; more than half a century later, the interlocks are still performing well. When the station was due to add a north bank extension, project owner Zambia Electricity Supply Corporation (ZESCO) recommended Castell to the project contractor SINOHYDRO.

Castell’s interlocks force workers to follow a predetermined process when operating or maintaining machinery and equipment, to prevent human error and safeguard workers’ access to dangerous areas.

Christy Zhang, senior sales manager at Castell China, said: “It is an honour for Castell to provide safety interlocks to the Kariba North Bank extension project. The client’s trust in us stems from the long-term performance of our interlocks.”

The Kariba hydropower station is located in the middle of the Zambezi River, 125 miles from Lusaka, Zambia’s capital. The extension project has added two 180 MW generator units, taking the total capacity to 1,080 MW and making Kariba the largest power station in Zambia.

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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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