Five ways trapped key interlocks protect tanker loading and unloading

Loading and unloading tankers carries significant risk. Procedures are often complicated, particularly when earth lines and valve systems are involved. Drivers have to consider variables such as load characteristics, the frequency of vehicle movement and the number of products to be loaded or unloaded.

Potential issues include:

• “Drive-aways” while tankers are connected to equipment or damage to extended gantries;
• The wrong substance being loaded or unloaded;
• Shortcuts being taken and steps in safe loading missed, such as earth line connections being made or hoses returned;
• The danger of loading or unloading hazardous or flammable substances;
• Product spillage;
• The environmental impact of product release.

Loading and unloading tankers carries significant risk

Trapped key interlocks (TKIs) provide specific protection and risk control in these types of application. TKIs encode procedures to ensure that systems can only operate one way: the safe way. Depending on the application, TKIs typically control five main risks:

1) They immobilise vehicles while loading and unloading is taking place by using an airline interlock or interlocking existing barriers. This prevents a “drive-away” while equipment is connected.

2) For multi-step processes, they force drivers to always follow the correct procedure and avoid shortcuts.

3) They ensure that valves can only be operated when it is safe to do so.

4) They make sure the correct substance can only be delivered or received by the appropriate tanker.

5) As primarily mechanical devices, they do not pose an ignition-source risk in hazardous areas.

Designing an effective TKI-controlled tanker loading system requires a clear understanding of the procedure involved and the equipment to be included in each stage of the process. This should be carried out in conjunction with a thorough risk assessment of the process itself.

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

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How trapped key interlocking protects workers at HV substations

Interlocking switchgear within HV substations ensures that personnel operate equipment safely, according to the correct procedures. Using a well-designed trapped key interlocking scheme will prevent personnel accessing potentially dangerous areas before the switchgear system has been put into a safe condition.

A good interlocking scheme will also ensure that the system functions correctly, so that there is no chance of, for example, switching two incoming feeds onto a common bus bar. This protects the equipment from damage and greatly reduces the risk of fire or arc flash.

A well-designed trapped key interlocking scheme will prevent personnel accessing potentially dangerous areas before the HV switchgear system has been put into a safe condition

There are four ways trapped key interlocks (TKIs) protect HV substations and their operators:

  1. Many HV substations are located in remote, unmanned sites which can attract attempted unauthorised access. TKIs help to safeguard this kind of vulnerable equipment.
  2. TKIs intended for HV substations have a proven design life of 45 years, allowing the safety devices to perform through decades of operation.
  3. Trapped key interlocking enforces the correct operation of equipment and therefore protects the continuity of supply.
  4. TKIs ensure that part of a system is isolated and correctly earthed before maintenance can be carried out on that section.

By: Adam Felton, Technical Marketing, Castell Safety International Ltd.

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How trapped key interlocking protects switchgear workers

The ability to work across HV, MV and LV switchgear means that a trapped key interlocking system can be used as a single solution to provide personnel safety and ensure equipment is used in the correct way.

Major switchgear manufacturers recognise the safety benefits that trapped key interlocks provide

Major switchgear manufacturers recognise the safety benefits that trapped key interlocks provide and design equipment to be able to accept this safety technology across their own breakers, isolators, switch disconnectors and earth switch mechanisms.

When used with switchgear, a well-designed trapped key interlocking scheme:

  • Forces operators to follow a predetermined switching schedule. This ensures the safe operation of switchgear and eliminates the risk of human error while switching between supplies.
  • Allows less-skilled operators to be able to switch between supplies comfortably as they are forced to follow a certain switching schedule, which enforces the safe operating process.
  • Protects workers by ensuring that personnel cannot access potentially dangerous areas without the switchgear system being put into a safe condition.

Trapped key interlocks provide a high level of safety for both operators and equipment as the operating procedure has to be strictly followed and cannot be circumvented.

By: Adam Felton, Technical Marketing, Castell Safety International Ltd.

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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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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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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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