Applying interlocking systems

Valve operation can be potentially dangerous if executed incorrectly, or in unsafe conditions. The scope for injury or damage is also significantly increased when high temperature, high pressure or a toxic product is present.

While good practice begins with good design - both are inevitably hostage to the ‘human factor’. 70% of reported incidents in the oil & gas industry worldwide are attributable to human error, accounting for in excess of 90% of the financial loss to the industry.

Typically key interlock systems are applied to valves, closures, switches or any form of equipment which is operated by human intervention

Modern processes are often highly automated, yet still require human intervention during essential maintenance procedures such as loading or unloading pig traps and the changeover of pressure relief valves so it is essential that processes are regulated.

Mechanical key interlocking can provide a simple, fail-safe way of keeping workers safe, even in hazardous and stressful conditions.

Mechanical key interlocks work by controlling the sequence of events in which valve process activities are conducted. They can be used on every form of valve as well as access hatches, doors and electrical isolating switchgear.

Interlocks are fitted to the valve without any modification to the host equipment and operate on a ‘key transfer’ principle which ensures an operation happens in the desired sequence only.

Typically key interlock systems are applied to valves, closures, switches or any form of equipment which is operated by human intervention.

The ‘OPEN’ or ‘CLOSED’ status of an interlocked valve, or the ‘ON’ or ‘OFF’ status of an interlocked switch, can only be changed by inserting a unique coded key.

Inserting the key unlocks the operating mechanism enabling operation of the valve or switch. Operating the unlocked equipment immediately traps the key.

When this operation is complete, a secondary key is released, thereby locking the equipment in the new position. This secondary key will be coded in common with the next lock in the sequence.

By this simple coded-key transfer principle, a “mechanical logic” system is created which denies the scope for operator error.

While popular Permit to Work (PtW), Lockout/Tagout procedures provide a ‘lock-off’ capability, they do not provide any control of the sequence of operations, nor do they assure or confirm the status of the equipment to which they are fixed which can create dangerous conditions through error or negligence.

Interlocks are ideally suited for integration with PtW procedures and provide an effective front-line safety management tool that mitigates the risk of human error.

Interlocks maintain productivity. The key transfer system is integrated with the operation to create a seamless sequence of events that ensures safety and peace of mind and eliminates the associated risks to people working on offshore platforms and processing plants.

Valve interlocks are mechanical and do not rely on a power supply. They can be fitted to motorised valves without compromising the valve’s function and failsafe features.

As a result, key interlocks provide independent control over the working of manually operated valves, end closures and motorised valves.

In practice, this simple concept saves lives and protects plant and personnel during valve operations worldwide.