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Netherlocks has been chosen to supply its trapped key interlocking safety systems to Larsen and Toubro, an Indian engineering and construction company.

The company ordered Netherlocks products to secure and safeguard ‘pigging’ operations for two projects.

One, in conjunction with Cairn Energy India, involves 39 pig launcher and receiver systems along a cross-country pipeline.

The other project is from the Larsen and Toubro Qatar office, with Qatar Petroleum for the SGP project, where, initially, 12 of the pigging systems will be protected by the interlocks.

Pigging is an effective and efficient cleaning method for pipelines; it does not interrupt the process but it does carry a potentially high risk factor due to the high pressures and dangerous gases involved.

There is always the chance – mostly attributable to human error – that the procedure itself will not be followed exactly.

The trapped key interlocking systems from Netherlocks ensure that each stage of the process can only be started – that each valve can only be operated – once the stage before has been safely completed.

In this way, the system mechanically enforces a strict adherence to safe procedures.

The exact number of locks required varies according to each individual pigging system and client specification, as their processes will be subject to differing numbers of variables, such as vent, drain, kicker, main, throttle and balance.

This then requires different complexities of interlocking systems such as locks on manually and motor-operated valves and closures.

As pigging procedures are often non-linear processes – requiring steps that may need to be repeated at different stages or that are dependent on several previous actions – Netherlocks designed the MPCU.

The MPCU acts as a ‘mechanical PLC’, checking each stage of the process and releasing keys according to pre-programmed parameters, meaning that the operation can only be performed according to safe procedure.

The simple principle of mechanically enforcing safe working methods reduces risk by taking the ‘human factor’ out of the equation, without negatively affecting performance.

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