Pipelines are routinely cleaned with the help of pigs that scrape the lines clean. This is done to remove any debris deposited thus preventing corrosion and undesirable pressure drops.

These pigs are also utilized for commissioning and decommissioning of pipelines as well as to detect and measure the pipeline defects such as corrosion, wall defects and cracks.

This is achieved with the help of Pig traps which launches the pigs into the piping network from one side and receive it at the other end in a safe and controlled manner.

Role of Interlocks

The process of launching and receiving pigs can be a hazardous operation if performed out of sequence. Therefore a safety system is required that can control the process without any dependence on human judgement.

Mechanical Key Interlocks will ensure that the sequence of valves and end closure operations is always performed in a predefined, single and unchanging path. Although there can be variations in the sequence to be performed, the following scenarios are always kept in mind:

• Avoiding unintended pressurisation of the pig trap.
• The quick opening/closure can only be operable after the depressurisation of traps.
• It should not be possible to open mainline and kicker line valves when the quick opening closure is open.

Advantages of Alcatraz Interlocks for pig trap applications:

1. With the piping networks becoming more and more extensive, pig traps may need to be located in remote locations and hence can be subject to extreme weather conditions. Alcatraz Interlocks can operate successfully in a wide variety of extreme weather conditions from a desert environment laden with moisture and very fine dust to extreme cold conditions with temperatures as low as -50°C.

2. As pig traps are used intermittently for maintenance purposes, so there can be quite a long time in which interlocks are not operated at all. Our interlocks are designed to avoid ingress of dirt or contamination by environmental factors irrespective of whether the key is inserted or not with the help of an automatic closing dust cap and keys which encapsulate the lock portion when entered. This helps in avoiding any surprises when the Interlocks need to be operated.

3. Easy to operate with gloves.

4. Sometimes the space available for Interlocks on pig traps system is limited (e.g. In FPSO’s). Our Interlocks can be installed in the most convenient way possible (even upside down) without any effect on the key operation. This is with the help of the partial linear and rotational action of the key.

5. The hand wheels/drive tubes all have a parallel splined connection. This spreads operating forces, prevents any loosening of hand wheels (even in scenarios with excessive vibrations) and higher HSE standards.

Chemical Delivery and Diesel Fuel Delivery Interlock

Chemical and Fuel Delivery Interlocks are common place at water treatment facilities where the need to capture fuel or chemical spillage is essential to maintain the health of the environment.

Tanker deliveries at these plants facilitates the offloading of essential chemicals used in the water treatment process, or diesel fuel used to run generators and pumps.

The chemical or fuel transfer task is carried out in a designated area where any spillages run to the surface drains.

During normal operations these surface drains allow rain water to run away to the water course. But during fuel or chemical transfer, valves are turned to ensure any liquids entering the surface drain is diverted into capture tanks.

Fitting an interlock to the drain / tank divert valve, and also to the chemical or fuel delivery kiosk ensures that the transfer cannot commence until the valves are set to divert any spillages to the tank.

With the divert valve being located below ground, the valve interlock is mounted on a pedestal above ground, enabling it to be operated conveniently with minimum duress on the operator.

Machine Guard Interlocks

In all manufacturing industries and factories, automated processes provide efficiency to complete their designated task in the quickest possible time. These machines present all types of risks to the workforce.

For this reason, machinery is set behind fences and guards to keep the workers safe.

When the need arises to enter through the guarded area, a trapped key interlock system can ensure that machinery is switched off prior to opening guards and gates. It can ensure that the machinery remains isolated while workers are within the guarded area.

There are many considerations to take into account. A risk assessment with help in that task. For example:

• Some machinery can continue to move even after it’s been switched off. Inertia in motors and flywheels are a common cause of this.
• Tension in long conveyor systems can also cause unexpected movement of machinery.
• Hydraulic systems retain pressure which if released unexpectedly, can also cause movement of machine parts leading to injury or even fatal accidents.

A well researched risk assessment will identify these issues and enable a robust trapped key interlock system to be installed, safeguarding workers against these unseen hazards.

Tanker loading operations demand high concentration by workers to ensure the tanker vehicle is immobilized during chemical transfer, and traffic barriers and couplings are all safely connected or stored prior to opening and closing of valves.

Pumps can be incorporated into the interlock sequence to ensure transfer can only commence once all safety criteria have been met.

Tankers, including sea, rail and road vehicles, departing their loading bay prematurely can cause catastrophic spillage of chemicals. A trapped key interlock system is a robust system to ensure procedures are correctly followed.

Interlock hardware can incorporate:

• Valves
• Hose connections
• Overhead gantries
• Road barriers
• Pumps