Stedenbaan 6, 5121 DP Rijen
The Netherlands

Customer: Air Liquide Singapore Pte Ltd
Site: Soitec Microelectronic Pte Ltd

Humans make mistakes; these can initially be small but can quickly turn catastrophic in the correct circumstances. “As the known proverb states, the butterfly effect in flapping its small wings can lead to natural disasters in far-off lands.” Meaning a simple small error at work, can have far-reaching consequences.

We are Realtec, the Alcatraz Interlocks partner based in Singapore. We support a wide selection of end-users within the SEA region with process safety and support services. One of our clients is Air Liquide, a supplier of cryogenic gases to a Semiconductor Plant in Singapore. The gases are used in manufacturing and testing of processes or removing excess heat from them. Any breakdown in the supply of these Cryogenic gases to the operational plant may cause a serious disruption, or even a possible shutdown.

Air Liquide interlock case study

To prevent this, standby tanks of Cryogenic gases are located onsite, and will be used if or when any disruption occurs to the supply chain, the host valves used to control the switch over from these different tanks are critical pieces of equipment, and their operational status needs to be clear.

The correct process method of switching over the supply of cryogenic gases from the various tanks is critical, any oversight made during this process, will cause further disruption of the supplied cryogenic gases into the Plant.

Traditional method

Host cryogenic valves can often be seen simply padlocked, using a traditional chain and padlock method. This simply prevents any unauthorised operation. A tag plate is then hanged from the valve to indicate its opened or closed status.

During the switching over procedure, an authorised member of staff, shall collect the padlock key from its designated cabinet, and proceed to the valves. They will conduct the procedure of switching over the supply of cryogenic gases from one tank to the other, before the gas supply is fully depleted from the current operational tank.

In this operation, the switching over procedure requires both cryogenic gas supply valves to be fully opened before you close the valve from the tank you wish to take offline. This is so the facility has a continuous supply of cryogenic gases, preventing again any trips within the plant.

However, switching over as written above can come with oversights and incidents, as there is no guide built in to support the operator.

HSE process review

Air Liquide wanted to further remove any possible chance of a switch over issue from happening, so a process review was conducted. They simulated a situation where a host valve supplying the cryogenic gases was closed, prior to the standby tank isolation valve being opened. What would be the consequences from this simple human error? The findings were, any disruption to the supply of cryogenic gases to the plant, would in turn cause the facility to trip and a minor shutdown lasting some hours would occur.

The secondary effect from this temporary shutdown would naturally be a loss in both man hours and production loss, both of which have a cost impact to the facility, and its supply chain.

Alcatraz Interlock Solution

To remove the chance of this oversight from ever happening, an Alcatraz interlock system was proposed and installed. Alcatraz products are mechanical mechanisms used to eliminate these errors, by effectively making it impossible to make this oversight in the process. They eliminate any human error by simply taking the clients written procedure and embedding these steps into the mechanical interlock. This then guides the operator via the correct steps through a predetermined sequence by a means of a mechanically coded key transfer.  

The interlock itself shall give a visual indication to the operator of each valves position current stance, however for more support, each interlock and operational key used within the host application comes tagged, and upon each tag plate it informs the operator again the current and next step to be taken.

This is an extra benefit, especially as valves in cryogenic services can quickly be encased in ice. Making it difficult to visually see the current position of the host globe valve. However, as the interlock is out of any direct exposure to the ice build up in this case, plus there is a clear indication upon the interlock housing, so the operator is always aware of the valve position.

Open key free, Valve locked open
Closed Key Free, Valve Locked Closed

According to HSE, human failure can be active or latent in general terminology.

Alcatraz Interlocking Systems main task is to eliminate these human failures regardless of whether it is active or latent, while also creating a safer industrial environment, thus protecting infrastructure and assets.

With the installation of an Alcatraz Interlock System, we do not just minimise the risk, we ELIMINATE