When an emergency occurs, there is no need for an entire plant shutdown
Simply putting a plant “on hold” instead of shutting it off, restarting production faster while taking all safety precautions – this is possible with a network of fibre optics and Siemens fail-safe control.
In the pharmaceutical and chemical production, but also in the beverage, agricultural and cosmetics industry, the problem is known and feared. If e.g. a solvent is escaping and there is a risk of fire, the emergency stop button is pressed. The entire production process stops and programs and recipes are cancelled. Even areas that are not affected at all by the danger does no longer work. Finding a reliable solution that would only stop the endangered area and the directly affected production facilities would be a great relief. This means that the production would get back up faster after the elimination of the hazard. Less loss of processed recipes, less production downtime and more efficiency at full safety. Why should it not work? Emergency stop really boosts innovation.
A new dimension in plant-wide safety
“On hold“ instead of emergency stop became possible through the combination of several innovative ideas. First of all, there is the network of glass fibres instead of copper. Glass fibre is more trouble-free, transfers data over long distances without sacrificing quality and speed and is simply faster. Second, the fail-safe control of Siemens, e.g. S7-416F, which – and this is new – can work with any transmission medium, whether copper or glass fibre.
And third, the automation specialist, of course, who brings everything together to a plant-wide security system by means of a risk assessment. A security system that, at the same time, puts units / subsystems on hold in a safety-related manner without completely turning them off. In addition, not affected production areas continue to run. This has the effect of minimizing production interruption and enabling production to be resumed as quickly as possible.
More safety at the speed of light
When networking large production facilities, glass fibre networks are essential. Only the fibre optic cables transmit the data over long distances trouble-free and fast with e.g. 1 Gbit / s. Even with a network of 1,200 m in length, as our case study presents, the “On Hold” in an emergency case comes into effect immediately. In addition, outdoor installation is no longer a problem, because glass fibre is resistant to electromagnetic interferences, e.g. Thunderstorm.
The glass fibre network combined with the fail-safe Siemens S7-416F controller is unbeatably fast and reliable in the event of an emergency “On hold“. In particular, the various commands that have to be executed in the event of an emergency “On hold“ are sent quickly and correctly to the appropriate actuators and production units in software-controlled mode: A hold for the units affected by the incident, and thus pumps “On hold“ and valves closed. At the same time, not affected units proceed. Such a production system “On hold“ can be restarted much faster and easier, since no programs and recipes have been aborted.
Emergency stop or “On Hold” – that’s not the question here
Let’s take a practical example: A manufacturer of pharmaceutical-optic devices has networked all its production from the tank farm via several production facilities to waste disposal with a fibre optic ring made of glass. All production subsystems can be monitored and controlled from several operating stations. Several Siemens switches and a redundancy manager ensure that the data in the ring always stays in the flow, no matter in which direction. Thanks to the fail-safe Siemens S7-416F control system, the signal packets are transmitted to the Remote IO (RIO) stations and controllers of the package in the subsystems or production plants. This ensures error-free and reliable transmission of all safety-relevant data. If a fault occurs in one area of this production cycle, this is reported immediately to all 7 operating stations. The emergency “On hold“ button activates the emergency “On hold“ system: the hazardous area is brought to a safe “On hold“ state. The remaining areas continue to work.
If solvents are used in the production process, special requirements for health and safety protection must be taken into account. The emergency “On Hold” system fully meets these requirements. With SIL1 and SIL2, signals for emergency “On Hold”, gas warning and fire protection can be integrated in the light wave network.
The factory has several separate production sectors. In case of a solvent leak, there is an acute fire hazard. Instead of triggering an emergency stop with hardware-assisted shutdown (PL) of the entire production, an emergency “On Hold” with software-aided stop (SIL) of the affected production area is triggered. At the same time, the solvent pumps are already stopped in the day-tank farm and the valves are closed. The day tank container itself is not affected by this incident. The stirrer continues to run and keeps the solvent homogeneous. The solvent discharge is only in emergency “On Hold”, in order not to supply the disturbed production sector. Once the damage has been repaired, production can be resumed very quickly.
The waste liquid cannot be picked up in time. The result: the waste tanks are full. A sensor in the upstream buffer tank farm determines that the waste liquid cannot be forwarded. The sensor starts the safety-oriented emergency “On Hold” system and places the day tank container in emergency “On Hold”. The production is also set “On Hold” – not shut off, whereby the stirrer in the day tank continues to run. Once the waste storage tank is emptied, the emergency “On Hold” will be acknowledged by the operator and the entire production will be resumed. In the GMP environment, this situation is documented in the batch record.
Competitive advantage thanks to emergency “On Hold”.
Every loss of production is involved with great costs. Hence, every company is interested in stopping production as rarely as necessary and as short as possible. In case of danger, there was no choice so far. With emergency stop, the entire production process is shut off, nothing runs anymore. All programs and recipes are aborted. Restarting production always involves a lot of effort, time and work, not to mention the lost raw materials.
Emergency “On Hold” does not simply shut off but stops intelligently. And only what really needs to be stopped for security reasons. Everything else can proceed with the result that the plant can produce faster, because only parts have to be rebooted. Emergency “On Hold” not only guarantees safety in the production process, it also offers the company a decisive competitive advantage.