Pneumatic Safety Components and Where to Apply Them
With the introduction of automated systems, building machines has become even more complex. This forced designers to devote more time to implementing newer safety standards. A good example of this is the revision of ISO 13849 in 2006, which meant that all machine builders now had to consider safety-rated components as part of their design process.
One particular aspect that must be taken into account is the safety of pneumatic systems. These systems are used extensively in many different industries, so it’s crucial to ensure that they are designed and built with safety in mind.
There are a few key components that should be included in any pneumatic system to ensure its safety. In this article, we’ll go over five of them.
Five Key Safety Functions in a Pneumatic System
1. Protection against unplanned machine start-ups.
One of the critical safety functions that must be present in any pneumatic or automated system is protection against machines turning on accidentally. This can be a dangerous situation because if a machine is turned off and then turned back on without proper safety procedures, it could cause serious injuries to anyone in the vicinity.
There are a few ways to achieve this, but one of the most common is using safety valves and switches.
These valves are designed to block the flow of air to the actuators, which prevents the machine from starting up. On the other hand, the switches are used to detect when there’s a loss of air pressure. This is usually an indication that something has gone wrong with the system, and the switches will then shut off the power to the machine.
Some machines have built-in electronics whose specific function is to prevent unplanned start-ups automatically. However, there are still products that require a safety PLC or an external safe relay to perform the same functions and comply with minimum safety certifications.
2. Exhaust or air pressure dump protection.
An exhaust or air pressure dump is a safety feature used to release pressure from the system in an emergency. This is important because if the pressure builds up too much, it could cause the system to fail, leading to serious injuries.
Most dumping and air pressure exhausting often occur simultaneously as an unexpected machine start-up. That’s why modern safety components generally combine the two functions.
There are two primary ways to get protected from this issue: using an exhaust valve and utilizing a dump valve.
The exhaust valve releases the pressure gradually, which prevents the system from failing abruptly. On the other hand, the dump valve is used to release the pressure all at once.
Machines based on newer technologies are starting to incorporate position sensors and soft-start valves to manage unexpected start-ups and pressure dumps.
3. Holding, blocking, and stopping.
The ability to stop, block, and stop operation equipment is another crucial safety function that pneumatic systems need. This is important because if something goes wrong with the machine, it needs to be able to be stopped quickly to prevent further damage or injury.
To do this, most pneumatic systems use various valves, such as check valves, pressure relief valves, and solenoid valves.
- Check valves are used to prevent flow in one direction. The are normally used for holding actuators in place at the loss of system pressure.
- Pressure relief valves are used to release pressure if it gets too high, which prevents the system from failing.
- Solenoid valves are used to control the flow of air, which allows the system to be turned on and off as needed.
A mechanical brake or lock may have to be installed on the cylinder’s piston rod in some complex applications. This is usually done in applications where there’s a need for high holding forces or where the machine needs to be able to stop quickly.
Additionally, some modern machines have additional safety components capable of monitoring the position of the equipment or its components. This allows the system to know when something is out of place and react accordingly.
4. Reversing cylinder movement.
In some cases, it’s necessary to be able to reverse the direction of a machine’s moving parts. This is usually done for safety reasons, such as if something is blocking the machine’s path. If ignored, this could cause the machine to fail, leading to serious injury to anyone within the machine’s vicinity.
The most common way to achieve this is by using a reversing valve. This valve is used to change the direction of the airflow, which then changes the direction of the equipment.
However, some complex applications may require a proportional valve, which allows for more precise control over the airflow. This is important because it allows the operator to slowly change the direction of the equipment, which is often necessary for delicate situations.
Spring-return solenoid valves can also accomplish this safety function. These valves are used to change the airflow direction, but they’re also able to return to their original position when the power is turned off.
5. Reducing speed.
Another safety function that’s often necessary is the ability to reduce the speed of the equipment. This is a vital safety function because it allows the operator to control the machine if something goes wrong. For example, if a piece of equipment is moving too fast and is in danger of hitting something, the operator can use a speed-reducing valve to slow it down.
Two primary valves are used for this purpose: pressure-reducing valves and flow-control valves.
- Pressure-reducing valves are used to reduce the air pressure that’s flowing into the system. This then reduces the speed of the equipment.
- Flow-control valves are used to regulate the amount of air that’s flowing into the system. This also reduces the speed of the equipment, but it’s more precise than using a pressure-reducing valve.
In some cases, both types of valves may be used to achieve the desired result. It’s also worth noting that some machines have built-in speed-reducing devices, such as a pulley system.
Take These Safety Components Seriously
Safety features are important for any machine, but they’re especially vital for pneumatic systems. This is because pneumatic systems are often used in hazardous environments and typically have moving parts.
It’s important to choose the right safety features for your application and ensure that they’re properly installed. Taking these functionalities seriously can lead to a safer and more efficient working environment.
If you have any questions about pneumatic safety or need help choosing the right safety components for your automated system, contact an expert at John Henry Foster. We are a leading provider of reliable pneumatic actuators and our team would be happy to answer your inquiries.