Functional Safety
If you've never seen a workplace accident, consider yourself lucky
But don’t let that false sense of security compromise the safety of everyone around you.
In any industrial setting, safety isn't just a regulatory checkbox, it's a fundamental part of system design, operation, and maintenance. Whether you're developing a safety system from the ground up or troubleshooting an existing one, understanding why safety measures exist is critical to doing the job right.
Why Safety Matters Even Without Accidents
A common sentiment often heard in the field is, “We’ve never had an accident, so why do we need all this safety equipment?” This mindset, while seemingly practical, ignores the core principle of safety: prevention.
If you've never experienced an industrial accident, consider yourself fortunate and also consider that the absence of accidents may well be due to the very safety protocols in place. Accidents come at a high cost, not just in terms of damaged equipment or injured personnel, but also emotionally. A serious incident affects not just those directly involved, but the morale and well-being of the entire workforce.
The purpose of a safety system is to minimize the opportunities for harm by proactively identifying and eliminating potential failure points.
Safety Systems and Common Failures
Let’s consider a few types of safety systems and how failures within them can create unsafe conditions:
1. Traditional MCR (Master Control Relay) Systems
In a basic MCR setup, you may see safety inputs such as Emergency Off Pushbuttons (EOPs) connected in series. These trigger a light or contact relay to indicate system status. While this seems straightforward, a single-point failure (like a contact sticking or falling off) can render the system ineffective.
2. Non-Configurable vs. Configurable Safety Relays
Non-configurable relays are commonly used, often identified by their yellow or orange housings. These typically rely on dual-channel wiring two contacts per EOP and two output contactors. Configurable relays, on the other hand, offer flexibility and diagnostic features that help identify failures more precisely.
3. Importance of Redundancy
One of the easiest ways to reduce risk is to build in redundancy. For example, if a single normally-closed contact on an EOP fails, it can lead to a dangerous condition. By adding a second, parallel contact, you introduce a level of redundancy that dramatically reduces the risk of failure going unnoticed.
Even then, redundancy must be actively monitored. The system should detect when contacts don’t open and close together a sign that something may be mechanically or electrically wrong.
4. Mechanical Limitations and Misconceptions
Some EOPs require a twist to reset after being pressed. Many believe this action contributes to the system’s safety, but it's not foolproof. In emergency situations, operators may press the button incompletely, or the contact may not engage fully resulting in an unsafe condition where the machine could reactivate unexpectedly.
Thus, a separate reset mechanism is often integrated to ensure that a full stop and reset cycle has occurred as designed.
The Danger of Single-Point Failures
A “single-point failure” is any individual failure that can cause the entire safety system to malfunction. This could be:
A stuck or worn contact
A mechanical failure in the button housing
An unauthorized jumper wire
A poorly designed reset sequence
In modern safety systems, these risks are mitigated not just by redundancy, but also by diagnostic logic that checks whether all parts of the system moved in unison. For example, if two contacts on an EOP don’t operate together, the system will prevent the machine from restarting, even after the button is pulled back out. Only once both channels are repaired and verified can the machine safely resume operation.
Designing for safety isn't just about preventing OSHA violations or satisfying insurance requirements, it’s about protecting people and equipment from real-world hazards. As we advance with smarter, more connected systems like those seen in DLR-influenced industrial automation. The emphasis must remain on preventing failure before it happens, not reacting after the fact.
Investing in safety is investing in people and that’s a philosophy no workplace can afford to ignore.