Application Overview – Brick Plant Pneumatic & Hydraulic Safety

Fluidsentry Pty Ltd monitored pneumatic & hydraulic safety valves have recently become key components in the safety upgrade of an ageing J.C Smale brick palletising line.

A purpose built valve bench fitted with a combination of Fluidsentry monitored safety valve systems was integrated with the brick palletising line, providing a fully redundant interface between the fluid power operation & the electrical safety circuits monitoring the emergency stops, guarding & associated interlocking devices. The Fluidsentry dual monitored safety valves prevent single faults within the fluid power safety system from leading to the loss of the safety function. Correct monitoring ensures single fault detection & prevents further operation of the secondary or redundant valve until the fault is corrected.

Pneumatic & hydraulic loads can be just as dangerous as electrically driven loads, so why should they have any less safety integrity?

When it comes to safeguarding machinery, many designers of safety systems do not look past electrical control, leaving pneumatic & hydraulic driven loads with only electrical safety integrity.

If an operator were exposed to a fault in the fluid power circuit of a brick palletising line, it could result in a serious injury, or even a potential fatality. The risk assessment process considers severity of injury, frequency of exposure & possibility of avoidance. When applying these factors to Appendix F of AS4024.1 safeguarding of machinery a risk category is derived. Five risk categories are considered – B,1,2,3 & 4. Category 4 being for the highest level of risk & highest level of safety. Our clients risk assessment indicated most hazards within the brick palletising line to be no lower than category 3. Several hazards were found to be category 4 risks.

A safety system, which isolates only the electrical solenoid of a non-monitored valve, may typically at best only meet category 1. According to AS4024.1 table 10.3 - categories of safety related parts of control systems, category 1 allows the loss of the safety function when a fault occurs without a requirement for detection. For example, if a valve spool fails to return to its home position, even by just 1mm, it can allow slow pressurisation of a fluid power system. Without high integrity monitoring, the fault may not be detected, and a serious accident could be the unfortunate result.

Companies invest many thousands of dollars protecting their employees from dangerous machinery. Many systems are designed with the goal of meeting single fault & detection requirements of categories 2, 3 & 4. Designers of safety systems should not only assess the dangers of fluid power loads. They also need to carefully consider all potential failure modes of their fluid power circuits, to ensure risk category compliance. Without consideration of the failure modes & installation of compliant fluid power control methods, the resulting safety system could comprise of high integrity interlocking & monitoring systems that provide very little to no fluid power safety. All Fluidsentry products undergo a complete F.M.E.A (Failure modes & effects analysis) in conjunction with third party conformity as part of our product ‘CE’ certification.

With the inclusion of Fluidsentry monitored valves our client was able to produce a safety system where both the electrical and fluid power systems met their risk category requirements. What they achieved is a practicable & complete solution for the safety related parts of their machine control system. They are now protecting operators from not only the electrically driven loads, but also from the hydraulic & pneumatic hazards within the dangerous area.

To learn more about how we can assist you with your fluid power safety applications, please contact our technical sales staff.