What is SIL safety PLC?
A Safety PLC is one of the 3 parts of a Safety Instrumented System (SIS). The SIS can also be referred to as the Safety Shutdown System. Stated simply, the SIS monitors the equipment or process and if an unacceptable condition or risk, or an unsafe condition occurs it reacts by the shutdown of the equipment or process.
How do you determine the required level of SIL?
Determine the hazard’s SIL level by calculating the target RRF of each SIF. Determine the SIF’s minimum RRF. This is the hazard’s frequency (without SIS) divided by the acceptable frequency. When the minimum RRF is known, the SIF’s target SIL level can be obtained from the SIL table.
What makes a safety PLC safe?
For a PLC to be considered a safety PLC, it must meet a set of rigorous international standards, specifically IEC 61508 – Functional Safety of Electrical/Electronic/Programmable Electronic Safety-related Systems. This standard covers design, design methods, and the testing of hardware and software.
What is SIL approval?
SIL certification is a tool to measure the amount of risk reduction provided by a Safety Instrumented Function. It assesses the tolerable/acceptable failure rate of an individual device. This is important when installing or retrofitting an instrument into a SIS.
What is SIL standard?
Safety integrity level (SIL) is defined as a relative levels of risk-reduction provided by a safety function, or to specify a target level of risk reduction. In simple terms, SIL is a measurement of performance required for a safety instrumented function (SIF).
What is the highest SIL rating?
SIL 4 has the highest level of safety – Level 1 the lowest. With the use of the Safe Failure Fraction and Probability of Failure on Demand values calculated during the product design and evaluation, SIL levels are determined using charts within the IEC 61508 standard.
What is the difference between safety relay and normal relay?
Usage. A safety relay is used for the combination of switches. Normal relay is used for linkage of contacts.
How does a safety relay work?
What Is a Safety Relay? Also called “All–or–Nothing Relays with Positively Driven Contacts”. Relays of this type have contacts that are mechanically connected together, such that if a normally open (NO) or make contact remains closed, a normally closed (NC) or break contact can not re–close.
Does SIL have to be the same for every safety function?
It is a common misconception that an entire system must have the same SIL level for each safety function. There are four discrete integrity levels associated with SIL: SIL 1, SIL 2, SIL 3, and SIL 4. The higher the SIL level, the higher the associated safety level, and the lower probability that a system will fail to perform properly.
What are SIL levels?
What Are SIL Levels? SIL is an acronym for “Safety Integrity Level” that comes from two voluntary standards used by plant owners/operators to quantify safety performance requirements for hazardous operations: As defined in the IEC standards, there are four SIL Levels (1-4).
How is a target SIL level assigned to a hazard?
For each hazard identified by the PHA and LOPA that requires an SIF, a target SIL level is assigned using the same methodology. Note that it is likely you will have various target SIL levels.
What is a SIL rating?
It is a very common misconception that individual products or components have SIL ratings. Rather, products and components are suitable for use within a given SIL environment but are not individually SIL rated. SIL levels apply to safety functions and safety systems (SIFs and SISs).