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An end users guide to select safety devices compliant with IEC 61508 / 61511
1. Introduction
Safety Instrumented Systems (SIS) play a significant role within the process industry. They reduce the likelihood of events causing harm to personnel, environment and assets by either preventing (PSD, ESD) or mitigating further escalation (F&G, Fire water control). IEC 61508 and IEC 61511 are international standards on best practices for the functional safety of devices used within the SIS. These standards are world wide considered good engineering practices and some countries incorporate them directly into their safety cases. For those instances it indeed has the force of law. Hence, compliance with the standards is seen as important from an end user perspective as it helps them to demonstrate ‘due diligence’ for other mandatory safe operating legislation such as Health and Safety at Work Act 1974, Management of Health and Safety at Work regs, 1999 and Control of Major Accident Hazards Regulation, 1999, see Figure below.
Read more...Dr. Michel Houtermans interviews Richard Harvey from Rotork
IFS: Rotork is well known around the world for their actuators, but can you tell us what kind of functional safety products Rotork has to offer today.
Richard Harvey: Rotork has a quite large array of products for use in the functional safety and SIL industry. Ranging from pneumatic, hydraulic, electro-hydraulic , electric actuators and also partial stroke testing systems. In the pneumatic field we range from small compact actuators up to very large actuators capable of 500’000 Newton Meters, and we have the same range in hydraulics as well. In our electro-hydraulic actuators, this gives us an equivalent of an electric actuator with a fail safe action, and again these are capable of up to 500’000 Newton Meters. To augment that we also have an electric actuator in the IQ range, which is actually certified suitable for use for SIL 2. And then to complete our range we now have partial stroke testing systems that work on all of our fluid powered based actuators.
IFS: The valves, in my view, are the most critical part of the safety function, because if you really, really look at it, in the end, this is the only part or component of the safety function that really, really needs to work. If we are now an end user, what kind of options do I have to get a really safe operating valve?
Read more...1. Introduction
Without exception, all electrical and electronic technologies emit electromagnetic (EM) energies into their environment. They – and the software or firmware that runs on them – are also without exception susceptible to suffering errors or malfunctions due to interference from EM energies, known as electromagnetic interference (EMI).
Electromagnetic compatibility (EMC) is the scientific/engineering discipline of ensuring that electrical and/or electronic technologies do not emit levels of EM energies that cause excessive EMI. It is also concerned with ensuring that they do not suffer untoward EMI during operation.
The conventional approach to EMC, developed over the last few decades, applies a fixed set of simple tests to new devices, products, equipment, systems or installations. These tests are usually performed in an “EMC test laboratory”, but sometimes on-site (in-situ), and they ignore all considerations of their design, and whether they are likely to maintain their EM characteristics over their anticipated lifetimes.
Read more...1. Introduction
There are two safety standards in the process industry, IEC 61508 [01] and IEC 61511 [02] which are used by hardware and software manufacturer, system integrator and end-user. Both standards deal with hazard and risk analysis and offer different methods to perform it. In the process industry, the HAZOP study has become preferred method to do hazard and risk analysis.
The HAZOP study background goes back early sixties of last century: the basis of HAZOP (Hazard and Operability) study was laid by ICI in 1963 and it was based on a so-called “critical examination” technique. The first guide for HAZOP was published by ICI and Chemical Industry Association in 1977 with the title “A guide to Hazard and Operability Studies” [04]. One of first main books was “HAZOP and HAZAN – Identifying and Assessing Industrial Hazards” by Institution of Chemical Engineering [05]. In US, the CCPS published a guideline in 1985 [38]. In UK, HSE published a good guideline about the HAZOP procedures for computer controlled plants in 1991 [07]. In 1991, the first paper about the HAZOP study of a Plant using DCS system was published [19]. Recently Foster Wheeler Energy [28] and the Safety Line Institute published guidelines about HAZOP [31].
Read more...Introduction on HIPPS
Engineering contractors are designing the plants, which are being build everywhere in the world. The latest version of the API Standard 521 [1] on pressure relieving and depressurization systems allows the use of HIPS (High-Integrity Protection System), which is discussed in detail in Annex E of the standard. It mentions the five principal uses of the HIPS:
- to eliminate a particular overpressure scenario from the design basis;
- to eliminate the need for a particular relief device;
- to provide system overpressure protection where a relief device is ineffective;
- to reduce the probability that several relief devices will have to operate simultaneously, thereby allowing for a reduction in the size of the disposal system;
- to reduce the demand rate on a relief device consequently reducing the risk
The term HIPS might be confusing, because it can be applied to any instrumented safety function, which has a certain Safety Integrity Level (SIL). Table 1 below shows the relation between a SIL number and the associated risk reduction factor.
Read more...The three decades-old problem of sudden unintended acceleration – that only occurs in cars fitted with automatic gearboxes and electronic systems directly controlling their throttles – has led us to write this letter. It explains why we believe that Government Regulators must now mandate the use of functional safety techniques in the automotive industry, based on the approach used in all other safety-related industries i.e. independent safety assessment to peer reviewed public functional safety standards.
Unlike other industries that use electronics to control safety-critical functions, the automobile industry does not employ peer-reviewed public functional safety standards, or independent safety assessors to verify conformance to such standards. Presently we are expected to simply trust whatever automakers assert about the safety of their products!
Read more...