Safety instrumentation categories

Safety integrity level (SIF) Discrete level (one out of a possible four SIL categories) used to specify the probability that a safety instrumented function will perform its required function under all operational states within a specified time. 

It should be noted that the above failure mode categories apply to an individual instrument and may not apply to the set of equipment that performs a safety instrumented function because the equipment set may contain redimdancy. It should be also made clear that the above listings are not intended to be comprehensive or representative of all component types. 

Problem A set of non-redundant (hardware fault tolerance = 0) safety equipment is used to perform a safety instrumented function in continuous demand mode. Diagnostic time is given as one second. The following failure rate data is obtained when adding the failure rates of the categories of all components ... 

Table XII/3.3.1 1 Relationship Between Safety Instrumentation System (SIS) and Category Classes ...

Chapter 5 is devoted to safety in offshore oil and gas industry. Some of the topics covered in this chapter are offshore industrial sector risk picture, offshore worker situation awareness concept, offshore industry accident reporting approach, and offshore industry accidents case studies. Chapter 6 is devoted to case studies of oil tanker spill-related accidents, oil tanker spill analysis, and oil spill causes. Chapter 7 presents various important aspects of human factors contribution to accidents in the oil and gas industry and fatalities in the industry. Some of the topics covered in this chapter are human factors that affect safety in general, categorization of accident-related human factors in the industrial sector, categories of human factors accident causation in the oil industry, and recommendations to reduce fatal oil and gas industry incidents. Chapter 8 is devoted to case studies of maintenance influence on major accidents in the oil and gas industry and safety-instrumented systems and their spurious activation in the oil and gas industry. 

Broadly speaking, safety instrumentation falls into two categories safety instmmented systems (SISs) and high integrity protection systems with its subset of high integrity pressure protection systems (HIPPSs) that are used to protect specifically against overpressure. 

Hence, it becomes possible to prevent electronic instrumentation from becoming a source of ignition in the plant areas if its temperature and stored energy levels can be limited by design, to values below the thresholds for the categories of gases on the plant. We know this from of protection as INTRINSIC SAFETY. This is a form of hazard prevention. It must not be confused with a safety instrumented system but it does feature in the list of risk reduction measures. 

Essentially the SIL table provides a class of safety integrity to meet a range of PFDavg values. Hence the performance level of safety instrumentation needed to meet the SIL is divided into a small number of categories or grades. 

One of the categories of inherent safety is simplification/error tolerance. What instrumentation could you add to the tank described in Problem 1-21 to eliminate problems ... 

Reactor Instrumentation categorizes Itself Into three basic classifications. Hie first division can be defined as Reactor Safety Circuit Instrumentation. Instruments In this classification provide Information on the status of the process by visual readout devices auid are connected directly Into the reactor safety circuits for automatic shutdown If preset limits are exceeded. They are responsible for maintaining the stemdards of reactor and nuclear safety at all times. The second category Is Reactor Procet... 

There are two categories of instrumentation equipment defined in lEC 61508 - Type A and Type B. A subsystem is classified as Type A "if, for the components required to achieve the safety function ... 

These monitors are located upstream of the safety relief valves on each pair of main steam lines. Detectors are mounted close to the process line to detect radioactivity due to a steam generator tube rupture. These monitors meet the requirements for Regulatory Guide 1.97 Category 2 instrumentation. 

These monitors cover areas containing equipment important to safety which may require personnel access after an accident. Locations of the monitors in the Nuclear Annex and Reactor Subsphere are determined based on post-accident shielding analysis and safety equipment access requirements. These monitors meet the requirements for Regulatory Guide 1.97 Category 3 instrumentation. 

The general scope of safety analysis for HWRs, covering the accident categories considered, safety barriers challenged, and the technical disciplines involved are summarized in Table 4.2. Failures in safety support systems (such as instrument air) are addressed in the PSA. 

Because of concerns over safety and reliability Categories 8 (medical devices) and 9 (monitoring and control instruments) were excluded from the RoHS Directive when it was originally adopted. However, ERA Technology has now been contracted by the European Commission to carry out a review of the Directive to determine whether these two categories can now be included within its scope. The results of this review will be used by the European Commission to prepare a proposal to the European Parliament and the Council which will act together to amend the Directive. 

The instrumentation and control systems important to safety fall into the following categories reactor protection systems, engineered safety features control systems, safe shutdovwi control systems and other information systems, control systems, and essential auxiliary systems important to safety. Appropriate surveillance procedures and setpoint methodology for instrumentation and control systems important to safety are required to ensure the system operability. 

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