Intrinsic safety intrinsically safe equipment

Ordinary electrical equipment cannot be installed in zone 0, even when it is flameproof protected. However, many chemical and oil-processing plants are entirely dependent upon instrumentation and data transmission for their safe operation. Therefore, very low-power instrumentation and data-transmission circuits can be used in special circumstances, but the equipment must be intrinsically safe, and used in conjunction with a safety barrier installed outside the hazardous area. Intrinsically safe equipment must be marked Ex ia or Ex s , specially certified for use in zone 0. 

The safety profile PROFlsafe defines the connection of intrinsically safe equipment (emergency stops, immaterial barriers, locks) to programmable controllers on PROFIBUS. The specific area of safety, most of whose constituents were previously connected by wire, may benefit from the multiple strengths of open communication on PROFIBUS. 

Intrinsic Safety. Static electrical concepts such as minimum ignition energy do not directly apply when assessing the safety of electrical circuits such as radios, flashlights and instmmentation. Intrinsically safe electrical equipment is usually available which has been subjected to fault analysis and testing. The equipment must be certified for the flammable atmosphere in which it will be used (NFPA 497). Refer to texts on Intrinsic Safety such as [63]. 

Processes can be divided into those that are intrinsically safe, and those for which the safety has to be engineered in. An intrinsically safe process is one in which safe operation is inherent in the nature of the process a process which causes no danger, or negligible danger, under all foreseeable circumstances (all possible deviations from the design operating conditions). The term inherently safe is often preferred to intrinsically safe, to avoid confusion with the narrower use of the term intrinsically safe as applied to electrical equipment (see Section 9.3.4). 

Intrinsic safety is based on the principal of restricting the electrical energy available in hazardous area circuits such that any sparks or hot surfaces that may occur as a result of electrical faults are too weak to cause an ignition. The useful power is about 1 watt, which is sufficient for most current instrumentation. It also provides a personnel safety factor since the voltages are low and it can allow field equipment to be maintained and calibrated "live" without the need for a gas free environment verification. Electrical components or equipment can be manufacturer as intrinsically safe and there readily usable in areas where combustible gases or vapors may be present. 

Low-level input sensors such as thermocouples, turbine meters, speed transmitters and a number of process analyzers complicate system selection. Signal conditioning equipment is required for low-level inputs to both the back-up system and computer data acquisition systems. If the system is to be installed as an intrinsically safe system, multiple grounding requirements conforming to intrinsic safety grounding must be referenced to the same safety ground to avoid multiple ground problems. 

The AMDR is equipped with some instruments that are used to detect the surrounding environment and transfer information back to the control centre. The explosion risk is very high when these instruments and equipments in service. So, we should use the intrinsically safe electrical equipment or other special design for the electrical equipment. In principle, the flame-proof equipment is not allowed to use in mine. But the intrinsically safe electrical equipment is very rarely at present, especially the power supply, motor and other key equipments. Therefore, the AMDR adopted the safety strategy of flame-proof after the redundant safety measures drawn up in the case of the basic principles of electric explosion-proof allowed. 

Intrinsic safety ia, ib, ic (note 2) EN 60079- 11 The equipment used in the explosion hazard zone only contains intrinsically safe circuits. A circuit is intrinsically safe if neither a spark nor a thermal effect can cause the ignition of a standard explosible atmosphere. The corresponding tests are carried out under standardized conditions, which comprise both normal operation and certain faulty states. Measurement and control devices, communication devices, sensors, actors... 

From the view of the managers, unsafe behavior of accidents will increase enterprise s safety management of pressure and affect the normal operation of the enterprise, further influence enterprise overall efficiency. At the same time, under pressure in the business, some managers will have to take the measures put into lower safety, but if the safety input is reduced, it will affect the equipment of intrinsically safe and safety training, this will cause unsafe behavior and the unsafe condition of the increase. It will lead to the increase of the accidents and form the vicious circle. 

On the contrary, if the managers take measures to reduce unsafe behavior and unsafe condition, it will lower accident rates. The managers can put the energy and resources into equipment of intrinsically safe and employee safety quality improvement. It will further enhance the enterprise the overall level of safety management. Thus, it can come to the managers of safety cognitive mode (see fig 3). 

By definition, an intrinsically safe circuit is one in which no spark or thermal effect is capable of causing ignition of a given explosive atmosphere. The intrinsic safety of the equipment in a hazardous area is assured by incorporating a Zener diode safety barrier into the control circuit such as that shown in Fig. 13.6. In normal operation, the voltage across a... 

Limiting the available volume of potable water and fire-fighting such that safety significant equipment cannot be affected makes for an intrinsically safe solution, as required by Engineering Key Principle 1. 

Establishing a procurement policy, which includes a pre-procurement risk assessment, will ensure that correct selection of plant and equipment for use in hazardous areas (where a flammable or explosive atmosphere has the potential to cause a fire or explosion) will minimise the risk relating to such equipment. BS EN 50020 2002, Electrical apparatus for potentially explosive atmospheres - Intrinsic safety i , specifies the construction and testing of intrinsically safe apparatus, intended for use in potentially explosive atmospheres and for associated apparatus, which is intended for connection to intrinsically safe circuits which enter such atmospheres. This document may well form the basis from which an organisation establishes its procurement policy for such equipment. 

Applying the barrier model can be complex, and in many cases safely integrity requirements are applied to equipment failure by a simpler means such as a risk classification scheme, as discussed in (Pierce 2005). There is no intrinsic problem with using this method provided that the function and performance requirements for the equipment in question are also shown to be correctly established and it is recognized that safety integrity requirements and function and performance re-qirirements are interdependent (Fowler et al. 2007). 

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