Instruments explosion protected

In classic intrinsically safe instrumentation multicore cables lead from the control room into the explosion protected system. Several sensors/actuators are wired to a terminal box and connected to the multicore cable. 

Above all, HART has succeeded in the field of process engineering, with feasibilities, e.g., to remotely change the meter range of an instrument or to interrogate diagnostic data. So, numerous products are available in an explosion protected design. A number of them are certified as intrinsically safe apparatus. 

The description of the different types of protection in Chapter 6 indicates that there are two very different ways to solve this problem - if an electrical transmission is required at all. One way is to use intrinsically safe circuits, the other one applies industrial equipment as usual, additionally explosion protected by an enclosure as appropriate, e.g. flameproof housings for smallsized devices. In the history of process instrumentation, the appearance of semiconductors and integrated circuits has drastically reduced the power consumption of field devices. So, intrinsically safe circuits dominate this field today. 

With the introduction of safety standards lEC 61508 and 61511 (for process industries), there is a defined need for proper implementation of safety systems embedded into the main system. The safety life cycle has various phases. Phases 1 and 2 have been discussed at length in previous chapters (Chapter VI and Chapter VII and to a certain extent in Chapter IX). In this part, detailed discussions have been presented to include Phases 3—7, that is, from safety-related systems (SRSs) to modifications. This has been done purposefully so that prior to looking at the detailed implementation part of the standard, readers need to have some knowledge of the safety instrumented system (SIS), safety integrity level (SIL), and their implementation in various instrumentation components. So, this part of the discussions in conjunction with previous chapters will complete the topic of lEC 61508/61511. Safety instrumentation cannot be complete without discussions on explosion protection. With reference to lEC 60079-(0,10,14,15,17, etc.) and NEC (497,499,70, etc.), electrical area, classification of plant, explosion protection, etc. also have been included as part of this chapter to make the system complete in all respects. In view of this, these are presented in two sections. Section 1 for lEC implementation and Section 2 for explosion protection. 

IS circuits IS in instmmentation and controls for hazardous areas is very important and a common means of explosion protection. Distribution of use of IS circuits among various types of instrumentation items is depicted in Fig. X/3.7-l based on data from... 

The two main methods of explosion hazard control are explosion prevention (e.g. preventing formation of explosible dust clouds, removing all possible ignition sources, creating an atmosphere that cannot support combustion) and explosion protection (e.g. venting, suppression, containment and/or isolation). Quite often it is difficult to guarantee explosion prevention (e.g. due to equipment/instrumentation failure and/or human error). Explosion protection usually is pursued to protect personnel and minimise plant damage. Despite the similarities with gas explosions, dust explosions can be quite different ... 

Prevention of fires is a form of hazard protection and the chances of avoiding ignition of fuels appear to be greater than is the case with flammable vapor clouds. Hence the elimination of sparking sources through explosion protection of electrical power equipment is a major protection measure. As noted before intrinsically safe instrumentation is another risk reduction measure. 

The control and subproducts for the instrumentation are governed by the general technical requirements for the other subproducts in the system. In addition, to fulfill all the general technical requirements, the encapsulation and protection of the environments in which the subproducts are used have to be considered, including danger of explosion, pollution, moisture, temperature, vibration, influence on heating and cooling, etc. See (Table 9.7). 

Arcing contacts in Division 2 areas must be installed in explosion-proof enclosures, be immersed in oil, be hermetically sealed, or be non-incendive. High-temperature devices must be installed in explosion-proof enclosures. Fuses must be enclosed in explosion-proof enclosures unless the fuses are preceded by an explosion-proof, hermetically sealed, or oil-immersed switch and the fuses are used for overcurrent protection of instrument circuits not subject to overloading in normal use. 

Temperature Control (Manual) (Automatic). Instruments Controls (Weather Protected) (Explosion ProoO Level Controls - To Be Pressure Gauges To Be Condenser Cooling Water ... 

When an explosive device is used to disperse radioactive, chemical, or biological materials, the treatment of casualties is more difficult because of the presence of contamination. In this situation, emergency responders could face a life-threatening situation unless appropriate precautions are taken. These precautions include using screening instruments (see Section 6.12) to assess hazard conditions before responding, then selecting the appropriate level of personal protective equipment (see Section 6.7) to provide protection from the hazard. 

Increased vigilance regarding security to protect against terrorist use of weapons of mass destruction, including especially explosive devices, as well as an increased interest in the comparison to the explosive detection capabilities of instrumental technologies, has led to increased scrutiny of canine explosive detection capabilities. 

Explosive Pipe Closure System. A fast, high-strength mechanism for closing off inaccessible pipes is explosively actuated. The system, devised to protect instrumentation mounted in pipes from flying debris during uunderground nu-... 

Protection against explosions is typically provided by explosion-venting, using panels or membranes which vent an incipient explosion before it can develop dangerous pressures (11,60). Protection from explosions can be provided by isolation, either by distance or barricades. Because of the destructive effects of explosions, improvement in explosion-prevention instrumentation, control systems, or overpressure protection should receive high priority. 

Development work in the pilot-plant production of the vinyl ether intermediate was performed on a Mettler Toledo ReactlR MP m. This instrument was the hrst generation of explosion-proof manufacturing technology available from Mettler Toledo. Setup requirements for the incorporation of the ReactlR monitoring system into the vinyl ether process in the pilot plant were minor. Installation of a fiber optics cable and protective conduit from the pilot-plant operations area to the control room, allowing communication between the acquisition computer (contained within the ReactlR MP ) and the monitoring station, was the most extensive mechanical modification. ... 

Sensitivity is not the issue since eleetronic noses like the zNose and traee deteetors like ion-mobility speetrometers (lonTrack IMS) have essentially equal speed and sensitivity to explosive compounds. Specificity is the issue and users should understand the different role each type of instrument ean undertake as part of an integrated seeurity, force protection, or general law enforeement sereening or investigative missions. 

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