Intrinsically safe operation

By using micro-scale equipment, the inventory can be greatly reduced, leading to an intrinsically safe operation. In addition, the gases can be mixed in a characteristic time lower than the induction time of the reaction. For example, in a first approximation, safe mixing of hydrogen and oxygen will occur at characteristic distances below 100 pm [22],... 

Displacer units are tolerant of specific gravity shifts within their range, require no power to operate, are intrinsically safe, and can be easily field cahbrated. A single displacer unit can control up to three alarm set points or up to three pumps with different spans. They can be caHbrated for set points or pump spans from 0.15—30 m from the top of the vessel mounting. 

Intrinsically safe Instruments that can be safely operated in an explosive or corrosive atmosphere. 

Benson and Ponton propose, based on this analysis, the concept of distributed manufacturing [139, 145], which will be referred to in detail in Volume 2 of this book series. Basically, they refer to small, transportable plants which are fed with reactants over the fence , hence using only non-hazardous, generally available materials by normal piping or standard transport. If an aggressive chemical is needed, it has to be made from environmentally friendly base materials as an intermediate on-site. Needless to say, effluents have to be completely harmless, plant operation has to be intrinsically safe, and the plant should be clean and quiet. 

Later, much more detailed predictions of safe operation in micro reactors in the explosive regime with the example of the hydrogen/oxygen reaction could be given [9,82,117,118], It was predicted that micro-channel processing under given conditions can be considered as intrinsically safe. 

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). 

In 1936, the first certificate was issued in Great Britain for an intrinsically safe electrical device which was not designed for application in mining operations. 

Until the 1950 s, the use of intrinsically safe electrical circuits had little application in other than just battery operated signaling devices. At this time due to advances in technology and an increase in the use of electrical equipment in hazardous locations, a new world-wide interest developed in the application of intrinsically safe electrical circuits beyond what had been its traditional role. 

The qualification being that it must fail safe not only in its normal mode of operation, but, also, under specific modes of failure. Therefore, it is not enough to state that the circuit is of low voltage, and because of this is intrinsically safe. This is only half of the requirement. To qualify as intrinsically safe, the circuit must also fail in such a way as to be incapable of causing ignition, and further, it must be either tested or analyzed according to prescribe methods. 

Fourthly, intrinsically safe electrical circuits are the easiest to maintain. Since intrinsically safe circuits by their nature are incapable of causing ignition, they can be maintained without regard to shutting down operations, nor are hot permits required, or is lengthly disassembly, assembly and recertification of added protection required. 

In one application, the same programmable controllor coordinating the actions of the machine is also providing control over an intrinsically safe robotic arm which loads and unloads the heavy projectiles being processed. In this way, the maximum protection is afforded not only to the operator, but also to the facility. 

The rules for intrinsically safe batch and semi-batch reactor operations are extensively discussed by Steensma [175] and Steinbach [177,178]. 

Suction-lift pumps are pneumatically operated and thus are intrinsically safe. 

Use intrinsically-safe and redundant safety control designs when using hydrogen. Intrinsically-safe and redundant control systems help to minimize operator mistakes, such as venting, door opening, air releasing, and backup safeties in the event of a hardware failure. 

Figure 8.8 Conceptual model of operation of a catalytic diffuser for intrinsically safe direct synthesis of H202- (Adapted from [71, 72]).

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