Safe Rated Equipment

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. 

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Available equip- Procure equipment that can be used in other ment determines processes (current or future) without operating the process chem- close to its operating envelope, istry selected., Provide equipment with comparable pressure Operating close to rating for the entire system the safe operating envelope of the batch sizes to equipment capabilities equipment and the relief capability. ... 

Equipment downstream of liquid outlet(s) can safely handle maximum gas rates that can be discharged through the liquid outlet(s), and vessel does not have an immersed heating element subject to excess temperature. Restrictions in the discharge line(s) may be used to limit the gas flow rate. 

When it comes to laboratory storage, it is safe to say that the space required is at least twice what a planner would estimate. Samples, reagents, and spare equipment will pile up at an alarming rate. To this should be added the fact that some items will have to be stored under controlled conditions and that valuable items will need to be kept in locked storage. Flammables, even in moderate amounts, need special storage. Since regulations vary from one area to another, this matter should be discussed with local fire department officials. 

In the explosives industry, precise control of temperature, mixing time, concentrations, heating, and cooling rates are maintained. Making these materials safely requires sophisticated equipment and technology to carry out the process even though the chemistry may appear simple. Under less than optimal conditions, some 2,3,5-trinitrotoluene, 3,5,6-trinitrotoluene, and 2,4,5-trinitrotoluene are produced, and they are much less stable than 2,4,6-TNT. A mixture of explosives is only as stable as its least stable... 

Simplify (simplification and error tolerance) Keep piping systems neat and visually easy to follow Design control panels that are easy to comprehend Design plants for easy and safe maintenance Pick equipment that requires less maintenance Pick equipment with low failure rates Add fire- and explosion-resistant barricades Separate systems and controls into blocks that are easy to comprehend and understand Label pipes for easy walking the line Label vessels and controls to enhance understanding... 

Availability. Both Underwriters Labatories and Factory Mutual Research publish yearly guides to electrical equipment which they have certified and continue to certify as being rated for use in hazardous environments. Many of the items contained in these guides are rated as intrinsically safe or as associated equipment for use with intrinsically safe equipment. Further, the amount of equipment available should increase each year as the demand increases for intrinsically safe electrical circuits. 

There are three main parameters tha determine the design of safe chemical processes (1) the potential energy of the chemicals involved, (2) the rates of their potential reactions and/or decompositions, and (3) the process equipment. This is illustrated as the triangle in Figure 1.1. 

Successful start-up of operations means that production is accomplished safely at planned rates and product is manufactured to the desired quality specifications. Experience shows that, in moving from small scale to commercial equipment, the following variables are important ... 

Post-installed bolts will be required at times for attachment of equipment which may be subjected to large accelerations during a blast. Expansion anchors should be avoided for most blast design applications unless the load levels are low. Typically "wedge" type anchors are qualified for dynamic loads although most of these ratings are for vibratory loads and are based on cyclic tests at low stress levels. These should only be used where ultimate loads are less than the rated capacity with a margin of safely. Epoxy anchors have shown excellent dynamic capacity and may be considered for critical applications. 

Quenching the vapour with cold air in the chamber may increase the rate of heat removal although excessive nucleation is likely and the product crystals will be very small. Condenser walls may be kept free of solid by using internal scrapers, brushes, and other devices, and all vapour lines in sublimation units should be of large diameter, be adequately insulated, and if necessary, be provided with supplementary heating to minimise blockage due to the buildup of sublimate. One of the main hazards of air-entrainment sublimation is the risk of explosion since many solids that are considered safe in their normal state can form explosive mixtures with air. All electrical equipment should therefore be flame-proof, and all parts of the plant should be efficiently earthed to avoid build-up of static electricity. 

The pressure vessel should be lined with Hastelloy-C, stainless steel, or other metal resistant to attack by hydrogen fluoride, because the latter substance is a by-product of the reaction. The pressure vessel employed should be safe for use at 500 atm. pressure and should be equipped with a rupture disk rated at 500 atm. If the equipment available is rated for use only at lower pressure, the size of the charge should be reduced appropriately. 

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