Hazards, chemical mechanical

Process Hazard Analysis (PHA) (Dowell, 1994, pp. 30-34.) The OSHA rule for Process Safety Management (PSM) of Highly Toxic Hazardous Chemicals, 29 CFR 1910.119, part (e), reqmres an initial PHA and an update every five years for processes that handle listed chemicals or contain over 10,000 lb (4356 kg) of flammable material. The PHA must be done by a team, must include employees such as operators and mechanics, and must have at least one person skilled in the methodology employed. Suggested methodologies from Process Safety Management are listed in Table 26-1. 

Equipment used to process, store, or handle highly hazardous chemicals must be designed constructed, installed and maintained to minimize the risk of release. A systematic, scheduled, test and maintenance program is preferred over "breakdown" maintenance " that could compromise safety. Elements of a mechanical integrity program include 1) identification and categorization of equipment and instrumentation, 2) documentation of manufacturer data on mean time to failure, 3 ) test and inspection frequencies, 4) maintenance procedures, 5) training of maintenance personnel, 6) test criteria, and 7) documentation of test and inspection results. 

An old pipeline, no longer used, was marked with chalk at the point at which it was to be cut. Before the mechanic could start work, heavy rain washed off the chalk mark. The mechanic "remembered" where the chalk mark had been and he was found cutting his way with a hacksaw through a line containing a hazardous chemical. 

Begun in 1944 with DDT and in 1947 with parathion, the present report includes analytical data secured from certain chemical, mechanical, and solvent actions on apples, pears, lemons, and oranges. In the absence of established tolerances for these two insecticidal materials, it is hardly possible to interpret the significance of many of these data with respect to consumer hazard. 

The mechanisms of each hazardous chemical s toxic effects differ and depend on many factors. The majority of substances take effects... 

Accident Mechanism The series of events which constitute the course of events culminating in the release of hazardous chemicals outside of their nomial containment. 

CHETAH calculations for energy/hazard of an hypothetical decomposition reaction to carbon, water and methane are reported [14]. An experimental study of deflagration and detonation aimed at understanding the chemical mechanisms has been reported [16]. 

As illustrated in the previous chapter, the human body can be exposed to a variety of toxicants that may be present in various environmental media such as air, soil, water, or food. However, just simply being exposed to these hazardous chemicals does not necessarily translate into a toxicological response. The mammalian body has several inherent defense mechanisms and membrane barriers that tend to prevent the entry or absorption and distribution of these toxicants once an exposure event has occurred. However, if the toxicant is readily absorbed into the body, there are still other anatomical and physiological barriers that may prevent distribution to the target tissue to elicit a toxic response. As the toxicological response is often related to the exposed dose, interactions between the toxicant and the body s barriers and defense mechanisms will have an effect on toxicant movement in the body, and ultimately modulate the rate and extent of toxicant absorption and distribution to the target tissue. 

Pre-employment instruction and pre-employment physical examinations are of critical importance in most work situations involving hazardous chemicals. The former should make clear the hazards involved, the need to avoid exposure under normal working conditions, and the mechanisms by which exposure is limited. Furthermore employees should understand how and when to contain spills and how and when to evacuate the area around the spill. Locations and use of emergency equipment, showers, eye washes, and so on, should also be given, and the most important procedures should be posted in the work area. 

Water and steam are nearly always present in most chemical processes. Their physical properties are generally well understood. Process perils are sometimes related to the infamous deeds of water and steam. The thrust of OSHAs Process Safety Management Law of 1992 focused on the processes that handled a list of 140 highly hazardous chemicals as well as processes that contained an over 10,000 pounds (4,540 kg) of flammable liquids or gases. Even after those chemicals are handled with higher levels of mechanical integrity and additional scrutiny, we will still need to keep our eye on water and its sometimes evil twin, steam. 

Fortunately, the lid was restrained by a short length of stout chain and did not rocket away. A loud report and a swish was heard as the compressed air was harmlessly released. If this unorthodox repair had been performed on a system containing a hazardous chemical, surely there would have been a lot more unwelcome problems. Good mechanical integrity training and adherence to well-written repair procedures can help prevent this type of predicament. 

Lood should be stored in cabinets or refrigerators designated for such use only. Mechanical pipetting devices should be used and mouth pipetting prohibited. All hazardous chemicals should be used in a chemical fume hood. 

Industrial and mining settings should require ear protection (plugs or muffs) for noise above a certain decibel level, hard hats for head protection, and steel-toed shoes for foot protection. A safety harness should be worn when sampling from heights. A full protective suit should be worn when in extreme heat or cold or near hazardous chemicals. Check to see whether mechanical equipment must be shut down to sample safely. Eye or face protection should be worn if hot gases may be released to the atmosphere. In some circumstances, weather may be a factor. In the field, local terrain may require special gear. 

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