Types of Engineering Controls

The most effective method of avoiding accidents is through intrinsic safety. For a piece of equipment to be intrinsically safesafety has been built into the design of the equipment and is not an add-on function. Intrinsic safety can be achieved by (1) eliminating the hazard entirely or (2) limiting the hazard to a level below which it can do no harm. Under either condition, no possible accident can result from the hazard in question. Hazard elimination 

If the hazard cannot be eliminated, then we can limit the level of the hazard so that no injury to workers or damage to equipment results. The energy available under any condition, even in a failure mode, should not be great enough to cause injury or death. Examples of methods to limit hazard levels include  

Fail-safe designs ensure that failures will leave the system unaffected or convert them to states in which no injury or damage will result. In most situations, this safeguard will result in the inactivation of the system. Fail-safe designs can be categorized into three types  

A fail-active design maintains an energized condition that keeps the system in a safe operating mode until (a) corrective and overriding action occurs or (b) activates an alternative system to eliminate the possibility of an accident 

A fail-active design might be a monitor system that activates a visual or audible indicator if a failure or adverse condition is detected in a critical operation. 

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There are many types of engineering controls (see Figure 11-1). Many ate expensive and complicated but are worth the installation and maintenance costs because they prevent catastrophic failures that can result in the loss of valuable equipment and human life. 

There are several types of engineering controls to limit dangerous exposures to radiation. Controls include limiting radiation emissions at the source, limiting time of exposure, extending the distance from a source, and shielding. Certain other controls will also help prevent dangerous exposures. 

The advent of the real time analyzer has simphfied the collection of octave band information and has decreased the amount of time required to obtain accurate data. Octave band data is useful not only in determining the best types of engineering controls, but also in providing enhanced selection of PPE. Understanding the noise lev-... 

Ventilation is one type of engineering control that is commonly used to protect employees from overexposure to solvents. The amount of ventilation and the t5rpe of ventilation system needed to protect workers depends on the duration of use, the amount of solvent, the size of the work area, and the solvent itself. 

Engine and vehicle technologies normally achieve their best emissions performance with high quality fuels. One property on which a great deal of attention has focussed is the sulphur content, partly because of the need to reduce PM and SO2 emissions and partly because fuel sulphur has an adverse effect on certain types of engine and exhaust after-treatment technology. In Europe the controls on fuel... 

The quantitative relationship between these product quality parameters and reactor operating conditions may be the least understood area of polymerization reaction engineering. Table VI summarizes both types of quality control measures. Because of the lack of on-line measurements for most of these product quality variables (molecular or otherwise), control of polymerization reactors is a special challenge. 

The most important reactions that occur in catalytic aftertreatment of emissions from an ethanol-fuelled diesel engine are listed in Table 2. For a catalyst involved in this type of pollution control one of the most important qualifications is the selectivity towards complete oxidation of ethanol. This is indicated by the formation of acetaldehyde, which is the major by-product formed. Over some of the catalysts other by-products such as acetic acid, diethyl ether, methane and ethylene are also formed, but to a much lower extent. The low-temperature... 

In this example, a gas is converted to a solid product rather than being emitted into the air. What implications might this have for engineering design Can you think of situations in which this type of pollution control scheme might cause problems ... 

Engineering and technological innovation remains the preferred type of hazard control. 

In addition, depending on the type of chemicals and type of exposure, the respiratory tract should also be protected against inhalation of airborne contaminants, which can be in the form of particles, vapors or gases. Also, hearing protectors should not be forgotten. The need to use hearing protectors starts when the noise level, in spite of engineering control measures, exceeds the national limit value, which is 90 or 85 dB in many countries (Korhonen 1997). 

To try to avoid gut feelings about safety. For example, many engineers believe that certain types of junction control are safer than others, based on personal preference or their design experience rather than accident data. 

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