Ventilation reliability

The units and ancillary equipment must be protected from mechanical damage and the effects of weather to ensure the reliable operation of an impressed current station. This is achieved by installing it in a weatherproof plastic housing (see Fig. 8-2). Sufficient ventilation must be provided to disperse heat. The ventilation holes should be protected with brass gauze to keep out animals. Transformer-rectifier units must be connected to a circuit that is continuously energized, especially if they are in a building where the current is turned off at night, e.g., gas stations that are not open for 24 h. 

Ensure the adequaey (in terms of quality, quantity and reliability) of serviees/utilities, e.g. steam, proeess/eooling water, eleetrieity, eompressed air, inert gas, fire suppression systems, ventilation. Stand-by or emergeney serviees may be required. Some general safety design eonsiderations are summarized in Table 12.11. 

Reliability of airflow measurements m assessing ventilation systems performance Cobalt - a review of properties, use and levels of exposure A review of respirable crystalline silica - Exposure and control... 

Define target levels for the ventilation system, such as reliability, energy consumption, investment, life cycle costs, etc. 

Define and get the customer s acceptance of the needs for ventilation system reliability, e.g., what is the allowed break-off time. 

The description of the physical characteristics of ventilation noise is based on more reliable knowledge than the description of the human effect. Misconceptions about the levels and frequency characteristics of ventilation noise are still common. This in turn has sometimes led to wrong suggestions about the measures that should be taken in order to eliminate the effects of a ventilation noise exposure. 

Ventilation components with small geometric detail Numerical modeling of diffusers with complex geometry is difficult. Therefore, it is more reliable to measure airflow around such devices at full scale. 

Nevertheless, in many cases, mean wind velocities can be assumed. In ventilation-system reliability studies, e.g., where minimum ventilation rates are to be determined, a calm situation with little wind must be assumed anyhow, and the need for accurate wind pressure coefficient data is not so obvious. 

The dewpoint hygrometer is claimed to be the most accurate instrument tor measuring air humidity. When properly calibrated, the inaccuracy can be 0.5% RH.- On the whole, the dewpoint hygrometer is a reliable lundamen-tal instrument suitable for many ventilation applications, but is more expen sive than other humidity instruments. 

Even when the time comes to make a purchasing decision, an energy-efficient motor purchase is not a certainty. Sometimes an energy-efficient motor will be the economically efficient choice at other times, not. The capital investment decision is based on the cost in relation to performance, efficiency and reliability. Moreover, the decision depends on the application and the amount of time the motor is in operation. It can be the major component of a product (drill or mixer), or a minor component (computer disk drive) it can be the major component cost of a product (fan), or it can be a minor component cost (stereo tape deck) it can run almost constantly (fan, pump, and machinery), or only a few minutes a day (vacuums and power tools). For example, contractors purchase circular saws almost solely based on performance and reliability. Time is money, and since the saw is operating only a few minutes a day and the contractor is often not responsible for the electricity costs to run the motor, energy efficiency is not a consideration performance and reliability are what matter most. On the other hand, an industrial user, who runs huge electric motors twenty-four hours a day to work pumps, machinery, and ventilation equipment, is very concerned tvitli energy efficiency as well as performance and reliability. 

While the air distribution must match the heat distribution, the position of extracts is not important. Direct return to air-handling units mounted around the room in numbers necessary for reliability is common practice. In the event of loss of one or more cooling modules a well-designed ventilated ceiling adds to reliability by distributing the reduced amount of air in the same proportions throughout the room. 

For enclosed areas, they can be considered adequately ventilated if they meet one of the following. Where artificial mechanisms are employed for ventilation assistance high reliability must be assured. 

Options. Traditional control options for overexposure are material substitution, process change, containment, enclosure, isolation, source reduction, ventilation, provide personal protection, change work practices, and improve housekeeping. A simple way of looking at selection of control options is to find the cheapest option that results in the desired amount of exposure reduction. It is not actually that simple, however, because the various options differ in ways other than cost and degree of control. Some of the other factors to consider in selection of control options are operability, reliability, and acceptability. 

Photo-acoustic Field Gas Monitor 1312 is a gas monitor based on PAS which is accurate, reliable and quantitatively stable. It can be used for on-line concentration monitoring of up to 5 components plus water vapor in gas mixtures. It can also be used to measure the ventilation rate by using tracer-gas and so on (INNOVA Air Tech., 1997). 

Sources of ignition must be kept away from these materials, and adequate, reliable ventilation and means of removing vapors must be provided in storage and processing areas. Their exists with the manufacturer of acrylic castings the situations of toxicity, flammability,... 

When used properly by trained personnel, employing adequate process controls, the LAP environment provides a reliable barrier to measurable airborne viable and non-viable, solid particulate contamination, which may defeat the aseptic process. LFCBs, BSCs, and heating, ventilation, and air conditioning (HVAC) installations are easily validated. These systems normally continue in operation with little or no variation in output quality for long periods of time, and are easily maintained and tested. 

These experimental results concur with maximum allowable concentration value of ozone of 0.1 p.p.m. for an 8-hour day, adopted by the American Conference of Governmental Industrial Hygienists in 1955 (1). However, it is very difficult to determine ozone reliably below 1 p.p.m. As the odor of ozone can be readily detected below 0.1 p.p.m. (1 ), the rule utilized in these laboratories is to maintain ventilation so that the odor of ozone cannot be perceived. 

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