Ventilation total

Drip- proof Force Ventilated Totally-Enclosed Inert Gas or Air Filled ... 

Dust from carbon black Master batches Local exhaust ventilation Totally enclosed systems Not by careful handling alone... 

Totally enclosed motors offer the greatest protection against moisture, corrosive vapors, dust, and dirt. Totally enclosed fan-cooled (TEFC) motors are the obvious choice rather than weather-protected below 186.5 kW (250 hp). Their internal and external ventilating air are kept separate external air never gets inside except for the small amount that enters by breathing. 

TEFC motors have both an internal fan for circiilating air within the motor and an external fan for forcing the air through or over the motor frame or heat exchanger. Small motors [approximately 2.238 kW (3 hp) and below] do not require ventilating fans these totally enclosed nonventilated motors are similar to TEFC with the fans omitted. 

Figure 1.20(a) Totally enclosed tube ventilated (TETV) squirrel cage motor (Cooling system IC5A111) (Courlesy BHEL)... 

The choice for severe applications below 250 hp is the totally enclosed fan-cooled (TEFC) motor (see Figure 7-1). TEFC motors separate the internal and external ventilating air. Breathing is the only way external air ever gets inside. At some size above 250 HP, manufacturers presently switch from a rib-cooled to an exchanger-cooled motor for totally... 

Some niekel eompounds may be irritant to skin and eyes and dermal eontaet with niekel ean result in allergie eontaet dermatitis. Niekel earbonyl is extremely toxie by inhalation and should be handled in totally enelosed systems or with extremely effieient ventilation. Air monitors linked to alarms may be required to deteet leaks. Respiratory equipment must be available for dealing with leaks. Biologieal eheeks (e.g. niekel in urine) should be eonsidered for routine operations involving niekel eatalysts. 

Report the total of all releases to the air that are not released through stacks, vents, ducts, pipes, or any other confined air stream. You must include (1) fugitive equipment leaks from valves, pump seals, flanges, compressors, sampling connections, open-ended lines, etc. (2) evaporative losses from surface impoundments and spills (3) releases from building ventilation systems and (4) any other fugitive or non-point air emissions. 

Calculate total loads (heat, humidity, contaminants) from different subprocesses and environment (building) to ventilated enclosure (zones). 

Since the OELs provide the basis for ventilation requirements, an astute designer tries to find out how secure the OELs of the chemicals which will be used in the plant he or she is planning. Some of the chemicals used may totally lack OELs. Therefore, it is advisable to become familiar with the relevant literature, preferably together with a specialist. It is clear that the ventilation engineer needs to be aware of the possible significance of toxicology for industrial ventilation construction. 

The airflow rate Q, for each air leakage path is expressed with Eqs. (7.237), (7.242), and (7.243) using the infotmation on effective leakage area, CjA, and a pressure difference across the path. The total pressure acting on an opening from the outside is the sum of the pressure due to wind, gravity forces, and mechanical ventilation performance, and the static pressure inside the building results from Eq. (7.244). 

When the gate is totally protected, there are no other openings in the building envelope and there is a balance between supply and exhaust ventilation systems, (Fig. 7.104). In this case the pressure difference across... 

A fan delivers air Co a ventilating system at total pressure difference 500 Pa, The fan is running at 10 rev s, and the shaft power needed in these conditions is 7.46 kW. Determine the volume flow, total pressure difference, and shaft power if the fan speed is increased to 12.5 rev... 

There are many possible ways to classify local ventilation systems. When local ventilation is used to describe exhaust hoods only, one classification is hoods that totally surround the contaminant source (enclosing hoods), hoods that partially surround the contaminant source (partially enclosing hoods), and hoods where the contaminant source is outside the hood (exterior hoods). A similar classification is used here for the exhaust hoods. Since local ventila tion, as described in this chapter, includes more than exhaust hoods, the following three main categories are used exhaust hoods, supply inlets, and combinations of exhaust hoods and supply inlets. (See Fig. 10.1.)... 

FIGURE I 0.2 Approximate leakage of local ventilation systems. The lower the value, the better the system. A value of I means no protection. For supply systems, which are not designed to capture contaminants, higher values mean greater protection, and a value of I means total protection. 

Capture efficiency can also be measured by first estimating workspace emission rates and local exhaust emissions. The local exhaust emission rate equals the duct concentration (mass/volume) multiplied by the duct flow rate (volume/time). The workspace emission rates can be calculated using appropriate mass balance models and measured ventilation rates and workspace concentrations. Capture efficiency is the ratio of duct emission rate to total emission rate (duct plus workspace). ... 

Access to the interior of the enclosure is much more restricted for a total enclosure than for a partial enclosure. So-called totally closed hoods, where all contact between inside and outside is through air locks or by robot or remote control (see Section 10.4.6.4), these are not only expensive to construct and operate, they also need specialized ventilation systems to function properly. 

When total isolation of the surroundings is necessary the contaminant source (or the worker) has to be placed in a volume that is physically dosed and has both supply and exhaust air. When these systems are situated m small rooms they function as both local and general ventilation. Some smaller systems that normally are of bench size are included in this section. 

FIGURE 11.13 The total age. There are two inlets at the ceiling and two exits at the sidewalls near the floor. (Reprinted from Building and Environmem. vot. 32. S.-H. Peng. S. Hoimberg, and L Oar/idson. "On the Assessment of Ventilation Performance witfi the Aid of Numerical Simulations," pp. 497-SOB. 1997, with permission from Elsevier Science.)... 

I he origins of the above two errors are chfferent in cause and nature. A sim ple example is, when the mass of a weight is less than its nominal value, a systematic error occurs, which is constant in absolute value and sign. This is a pure systematic error. A ventilation-related example is, when the instrument faaor of a Pitot-static tube, which defines the relationship between the measured pressure difference and the velocity, is incorrect, a systematic error occurs. On the other hand, if a Pitot-static tube is positioned manually in a duct in such a way that the tube tip is randomly on either side of the intended measurement point, a random error occurs. This way, different phenomena create different ty pes of error. I he (total) error of measurement usually is a combination of the above two types. 

The air volume flow rate plays a major role in planning, commissioning, and running industrial ventilation systems, in the planning phase of a system, the supply, exhaust flows, and total flow rates are specified. When the system is built and running, the contractor and/or the client measures the airflows to determine if they agree with the specification. In such a situation, it is of interest to... 

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