Air handling systems

Another serious distraction to a process operator is the multiple alarm event, where a single event within the process results in iTuuti-ple alarms. When the operator must individually acknowledge each alarm, considerable time can be lost in silencing the obnoxious annunciator before the real problem is addressed. Air-handling systems are especially vulnerable to this, where any fluctuation in pressure (for example, resulting from a blower trip) can cause a number of pressure alarms to occur. Point alarms (high alarms, low alarms, status alarms, etc.) are especially vulnerable to the multiple alarm event. This can be addressed in one of two ways ... 

Aims of an Air-Handling System, Including the Unit and Ductwork 680... 

These issues relate certain requirements of the layout of the air-handling system and individual units, including the question of whether to select centralized or decentralized systems, and the number of units required in the building. 

SOUND REDUCTION IN AIR-HANDLING SYSTEMS 9.8.1 Basic Concepts... 

Space requirements for air-handling systems are briefly described in the draft European Standard prEN 13779, which, however, is targeted to commercial, public, and office buildings. These requirements also take into account the need for service and maintenance. In industrial applications the... 

In the design of air-handling systems, a reasonable energy efficiency can be achieved by relatively simple means, just paying attention to some basic principles. 

Air terminals and functional factors affecting the air handling systems Some basic principles are presented in Chapter 8. However, more attention has to be paid to minimizing the leakages and to sound attenuation. 

Commercial products do exist that integrate shrouded and ventilated grinding wheels and other hand-held tools. It may be possible to find an existing LVHV-type product that will work well for some applications, requiring only to be connected to an appropriate air handling system. However, it is also sometimes necessary to make custom-fabricated LVHV nozzles for some hand-held tools and for essentially all fixed-machine dust-generating tools. I he best approach is to consider the following ... 

Comprehensive experiment-based preparation for the selection of air-handling system elements... 

Pressurize the house using the air-handling system (concurrently adding ventilation air). 

Figure 10. Elements of a typical air handling system for fluid bed coating.

In office buildings it is very common to have plenums, i.e. spaces above rooms where the air handling system is located, together with electrical wires and cables, as well as abundant wood and other construction materials. These concealed spaces are usually ca. 1 m (3 ft) high and are invisible from the room below. 

Each hood intended for toxic work must have a face velocity of 100 linear feet per minute. When many hoods are employed, the volume of tempered air that must be supplied (summer and winter) is quite large. The required airhandling equipment is so massive that minor misadjustments may make it difficult to get out of a room because of air pressure on a door. One way to deal with this is to vent the doors and keep the hallways at a slightly higher pressure than the labs. When an airhandling (supply) unit falls short, the hallway provides needed makeup air. Computers can operate air handling systems more precisely than can traditional systems and an alarm system that pinpoints defective elements for early repair can help avoid gross imbalances. 

Hoods for toxic work should be easily decontaminatable with a catch basin leading to a toxic sump. The hoods should be made of stainless steel and be conveniently locked. Provision should be made for limiting travel of the hood door to that opening which can be supported by the hood fans and the air handling system. These stops should be sturdy but adjustable. 

Switchgear and relay rooms are required to have smoke detection per NFPA 850, section 5.8.4 and IEEE 979, section 2.7. The activation of the fire alarm should shut down the air handling system. If the facility is especially critical to the continued hydrocarbon process consideration of a fixed fire protection system should be evaluated. 

Combustible gas detection for air intakes should be considered when the enclosures are in proximity to hydrocarbon processes. This is especially important when the processes can be demonstrated to be within areas where a WCCE release will not have dissipated at the distance the facility is placed from it. An alternative is to have the air handling system self circulating so it does not direct fresh air supplies in from the outside. Such systems are normally provided at unmanned shelters. 

Instead, the first step should be a thorough review of processes, machinery variations, employee job functions for all affected job classifications, dust generation points, dust control equipment, and air handling systems (1 ). With this data In hand, and an accurate layout of the plant, one can begin the three-stage process of selecting plant sampling positions. 

How do air handling systems and dust control units affect dust levels throughout the area ... 

Doors, windows, and air handling systems should be arranged to automatically close or shut down prior to CO2 discharge. The concentrations of CO2... 

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