Air Intake Filters

Any maehine that uses air in a combustion chamber to bum liquid or gaseous fuel must filter the air, to prevent ingress of solid partieles that would cause wear in the piston-eylinder system or of the blades of a turbine. Filtration is also necessary of the air sueked into a compressor or large fan, similarly to prevent internal damage. 

The simplest form of an effective maehine intake filter is an element of pleated impregnated paper, housed in a suitable casing. The pleats provide both rigidity for the element, so that it requires a minimum of support, and at the same time a large surfaee area for filtration. This area may be further increased by corrugating as well as pleating the paper. 

Two-stage air intake filter/silencers are usually of the panel type and are suited for centrifugal and axial compressors. 

Stationary machines installed in factories and power stations are normally located in machine honses or separate rooms taking in air throngh ducting from the ontside walls with suitable filters incorporated. Alternatively, the complete machine house is treated as a clean room, in which case a barrier system of conventional panel intake filters are usually installed in one wall. 

A self-cleaning cycle can be performed by a timing mechanism, using compressed air blown in short bursts through horizontal blow pipes into the filter chamber. This brief pressurization causes the accumulated particles to become dislodged from the filter elements. The dust is then pulled by a separate air fan into a secondary cleaning circuit, which exhausts the particles to the atmosphere away from the inlet 

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In the context of industrial compressors, dust is a major consideration. Such compressors have a very high throughput of air, and even in apparently clean atmospheres, the quantity of airborne dirt is sufficient to cause trouble if the compressor is not fitted with an air-intake filter. Many of the airborne particles in an industrial atmosphere are abrasive, and they cause accelerated rates of wear in any compressor with sliding components in the compressor chamber. The dirt passes into the oil, where it may accumulate and contribute very seriously to the carbon deposits in valves and outlet pipes. Another consideration is that dirt in oil is likely to act as a catalyst, thus encouraging oxidation. 

Here is a problem that came up on a sulfur recovery facility in Punto Fijo, Venezuela. The combustion air blower, shown in Fig. 28.8, was a fixed-speed, motor-driven centrifugal machine. The air intake filters were severely fouled. They had a pressure drop of about 8 in H/). The atmospheric vent valve, used to control the discharge pressure at a constant 12 psig, was 50 percent open. The unit engineer had been asked to calculate the incentive in electrical power savings that would result from cleaning the filters. 

Dreetz CD, Lund W. 1992. Air-intake filters used for multi-element analysis of airborne particulate matter by inductively coupled plasma atomic emission spectrometry. Anal Chim Acta 262 299-305. 

Vibration welding techniques have found several applications in the automobile industry including emission control canisters, fuel pumps and tanks, head and tail light assemblies, heater valves, air intake filters, water pump housings, and bumper assemblies. They have also been used for joining pressure vessels and for batteries, motor housings, and butane gas lighter tanks. 

Plugging of the air intake filters. Anything over a few inches of mercury pressure drop on these filters is excessive. 

Air intake filters plugged Pressure restriction of blower discharge Increased ambient temperature Compressor rotor fouled Blower turbine running slow Wet gas compressor problems Fractionator condensers plugged... 

In the most simple case as shown in Fig. 4.20, an active air supply subsystem consists of an air intake filter to remove particles and possibly impurities poisoning the cathode catalysts, a compressor or blower and an air humidifier that can also include the function of an air cooler. 

Nanofibre filter fabrics are frequently in pleated constmctions for air filtration, such as pleated dust collection and engine air intake filters. They could be used to fill the... 

Industrial stationary compressors are normally installed in separate rooms, drawing in air from the outside atmosphere, free of factory contaminants. When the level of dust concentration in the intake air is likely to be of the order of 10-50 mg/m, it is standard practice to fit the compressor with an intake filter (usually a panel filter or a paper cartridge type, depending on the size of the compressor), having an efficiency of 99.9% based on the dust concentration present in the ambient air. The air intake filter can, therefore, be expected to pass all particles smaller than 5 pm, as well as a proportion of larger ones, in addition to atmospheric water vapour. It will also pass all gases, vapours, odours, bacteria and viruses. 

To check the condition of a unit, e.g., if the compressor has to be cleaned, an output check can be carried out. Such a check means that the actual output is measured, corrected due to deviating ambient air conditions, and then compared to a reference value. Allowable output loss is stated in a compressor cleaning instruction. Other reasons for output loss are clogged air intake filters, worn down or damaged turbine buckets, air/gas leakage, etc. 

Here is a problem that came up on a sulfur recovery facility in Punto Fijo, Venezuela. The combustion air blower, shown in Fig. 35.8, was a fixed-speed, motor-driven centrifugal machine. The air intake filters... 

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