Fans, extractor

This merhod ot ventilation uses extractor fans. A fan will create a negative pressure within the space. With this method, a set flow rate can be achieved, as the fan will overcome the stack and wind effects hence, the system is not at the mercy of the weather. This system causes the inside of the building to be held at a negative pressure, so air will be drawn in from outside or from surrounding spaces that are at a high pressure. 

Fume cupboards fitted with powerful extractor fans capable of rapidly changing all the air in the laboratory. 

Overheating the microwave oven tends to result in boiling or excessively rapid evaporation of fluids such as ethanol used for dehydration, formaldehyde employed for fixation, and the antigen retrieval fluid. As a result, flammable and/or toxic materials are released in the microwave oven. Even without overheating, vapors are produced because containers are kept open in the oven to prevent pressurization. Transparent microwave containers should be used, fluid volumes should be -100ml. Microwave ovens with attached efficient extractor fans are commercially available, as are microwave ovens with temperature probes. To avoid possible exposure to toxic vapors, the face should be turned away when the oven door is opened (Horobin and Fleming, 1990). The oven door should not be opened or closed to turn the microwave power on and off. 

After the run the paper is dried in a warm air oven fitted with an extractor fan and racks for hanging the papers. The wicks and polythene sheets can be reused several times. 

Pick up the beaker without holding on to the mat. Note that ammonia gas is produced in the reaction - after a few minutes place the beaker in the fume cupboard and switch the extractor fan on. 

Close the fume cupboard door and switch on the extractor fan. Wait a few seconds. 

Groundnuts . Comminuted material (50 g) is extracted with hexane in a Soxhlet extractor for 3-4 h. Residual solvent is removed from the solid in a warm oven with an appropriate extractor fan. To 10 g of defatted material, in a 250 ml stoppered flask, 10 ml of water is added and mixed thoroughly using a glass rod. Chloroform (100 ml) is added, the flask stoppered, and the mixture shaken on a wrist shaker for 30 min. The extract is filtered, a measured volume taken to dryness under a stream of nitrogen, transferred to a vial in a known volume of chloroform, and retained for subsequent analysis. 

In pharmacy practice mainly the ducted type of flowhood is used, which is not recirculating the air into the room. The air in the hood, evenmaUy mixed with the volatiles is discharged into the open air outside the building, often by flexible special ducting. The extractor (fan) of a fume cupboard does not come in contact with these volatiles. This is the reason why explosive or highly combustible material can be exhausted safe. 

In bathroom, there are 2 times 40W bulb, a hairdryer, an electrical shaver and an extractor fan. Total electrical energy requirement is 2100 Watts. Usage hours and electrical consumptions of the appliances of the bathroom are shown in the tables C.9 and C.IO, respectively. 

Mineral-insulated, metal-sheathed (MIMS) cable is suitable for use in most environments, but it is not so suitable for use where there may be vibration. In an old paint spray booth which predated the Highly Flammable Liquids and Liquefied Petroleum Gases Regulations, a spider-frame-mounted, electrical extractor fan had been positioned at the mouth of the extract duct and connected by MIMS cable. The fan motor was totally enclosed and explosion-protected as the paints used were flammable. The maintenance was poor and paint accumulations were allowed to build up on the fan blades causing an imbalance and vibration. This led to embrittlement of the copper sheath of the cable, which cracked and broke. Then one of the conductors fractured and sparking occurred between the ends. Ignition of the spray started a fire in the paint accumulations on nearby surfaces and the factory was burnt down. 

Figure 15.4 is a single line circuit diagram. The gas detectors GDI and GD2, their controllers and the alarm are powered from the supply or from an inverter which is battery energised so an alarm would be given should a gas leak occur when the plant is shut down or the supply fails. Under normal conditions, the extractor fan is controlled by the non-explosion protected two-way switches in the safe area and compressor room, but in the event of a leak gas detector GDI would operate. This would shut down the compressor room installation and automatically disengage these switches and their associated non-pro-... 

Flexible cables are often used to supply extractor fans, immersion heaters, pumps and controls for the central heating and domestic hot water systems. They are subject to the same requirements as for fixed wiring and where accessible should be secured so as to reheve their terminations of strain. Check the condition of lighting pendants which may have deteriorated from age or been damaged by a hot lampholder. 

Diffusion coefficients are of the greatest importtmce for discussing the spread of pollutants in lakes and through the atmosphere. In both cases, the spread of pollutant maybe assisted—and is normally greatly dominated—by bulk motion of the fluid as a whole (as when a wind blows in the atmosphere). This motion is called convection. Because diffusion is often a slow process, we speed up the spread of solute molecules by inducing convection by stirring a fluid or turning on an extractor fan. 

Accidental fire in dust extract ducting Dust ignited by heat from overheated extractor fan bearing Lack of maintenance of extract system Failure of planned preventive maintenance programme for the extract system Failure of management to monitor the PPM system Lack of adequate fire risk assessment... 

The MOG should be eliminated as quickly as possible, preferably before becoming covered in juice. It is usually removed by blowers. Extractor fans placed above the conveyor belt are effective. When these extractors are properly adjusted and combined with destenuning screens, they are capable of reducing the rate of misceUaueous rubbish to 0.5%. The crop is generally stored temporarily in one or two hoppers with a capacity of 8-20 hi. These hoppers are capable of dumping the crop directly into Ae transport containers. 

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