Suction contamination

It is often important to quantify the contamination of pore fluid in the unsaturated soil 2one, where monitoring wells are ineffective. In this region, suction cup lysimeters are useful (7). These samplers consist of a porous cup, typically ceramic, having two access tubes which are usually Teflon. One access tube provides a pressure-vacuum, the other discharges the sampled fluid to the surface. The porous cup, typically between 2 and 5 cm in diameter, is attached to a PVC sample accumulation chamber. 

Tank settling as a means of contaminant removal is not very efficient with fuels having the viscosity of kerosene. It is common practice to design tanks with cone-down drains and floating suctions to facilitate water and solids removal. 

The rim exhaust is a source of suction that is placed along one or more sides of the area source. Air is drawn across the surface of the source and contaminated air is drawn into the hood. Specific examples of rim exhaust include open-surface tank exhaust such as electroplating, cleaning, degreasing table exhaust such as mortuary tables and exhaust used during container filling such as barrel filling. 

Gases, vapors, and fumes usually do not exhibit significant inertial effects. In addition, some fine dusts, 5 to 10 micrometers or less in diameter, will not exhibit significant inertial effects. These contaminants will be transported with the surrounding air motion such as thermal air current, motion of machinery, movement of operators, and/or other room air currents. In such cases, the exterior hood needs to generate an airflow pattern and capture velocity sufficient to control the motion of the contaminants. However, as the airflow pattern created around a suction opening is not effective over a large distance, it is very difficult to control contaminants emitted from a source located at a di,stance from the exhaust outlet. In such a case, a low-momentum airflow is supplied across the contaminant source and toward the exhaust hood. The... 

The inlet opening that supplies the low-momentum airflow should be sufficiently wide to cover the contaminant source and should face toward the inlet of exterior hood. The airflow functions to transport contaminants emitted within the flow to the exterior hood. The exhaust airflow created around the suction opening must exhaust all of the contaminants transported by the supplied airflow. From this point of view, the low-momentum... 

Figure 10.87 shows the fundamental operation of the push-pull flow. The suction hood should simultaneously exhaust the pushed air (contaminated supply... 

The contaminants are transported into the exhaust opening, from the table, by suction into the supply air (jet) and the movement of the exhau.sted flow over the table. 

Such a combination demands careful analysis of distances, air velocities, air directions, and contaminant generation direction and rate. It is necessary to direct the jet into the hood with the correct velocity and flow rate. High velocities or flow rates could result in more spreading of contaminants than without the jet, but the velocity must be large enough to prevent the jet from collapsing into itself due to suction. 

An equation can be developed which expresses the ratio of spilled contaminant to total contaminant in terms of the ratio of hood suction to plume flow rate. This equation is as follows ... 

The final consideration in suction piping design is the method used to reduce the pipe diameter (i.e. 1.5 or greater than the pump s inlet flange) so that it can be attached to the pump. Care must be taken to ensure that the reduction method does not cause a void where air can be trapped or a low spot that will permit buildup of solid contaminates. 

The inside of the reservoir generally will have baffles to prevent excessive sloshing of the fluid and to put a partition between the fluid return line and the pump suction or inlet line. The partition forces the returning fluid to travel farther around the tank before being drawn back into the active system through the pump inlet line. This aids in settling the contamination and separating air entrained in the fluid. 

The supply of water is usually limited and requires the use of a cooling tower. Other possibilities are worth investigation for example, in the food industries, large quantities of water are used for processing the product, and this could be passed first through the condensers if precautions are taken to avoid contamination. Also, where ground water is present, it could be taken from a borehole and afterwards returned to the ground at some distance from the suction. In both... 

To a solution of 130 g. (0.6 mole) of arsanilic acid (Org. Syn. 3, 13) in 600 cc. (0.6 mole) of normal sodium hydroxide is added 52 g. (0.62 mole) of sodium bicarbonate and 70 g. (0.75 mole) of chloroacetamide (Org. Syn. 7, 16). The mixture is heated 011 a water bath to 90-1000 and a steady evolution of carbon dioxide occurs. At the end of two hours, when gas evolution has practically ceased, the mixture is cooled to 40° C., stirred vigorously and 150 cc. of 1 1 hydrochloric acid poured in rapidly. /i-Arsonophenylglycinamide crystallizes at once and, after cooling to room temperature, is filtered by suction and washed once with 2 per cent hydrochloric acid (Note 1), then with cold water. The crude product thus obtained is contaminated with some arsanilic acid and possibly other products. These are removed during purification. The crude product is suspended in about 400 cc. of water and with vigorous stirring, treated carefully with 25 per cent aqueous sodium hydroxide until solution is just complete. At this point the mixture is still acid to litmus and an excess of sodium hydroxide is to be avoided to prevent decomposition of the product. About 15 g. of boneblack... 

Case Study. Such a situation was found to occur in the duct network shown in Fig. 21 and installed to extract iron oxide dust at various points along a cold strip processing line. The stated problems were insufficient suction at the hoods, buildup of contaminant in the hoods and along the processing line (causing cleanup problems due to eventual mixing with hydraulic fluid, lubricant, water, etc.). Analysis of the system found the following ... 

Bioslurping is most effective in fine- to medium-textured soils, where there is a significant quantity of LNAPL and associated soil contamination at the water table, with minimum drawdown and groundwater extraction. The practical maximum depth of liquid recovery is suction lift (27 ft of water column). 

Exhaust ventilation is used to remove contaminants by suction at the source, transport them to a collecting area, and dispose of them. An exhaust system is more expensive to install and maintain than a dilution system, but because it is specific to the source or sources of contamination, it is more effective in its action. 

The function of a hood is to concentrate the suction as close to the source of contamination as possible. It should be placed as close to the work as feasible while ensuring that the worker s breathing zone is not contaminated, for example, by forcing him to place his head close to the hood or even beneath it. 

Leakages in the system should be prevented or eliminated. Leakages not only reduce the available suction but also allow contaminants to disperse into the surrounding area. To maintain the integrity of the system and reduce leakage and clogging, a regular schedule of maintenance should be instituted. 

Never use your mouth instead of a suction bulb to draw a liquid into a pipette. The liquid could be corrosive or poisonous. As well, you would contaminate the glass stem. 

When a booster fire water pump takes suction from a public main, the design should be such that operation of the pump at 150% of rated capacity will not reduce the public main pressure below 20 psi (137.9 kPa). Provisions against contamination of the municipal system should be made by adding a backflow device is typically required. Local agencies generally have specific requirements. Some locations do not allow direct suction from public water mains. 

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