Pumps, vacuum safety

Occasionally the odor of hydrogen cyanide can be detected during the distillation, even when a trap filled with sodium hydroxide pellets precedes the usual trap cooled in dry ice and acetone to protect the pump. For safety, the vacuum pump should be placed in a hood, or provision should be made for the pump exhaust to be vented into a hood or out-of-doors during the distillation. 

Low-pressure systems can have many configurations and components. This system shows a (1) manifold, (2) reaction flask, (3) trap, (4) manometer, (5) Dewar flask, (6) vacuum pump, (7) safety shield, and (8) storage bulb. (Photo courtesy of T. Leon Venable, Agnes Scott College, Decatur, Georgia.)... 

Figure 2.253 Cross-section of a two-stage rotary vane vacuum pump. 1. Start-up control, 2. exhaust, 3. aeration valve, 4. pump stage 1, 5. high vacuum safety valve, 6. pump stage 2, 7. motor coupling, 8. motor and 9 gas ballast valve. (Pfeiffer Vacuum, 2003).

Few of the naturally occurring elements have significant amounts of radioactive isotopes, but there are many artificially produced radioactive species. Mass spectrometry can measure both radioactive and nonradioactive isotope ratios, but there are health and safety issues for the radioactive ones. However, modem isotope instmments are becoming so sensitive that only very small amounts of sample are needed. Where radioactive isotopes are a serious issue, the radioactive hazards can be minimized by using special inlet systems and ion pumps in place of rotary pumps for maintaining a vacuum. For example, mass spectrometry is now used in the analysis of Pu/ Pu ratios. 

The theoretical maximum suction lift at sea level for water (14.7 psi) (2.31 fi/psi) = 34 ft. However, due to flow resistance, this value is never attainable. For safety, 15 feet is considered the practical limit, although some pumps will lift somewhat higher columns of water. WTen sealing a vacuum condition above a pump, or the pump pumps from a vessel, a seal allowance to atmosphere is almost always taken as 34 feet of water. High suction lift causes a reduction in pump capacity, noisy operation due to release of air and vapor bubbles, vibration and erosion, or pitting (cavitation) of the impeller and some parts of the casing. (The extent of the damage depends on the materials of construction.)... 

Safety around mechanical vacuum pumps is possibly no different than that for other process mechanical rotating machinery. However, there is a decided danger of an... 

The synthesis of aromatic amines is an active and important area of research.2 Many methods are available in the literature for the synthesis of these compounds. Though some of these are widely used, still they have limitations based on safety or handling considerations. For example, catalytic hydrogenation3 of nitro or azido compounds in the presence of metals such as palladium on carbon or Raney nickel require stringent precautions because of their flammable nature in the presence of air. In addition, these methods require compressed hydrogen gas and a vacuum pump to create high pressure within the reaction flask. To overcome these difficulties, several new methods have been reported in the... 

Two 4 1 cylindrical glass(QVF) vessels with stainless steel end plates, serve as reservoirs(Figure 1) for surfactant solution(B) and water(9). Facility is available to evacuate these vessels as required by means of a rotary vacuum pump with glass cold trap in line to minimise water vapour. Another pipeline permits supply of pure nitrogen, or other gas, at low pressure, to the vessels, to provide a blanket, as desired. Proper operation and safety from over pressure is ensured by a pressure relief valve(10 in Figure 1) and the pressure gauge(P in Figure 1). 

Drilling muds are fluids that are pumped into the bore holes to aid in the drilling process. Most are water based and contain barite, hgnite, chrome lignosulfate, and sodium hydroxide [11], but oil-based drilling muds are still used for economic and safety reasons [12]. Used muds can be removed by vacuum trucks, pumped down the well annulus, or allowed to dewater in pits, which are then covered with soil or disposed of by land farming. 

High vacuum flange Pump casing Forevacuum flange Safety valve for gas dixharge Thermal radiation shield Baffle... 

In addition to the vacuum valves, which perform solely an isolation function (fully open - fully closed position), special valves are needed for special functions. Typical are variable leak valves, which cover the leakage range from 10" ° cm /s (NTP) up to 1.6 10 cm /s (NTP). These valves are usually motor driven and suitable for remote control and when they are connected to a pressure gauge, the process pressures can be set and maintained. Other special valves fulfill safety functions, such as rapid, automatic cut-off of diffusion pumps or vacuum systems in the event of a power failure. For example, SECUVAC valves belong to this group. In the event of a power failure, they cut off the vacuum system from the pumping system and vent the forevacuum system. The vacuum system is enabled only after a certain minimum pressure (about 200 mbar) has been attained once the power has been restored. 

The exhaust from a rotary pump, especially if it is being run in the ballast mode, i.e. pumping a fair quantity of air or other gas, is an aerosol of oil in the gases from the line. A variety of filters is now available commercially for cleaning exhaust gas, but a good additional safety precaution is a wide tube fitted to the outlet so that the gas stream can be vented to the nearest fume-cupboard or window. The pumping efficiency of a rotary pump drops off rapidly below ca. 10 Torr even under optimum conditions, and such pumps are therefore usually installed as a back-up to a more efficient high vacuum pump, such as a diffusion or a turbomolecular pump. 

For the more complete separation of the filtrate from the precipitate, press the latter slightly against the funnel bottom with a glass stopper. Filtration is considered to be complete if filtrate drops no longer appear at the tip of the funnel. Prior to closing the cock of the water-jet pump, extinguish the vacuum in the suction flask. To do this, open the safety clamp on the outlet tube or extract the stopper with the funnel from the suction flask. 

The powder is spread on cotton muslin stretched over wooden frames and placed on the shelves. The drier is then closed and the vacuum pump set in motion. The pump usually operates a pressure of 100-150 mm Hg. When the pressure becomes steady, the screws clamping the lids are released, but the lids continue to adhere hermetically to the drier, owing to the reduced pressure created inside. As a safety precaution the driers work in this manner until drying has been completed. Thus should ignition occur the lids are freely detached. This prevents thepowder from burning in a confined space, and exploding, and so destroying the drier. The capacity of the... 

Figure 6. Block drawing of the pilot installation for the production of trichloromethyl chloroformate by exhaustive photochlorination [39] 1 Dryer for gaseous Cl2 (H2S04 cone.). 2 Safety tank. 3 Thermoregulated immersion-type photochemical reactor. 4 Raschig column. 5 Cl2 detection system (1,2,4-trichlorobenzene). 6 Neutralization tank (20% NaOH). 7 Reservoir of 20% NaOH. 8 Buffer to atmospheric pressure (20% NaOH). 9 Active carbon filter. 10 Reservoir of crude trichloromethyl chloroformate. 11 Buffer to normal atmosphere via CaCl2 filter and direct entry for trichloromethyl chloroformate to be distilled. 12 Distillation flask with Vigreux column. 13 Exit to vacuum pump. 14 Solid NaOH filter before pump. 15 Cooling water alarm linked to power supply of the light source. 16 Medium pressure mercury arc. 17 Heater for distillation apparatus. 18 Magnetic stirrers. /T thermometer /P manometer.

A storage tank has a diameter of 80 ft, a height of 25 ft, and contains oil to a height of 15 ft. The suction pumps, which can handle 15,000 bbl/d, are started, but the safety valves are clogged and a vacuum is drawn in the tank. The roof is flat and rated to withstand 1.0 oz/sq in. before collapsing. The barometric pressure is 30 in Hg. How long will it take the tank to collapse What is the total force on the roof at collapse How would more oil in the tank have affected the collapse time Explain. 

Provided the vacuum pump exhaust is appropriately vented and suitable caution is observed in cleaning out the cold trap, the VDP parylene process has an inherently low potential for operator contact with hazardous chemicals. Before using the process chemicals, operators must read and understand the current Material Safety Data Sheets, which are available from the manufacturers. 

To use the bomb, the vessel A is set in an upright position and charged with reactants and solvent B is then pushed home into A with the valve F open and the securing collar D is screwed down hand-tight.t The vessel is evacuated with a vacuum pump attached to the nozzle of F, the valve is closed and the vacuum line removed. The bomb is then positioned behind adequate safety shielding, preferably in an isolated position, and heated in an oil bath or preferably by an electrical heating tape wound around the barrel A. 

When an O-ring needs replacement (such as in a mechanical vacuum pump), the manufacturer can provide, or recommend, an O-ring that will be resistant to the pump s vacuum fluid. On the other hand, when an O-ring is being used in varying conditions, you will be responsible for the selection of the proper O-ring material to maintain the integrity of your system and the health and safety of the operators. 

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