Diffusion pumps safety

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. 

In contrast to the diffusion pump, the turbomolecular pump can be connected in series between the backing pump and the system. Commercially available pumps usually have a cut-out mechanism which turns the pump off when the resistance in the system, due to increased pressure, slows the rotation of the pump to about 90% of its top speed. This is a safety... 

To clean a metal diffusion pump, it must be removed from the rest of the system. Pour the used oil (or mercury) into a proper receptacle. Do not throw the mercury away because it is a toxic waste (a heavy metal). Fortunately, mercury may be reclaimed and reused. As far as diffusion pump oils, check with the health and safety and/or environmental officer in your institution and/or the waste disposal management of your city. Be sure to mention any hazardous materials that may have been absorbed by the pump oil during its operation to the proper authorities. 

The cleaning of a mercury diffusion pump is somewhat simpler because mercury does not break down as most pump oils do. However, mercury gets dirty, and a dirty mercury pump still needs to be cleaned. After you have drained the mercury out of a glass diffusion pump, refill the pump with approximately a 6 molar nitric acid solution and let it sit until the mercury has been removed. Do not pour this liquid down the sink Check with local waste management and/or your health and safety officer. The pump should be flushed with distilled water and then rinsed with methanol for drying. 

Two very different kinds of pump fluids have been employed in diffusion pumps. For many years, mercuiy diffusion pumps, were used in small laboratory-bench glass vacuum systems. Mercury pumps are now seldom used owing to the health hazards associated with mercury and the high probability of contamination of the vacuum system with mercury unless a cold trap is used (the vapor pressure of mercury at room temperature is —1.5 mTorr). The oil diffusion pump eliminates the safety hazard and can serve for both small glass and larger metal vacuum systems. 

Explosion. If signiflcant quantities of a gas have been liquefied or taken up by an adsorbent at low temperature, an explosion can result when the system warms up if adequate vents or safety valves have not been provided. An explosion of a different kind can take place if an oil diffusion pump (particularly a glass one) is vented to air while hot. 

The diffuser pump is controlled by a switch on the console and has a local isolation safety switch near the pump. When the diffuser pump is turned on, another pump, the whale pump located under the catwalk deck plates on the north side, is also turned on. Both pumps have indicating lights on the console to show that they are running. If, when the diffuser pump is turned on, the indicating light for the whale pump does not light and is not burned out, the operator should suspect that the whale pump has lost its prime or is isolated at its local controller. In either case, the operator will require assistance in making the correct determination. 

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. 

There are two types of process equipment to feed hypochlorite solution (a) basic system and (b) complex systems. Both basic and complex systems are electrically and hydraulically activated. The basic liquid hypochlorination systems include two metering pumps (one serving as a standby), a solution tank, diffuser, and appropriate quantities of tubing. The more complex system adds a diffuser corporation cock, antisiphon backflow preventer, a safety housing enclosure, a flow pacing system, and a flow meter and signal. 

Funnel, Buchner, 5 cm Gas diffusion tube Gloves, plastic Goggles, safety Hollow cathode, Hg Hot plate Paper, filter, 5 cm Pipet, delivery, 1 mL Pipet, Mohr, 1.0 mL Pump, diaphragm, like Neptune Dyna-pump... 

A few of these devices rely on air contact with the tube through diffusion, and thus operate passively. Tubes used with battery-operated pump or those that sample the air through diffusion are used to determine time-weighed average concentrations of the workplace air contaminant of interest, while all the tubes used with a hand-operated vacuum pump are intended for measuring more or less instantaneous concentrations. The Safety Equipment Institute (USA) currently certifies chemical indicator tubes based on American National Standards Institute/In-ternational Safety Equipment Association standard 102 (1996). 

Covox DS system for CO delivery. The Covox DS system is a complex machine consisting of pumps and safety valves which can repeatedly control the amount of carboxy-haemoglobin (CO-Hb) within healthy human patients. The problem with administering CO as a gas is that the CO can freely diffuse throughout the blood stream to all areas of the patient and can pass through all cell membranes. It seems somewhat inefficient to have compound evenly distributed throughout an entire system, when it may only be required in localised environments. The Covox DS system was used on healthy patients, and it is not known if CO delivered in this way could be beneficial. 

---