Back-flow preventer

Oxygen Entered Nitrogen Header from Back Flow-Preventer Device Failure + NA + ... 

An example of such a product is ioBio , marketed by Baltimore Aircoil Co. (BAC). It is proposed for small cooling systems. This system is, in effect, an in-line dispenser of prilled elemental iodine (U), with replaceable iodine canisters available. The equipment is placed in the makeup waterline to the tower, and in-line options include filters, water meters, and back-flow prevention devices. Claims made are that the biocidal action of the elemental iodine is not affected by changes in temperature, system load, or water chemistry. Also, the system is compatible with virtually all scale and corrosion inhibitors and does not contribute to the corrosion of metal surfaces. 

Water supply is typically supplied through a properly installed fast-fill connection, whereby the entire system volume can be made up within 2 to 4 hours. Such fast-fill connections normally require a solid connection from a boosted water pressure source, with a double back-flow preventer and a pressure-limiting valve. 

The availability of a sanitary sewer near the point of chlorinated water release, and the capacities of the sanitary sewer and the wastewater treatment plant to handle the additional load, are the primary limitations in this method. Potential upset of treatment plant operations due to chlorinated water release must also be evaluated. A back-flow prevention device or an air gap method must he used to prevent cross-connection problems. 

Process drains must have adequate back-flow prevention devices (deep-seal traps) at tie-in to sewer line. 

Verification of utilities design, mix-up, identification, check valves, and back-flow prevention. 

Usually, immediately upon entering the plant, supply water is split into potable water and process water. This is done by using an air break or back flow preventers. This is a precaution against process contaminants backing up into potable or city water and vice versa. Often a break tank is used as the air break since it also provides storage capacity for demand surges at the use points. 

Any installedcentralvacuumsystemisnottoserveany areas outside the facility. In-line HEPA filters are to be placed as near as practicable to each use point or service connection. Filters are to be installed to permit in-place decontaminationandreplacement. Other liquid and gas services to the facility are to be protected by back-flow prevention... 

Will necessary excess flow and back-flow prevention measures be provided ... 

Unless provided with a back-flow prevention system, compressed gas containers must not be connected to process piping where the container may be contaminated by the backflow of other process materials. Certain noncryogenic liquefied gases may be especially susceptible to this type of contamination due to their relatively low vapor pressures at ambient temperatures. In cases where such a possibility may exist, design consideration must include the use of check valves or traps, or both for this purpose. 

Domestic water supply to laboratories may require installation of back-flow preventers, special devices that provide positive protection against siphoning laboratory water into the potable water system should the supply pressure drop. Building drinking fountain, cafeteria, and rest room water supplies must be on the potable water supply rather than the laboratory water supply system. Unfortunately, this is not the case in many existing laboratory buildings. 

Screws and cylinders for thermosets are treated, for example Arbid. The screws have a special geometry, a suitable tip and no back-flow prevention valve. Other versions with back-flow prevention valves are also available. 

Use a screw with back-flow prevention valve... 

NB To keep cylinder temperature at 5 to 25 C, the cooling jackets will be connected directly to a cooling water distributor. To reach extremely low temperatures an external cooling device can be used. For injection a single-stage non-compression mixing screw with back flow prevention valve is used. 

Gas Distrihutor The gas distributor has a considerable effect on proper operation of the flmdized bed. Basically there are two types (1) For use when the inlet gas contains solids and (2) for use when the inlet gas is clean. In the latter case, the distributor is designed to prevent Back flow of sohds during normal operation, and in many cases it is designed to prevent back flow during shutdown. In order to provide distribution, it is necessary to restrict the gas or gas and solids flow so that pressure drops across the restriction amount to from 0.5 kPa (2 in of water) to 20 kPa (3 Ibf/iu ). 

Use dedicated exhaust ducts Vent individual pieces of equipment through conservation vents to prevent back flow Install flame arresters at vessel vents, where applicable... 

Non-return valves are used to prevent back-flow of fluid in a process line. They do not normally give an absolute shut-off of the reverse flow. A typical design is shown in Figure 5.5g. 

The principles of fluidisation, discussed in Chapter 6, are applied in this type of dryer, shown typically in Figure 16.25. Heated air, or hot gas from a burner, is passed by way of a plenum chamber and a diffuser plate, fitted with suitable nozzles to prevent any back-flow of solids, into the fluidised bed of material, from which it passes to a dust separator. Wet material is fed continuously into the bed through a rotary valve, and this mixes immediately with the dry charge. Dry material overflows through a downcomer to an integral after-cooler. An alternative design of this type of dryer is one in which a thin bed is used. 

Blood is pumped away from the heart through arteries it permeates the tissues through networks of very small capillaries where nutrient delivery, gas exchange and waste removal occur and is finally returned to the heart via the veins. The structures of the arteries and veins differ in important ways. First, the veins have one-way valves which prevent the back-flow of blood and second, the walls of the arteries are much thicker, due largely to the layer of smooth muscle cells. Both types of vessel are lined on their inner surface with endothelial cells. Refer to Figure 5.2. 

If the air does not back-flow, continue to film. If the smoke back-flows to the critical working area at any point during this operation, procedures must be established to prevent cross-contamination and reentry into these areas. If the unit passes, proceed. 

When running a line, make provisions to adequately alarm the operator if one of the plasticators trips out. This will prevent melt from back flowing into the stopped machine and creating a blockage in the feed section that could become hazardous. 

PCV - 34 Malfunction Flow releasee to flare, including recycle froai compressors 1natall check valve downstreaai of ESV to prevent back flow of gas froai the compressors tilth block valve and one-inch bypass for starting end purging NOTE Check valve and one inch bypass Installed refer to revised PtIO Rev. 0 Recycle on compressor will open - system will not shut down... 

Before selecting a valve, the function of each valve type must be considered first. Several valve types, listed in Table 8.1, are used for on-off service, prevention of back flow, and throttling. Figure 8.2 to 8.4 shows only a few examples of valve types. For a discussion of many other valve types see Reference 8.2. 

Check valves prevent back flow. The ball check valve, shown in Figure 8.3, is particularly simple in that it has no moving parts requiring close clearances bet-... 

If the level of amine is still too high, it can be lowered by distillation of the DMF. Add an equal volume of dry benzene (CAUTION carcinogen) to the DMF and distil at atmospheric pressure until the benzene is removed. Distil the DMF under water-aspirator vacuum, using a drying tube in the line to prevent back-flow of water vapor from the aspirator. The amine content, as indicated by the DNFB test, should now be satisfactorily low. 

A non-retum valve fitted to the pump inlet will reduce this hazard. A Buchner flask fitted with a rubber stopper carrying a vacuum release stopcock and a glass tube reaching to the bottom of the flask will provide a means of preventing a back flow of water into the evacuated system. Should the back flow of water be insufficient to close the non-retum valve, then it will be seen to enter the Buchner flask. The stopcock can be opened very slightly, the resulting increase of pressure in the flask will... 

A squeeze bottle is regarded as an open system. There is no valve or similar mechanism that seals acceptably and prevents contamination of the contents. The nasal tip, which is usually in contact with the nostril during actuation, naturally becomes contaminated. After releasing the pressure on the bottle, the back flow of the liquid enables bacteria to enter the system. After appropriate incubation time, contamination will occur in the container. Of course, preservatives do oppose the bioburden, but the efficacy of a preservative is limited. 

HEPA filter on the discharge duct to prevent back-flow contamination... 

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