Automatic venting devices

The secondary relief device is usually sized to a much lower discharge rate than the primary. The secondary relief device can be a safety valve, a bursting disk, an automatic pressure-controlled vent valve, or a high-pressiu-e switch that opens an automatic vent. If the secondary device is a relief V2dve or a bursting disk, credit for its rate of discharge can be teiken when sizing the primary relief device. 

Stopping electrolysis for every small upset elsewhere in the process is clearly undesirable. In order to provide a degree of redundancy to automatic shutdown devices, then, normal practice is to provide relief in the form of a water seal that allows the cell gas to vent at a rate equal to its production. The chlorine in this vent must not he allowed to enter the atmosphere. Its confinement is the subject of Section 9.1.10.3. 

For a long time automatic refilling devices for purified water have made maintenance easier these are well known and reliable (Figure 5.9). There are two systems. The first is controlled by a vent plug with a mechanical working level indication, allowing... 

Safety features are essential to a microwave apparatus. An exhaust fan draws the air from the oven to a solvent vapor detector. Should solvent vapors be detected, the magnetron is shut off automatically while the fan keeps running. Each vessel has a rupture membrane that breaks if the pressure in the vessel exceeds the preset limit. In the case of a membrane rupture, solvent vapor escapes into an expansion chamber, which is connected to the vessels through vent tubing. To prevent excessive pressure buildup, some manufacturer use resealable vessels. A spring device allows the vessel to open and close quickly, releasing the excess pressure. 

A simple solution is to use a dual-conductivity-probe level control to activate an automatic valve for venting the gases from the vessel. And even a severe scaling problem does not affect this device, as it would the differential pressure cell and the nuclear level detectors. 

One way to do this is to use pressurized enclosures for electrical components. They maintain a slightly higher pressure inside than the atmosphere outside them, so if a leak does occur in the enclosure, it will vent outward and will not allow a flammable hydrogen and air mixture to go inside. If the pressure inside falls below a certain point, an alert occurs and the system is shut down. This can be done in different ways depending on the circumstances. Most systems have an audio alert as well as a visual indicator such as a blinking LED. In addition to this, upon loss of pressure a circuit will immediately disengage the power supply to any circuits and electrical devices within the enclosure, and the system will be shut down automatically. If you have an experimental device that is constantly attended while in the operation, a simple cutoff switch that is operator activated and approved for hazardous atmospheres will suffice. 

If the column has a total condenser operating close to its maximum capacity, a secondary relief device, preferably an automatic high-pressure vent, is most beneficial. In one column that did not contain such a device, the relief valve lifted each time a significant amount of lights entered or accumulated in the column (239). 

In some cases, a secondary relief device can discharge into a low-pressure system (e.g., fuel gas). This minimizes product loss. An automatic pressure-controlled vent is most suitable for this purpose. This technique can only be applied when the secondary discharge rate is small enough not to upset the low-pressure system. The secondary relief device must be carefully sized accordingly. 

Filtration of oxidizable materials can constitute a serious fire hazard. The ignition source can be a burning particle from the dryer or the static charge carried by the dust particle. Because of this, bag-house systems should be equipped with automatic devices for closing off the airflow in case of fire, should be provided with adequate sprinklers or chemical fire control apparatus, and vents should be provided on the side containing the dust particles. 

With active systems, the controls are mostly automatic, heat flows are well contained, and heat transfer processes are accrrrately predictable. With passive systems, heat flows are more diffuse and complex interchanges occttr, which can be grossly influenced by user interference. Often the appropriate adjustment of controls (e.g., of shading devices or of Trombe-wall vents) by the user at the right time is reqtrired to achieve optimttm performance of the system. Both the competence and the attitude of the user can drastically influence the resrrlts. 

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