Vacuum breakers

Amhient Influences If cooling results in a vacuum, the design must provide for external pressure or a vacuum breaker installed also provision must be made For thermal expansion of contents trapped... 

When using explosion doors that close the vent area after the explosion, the coohng of the hot gases of combustion may create a vacuum in the vessel, resulting in its deformation. In order to prevent this from happening, vacuum breakers have to be provided. 

SFg breaker 7.5 kV + 5.4 kV = 12.9 kV Vacuum breaker with copper-chromium contacts ... 

Vacuum breaker with copper-bismuth contacts ... 

Vacuum breakers have a few disadvantages as noted below ... 

Concerning condensing turbines, be sure to obtain an adequately sized vacuum breaker for the condenser. There are no words to describe the agony of watching a turbine or the driven compressor tear itself up. 

Vacuum breaker, 291 Vacuum pump, 9 Vacuum service, 10 ejectors in, 11 liquid pi.ston, 9 liquid piston, 130 sliding vane, 10 Valve design, 62 Valve loss, reciprocating, 62 Valve unloader, 81 Valve velocity, 62 Valves... 

In general, vacuum vents and inert or gas repressuring systems are not considered an acceptable alternative to vacuum design for process equipment. Repressuring systems may be provided for process reasons, but they are not considered sufficiently reliable for equipment protection. Vacuum breakers are difficult to maintain tight and may admit air into the equipment. 

P—Personnel Protection QO—Quick Opening SG—Sample Protection SO—Steam Out TSO—Tight Shut Off VB—Vacuum Breaker... 

Safety valves and vacuum breakers, per inch of nominal size. 1.0... 

Condensate from the low-pressure coil together with that from the flash vessel will then drain to a collecting tank, or direct to a condensate pump, for return to the boiler plant. If the pressure of the flash steam is left to find its own level it will often be sub-atmospheric. As the condensate must then drain by gravity through the steam traps these also must be sufficiently below the condensate drain points to provide an appropriate hydraulic head, and a vacuum breaker fitted above the coil. The alternatives are to allow the condensate to drain directly to a condensate pump, or to supply additional low-pressure steam through a pressure-reducing valve, to maintain a positive pressure in the coil and flash vessel. 

Vessels subject to external pressure should be designed to resist the maximum differential pressure that is likely to occur in service. Vessels likely to be subjected to vacuum should be designed for a full negative pressure of 1 bar, unless fitted with an effective, and reliable, vacuum breaker. 

Inadequate or incorrect maintenance. Mechanical devices such as vacuum breakers and flame arrestors require routine maintenance attention to ensure that they provide their intended protective function. Incorrect maintenance (e.g., changing the vacuum breaker set pressure) could defeat the intended protection. 

Where process, safety, and environmental considerations permit, vacuum protection may be provided by properly sized ever-open vents. Alternatively, active protective devices and systems are required. Vacuum breaker valves designed to open and admit air at a predetermined vacuum in the vessel are commonly used on storage tanks, but may not be suitable for some applications involving flammable liquids. Inert gas blanketing systems may be used if adequate capacity and reliability can be ensured. Where the source of the vacuum can be deenergized or isolated, suitably reliable safety instrumented systems (e.g, interlocks) can be provided. 

Investigators observed a device that appeared to be a combination safety relief valve and a vacuum breaker. The information on this chrome-topped instrument read, Press 26,700... 

Every low-pressure, closed-top tank with an overflow line should be equipped with some type of device to prevent collapse from an overfilling operation. A large open nozzle, a high-level alarm and/or shutdown system, vacuum breakers or separate vent lines are some appropriate safeguards. 

No one was injured there was no fire or significant release. After this incident, the operating company had vacuum breakers installed on all of the vessels in this process that were not designed for full vacuum. In addition, they rerouted the stripper vent line. Operations started up without this stripper and operated for nearly a month during which time a new column was being built in the United States on an emergency basis and airlifted to the Caribbean island. [5]... 

The possibility of equipment, which normally runs at or near atmospheric pressure, going into a vacuum condition should also be considered. Vacuum relief systems and vacuum breakers don t always work. On a hot summer day, a sudden rainstorm can cool a large tank or hopper very rapidly. This can cause rapid cooling and contraction of air inside the tank and condensation of vapors, if they are present. This can cause very rapid lowering of pressure inside the tank, which can implode the tank if insufficient provisions have been made for air to enter the tank. These conditions are common in northern climates where the rate at which a vacuum can be produced may be increased in cold weather. In many instances, vacuum devices that are supposed to work are frozen and inoperative and the tank implodes. It may be inherently safer to design tanks to handle a vacuum than to depend on vacuum relief devices alone. 

No one was injured there was no fire or significant release. After this incident, the operating company had vacuum breakers installed on all of the vessels in this process that... 

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