Quick opening valve

Eliminating open-ended, quick-opening valves in hazardous service... 

Explosion Pulping. In this process, wood chips about % inch long are fed into a battery of digesters (called gnns), in which the chips are steamed gradually to a pressure of 1100 to 1200 psi and then, after holding at that pressure for about 5 secs, / are released by means of a quick-opening valve into a cyclone. The explosive effect... 

Figure 15.18 shows how7(x) varies with stem position for three types of valves a quick opening valve, an equal percentage valve, and a linear valve, where... 

Often a redundancy is renounced as well, if the protective measure is realized by equipment designed, manufacmred and tested according to the state of technology like pressure vessels, safety valves, bursting discs and shut-olf and quick opening valves operated with auxiliary power. Equipment satisfying the criteria of the state of technology is normally not supposed to fail. 

There shall be a supply of clean, cold water near each tank containing liqnid that may be harmful to the skin if splashed on the worker s body. The water pipe shall be provided with a quick opening valve and at least 48 inches of hose not smaller than V4 inch. Alternatively, deluge shower and eye flushes must be provided. 

FIG 2.9. Line resistance distorts a linear characteristic toward that of a quick-opening valve. 

Shock load conditions are simulated by evacuating the loading cylinder, pressurizing the storage container and then operating the quick opening valve to provide rapid loading. 

Pp subject to high-pressure limit Pp Pressure-operated overrides (see Chapter 16) should be placed on the reactor level controller and on any flow controllers that feed or empty the reactor. To ensure that this hard constraint is never violated, a quick opening valve and rupture disk should be installed in a separate line leading to a flare or blow-down tank. 

A unique explosion process for defibering wood was developed by W. H. Mason. Wood chips, about inch long, prepared in conventional chippers and screened, are subjected to high pressure, in a cylinder, commonly called a gun, about 2x6 feet in size, and ejected through a quick-opening valve. The elevated temperature softens the chips, and, upon ejection, they explode into a fluffy mass of fibers and fiber bundles. The process involves thermal plasticization of the lignin, partial hydrolysis, and disintegration by the sudden expansion of the steam within the chip. 

Another factor that affects the linearity of the response is the characteristic of the valve selected. Three of the most common valve characteristics include quick opening, linear, and equal percentage. If the majority of the system pressure drop is taken across the valve, then a linear valve should be used since its installed characteristic will also be linear, giving the linear response desired. However, if the pressure drop across the valve is a small part of the total line drop and is not constant, then an equal percentage valve can be used since its installed characteristic will be close to linear. Quick-opening valves are most commonly used with on-off controllers where a large flow is needed as soon as the valve begins to open. More information on these valve flow characteristics can be found in Chapter 2. 

In the General Requirements for Dipping and Coating Operations standard (29 CFR 1910.124), drench hoses are allowed in lieu of an eyewash and shower at open-surface tanks containing hazardous liquids. The device must supply clean water provided by a hose ) -inch in diameter, 48 inches or longer, with a quick opening valve. Pressure should not exceed 25 psi. 

Quick opening valve that remains open (simple to operate in <1 second). 

---