Pressure locking

The liquid levels of products that have a Reid vapor pressure of 40 lb or more are generally determined by the use of gauge glasses, rotary or slip-tube gauges, tapes and bobs through pressure locks, or other types of gauging equipment. The type of gauging equipment depends on the size and type of the pressure tank. 

A screw conveyor takes the comminuted raw material into a coaxial cylindrical chamber. On the left-hand side, this chamber features a reciprocating annular piston actuated hydraulically at a frequency of 120 strokes per minute to form a plug of compressed raw material serving as a pressure lock between the ambient atmosphere and the hydrolysis reactor. Due to its high frequency of operation, this feeder is likened to a machine gun. On the right-hand side, the chamber features a choke applying an adjustable pressure on the plug of raw material, and... 

The evolution of carbon dioxide was monitored by gas chromatograph (Hewlett-Packard model 5890) equipped with an HP thermal-conductivity detector and a Hayesep 100-120-mesh packed column (10 m X 3.2 mm). Helium was the carrier gas, and its flow rate was 28 mL/min. In each run, 0.5 mL of the gas mixture in the headspace was withdrawn from the test tube by using a pressure-lock gas syringe and injected into the GC column. The calibration curve was made by acidifying a known amount of potassium bicarbonate in the reaction tube under conditions similar to those of the corresponding experimental conditions. Standard carbon dioxide gas (Supelco) was used to confirm the formation of carbon dioxide. 

Fig. 10.9. A typical circulating fluidized bed combustor design [63]. The furnace (riser) is normally operated in the fast fluidization regime. The ash which is entrained from the furnace is separated from the flue gas in the cyclone. Most of the ash particles are sent into the siphon. The siphon is a small bubbling fluidized bed acting as a pressure lock. From the siphon the ash flows back into the riser. Reprinted with permission from Elsevier, copyright Elsevier 2007.

Solid transport Continuous Screw conveyor, vacuum-pressure lock... 

In the University of Utah process (Figure 19.18), crushed coal is impregnated with zinc chloride (approximately 3% w/w of the coal) and the mix is fed from pressurized lock-hoppers into... 

The head of the transfer bellows contains a winch and a hand operated grab which Is coupled to the plug unit to release the pressure lock as the closure Is unlocked. The winch Is now used to partially lift the plug unit out of the reactor to a height at which the grab Is locked within the bellows head. The pile cap crane Is then used to extend the bellows and fully withdraw the plug unit from the channel so that It Is contained within the transfer bellows. 

The original Cyanamid process used a single phase fusion melt of an acrylonitrile copolymer (molecular weight 30,000 60,000) and water and extruded, at about 50 bar, through a spinneret (hole size 60-160 pm) directly into a steam pressurized solidification zone, such that the subsequent release of water from the extrudate avoided any deformation of the extruded filaments and their condition remained such that they could be stretched up to some 25 times. The fiber was cooled with water and passed to the atmosphere by way of a pressure lock. 

Saturated steam> 1 Pa Take-up Drawing Cooling water Pressure lock P... 

Body cavity pressure lock on certain designs... 

Regarding pressure locking and thermal binding, the nuclear power plants have evaluated potential for pressure locking and thermal binding of gate valves and have taken action (modifications) to ensure that these phenomena do not affect the capability of power-operated gate valves to perform their safety related functions. 

Also, regulatory body requested that NPPs ensure reliability of the safety related power-operated Gate Valves that are susceptible to pressure locking or thermal binding. 

USNRC Generic Letter 95-07 (August 17, 1995), "Pressure locking and thermal binding of safety related power operated gate valves."... 

Table 8.5 High pressure lock systems for continuous extraction of solid material...

The filter cake can be separated from the drum by means of the various discharge methods described previously for vacuum drum filters. Doctor blade and roller removal are preferred for reasons of construction space. The solid is removed from the volute in the surge chamber and transported to the laterally positioned discharge chute. Depending on the mode of operation and the consistency of the filter cake a pump, pressure lock or valve is employed for the final discharge of the solids from the pressure vessel. 

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