Vacuum service

Vacuum Service - The o-ring is the only common popular elastomeric form that seals in both directions. 

Available in metal only, compared more with tray type performance than other packing materials. About same HETP as Spraypak for available data. Used In towers 24 inches and larger. Shows some performance advantage over bubble cap trays up to 75 psia in fractionation service, but reduced advantages above this pressure or in vacuum service. 

If the system differential pressure requirements are low, sometimes a fan can be used. A fan is limited to a maximum of about 65 inches of water (just over 2psi) in vacuum service or 77 inches of water in pressure service (just under 3psi). To estimate fan horsepower use the equations found in Chapter 6 in the section entitled Horsepower Calculation. In lieu of manufacturer s data use an adiabatic efficiency of 50% for initial work. 

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... 

Criteria for Sizing Connecting Lines in Vacuum Service... 

VENTILATING FANS FOR MINES a TUNNELS, ETC. EXHAUSTERS FOR LOW VACUUM SERVICE... 

Reference [11] provides a complete procedure for testing ejector units in vacuum service, and the charts and calculation procedures for the tests. 

Tray spacing can usually be about 6 in. less than for a corresponding bubble tray. Sieve trays are operating on spac-ings of 9 in. and up to 30 in., the latter being necessary for high vacuum service. Spacing of 12-16 in. is common. 

Vacuum distillation varies with the system tmd particularly with the absolute pressure required at the bottom of the column normally select low pressure drop in the range of 0.1 to 0.2 in. water/ft of packing. For in vacuum service of 75 mm Hg and lower, the pressure drop obtained from the GPDC,... 

Vacuum service requires recognition of minimum liquid flow refer to section on minimum wetting rate. Pressure drops are designed to be low, but normally not lower than 0.10 in. water/ft. 

Inlet and oudet liquid nozzles are sized by conventional pressure drop evaluations or by the more common velocity guides. For low-pressure vacuum services, velocities should not be used to establish any critical connection size. (Figure 10-63 is a useful guide for the usual case.)... 

At pressures greater than about 100 psig, the slope of the vapor pressure curve, (At/Ap) is low enough not to influence the sensible heating zone equation, as most of the tube is in vaporization. However, at low pressures and vacuum service, a large portion of the tube is in sensible heat. 

In vacuum service, the large fraction of the tube length used for sensible heating leaves little density difference for thermal circulation. This fact, plus the frequent need for circulating viscous materials, points towards forced-circulation reboilers for vacuum service. 

Not too suitable for vacuum services due to pressure drop limitations but are used in application. 

Figures 12-104 and 12-105 illustrate system connections for gas compression and vacuum service.

Because these machines require internal lubrication of the sliding-vane surface, no extreme effort is made to arrange special bearing and shaft seals, except that a gas seal of the conventional mechanical design is usually used to prevent gas from escaping to the outside or to prevent air inleakage in the case of vacuum service. For hazardous or... 

Lines in vacuum service, 135—141 Line symbols, 17, 23 Numbering, 23 Lined centrifugal pumps, 171 Liquid-solid particle, separators, 228 Baffle type specifications, 248 Baffle type, 247, 248 Centrifugal, 256, 259-261 Chcvron-vanc, 248, 235 Comparison chart, 230 Cyclone, 259 Specification form, 268 Vane, 259 Wire mesh, 246 York-vane, 248 Low pressure storage... 

Mode of operation Generic type Feed condition Specific dryer types Jack- eted Suitable for heat-sensitive materials Suitable for vacuum service Retention or cycle time Heat transfer method Capacity Typical evaporation capacity... 

In many applications the pressure drop available to drive the fluids through the exchanger will be set by the process conditions, and the available pressure drop will vary from a few millibars in vacuum service to several bars in pressure systems. 

The tube lengths used for vertical thermosyphon reboilers vary from 1.83 m (6 ft) for vacuum service to 3.66 m (12 ft) for pressure operation. A good size for general applications is 2.44 m (8 ft) by 25 mm internal diameter. Larger tube diameters, up to 50 mm, are used for fouling systems. 

An important problem with rupture discs is the flexing of the metal as process pressures change. Flexing could lead to premature failure at pressures below the set pressure. For this reason some rupture disc systems are designed to operate at pressures well below the set pressure. In addition, vacuum service may cause rupture disc failure if the relief system is not specifically designed for this service. 

They clamped a 100-psi air hose to a nipple on the tank. A busy instrument worker gave them a gauge. The gauge was incorrectly chosen for vacuum service and not pressure because the vacuum identifier was small. 

Moisture and corrosives content are the major gas stream characteristics requiring design consideration. Standard fabric filters can be used in pressure or vacuum service, but only within the range of about 640 mm of water column (25 inches of water column). Well-designed and operated baghouses have... 

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