Steam chest

Steam-Chest Expansion. In steam-chest expansion the resin beads in which gas is already present are poured into molds into which steam is injected. The steam increases the temperature close to the melting point and expands within the stmcture to create beads with food cushioning and insulating properties. Expanded polystyrene is widely used in this process for thermal insulation of frozen food packaging. 

Calculated from measured steam chest and vapor-head pressures. 

To nelp consei ve steam economy, venting is usually done from the steam chest of one effecl to the steam chest of the next. In this way, excess vapor in one vent does useful evaporation at a steam economy only about one less than the overall steam economy. Only when there are large amounts of noncondensable gases present, as in beet-sugar evaporation, is it desirable to pass the vents directly to the condenser to avoid serious losses in heat-transfer rates. In such cases, it can be worthwhile to recover heat from the vents in separate heat exchangers, which preheat the entering feed. 

Figures 29-19 and 29-20 illustrate two different mecbanical-hydraulic systems. Figure 29-19 is a bar-lift steam chest with a heavy-duty hydraulic seivo. The speed-sensing element is a flyball assembly attached to a rotating pilot. This rotating pilot sends a control-pressure signal that is proportional to speed to a bellows on the seivo. A change in control pressure initiated through the rotating pilot by either speed or speed changer deflects the bellows and seivo pilot valve. The seivopiston position is proportional to the control pressure.

If the process demand is light and high-extraction flow is not required, then most of the power wiU be from the condensing flow. The choice would be to save cost by a smaller inlet and steam chest, which would terminate the total-extraction hne at D and the zero-extraction line at A,... 

It is easy to improperly design a steam trap. The design must work for two circumstances and often a designer will check only one of these. The circumstance often overlooked is as follows On startup or upset the steam control valve can open wide so that the steam chest (assume for this discussion that we are speaking of a reboiler) pressure rises to full steam line pressure. At a... 

The required orifice continuous flow capacity is determined at steam chest pressure to condensate system pressure at a flow 6 to 8 times design. If designed for normal flow the trap would have to be open 100% of the time. Then, as stated above, a body size is selected that can contain the required orifice (not be above the stated... 

Evaporators, Horizontal-Tube Type - The basic horizontal-tube evaporator is illustrated in Figure 12. The body of this evaporator is the liquor compartment and is in the form of a vertical cylinder. It is closed, top and bottom, with dished heads, although the bottom may be conical. The lower body ring is provided on opposite sides with steam compartments, closed on the outside by cover plates and on the inside by tube sheets. Between these tube sheets are fastened a number of horizontal tubes. The two steam chests with their connecting mbes form the steam compartment, and the tube wall heating surface. Steam is introduced into one steam chest and as it flows through the tubes it washes non-condensed gases and condensate ahead of it, so that these are withdrawn from the opposite steam chest. 

In ordinary operation only condensate and non-condensed gases are removed from the exit steam chest. The connection for feeding the liquid to be evaporated may be attached to the body at any convenient point (D), but the discharge for thick liquor is usually in the center of the bottom (E). Suitable brackets are cast on the bottom to rest on the supporting steel. Most evaporators are provided with sight glasses. 

Dampf-kanal, m. steam pipe steam port, -kasten, m. steam box, steam chest steaming chamber. 

Steam Goge(s Steam Chest. Panel Mounted ... 

A calorifier has a heating surface area of 2m and is required to heat a flow of water from 65°C to 80°C. The U value has been found to be 1250 W/m °C, and steam can be supplied at a gauge pressure of 2 bar in the steam chest. What rate of water flow can the calorifier handle (see Figure 22.3). From Equation (22.2) ... 

Assuming that the discharge pressure from the ejector, that is in the steam-chest, is 170 kN/m2 at which the latent heat, A.0 = 2216 kN/m2, then a heat balance across the unit gives ... 

Examination of the data indicates one obvious point in that the temperatures in the steam chests in effects 2 and 3 are higher than the temperatures of the boiling solution in the previous effects. The explanation for this is not clear although a steam leak in the previous effect is a possibility. Further calculations may be made as follows, starting with a mass balance on the basis of 1 kg feed. 

An evaporator operating on the thermo-recompression principle employs a steam ejector to maintain atmospheric pressure over the boiling liquid. The ejector uses 0.14 kg/s of steam at 650 kN/m2, and is superheated by 100 K and the pressure in the steam chest is 205 kN/m2. A condenser removes surplus vapour from the atmospheric pressure line. What is the capacity and economy of the system and how could the economy be improved ... 

Steam atmosphere pyrolysis, 27 466 Steam balances, 70 146, 147, 148t Steam blanketing, 26 130 Steam bleeds, 70 160 Steam-chest expanded food packaging, 73 48... 

The 300-psig steam next passes through the steam nozzle. This is an ordinary nozzle. It screws into a hole in the wall, which separates the steam chest from the turbine case. The nozzle is shaped to efficiently convert the pressure of the 300 psig to steam velocity. The pressure of the steam, as soon as it escapes from the steam nozzle, is already the same as the exhaust steam pressure (100 psig). 

Step 1. The motive steam conditions are 375°F and 160 psia, which determine point A. Note that the motive-steam pressure is the pressure in the steam chest. 

The escape, or exit, velocity of this steam is a function of the steam pressure in the steam chest. If we raise the pressure in the steam chest by 30 percent, then the velocity of the steam leaving the nozzle would go up by 30 percent as well. It is true that I could simply open up the governor, and reduce the pressure drop of the steam across the gover-... 

What I wish to achieve is to maintain the same horsepower output from the turbine. But at the same time, I want to force open the governor speed-control valve, raise the pressure in the steam chest, but decrease the steam flow through the steam nozzle. The only way this can be done is to make the nozzle smaller. 

We could shut down the turbine and unbolt the steam chest, to expose the nozzle block, which is the wall that separates the steam chest from the turbine case. We could unscrew the existing nozzle, and replace it with a smaller nozzle. A nozzle of 20 percent less diameter would reduce the nozzle cross-sectional area by 36 percent ... 

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