Condensate removal Steam traps

During this process some water will have condensed in the steam-trap D and also in the distillation bulb F. If at the end of the steaming-out process, the Bunsen burner is removed from the generator A, the pressure in A will be reduced owing to steam condensation, and the liquid in F will be sucked back into D provided that the benL-over tube is carefully adjusted, the bulb F may be almost completely emptied of liquid as desired. Finally the condensed water in the steam-trap D may be run out by op ing the tap Tj. 

For a steam coil to operate efficiently, it must have all the latent heat in the steam. This is achieved by the use of a steam trap. The correct trap type must be selected for the particular application in order to prevent waterlogging. All condensate, air, or other noncondensable must be removed from the system without delay otherwise,... 

Steam traps are installed in condensate, mechanical return systems and are a frequently overlooked item for reducing operating costs. Large industrial process plants typically have many hundreds of steam traps installed to recover low-energy condensate and remove (potentially corrosive) air and carbon dioxide. 

Steam traps are automatic mechanisms that remove low heat-content air and condensate from the steam delivery system. The lack of steam traps or use of traps that fail to function properly leads to a gradual decline in heat-transfer efficiency, waterlogged heat exchangers, and water hammer (which may in turn result in ruptured pipes). When adequate maintenance of steam traps is neglected, this ultimately leads to a serious overall loss of operating efficiency. There are various types of steam traps, each designed for a specific function. Some common variations are discussed in the following sections. 

Inverted-bucket steam traps contain a small bucket that becomes buoyant if steam is present and shuts off a discharge valve. The presence of condensate causes the bucket to sink and the discharge valve to open. Any entrained air is removed through a small hole in the bucket. 

A superheater obtained from the Fisher Scientific Company was used. It was preceded by the usual steam trap to remove the condensed water. The thermometer in the superheater recorded 260°. 

A thermostatic steam trap to efficiently remove condensate from the chamber. This is open when cool and closed when in contact with steam. As condensate collects, the trap opens due to the slight temperature reduction, and the condensate is discharged. There is also a trap to remove condensate from the steam jacket. 

Figure 3.9. Steam heaters, (a) Flow of steam is controlled off the PF outlet temperature, and condensate is removed with a steam trap or under liquid level control. Subject to difficulties when condensation pressure is below atmospheric, (b) Temperature control on the condensate removal has the effect of varying the amount of flooding of the heat transfer surface and hence the rate of condensation. Because the flow of condensate through the valve is relatively slow, this mode of control is sluggish compared with (a). However, the liquid valve is cheaper than the vapor one. (c) Bypass of process fluid around the exchanger. The condensing pressure is maintained above atmospheric so that the trap can discharge freely, (d) Cascade control. The steam pressure responds quickly to upsets in steam supply conditions. The more sluggish PF temperature is used to adjust the pressure so as to maintain the proper rate of heat transfer.

The downstream piping must be adequately sized to effectively handle this volume. An undersized condensate returnline results in a high flash-steam velocity, which may cause waterhammer (due to wave formation), hydrodynamic noise, premature erosion, and high backpressure. The latter condition reduces the available working differential pressure and, hence, the condensate removal capability of the steam trap. In fact, with some traps, excessive backpressure causes partial or full failure. 

To a lOO-mL round-bottomed flask add 1-chlorobutane (25 mL,21.6 g,0.23 mole), sulfuryl chloride (8 mL, 13.5 g, 0.10 mole), 2,2 -azobis-(2-meth-ylpropionitrile) (0.1 g) and a boiling chip. Equip the flask with a condenser and gas trap as seen in Fig. 1. Heat the mixture to gentle reflux on the steam bath for 20 min. Remove the flask from the steam bath, allow it to cool somewhat and quickly, to minimize the escape of sulfur dioxide and hydrochloric acid, lift the condenser from the flask and add a second 0.1-g portion of the initiator. Heat the reaction mixture for an additional 10 min, remove the flask and condenser from the steam bath, and cool the flask in a beaker of water. Pour the contents of the flask through a funnel into about 50 mL of water in a small separatory funnel, shake the mixture, and separate the two phases. Wash the organic phase with two 20-mL portions of 5% sodium bicarbonate solution, once with a 20-mL portion of water, and then dry the organic layer over anhydrous calcium chloride (about 4 g) in a dry Erlenmeyer flask. The mixture can be analyzed by gas chromatography at this point or the unreacted 1-chlorobutane can be removed by fractional distillation (up to bp 85°C) and the pot residue analyzed by gas chromatography. 

Steam-heated calandrias with process boiling temperature less than 100°C can present control problems, especially at reduced rates and during start-up. In most such cases, low-pressure steam is used for heating. Control is usually achieved by throttling the entering steam in order to reduce the pressure at which it is condensed. At reduced rates this often results in steam pressures less than atmospheric or less than the steam condensate return system pressure. The steam is usually removed through steam traps which require a positive pressure differential to fiinction. In order for the trap to function, steam condensate floods part of the steam chamber imtil the steam pressure is sufficient to operate the trap. This leads to poor control and all the problems associated with condensate flooding. 

A section of a carbon steel pipe 5 m long (12 cm OD and 10 cm ID) is insulated with 20-cm-OD 85% magnesia insulation. Saturated steam at 25 psi is admitted at one end. condensation occurs within the pipe, and saturated liquid is removed at the other end by a steam trap (Fig, 2P-5). 

To overcome this problem, a submerged condensate pot is often installed instead of the steam trap (Fig. 17.le) as described earlier (item 5 above). An alternative remedy is replacing the steam trap by a level condensate pot (Fig. 17.1/). By varying the level control set point, the surface in the reboiler can be adjusted so that the reboiler operates at a pressure high enough to ensure condensate removal at all times without a pump. Note that the bottom of this drum is located below the bottom of the condensing side of the reboiler (189) otherwise, "dry reboiler operation at high rates will not be possible, and reboiler capacity will be reduced. 

Pressure tests of pipelines, jackets, steam coils, and arrangement to isolate and take out coils for maintenance are necessary. Steam traps shall be selected for the removal of condensate as soon as formed. There shall be no cooling of condensate in the jacket or coils (unless system is specially designed to recover heat from hot condensate also). 

Suitable steam traps shall be provided instead of providing valves for automatic removal of the condensate. 

Bimetallic trap An oil-filled element expands if it comes in contact with live steam and it closes the condensate exit valve. It may be possible to adjust the discharge temperature of the condensate from the trap. Hence, they can hold back condensate till it cools sufficientiy. The condensate is not removed immediately as soon as it is formed. The heat tranter coefficient in the system being heated is less due to this. 

Ovens must be provided with a system to deal with a fire, should it occur. Carbon dioxide or steam are probably the most efficient media. It should be remembered that CO2 is asphyxiating and a flow of CO2 gas can produce a static discharge. If steam is used, then a steam trap must be employed to remove condensed steam, which would otherwise form a lock of condensed steam and prevent the flow of steam when required in the event of a fire. 

The steam trap is an automatic valve used in every steam system to remove condensate and noncondensables. For process heating, steam traps keep the steam inside the equipment until the steam condenses so that the steam latent heat is (ransferred to the process. When steam condenses to condensate, steam trap valves open and remove... 

The objective of a steam trap is to remove noncondensable and condensate from steam with minimal loss of useful steam. While accomplishing this objective, a good steam trap should posses the following does not freeze in cold weather, adaptable to the full range of loads for the given application, requires minimal maintenance, and lasts a long time. 

The major problem with steam distribution is condensate removal. If steam traps are working properly while significant steam loss stiU occurs, the c ause may be inadequate drainage in condensate discharge locations (CDLs). The consequence is condensate backing up in the system due to blocked traps and plugged drains. The water falls to the bottom of the pipe, which could cause water hammer and lower heat transfer efficiency. 

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