Steam traps

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 

There are hundreds of steam traps all over the place in a site and many of them could malfunction if there is no best practice of maintenance in place. That is the reason why the most common energy waste is steam leakage from bad steam traps. 

The leakage rate can be easily estimated by using the general orifice equation  

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Steaming-out the steam distillation apparatus. After the cleaned steam -distillation apparatus (Fig. 88) has been assembled, it is essential to pass steam through it for some time to remove readily soluble alkali. All the taps on the apparatus are opened and the water in the steam generator boiled vigorously. The steam will gradually pass into the apparatus. After a few minutes, the tap of the tap-funnel C may be closed and soon afterwards the tap Ti of the steam-trap finally the tap Tj of the funnel G may be closed, Steaming-out should then be continued for not less than one hour, the receiver J not being in place. 

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. 

Distillation of the ammonia. The ammonia which has been liberated quantitatively in the bulb F must now be distilled completely into the receiver J. The tap Ti on the steam-trap is therefore closed and tap T2 opened so that the steam is delivered into the bulb F, which at the same time is heated directly with the flame of a micro-Bunsen... 

Condensa.te Return Systems. Ia a process plant, steam traps are used to drain and return condensate. Given proper appHcation and continuous maintenance, these can operate with minimal steam leakage. Correct iastaHation is also important (12). 

For draining principal items of process equipment, level-controUed condensate chambers provide much better performance and rehabiUty than steam traps. Usage is generally justified when condensate flow is greater than 4500 kg /h. 

F. S. Pychewic2, "Steam Traps—The Oft Forgotten Energy Conservation Treasure," Proceedings, 1985 Industrial Energy Conservation Technology Conference, Texas Industdal Commission, Houston, Tex., p. 392. 

High reliability. Many things can go wrong with a steam tracing system but, very few of the potential problems lead to a heat tracing failure. Steam traps fail, but they usually fail in the open position. 

High in stalled co.sts. The incremental piping required for the steam supply system and the condensate return system must be installed, insulated, and, in the case of the supply system, additional steam traps are often required. The tracer itself is not expensive, but the labor required for installation is relatively high. Studies have shown that steam tracing svstems typically cost from 50 to 150 percent more than a comparable electric tracing system. 

High maintenance co.st.s. Leaks must be repaired and steam traps must be checked and replaced if they have failed. Numerous studies have shown that, due to the energy lost through leaks and failed steam traps, an extensive maintenance program is an excellent investment. Steam maintenance costs are so high that for low-... 

Always provide a suitable knockout pot ahead of the jets. Water droplets can quickly damage a jet. The steam should enter the pot tangentially. Any condensate leaves through a steam trap at the bottom. It is a good idea to provide a donut baffle near the top to knock back any water creeping up the vessel walls. 

One pound of steam at Opsig occupies 1,600 times the volume of a pound of water at atmospheric conditions. This ratio drops proportionately as the pressure increases. When the steam collapses, water is accelerated into the resulting vacuum from all directions. This happens when a steam trap discharges relatively high-pressure flashing condensate into a pump discharge line. 

Water hammer can also occur in steam mains, condensate return lines, and heat exchange equipment where steam entrapment can take place (Fig. I). A coil constructed and installed as shown here, except with just a steam trap at the outlet, permits steam from the control valve to be directed through the center tube(s) first. Steam then gets into the return header before the top and bottom tubes are filled with steam. Consequently, these top and bottom tubes are fed with steam from both ends. Waves of condensate are moved toward each other from both ends, and steam can be trapped between the waves. 

No section on energy conservation would be complete without rules of thumb on steam traps. Here are three handy correlations for steam traps ... 

The Cv Concept. From a quantitative standpoint, steam loss can be estimated through the application of the C, concept. A familiar term in control valve technology, C, expresses the flow capability of a fluid-controlling device—in this case, a steam trap. A large C,. means a high flow rate a low C, means a low flow rate. 

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... 

Vallery, S. J., Setting Up a Steam-Trap Standard, Chemical Engineering, February 9, 1981. 

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,... 

The incident occurred soon after the main had been brought back into use after a turnaround. It was up to pressure, but there was no flow along it. The steam trap was leaking and had been isolated. An attempt was made to get rid of condensate through the bypass valve. But steam entered the condensate header, and the line was isolated, as shown in Figure 9-9. Condensate then accumulated in the steam main. 

Figure 10-11. Condensate in the steam—the result of too few steam traps-knocked off the impingement plate and damaged the calandria tubes.

The steam supplied to the shell of a distillation column reboiler was very wet, as there was only one steam trap on the supply line although at least three were needed. In addition, condensate in the reboiler drained away only slowly because the level in the drum into which it drained was only 1.4 m below the level in the reboiler. 

Kondens-rohr, n. condenser tube, -topf, m. condensing pot steam trap, -wasser, n. condensation water, condensed water, condensing water. 

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