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Piping and Installation of Steam Traps – Technical Department, Hangzhou Watt Energy Saving Engineering Co., Ltd., Zhong Yuyu. For steam traps to function properly, in addition to selecting the right type of trap, it is also necessary to ensure proper piping and installation before and after the trap. The pipeline before the steam trap refers mainly to the drainage system from the equipment to the trap. The condensate flows to the steam trap through the drainage outlet of the steam-using equipment; since the pressure inside the equipment and the steam trap is the same, the flow is driven by the gravity of the condensate. Therefore, the steam trap must be installed below the equipment. The piping layout between the device’s drainage point and the steam trap should have a certain slope. If it is not possible to adjust the installation of the steam trap at the lowest point on site, a sleeve siphon mechanism must be used. Watt Energy-saving steam engineers recommend to customers a flow rate that is based on maintaining the lowest possible pressure drop. The diameter of the drain valve does not necessarily have to be the same as the diameter of the drain pipe connection. Because the equipment must be designed to handle different working pressures and flow rates. When selecting the diameter of the condensate pipe, the amount of condensate allowed to be discharged is not necessarily the drainage volume when the equipment is operating at full load. When the equipment starts up, the amount of condensate water can be as much as twice the operating load. At the same time, there is also air in this section of the piping system. Typically, the calculated displacement is actually based on twice the steam load and 1.4 mbar of frictional resistance per meter. The condensate pipeline downstream of the steam trap, that is, the trap discharge pipeline, refers to the condensate pipeline from the outlet of the steam trap to the main condensate recovery pipe or the atmosphere. This pipeline contains not only condensate, air, and other non-condensable gases, but also secondary steam generated as a result of pressure reduction. Whenever possible, the piping should be as low as possible. Consider the various actual conditions: at startup, the condensate is relatively cold, and there is little or no secondary steam. But at the same time, the amount of condensate water is the greatest, and it also includes some air. The diameter of the pipe must be at least the same as the diameter of the steam trap inlet. After running for a period of time, the condensate volume stabilizes at the operating load. But as the temperature of the condensate rises to near the steam saturation temperature, secondary steam is also generated. When selecting the drain pipe for a steam trap, the amount of secondary steam is the most important parameter. The selection of the condensate pipe downstream of the steam trap is based on the diameter chosen for the secondary steam. Considering costs, the condensate main is always made as small as possible. Usually, the amount of water to be treated is taken into consideration during design, but in reality, what is discharged from the steam trap is always a mixture of condensate and secondary steam. Not everyone is aware that the volume of secondary steam can be as high as 400 times that of the condensed water. This indicates that the diameter of the condensate recovery pipeline should be determined based on the steam volume rather than the condensate volume. At saturated temperature discharge, secondary steam accounts for over 99% of the total volume in the condensate pipeline, while the volume of condensate makes up less than 1%. The secondary steam occupies almost the entire volume of the pipe. The condensate will flow at the bottom of the pipe, at a speed lower than that of the secondary steam. Its mass flow rate, plus the mass flow rate of steam, constitutes the total mass flow rate of the fluid passing through the steam trap. Due to the condensate water at the bottom of the pipes, the steam will inevitably be humid; therefore, the flow velocity of the secondary steam must be limited to 15 m/s, otherwise water hammer and erosion will occur in the curved sections. In their daily work, Watt Energy-saving’s steam engineers have found that the feasibility of connecting several steam traps operating at different pressures to a single common recovery main is often questioned. This is because it is believed that high-pressure condensate may interfere with the discharge of low-pressure condensate. However, one fact is overlooked: high or low pressure exists only within each trap; at the outlet of the trap, the pressure is that of the common recovery pipe, perhaps plus the back pressure generated by the movement of secondary steam. If the pipe size is chosen too small, it is certainly possible for the back pressure to rise excessively, thereby restricting or even hindering the operation of the steam trap.