How to install steam trap correctly

The drain valve should work normally. In addition to the correct selection of the drain valve, it is also necessary to install the correct pipes before and after the drain valve. The pipeline in front of the steam trap mainly refers to the drainage system from the equipment to the steam trap, and the condensate flows to the steam trap through the drainage outlet of the equipment. The pressure in the equipment and steam trap is the same, so the flow will depend on the gravity of the condensate. Therefore, the steam trap needs to be installed under the equipment, and the pipeline layout from the drainage point of the equipment to the steam trap should have a certain drop. If the low point of the drain valve installed on site is not adjusted, the casing siphon mechanism is required.

The diameter of the drain valve is not necessarily the same as the diameter of the drain pipe interface, because the equipment needs to be designed for different working pressure and flow. When selecting the diameter of the condensate pipe, the allowable condensate discharge is not necessarily the discharge when the equipment is at full load. When the equipment is started, the amount of condensate can be up to twice the operating load. At the same time, there is air in this part of the piping system. Generally, the calculated displacement is actually based on twice the steam load and 1.4 mbar friction resistance per meter. The condensate pipe behind the steam trap, namely the drain pipe of the steam trap, refers to the condensate pipe from the outlet of the steam trap to the condensate recovery header or in front of the atmosphere. There are not only condensate, air and other non-condensable gases in the pipeline, but also secondary steam generated due to pressure reduction. Wherever possible, pipes should be as low as possible.


Consider the actual situation: the condensate is relatively cold during startup, and the secondary steam volume is little or even no. But at the same time, the condensate water is relatively large, including some air. The diameter of the pipe should be at least the same as the diameter of the steam trap inlet. After running for a period of time, the condensed water will stabilize to the operating load. However, when the temperature of condensed water rises to the saturation temperature of steam, secondary steam will also be generated. The quantity of secondary steam is an important parameter when selecting the drain pipe of the steam trap. The selection of the condensate pipe behind the steam trap is based on the diameter of the secondary steam. Considering the cost, the smaller the condenser header is, the better.

Generally, the treatment water volume will be considered in the design, but in fact, the mixed fluid of condensate and secondary steam is always discharged from the steam trap. When discharging at saturation temperature, the secondary steam in the condensate pipe accounts for more than 99% of the total volume, and the condensate volume accounts for less than 1%. The secondary steam occupies almost all the volume of the pipe, and the condensate will flow at a lower speed than the secondary steam at the bottom of the pipe. Its mass flow plus the mass flow of steam is the total mass flow of the fluid passing through the trap. Due to the condensed water at the bottom of the pipe, the steam must be very wet, so the flow of the secondary steam needs to be limited within 15m/s, otherwise water hammer and erosion will occur in the bending part.

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