How To Select Steam Traps

How to select steam traps

When choosing a steam trap, you cannot simply choose from the maximum discharge volume. Special attention should be paid to: "It is never allowed to apply a steam trap only based on the pipe diameter." It must be selected according to the principle of selection of traps and the specific conditions of the condensate system. In general, it should be selected according to the following three aspects.

1. First, select and determine the type of steam trap according to the heating equipment and the requirements for draining condensed water.

For heating equipment that requires the fastest heating speed and strict heating temperature control, it must be kept in the heating equipment so that no condensation water can accumulate. As long as there is water, it must be drained. It is best to choose a mechanical steam trap that can drain saturated water. . Because it is a trap that drains when there is water, it can eliminate the adverse consequences caused by the accumulation of water in the equipment in time, and quickly improve and ensure the heating efficiency required by the equipment.

For heating equipment that has a large heating surface and does not require strict heating speed and heating temperature control, water accumulation can be allowed, such as steam heating drainage, process heat tracing pipeline drainage, etc. It is best to choose a thermostatic steam trap.

For medium and low pressure steam transmission pipelines, the condensed water generated in the pipeline must be quickly and completely removed, otherwise it is easy to cause water hammer accidents. The increase in the water content of the steam reduces the temperature of the steam, which cannot meet the process requirements of the steam equipment. Therefore, mechanical steam traps are the best choice for medium and low pressure steam transmission pipelines.

2. Secondly, according to the maximum working pressure and maximum working temperature of the steam equipment, determine the nominal pressure of the steam trap and the material of the valve body; determine the connection method and installation method of the steam trap.

The nominal pressure of the steam trap is generally divided into: 0.6Mpa, 1.0Mpa, 2.0Mpa, 0.6Mpa, 2.5Mpa, 4.0Mpa, 5.0Mpa. When selecting, the nominal pressure of the steam trap cannot be lower than the maximum working pressure of the steam using equipment. At the same time, the material of the valve body is selected according to the nominal pressure of the trap, the maximum working temperature, and the installation environment. Nominal pressure ≤1.0Mpa, use cast iron or carbon cast steel; Nominal pressure ﹥1.0Mpa, use carbon cast steel or alloy cast steel.

The maximum working temperature of the steam trap is determined according to the steam used by the steam-using equipment, and the selection should not be lower than the temperature of the steam used.

The steam trap has two installation methods, horizontal and vertical, which is determined by the connection position of the pipeline and the steam trap. The connection methods of the steam trap include thread, flange, welding, butt clamp, etc., which must be determined according to the highest working pressure, the highest working temperature of the steam trap and the requirements of the corresponding connection part of the steam using equipment.

3. Finally, select and determine the performance parameters of the steam trap according to the size of the displacement.

In addition to the parameters such as the pressure and temperature of the steam trap, which should match the conditions of the equipment used, the drainage volume of the steam trap under various pressure differences is an important factor in the selection of the steam trap. If the drainage volume of the selected steam trap is too small, all the condensed water that has reached the trap cannot be removed in time, which will hinder the condensed water from flowing back, which will eventually cause blockage and significantly reduce the heating efficiency of the equipment. On the contrary, the selection of a steam trap with a large displacement will cause premature wear and failure of the valve closure. As the valve body increases, its manufacturing cost will also increase, which is not economical. Therefore, the amount of condensed water generated in the equipment or pipeline must be correctly measured or calculated according to the calculation formula to provide conditions for the correct selection of steam traps.

Therefore, when determining the drainage volume of the steam trap, the "safety factor K" should be determined according to the characteristics of various steam-using equipment and the discharge form of the trap. Generally, it should be calculated as follows:

The hourly drainage volume of the trap = the hourly condensate volume of the equipment or pipeline × the safety factor K

The amount of condensate produced by the equipment per hour is the steam consumption of the equipment per hour. The safety factor K is not stipulated in theory, nor can it be obtained by calculation, but is data derived from experience. The determination of the safety factor K has two main factors: one is the drainage performance of the steam trap. Due to the limited ability of the steam trap to adapt to the system pressure difference and flow rate changes, and the capacity of the steam trap provided by the manufacturer to the user is expressed in terms of continuous discharge per hour, but in most cases the steam trap is intermittent Discharged. Another aspect is the type of steam-using equipment. Different steam using equipment has different load characteristics of condensate generated during its operation. It is necessary to consider the large amount of condensed water generated when the steam-using equipment is started and the change of its condensate water discharge during normal operation; at the same time, different conditions such as continuous operation or intermittent operation of the equipment should also be considered. If the drainage characteristics change greatly and the equipment is operated intermittently, then the safety factor should be selected to be too large, otherwise it is better to choose a small. Considering all factors, it is recommended to take safety factor K=2～4 for different steam using equipment.