How to choose the steam trap correctly

How to choose the steam trap correctly

An important understanding of trap selection is that there are general purpose traps for all applications and no compromise solution. The normal operation, displacement, energy efficiency, service life and cost of the trap are all considerations for the selection of the trap.

From the working principle, the Watt DT inverted bucket steam trap can be used in almost every application, but in fact it is not the case. Bi-metal steam traps are often installed on the steam mains with smaller installation space, and the requirements are In applications where subcooled drainage is used to absorb sensible heat from the condensate, inverted bucket traps are not suitable.

The simple technology of the steam trap allows customers to often try to meet all requirements with a trap, such as an inverted bucket trap. However, the difference in application requirements and equipment performance means that a trap cannot be used for all applications, otherwise it will affect the efficiency of the entire system.

Therefore, in order to ensure the correct selection of steam traps, the following factors should be considered: application, maximum load, system pressure, equipment type, minimum load, material, safety factor, back pressure, connection method, steam temperature, temperature control, Whether the condensate is recovered, the pressure difference, the lifting height after the trap, whether the venting device is installed, etc.

To understand the details of the use of traps, Watt energy-saving steam engineers must master the following. Usually the application can make the correct selection based on this information and experience. Special or less common applications require further consideration.

What is the application?

Is it a critical device?

Does the condensate need to be discharged in a supercooled state?

Does the equipment work continuously or in batches?

How much is the system pressure?

What is the maximum pressure upstream?

What is the maximum pressure/back pressure downstream?

What is the maximum/minimum pressure difference?

What is the steam temperature?

Is it saturated steam?

Is it superheated steam?

What is the degree of superheat?

What is the condensate load?

We need to calculate or estimate the maximum and minimum condensate loads and consider the safety factor based on the application. Whether there is a lifting pipe after the steam trap, the lifting pipe will increase the back pressure to reduce the pressure difference. The lifting height of 1 meter is equivalent to a back pressure of 0.11 barg.

Is there a temperature control system installed? The degree/pressure control valve affects the upstream pressure of the steam trap, thereby reducing the differential pressure and affecting the performance of the trap. This type of application (especially heat exchangers) requires a trap to react immediately to fluctuations in condensate volume and pressure.

The material of the trap, different application systems need to indicate the body material, there are many options such as cast iron / ductile iron / carbon steel / alloy steel / stainless steel (including 316L).

The connection method of the steam trap, considering the system pressure and customer preference, choose the appropriate connection method. The following connection options are available - threaded connections: -BSP/NPT, sleeve welding, butt welding, flanges, pipe joints and clean system sanitary clamps.

Will the ambient temperature be below zero? Freezing can cause some damage to the trap, especially for brass or cast iron valves.

Sometimes we also need to consider whether there are serious vibrations in the system that affect the operation of the trap. How much air will there be in the start/run phase system? Air has an effect on the trap.

Most of the above questions are easy to answer so that you can know the material, connection method, maximum condensate load and minimum differential pressure associated with the trap.

The following factors are especially important:

• System pressure

• Is it a critical device?

• Is it saturated steam?

• Is there temperature control?

• How much air is present in the system?

We know that some types of steam traps, such as thermostatic traps, not only prevent steam waste, but also reduce the condensate discharge temperature to facilitate sensible heat in the process condensate. This type of trap is mainly used on some non-critical equipment, such as heat pipes and oversized heating coils.

The sensible heat can be absorbed or heated for another process. Alternatively, install a cooling tube in front of the trap to ensure accurate condensate discharge temperature. Water is not allowed in many applications because water can cause the following problems:

• Reduce production

• Corrosion condensate pipe

• Insufficient supervisor hydrophobic

Therefore, for critical equipment that needs to discharge condensate at steam saturation temperatures, such as:

• Temperature control equipment such as heat exchangers.

• Steam heating equipment with a small space.

Only inverted bucket steam traps or float steam traps can be considered. Other types of traps can cause chilled water in the supercooled state.

We know that it is necessary to remove the air in the system in time (most systems are like this, especially during the start-up phase). At this time, the inverted bucket trap is not suitable because the exhaust hole on the inverted bucket is relatively small and the exhaust is very slow. (unless a separate exhaust valve is installed). Watt's BW11 thermostatic trap and FQ float trap with venting have good venting performance.

The exact model of the Watt trap can be selected based on its ability to handle the following issues:

• Water hammer

• Corrosion and impurities

Any equipment should be designed to avoid water hammer. Some types of traps have better water hammer resistance than other types of traps if they occur.

Generally, steam traps are always affected by impurities in the carrier or pipeline. If the trap contains a built-in filter (such as DT580 inverted bucket trap), the benefits are obvious. Since the drain hole of the trap is relatively small and is easily blocked by impurities or pipe slag, it is recommended that a filter be installed upstream of any type of trap.

Different types of steam traps are available to meet specific industrial and application requirements. For example, stainless steel steam traps designed for clean steam systems can be used in the food, pharmaceutical and other industries. Specific types of traps are available for specific applications, such as the Watt BW11S heat trace trap.

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