Five steps to correctly size a Venturi Orifice Steam Trap

Five Steps to Correctly Size a Venturi Orifice Steam Trap

Steam traps can come in multiple sizes for a myriad of operating conditions meaning that it is important to select the right size. The reason it is critical to accurately size a steam trap is because it ensures the performance and reliability of your steam system. An incorrectly sized steam trap can lead to energy loss, equipment failure and operational inefficiencies. In this article, we’ll go through the steps required to determine the correct steam trap size.

Step 1: Identify the connection type and industry standards

The first step in sizing your steam trap is to identify the type of connection each system requires. Globally it is accepted that the most applicable flange standards are either the American ANSI or the European ISO standards. To meet these requirements suppliers need to know which standards the customers are using. Furthermore the connections can either be flanged or threaded:

Flanged connections – Are classified according to ANSI or DIN standards. For ANSI, you need to know the pressure class (e.g. #150, #300, #600) and the nominal diameter (e.g. ½”, ¾”, 1″). For DIN, we supply PN40 as standard, but you must specify the nominal diameter (e.g. DN15, DN20, DN25).

Threaded connections: For NPT or BSP connections, please note the nominal diameter (e.g. ½”, ¾”, 1″).

To ensure compatibility and achieve the desired results, it is important to know the connection types and standards used in the individual plants.

Step 2: Define the heating application

The heat load on the application determines the volume of condensate produced. This has a significant impact on the sizing of the steam trap. An example of low condensate volume would be line drainage or trace heating. Whereas an example of high condensate volume would be air heaters or plate heat exchanges. Each application has its own specific requirements depend on it’s heat load. At this point, it is important to determine whether the trap is intended for line drainage, trace heating or another type of heat exchanger.

Step 3: Specify the parameters of the steam system

To ensure that the steam trap is an accurate size the suppliers need to provide detailed steam system parameter. The key information that needs to be considered are;

– What is the main steam pressure?

– How much pressure is used in the application?

– What are the condensate back pressure? If any?

– Whether the condensate is vented to the atmosphere?

This key data helps to understand the operating conditions and limitations of the system.

Step 4: Detailed information on the operating conditions

The operating conditions, including the condensate load and heat load for the application, are critical to the sizing of the steam trap. The information on operating conditions can be acquired in two ways:

The customer should specify the condensate load an heat load in kW, KJ or another thermal unit of measure


If not, EBE can calculate the required energy based on the following information: Vapour pressure into the process, condensate pressure out of the process, start and end temperature, required cycle time for batch processes, material to be heated (e.g. rubber, water, air) and the material volume.

Step 5: Utilise experience and data

The data and experience from similar previous application can be used in different plants. In most cases, it is likely that a system that works in one plant is also suitable for another plant. This approach can streamline the design process and ensure consistency between plants.

Once the correct sized steam trap has been installed in an application and its performance has been verified, it can serve as a model for duplicating in similar systems. Top of Form


By following these steps, you can ensure that your steam traps are properly sized to efficiently and effectively meet the needs of your plant. Remember, the most critical information is the connection sizes used in different plants. If you have any questions or need more information, please do not hesitate to contact us.

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