Low, Medium and High Pressure Boiler Tube

Boiler tubes are important components in steam boilers used for power generation and heating. According to the pressure levels these tubes can withstand, they are divided into three categories: low-pressure, medium-pressure and high-pressure, with significant differences in material selection, manufacturing standards and application scenarios. The following is an overview of each type.

Low Pressure Boiler Tubes:
Application: Low-pressure boiler tubes are designed for applications with working pressures not exceeding 15 psi (pounds per square inch) or 1.03 MPa (megapascals).
Material: Common materials for low-pressure boiler tubes include ASTM A179, ASTM A192, etc. These materials have good heat transfer properties and are suitable for relatively low-pressure steam applications.

Usage: Low-pressure boilers are generally used in heating applications and industries where medium temperatures and pressures are sufficient, such as domestic hot water heating, food processing equipment, small industrial equipment, etc.

Medium Pressure Boiler Tubes:
Application: Medium-pressure boiler tubes are designed to withstand pressures between 15 and 100 psi (1.03 to 6.89 MPa).
Material: ASTM A210 and ASTM A213 are commonly used materials for medium-pressure boiler tubes. These materials have better mechanical properties and can withstand higher pressures and temperatures than low-pressure tubes.
Usage: Medium-pressure boilers are often used in industrial processes that require higher temperatures and pressures, such as manufacturing and power generation, medium-sized power station boilers, steam supply for the chemical industry, and ship auxiliary boilers.

High Pressure Boiler Tubes:
Applications: High-pressure boiler tubes are designed to handle pressures exceeding 100 psi (6.89 MPa).
Material: Common materials for high-pressure boiler tubes are ASTM A192, ASTM A210, ASTM A213, ASTM A335, etc. These materials are selected because of their high tensile strength, corrosion resistance, and ability to withstand high temperatures.
Usage: High-pressure boilers are vital in power plants, which require high-temperature and high-pressure steam to drive turbines to generate electricity.

In addition to pressure considerations, other factors such as temperature, corrosion resistance, and mechanical properties also play a vital role in choosing the right boiler tube material. Both welded pipes and seamless pipes are used, and seamless pipes are usually more suitable for high-pressure applications due to their high strength and reliability.

Notes on boiler tube selection:

1. Pressure and temperature matching
Using 20# (ASTM A192) steel in low-pressure environments can reduce costs, but alloy steel (such as 12Cr1MoVG) must be selected for high temperature and high pressure.

2. Medium corrosiveness
If the flue gas contains sulfur (such as coal-fired boilers), high-pressure pipes must use sulfur-resistant materials such as T91/P91.

3. Welding process
Preheating and post-weld heat treatment (PWHT) are required for high-pressure boiler tube welding to prevent cold cracks.

Common questions:

Can medium-pressure boilers be replaced by high-pressure boiler tubes?
Yes, but the cost is high; otherwise it is strictly prohibited (medium-pressure tubes will burst in high-pressure conditions).

How to determine boiler tube failure?

Regularly check the wall thickness (ultrasonic) and observe surface oxide peeling or cracks (metallographic analysis).

Read more: Boiler Tube Size Chart or Carbon steel ERW boiler tube & air heater tube specification