ASME U stamp shell and tube heat exchanger designed and manufactured by Sterling Thermal Technology

ASME U-stamp explained

What is an ASME certification?

ASME is the American Society of Mechanical Engineers. ASME certifications are used to determine the proper design, installation, inspection, and maintenance of various equipment, ranging from pharmaceutical to nuclear. The certification is a universally recognised way of informing users, regulators and customers that your products are high-quality and safe.

Within the ASME, there are multiple different accreditation and certification programs, including:

In this article, we will be talking about the latter. Manufacturers of boilers and pressure vessels that meet ASME’s code (the BPVC, Boiler and Pressure Vessel Code) can stamp their products with the “U-Stamp”.

Why Sterling TT needs an ASME U-Stamp?

As a heat exchange solution manufacturer, the ASME U-Stamp shows our dedication to high-quality boilers and pressure vessels. It shows that your goods have been thoroughly tested, are reliable, and meet rigorous industry standards.

As a highly regarded certification, it is often vital to businesses that pressure vessel manufacturers obtain and retain their certification.

Also, becoming  ASME certified, following ASME standards is the best way to keep staff sage in the production line.

Are ASME U stamps mandatory?

There is no legal compulsion to adhere to ASME standards — ASME describes them as guidelines. However, legal contracts (such as between a manufacturer and a customer) might require that a product be sold with a U-Stamp.

Types of U-Stamp

The U in U-stamp stands for “unfired”. This stamp applies to heat exchangers, which are unfired pressure vessels. There are multiple divisions of unfired pressure vessels according to ASME’s code, and each has its stamp.


An ASME U stamp certifies that a manufacturer has met the quality control requirements laid out by the ASME Boiler and Vessel Code, specifically Section VIII Division 1. A Manufacturer that holds this stamp is permitted to design, inspect, fabricate, and test unfired pressure vessels.


A U2 stamp will require you to meet Section VIII Division 2 of the BPVC guidelines. This is an alternative to the U stamp but broadly has the same purpose.


The U3 stamp is used for high-pressure vessels. The pressure vessels in question must meet the guidelines laid out in Section VIII Division 3 of the BPVC code.


The UM stamp is for miniature pressure vessels. These stamps are issued to pressure vessels with a smaller volume to show compliance with BPVC’s guidelines.


The UV stamp is specifically for the certification of the assembly of pressure relief valves. This is per the BPVC’s section VIII guides.


The ASME UD stamp is the code given to pressure relief devices. This code is issued to a ruptured or bursting disk, that complies with the BPVC guidelines. When issued, this stamp shows that the product in question has been thoroughly safety and quality tested.

In total, ASME offers 25 boiler and pressure vessel certifications for various types of products and stages in the manufacturing process. Find out more on ASME’s website.

Becoming ASME certified

Before submitting an ASME application, the ASME recommends all applicants thoroughly review all information related to their program. This includes any applicable forms, checklists and associated fees. By doing this, applicants ensure they understand what certification they are applying for and what is expected of them to achieve that accreditation.

To become ASME certified and gain an ASME U stamp, a manufacturer, like Sterling TT, will undergo an inspection process, typically around 6 months long. During the inspection process, they must be prepared for everything to be assessed by the inspector. This includes not only the products manufactured but also the team manning the production and any manuals provided to the staff .

If you want to learn more, further reading is available on the ASME website.

Boiler and pressure vessel certification

Within the ASME certification comes more specialised certifications for different areas of work. This is where the Boiler and Pressure Vessel Certification (BPVC) comes in.

The BPVC is used to assess and inspect products such as, but not limited to, power boilers, heating boilers, pressure vessels, fibre-reinforced plastic vessels, transport tanks and valves.

Should an item pass the Boiler and Pressure Vessel inspection, then it will be awarded with an ASME U stamp.

Why is this important for heat exchangers?

Heat exchangers are usually unfired pressure vessels, so the Boiler and Pressure Vessel Certification applies to them. Being stamped with an ASME U, U2 or UM shows that the vessel has been designed, built, and tested in accordance with ASME regulations.

Having this mark means a mark of the quality and functionality of the heat exchanger.

If you want to learn more about industry standards that apply to heat exchangers, read through our heat exchanger standards blog now.

How often are ASME standards released?

The Boiler and Pressure Vessel code is reviewed and reissued every 2 years. This allows inspectors, manufacturers and installers to stay on top of what is considered “best practice” in an ever-changing industry.

With this in mind, anyone who is currently ASME certified will have to purchase the most up-to-date version of the code to stay ASME certified.

 How Sterling TT can help

Sterling Thermal Technology cares deeply about meeting the highest manufacturing standards, and we can demonstrate this commitment with our certifications.

If you are looking for a heat exchanger partner who builds their pressure vessels to U-Stamp standards, contact our team of experts today, or read more about our manufacturing services.

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