Code standards save lives. For building and maintaining pressure vessels, stainless steel tanks, and other components, meeting code standards is essential. The American Society of Mechanical Engineers (ASME) provides internationally recognized standards for how these products are designed, fabricated, inspected, and repaired.
However, different applications and vessel types require different levels of certification, which is where ASME’s stamp system comes into play.
Spokane Stainless Technologies maintains several critical ASME and National Board stamps including the U, UM, H, and R stamps. In addition to these stamps, we have a Certified Weld Inspector (CWI) and Certified Individual (CI) on staff to ensure every vessel meets the highest standards of quality, safety, and code compliance. These certifications reflect our commitment to building safe, compliant, and expertly engineered vessels to meet a wide range of customer needs.
What is the ASME U Stamp?
The ASME U stamp is one of the most recognized and widely used pressure vessel certifications. It indicates that a manufacturer is authorized to build pressure vessels in full compliance with Section VIII, Division 1 of the ASME Boiler and Pressure Vessel Code.
In simplified terms, a U stamp indicates the vessel has been designed, fabricated, inspected, and tested to meet strict code requirements for safety, strength, and reliability.
What does that process look like at Spokane Stainless Technologies?
- Rigorous design calculations
- Material traceability and certification
- Qualified in-house welding procedures
- Quality control and quality assurance
- Final testing and official stamping
The U stamp applies to a broad range of pressure vessels and signals to customers that the product is built to perform.
At Spokane Stainless Technologies, holding a U stamp signifies we have the expertise, processes, and oversight to deliver vessels that meet these requirements.
What is the ASME UM Stamp?
The ASME UM stamp is similar to the U stamp but applies to smaller pressure vessels. Eligibility for the UM stamp is based on specific limits for volume and pressure. For example, vessels up to 5 cubic feet must not exceed 250 psi, while vessels up to 3 cubic feet may operate at 350 psi, and those up to 1.5 cubic feet can reach pressures of up to 600 psi. The UM stamp ensures that even smaller vessels are designed, fabricated, and tested to the same high standards of quality and safety that apply to larger vessels stamped with the U.
At Spokane Stainless Technologies, we hold the UM stamp as part of our certification portfolio. This allows us to manufacture smaller vessels with the same level of expertise, code compliance, and attention to detail that would be found from any ASME-certified product.
What makes UM-stamped vessels different?
- They are smaller in both size and capacity
- Inspection process is the same, but does not require a third-party inspector
- They are often more cost-effective to produce and purchase
It is important to note that while UM stamp applies to smaller vessels the materials, fabrication processes, and safety expectations remain just as high as larger, U-stamped vessels. At Spokane Stainless Technologies, we apply the same craftsmanship and quality controls to UM-stamped vessels, which are engineered for specific applications requiring smaller sizes without compromising performance or compliance.
What is the ASME H Stamp?
The ASME H stamp certifies the manufacture of heating boilers and related pressure vessels that operate under relatively low pressure and temperature, as specified in Section IV of the ASME Boiler and Pressure Vessel Code.
This certification ensures that heating boilers, such as hot water boilers, low-pressure steam boilers, and heat exchangers, are designed and fabricated to meet rigorous safety and quality standards.
The H stamp is the confirmation that the equipment can safely handle the intended pressure and temperature ranges, preventing failures and ensuring longevity.
Holding this stamp symbolizes that our team has the expertise, processes, and quality controls necessary to deliver heating boilers and vessels that comply with these standards. Our H-stamped products will provide peace of mind through certified safety and performance.
What is the ASME R Stamp?
The ASME R stamp is a certification granted by the National Board of Boiler and Pressure Vessel Inspectors that authorizes a facility to perform repairs and alterations on pressure vessels and boilers.
Unlike the U, UM, and H stamps, which certify original fabrication, the R stamp focuses specifically on ensuring repairs meet stringent safety and code requirements.
This certification requires that all repairs and modifications are done in accordance with the National Board of Boiler and Pressure Vessel Code and that all work is properly documented to help maintain the integrity, safety, and compliance of pressure equipment throughout its service life.
Our R stamp certification enables us to provide our customers with trusted repair and alteration services, extending the life of your pressure vessels and ensuring they continue to operate safely and efficiently within code requirements.
Why These Certifications Matter
Holding multiple ASME and National Board certifications means more to us than just meeting regulatory requirements. It reflects our deep commitment to quality, safety, and precision at every stage of manufacturing and service.
Our comprehensive portfolio allows us to serve a wide range of pressure vessel needs, from new builds to repairs, across various applications. However, to truly set ourselves apart, we leverage these certifications to enforce thorough quality control and quality assurance processes.
Every vessel and component we produce undergoes strict inspections and testing, documented traceability, and thorough reviews to ensure compliance with ASME codes and customer specifications.
Our quality control is designed to minimize risk and deliver consistent performance to our clients. When you choose Spokane Stainless, you’re not just getting certified vessels, but assurance that comes from expert craftsmanship backed by uncompromising quality management systems.
Ready to work with a trusted partner who delivers ASME-certified pressure vessels with unmatched quality and expertise? Contact Spokane Stainless Technologies today to discuss your project needs and discover how our certified capabilities ensure your equipment meets the highest standards.
