Pressure vessel fabrication is a cornerstone of industrial processing. From refineries and chemical plants to power generation and pharmaceutical manufacturing, these vessels are engineered to safely contain substances under pressure. At Scott Process, pressure vessel fabrication is more than just a service, it’s a combination of engineering expertise, certified welding procedures, and rigorous testing backed by industry standards.
In this guide, we explore what pressure vessel fabrication entails, key design considerations, materials used, and the inspection processes that validate their integrity.
What Is Pressure Vessel Fabrication?
Pressure vessel fabrication refers to the engineering and manufacturing process of creating containers that hold gases or liquids at a pressure substantially different from the ambient pressure. These vessels must be built to withstand high internal or external pressures, thermal stress, and corrosion, all while meeting strict safety and quality standards.
The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPVC) is the gold standard governing the fabrication and inspection of these vessels. Scott Process holds an ASME U stamp, demonstrating our ability to manufacture pressure vessels in compliance with these widely accepted safety and performance requirements.
Design Considerations in Pressure Vessel Fabrication
The fabrication process begins with design, a phase that demands a deep understanding of physics, process engineering, and end-use requirements. Several key factors influence vessel design:
- Pressure and Temperature Requirements: Designers must calculate maximum allowable working pressure (MAWP) and design temperature using ASME formulas.
- Volume and Geometry: The vessel’s shape, volume, and orientation (vertical or horizontal) impact material choice and structural supports.
- Corrosion Allowances: Based on process media, designers include additional material thickness to account for anticipated corrosion.
- Nozzle Placement and Internal Components: Agitators, baffles, and heat transfer coils must be integrated without weakening structural integrity.
Scott Process works closely with clients to review process conditions and customize vessel designs that match the application — whether it’s for a chemical reaction, mixing, or storage.
Materials Used in Pressure Vessel Fabrication
Material selection plays a critical role in pressure vessel fabrication. The choice is influenced by the vessel’s contents, operating pressure and temperature, and external environmental conditions.
Common Materials:
- Carbon Steel: Ideal for low to moderate pressure and temperature applications, carbon steel is cost-effective and easy to weld.
- Stainless Steel: Used when corrosion resistance is essential. Grades like 304 and 316 are common in food, pharmaceutical, and chemical industries.
- Chrome-Moly Alloys: These are chosen for high-temperature services, often in power and petrochemical plants.
- Duplex Stainless Steels and Nickel Alloys: Specialized materials used for highly corrosive or extreme pressure environments.
Each material must meet ASTM or ASME material specifications before entering the fabrication process. Scott Process sources all materials from trusted suppliers and maintains traceability from mill certification through final delivery.
Fabrication Techniques
Once the design and materials are approved, fabrication begins. Scott Process performs every step in-house for full control over quality and schedule.
Cutting and Forming
Plates or pipe are cut using CNC plasma or laser systems. Bending, rolling, and pressing are used to achieve the desired shape, often cylindrical shells with domed heads.
Welding
Welding is at the heart of vessel fabrication. Scott Process uses approved Welding Procedure Specifications (WPSs) for each material and joint type. Welders are qualified per ASME Section IX and perform:
- Gas Tungsten Arc Welding (GTAW/TIG)
- Gas Metal Arc Welding (GMAW/MIG)
- Shielded Metal Arc Welding (SMAW)
- Flux-Cored Arc Welding (FCAW)
Precision and consistency are vital. Any defects in welding can lead to catastrophic failure, which is why Scott Process emphasizes proper joint preparation, interpass temperature control, and non-destructive testing after completion.
Heat Treatment
Certain vessels undergo Post Weld Heat Treatment (PWHT) to relieve residual stresses. This is particularly important for thick-walled vessels or those fabricated from high-strength materials. The heat treatment process is monitored and recorded to meet client and code requirements.
Internal Linings and Coatings
Depending on the service environment, vessels may require rubber linings, epoxy coatings, or specialized cladding. These are applied after fabrication and before final testing.
Inspection and Quality Testing
Before a pressure vessel can be released for use, it must undergo thorough inspection. Scott Process conducts 100% in-house testing to verify code compliance and client specifications.
Non-Destructive Examination (NDE)
- Radiographic Testing (RT): Used to detect internal weld flaws.
- Ultrasonic Testing (UT): Assesses wall thickness and detects cracks.
- Magnetic Particle Testing (MT) and Dye Penetrant Testing (PT): Surface inspection methods.
- Hardness Testing: Verifies proper material properties post-weld.
Hydrostatic Testing
All ASME vessels undergo a hydrostatic pressure test, where the vessel is filled with water and pressurized above its MAWP. This confirms the vessel’s ability to contain pressure without leaks or deformation.
For more on inspection standards, refer to the National Board of Boiler and Pressure Vessel Inspectors.
Documentation and Compliance
Every pressure vessel fabricated by Scott Process comes with a comprehensive data package, which may include:
- ASME U-1 Manufacturer’s Data Report
- Material Test Reports (MTRs)
- Welding maps and WPSs
- Inspection and NDE reports
- Heat treatment charts
- Shipping and lifting instructions
These records demonstrate compliance with ASME, customer requirements, and industry standards.
Industries That Rely on Pressure Vessel Fabrication
Scott Process serves clients in a variety of industries where reliable vessel fabrication is non-negotiable:
- Chemical: Reactors, distillation columns, and storage tanks for hazardous fluids.
- Pharmaceutical: Sterile mixing tanks and jacketed vessels.
- Power Generation: Feedwater heaters, separators, and scrubbers.
- Oil & Gas: Pressure separators, gas scrubbers, and heat exchangers.
- Food and Beverage: Sanitary tanks for mixing, fermenting, and storing.
Why Work with Scott Process for Pressure Vessel Fabrication?
Our team combines certified expertise with high-performance equipment to fabricate vessels that meet or exceed expectations. With our ASME U stamp and full-service shop, Scott Process can handle complex designs, exotic materials, and tight timelines, all while upholding the highest safety and quality standards.
When you work with Scott Process, you’re not just buying a vessel — you’re gaining a partner who understands your process, complies with strict regulations, and delivers results with precision.