How to Build Stainless Steel Pressure Vessels

Stainless steel pressure vessels provide a variety of benefits to industrial customers. They allow for the safe containment of oils and different types of gases. Stainless steel pressure vessels are known for their durability, and can be used safely in industrial applications for many years. Let’s see how they are designed and constructed.


  1. 1
    List the Design Criteria. The first and most important step is to sit down with the client and understand his requirements. Make sure you agree upon the size and shape of the vessel, whether he wants it to be a spherical or cylindrical shaped vessel. Confirm details such as length, inner diameter, outer diameter, internal pressure, and bolt diameters. Also, decide on the minimum wall thickness, number of bolts, allowable normal stress of the stainless material, and allowable normal stress of the bolt material. Confirm with the client whether he wants ASME Code or Non Code pressure vessel. Enquire and list his welding requirements.
  2. 2
    Create a Basic Layout. Once you have all the specifications, it is best that you draw the basic design layout on paper. List all the design criteria mentioned above in the layout. Once the layout has been completed, you can move onto computer design.
  3. 3
    Upload the Layout onto Engineering Software. Scan and upload the layout onto engineering software. Autodesk and AutoCAD are the most well-known software. Create a 3D model and simulation of the pressure vessel with single or multiple nozzles, depending on the requirement. Use the software to apply constraints and loads such as thermal loads or pressure loads. You can also take into account considerations such as thermo analysis and cycling. You can review the results and understand factors like displacement and stresses. Once the design is complete, get it approved by the client.
  4. 4
    Cut The Steel using Gas Metal Cutting Process. Once the design has been approved, the next step is cutting the steel into the required size and length. Gas metal cutting is the accepted method of cutting the steel. Use a specialized welding torch along with an additional device to supply the gas or oxygen. Use the torch to quickly and accurately cut the steel.
  5. 5
    Create Grooves for the Nozzles. To install pressure vessel head nozzles, you need to cut holes into the vessel head steel plate. The cutting of stainless steel is done by using plasma-arc cutting torch, and grinding is done manually. When grinding, create V or a U shaped grooves so the complete penetration of the weld metal can be secured.
  6. 6
    Roll the Steel. Once the grooves have been created, the steel needs to be hot or cold rolled to provide uniform thickness and the desired curvature for the pressure vessel. Pass the steel plates through large rolling machines, which will help to reduce the thickness of the steel.
  7. 7
    Commence the Welding Process. Next, the steel is welded into the desired pressure vessel shape. Perform Tungsten Inert Gas or TIG welding to accomplish this. TIG welding is an arc welding process that utilizes tungsten electrodes to create the weld.
  8. 8
    Perform Autofrettage. After the welding process has been completed, the vessel is subjected to autofrettage. Use a mandrel to subject the pressure vessel to enormous pressures. The vessel gets stretched to cause compressive residual stresses within the vessel. This makes it resistant to external stresses, corrosion, and cracking.
  9. 9
    Cut the Steel for the Pressure Vessel Head. Using the gas metal cutting process, cut the steel for the pressure vessel head and its various components. These include nozzle holes and manholes.
  10. 10
    Form the Pressure Vessel Head. Pressure vessel heads are formed using a combination of two techniques – flanging and spinning. In flanging, the dished head is cold pressed into the required cap shape and then flanged. The head then goes through a spinning process to achieve the required cylindrical or spherical radius.
  11. 11
    Cut the Reinforcement Pads. To ensure that the oil and gas are properly contained, reinforcement pads are cut to support the pressure head nozzles. You need to cut these pads into semi circular shapes. Once you are done with the cutting process, they should be joined together using TIG welding.
  12. 12
    Assemble the Head. The pressure vessel head assembly process comprises welding all the necessary components – man holes, reinforcement pads, and nozzles and welding them onto the vessel head. Use TIG welding or robotic welding to perform this step.
  13. 13
    Complete the Pressure Vessel Assembly. Once both heads are completed, the assembly of the pressure vessel takes place. Attach the heads to the cylinder to complete the assembly. Perform TIG welding to ensure that all the components are perfectly joined together.
  14. 14
    Cut and Assemble the Lugs. Lugs are lifting and tailing devices that are used to erect the pressure vessel onsite. Weld four pieces of steel to form the lugs and attach them to the vessel and the stands that support the vessel. Depending on the size of the vessel; lugs are either attached to the top of the vessel or the vessel shell.
  15. 15
    Commence the Final Vessel Assembly. Once all these processes are completed, the final assembly of the pressure vessel takes place. The lugs are welded onto the stands, which are then welded onto the pressure vessel.

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