How to Specify a Pressure Vessel

How to Specify a Pressure Vessel


Brimstone design, manufacture and install bespoke high pressure testing systems including high pressure, high temperature vessels and autoclaves, pressure & temperature control systems and pressure testing equipment accessories. Pressure vessels and autoclaves are highly regulated equipment and if you’re looking to install your own pressure test system, we need to know some information. This guide will help you to provide us with the basic information we need to determine the right vessel and develop a solution for your application.

Vessel Size

When it comes to pressure vessels, size matters and this is mainly influenced by the devices you’d like to test. In some design codes, the volume determines the hazard category of the vessel which dictates how the vessel is assessed by the notified body. It also influences the materials and processes that can be used to manufacture the vessel – whether it’s a machined mono-block, fabricated or forged shell.

All we need to know is the internal diameter and internal length of the vessel and we’ll do the rest.

For example, 300mm internal diameter, 1500mm usable internal length.

Test Media (Liquid/Gas)

Hydrostatic pressure is exerted by liquids such as water and hyperbaric pressure is exerted by gases such as nitrogen or air. The media type will be determined by your requirements and it’s important that we know which type as it influences a number of factors such as sealing methodology, materials, hazard category and safety systems. Some media types are inherently hazardous, such as flammable or toxic substances and require additional certification or design features to ensure safety.

To design a vessel, we need to know the test media type or types as a minimum. If low temperature testing is required then an antifreeze such as ethylene glycol will be required and material/coating selection will become a factor to prevent corrosion.

For example, water/glycol solution suitable for -10°C testing

Pressure & Number of Cycles

Applying pressure to your test assembly is why you need a vessel and whether it’s 50bar or 3000bar, it’s important that we know the maximum pressure and how that pressure needs to be applied. There may be a particular rate of pressure change that you need to achieve to meet an industry standard. The rate of change in pressure will also help to decide the sealing materials we use in your vessel. Your test program or production output may dictate a high number of pressure cycles. Material fatigue is influenced by a cyclic loading and its important that we select the right materials for your application.

We need to know the maximum test pressure required, the total number of pressure cycles and the required design life.

For example, 3000bar, 10,000 cycles, 15 years. If you’re not sure on the number of cycles, then we can propose a figure for review.

Temperature (Min & Max)

Some of our customers need to test their products at different temperatures at pressure, to suit their intended environment or an industry specification and temperature is a major factor in vessel design. Hot and cold temperatures affect the mechanical properties of materials and it’s important that we know the temperature range you will be operating in, so that we can design a vessel and heat exchanger for your application. We offer electrical heater bands, liquid driver heat exchangers and insulations jackets for heating and cooling of vessels.

We need to know the temperature range and the time you’d like to achieve that temperature in.

For example, -5⁰C to 125⁰C, 12 hours from ambient temperature.

Design Codes & Standards

There are several design codes and standards which govern pressure vessel and pressure equipment design and Brimstone can deliver solutions to the following:

  • EN 13445
  • PD 5500
  • ASME BPVC Section VIII Div. 1, 2 & 3
  • PESR 2016
  • PSSR 2000
  • API 6A
  • ASME B31
  • BS EN 13480

You may require your vessel to be developed to a particular standard due to regulatory or insurance requirements or you may not have a specific preference. EN 13445 is particularly common in the UK and Europe as this is the harmonised standard used for UKCA and CE marking whereas ASME BPVC is more common in the USA.

If you require a particular design code, then we need to know which one. If not we can propose one to suit your application.

For example, EN 13445 with UKCA marking.

Portability Requirements – Fixed or Portable

You may require multiple vessels but have limited space in your pressure test facilities to accommodate them. In this instance, a highly portable solution may be preferable to enable ease of storage when the vessel isn’t in use. Or you may prefer a vessel that is fixed which you have no intention of moving once installed. Brimstone offers fixed and portable vessels to suit customer requirements. We also offer integrated solutions where the vessel and pressure pumping system are mounted onto a portable trolley to give maximum flexibility to our customers.

We simply need to know whether you require a fixed, portable or integrated solution. If you have no preference then we can propose a system for review.

For example, portable vessel with integrated pressure pumping system.

Vessel Orientation & Support Requirements

Vessels can be mounted horizontally or vertically depending on the test requirements of your product. They can even be mounted on support stands which allow the vessel to be positioned in any orientation. Vertical vessels can allow better access for loading with overhead cranes and horizontal vessels can allow better access from both ends of the vessel. Space constraints can often play a major factor in the orientation of the vessel. Brimstone can offer both supported and free standing vessels depending on your access requirements.

We will need to know which orientation you require the vessel, your access requirements and whether you require tilting capability.

For example. Horizontal/vertical, access required from both sides, 90⁰ tilting capability required.

If you’re not sure on what you can accommodate in your facility, or what would suit your requirements best, then Brimstone can conduct a site survey and propose options which suit your application.

Closure Type & Quantity

A closure simply allows you to open and close the vessel to access the internal bore. Single closure vessels allow access from one end of the vessel only and dual closures allow access from both ends. Some customers require several closures where side entry is required.

There are many types of closure which can be incorporated into your vessel depending on how quickly you need to open and close your vessel. If the vessel is intended for qualification of products, a flanged or threaded closure may be the most cost-effective solution. If the vessel is intended for use in factory-acceptance testing of products which are mass produced, then a manual or automated twist lock closure will maximise time efficiency.

We need to know how many closures you require, how quickly you need to open the vessel and whether you require automated closures.

For example, dual closure, 5 minutes to open after vessel drained, automated.

If you have any requirements for penetrations of feedthroughs, then this can also influence the type of closure on the vessel. Contact us for further information on the types of closure we offer.

Port requirements

Ports are used for filling, pressurising, depressurising, and draining the vessel. They also allow mounting of support hardware such as pressure transducers and thermocouples. The type of port is determined by the pressure rating of the vessel, purpose of the port and sometimes our customers have a specific preference. The size of the ports is influenced by the hardware to be mounted and the wall thickness of the vessel as there are limitations on the size of hole which can be drilled through thick-walled vessels.

We simply need to know the number of ports you require and whether you have any preferences on the type of port.

For example, 6 ports, no NPT threads.

If you have any additional hardware that you are looking to mount, such as dataloggers or sensors, then we will need to accommodate this.

Material & Coating Requirements

Material selection is predominantly influenced by the pressure and temperature of the vessel but some of our customers have specific requirements. Carbon steel vessels in various grades offer a cost-effective solution but require anti-corrosive coatings and ongoing maintenance, particularly if subjected to cyclic loading. Stainless steel vessels have greater corrosion resistance but are typically more costly. Some of our customers have products which are manufactured from exotic materials and cannot risk exposure to ferrites. In this instance, a stainless steel grade such as 17-4PH is more suitable due to its corrosion resistance properties.

If you have particular material requirements, then it’s important that we know prior to quotation as the material grades are a major factor in the vessel price.

For example, Corrosion resistant materials required to prevent exposure of products to media born contamination.

  • February 1743, 2023
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