Pressure vessels, steam accumulator and buffer tanks

Products

West Welding designs and manufactures industrial pressure accumulators for demanding processes. Among other products, we supply steam accumulators and pressurized buffer tanks, which are used to compensate for fluctuations in process pressure, flow, or energy demand and ensure reliable operation even during temporary consumption peaks.

The pressure accumulators we manufacture are industrial pressure vessels designed on a project-by-project basis. They are not the small diaphragm, bladder, or piston accumulators used in hydraulic systems, but rather large welded pressure vessels designed for the needs of the process and energy industries.

During its service life, a pressure accumulator may be exposed to repeated and significant fluctuations in pressure or temperature. Therefore, potential cyclic or fatigue loading must be taken into account in the design, material selection, welding, inspections, and documentation from the early stages of the project.

The industrial pressure accumulators we supply include:

  • steam accumulators
  • pressurized buffer tanks
  • other process-specific pressure accumulators customized to the agreed scope of supply
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What is an industrial pressure accumulator?

An industrial pressure accumulator is a pressure vessel that stores energy or a process medium and releases it as required. A pressure accumulator acts as a buffer in the process: it can smooth out consumption peaks, pressure fluctuations, or flow variations and reduce instantaneous loads on the rest of the system.

The operation, contents, and structure of a pressure accumulator are always determined by its specific application. In a steam system, a steam accumulator can be used to store thermal energy. In other processes, a pressurized buffer tank can regulate the supply of gas or liquid, accommodate temporary overproduction, or maintain the reserve required by the process.

Steam accumulators smooth out fluctuations in steam consumption

A steam accumulator is a pressure vessel that is partially filled with hot, pressurized water. When steam production exceeds instantaneous consumption, the excess steam is directed into the water, where the energy is stored as thermal energy. When the demand for steam increases and the pressure in the accumulator drops, some of the hot water immediately vaporizes and releases steam into the network.

Thus, a steam accumulator does not primarily store large amounts of ready-to-use steam, but rather thermal energy in pressurized hot water.

When properly sized, a steam accumulator can:

  • respond to short-term spikes in steam consumption
  • smooth out the load on the boiler plant
  • stabilize the pressure in the steam network
  • allow the boiler time to increase its output in a controlled manner
  • support a more consistent and predictable process

Key factors in sizing a steam accumulator include the boiler capacity, charging pressure, minimum steam network pressure, magnitude and duration of peak demand, frequency of demand peaks, and the time available for charging. Adequate water inventory, sufficient water-steam interface area, and steam space are essential to ensure that steam can be discharged at the required flow rate and quality.

Pressurized buffer tanks as process buffers

A buffer tank evens out fluctuations between process feed and consumption. A pressurized buffer tank can temporarily store gas, liquid, or other process media and release it when required by the next stage of the process.

The purpose of a buffer tank can be, for example:

  • smoothing out pressure or flow fluctuations
  • Compensating for temporary overproduction or underproduction
  • Functionally separating process stages from one another
  • Managing fluctuations caused by startups, shutdowns, or batch processes

Not all buffer tanks are pressure vessels. The buffer tanks presented on this page are pressurized vessels tailored to industrial processes where the application requires pressure vessel construction and compliance with applicable pressure equipment regulations.

Steam accumulator and buffer tank

HöyryakkuPaineellinen bufferisäiliö
PäätehtäväLämpöenergian varastointi ja höyryntuotannon kulutuspiikkien tasaaminenVäliaineen, paineen tai virtauksen puskurointi prosessissa
Tyypillinen sisältöPaineistettu kuuma vesi ja höyryProsessikohtainen kaasu, neste tai muu soveltuva väliaine
PurkautuminenPaineen laskiessa osa kuumasta vedestä höyrystyyVäliainetta vapautetaan prosessin tarpeen mukaan
Keskeiset mitoitustiedotHöyrykuorma, paine-ero, piikin kesto, latausaika ja höyryn vapautumisnopeusTilavuus, paine- ja virtausprofiili, väliaine, viipymä ja prosessin toimintalogiikka

The appropriate solution is selected based on the operational requirements of the process. The required tank capacity and mechanical design can be determined only once the process pressure, temperature, flow, and time data are known.

Design of a Cyclically Charged Pressure Accumulator

The use of pressure accumulators often involves repeated charging and discharging. As a result, pressure and potentially temperature fluctuate during operation, causing cyclic stresses in the structure. Over time, repeated loading can lead to fatigue damage unless it is properly taken into account during design and manufacturing.

When assessing fatigue, the number of cycles alone is not decisive. The magnitude of pressure and temperature fluctuations, the rate of change, load combinations, local stress concentrations, and the equipment’s design service life also influence the design.

When designing a pressure accumulator for cyclically loaded industrial applications, the following factors are taken into account as required:

  • design pressure and temperature history, as well as operating cycles
  • fatigue design in accordance with the applicable design code
  • strength, toughness, and fatigue properties of materials
  • geometry and quality of welded joints
  • control of stress concentrations at nozzles, supports, and other critical locations
  • scope of inspection and NDT methods
  • requirements for in-service monitoring, inspections, and maintenance

West Welding performs the mechanical design and strength calculations for pressure accumulators based on the agreed input data. We can design pressure equipment in accordance with EN or ASME standards.

Materials, Welding, and Quality Assurance for Pressure Accumulators

The materials for pressure accumulators are selected based on pressure, temperature, process medium, corrosion, cyclic loading, and the applicable design code. West Welding works with a wide range of materials, including carbon steels, stainless steels, nickel alloys, duplex stainless steels, other specialty steels, titanium, and composite materials.

Manufacturing is carried out at our own manufacturing facility in Teuva in accordance with certified quality and welding systems. We have approximately 280 qualified welding procedures. Manufacturing can include NDT and DT inspections in accordance with the agreed inspection plan, pressure and leak testing, as well as third-party inspections required by the pressure equipment class and conformity assessment procedure.

The requirements for pressure accumulators supplied to the European Economic Area are determined based on the Pressure Equipment Directive 2014/68/EU, applicable standards, and the regulations of the destination country. The PED applies to pressure equipment falling within the scope of the Directive when the maximum allowable pressure exceeds 0.5 bar. The classification of the equipment, conformity assessment, and CE marking are determined based on the equipment’s characteristics and the scope of supply.

Pressure Accumulators: From Design to Commissioning

West Welding can handle the delivery of pressure vessels as a turnkey project. The delivery may include:

  1. definition of input data, interfaces, and applicable requirements
  2. mechanical design, strength and fatigue calculations, and manufacturing design
  3. material procurement, manufacturing, and quality assurance
  4. inspections, testing, and final documentation
  5. transportation, lifting, and installation planning
  6. support for transportation, installation, and commissioning to the agreed extent

We also offer annual and scheduled maintenance for the products we manufacture. This helps ensure the safe and intended use of the pressure accumulator throughout its service life.

Why choose West Welding as your pressure accumulator manufacturer?

West Welding has been manufacturing demanding pressure and process equipment in Finland since 1983. Our strengths include the mechanical design of large, custom-built pressure vessels, welding of demanding materials, consideration of cyclic loading, certified quality management, and comprehensive project responsibility from design and manufacturing to transportation and installation.

We have completed over a thousand pressure vessel and steel structure projects and delivered products to more than 20 countries across five continents. Our customers benefit from the expertise of our entire project team, from designers and production planners to welding, quality assurance, and project logistics specialists.

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FAQ

An industrial pressure accumulator is a pressure vessel that stores energy or a process medium and releases it in a controlled manner as demand changes. Its purpose is, for example, to balance pressure, flow, or consumption peaks. The pressure accumulators manufactured by West Welding are large, welded pressure vessels for the process industry, not small hydraulic accumulators.

A steam storage system stores thermal energy in pressurized hot water. When there is more steam available than is being consumed, the system is charged by directing steam into the water. During peak demand, the pressure drops, causing some of the hot water to vaporize and release steam into the grid.

A properly sized steam accumulator can smooth out short-term consumption peaks, stabilize the pressure in the steam network, and reduce sudden changes in boiler load. The benefits depend on the consumption profile, pressure differential, charging time, and other process parameters.

A steam accumulator stores thermal energy in hot, pressurized water and releases steam as the pressure drops. A buffer tank is a more general type of process vessel that smooths out fluctuations in the quantity, pressure, or flow of a process medium. A steam accumulator is therefore a pressure accumulator designed for a specific function in a steam system, whereas the contents and operating principle of a buffer tank are process-specific.

Fatigue loading must be evaluated when pressure, temperature, or other loads on a pressure accumulator fluctuate repeatedly during operation. The assessment is based not only on the number of cycles, but also on the magnitude of the fluctuations, the rate of change, local stresses, and the design service life. The need for fatigue assessment is determined in accordance with the applicable design code.

Available materials include carbon steels, stainless steels, nickel alloys, duplex stainless steels, other specialty steels, titanium, and composite materials. Material selection is always based on pressure, temperature, the process medium, corrosion, cyclic loading, and the applicable design code.

When requesting a quote, it is advisable to provide the intended use of the pressure accumulator, pressure and temperature values, process medium, required capacity or process data, estimated operating cycles, preliminary dimensions, nozzles, the applicable design code, destination country, scope of supply, and target schedule. For a steam accumulator, the steam consumption profile, charging and discharging pressures, and the duration and frequency of consumption peaks are also required.

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