Industrial Catalog
Pressure Tanks
Stainless steel tanks for storage and stabilization of hydraulic systems.
Pressure Tanks · Specification range
A pressure tank (also called an expansion vessel or hydropneumatic tank) is a closed vessel in which part of the volume is occupied by compressed air and the rest by water, allowing the hydraulic network to maintain stable pressure between consecutive pump starts. JOVAL stocks in Portugal two families of pressure tanks in AISI 304 stainless steel: with a replaceable membrane (VIM series) and membrane-free (VI series).
- Material
- AISI 304 stainless steel (1.4301)
- Capacities (with membrane)
- 20 – 200 L
- Capacities (membrane-free)
- 60 – 600 L
- Max pressure
- 5 / 6 / 8 bar (pre-charge 2 bar)
- Membrane
- Replaceable EPDM (or membrane-free)
- Standards
- European PED Directive
Pressure Tanks · Technical Overview
Tanks with membrane integrate a replaceable EPDM membrane that fully separates water from air, preventing water from touching the vessel walls and extending the service life of the installation. The range covers capacities of 20, 24, 50, 70, 100 and 200 L in vertical format, with maximum pressures of 5, 6 or 8 bar depending on the model, a factory pre-charge of 2 bar, operating temperatures from 0 °C to 70 °C and threaded connections from 1" to 1"¼. All models comply with the European PED directive for pressure equipment.
The membrane-free tanks (VI series) are cylindrical vessels in AISI 304 with no separation between air and water, used in applications where direct contact is not an issue — typically clean-water boreholes or industrial pre-mix systems. The range runs from 60 to 600 L, with maximum pressures of 6 or 8 bar and threaded connections from 1" to 1"¼. They also comply with the PED directive.
Tank volume sizing depends on pump flow, the pressure differential of the network and the maximum acceptable number of starts per hour. As a rule of thumb, a booster set for flows of 2 to 3 m³/h is paired with a 100 L tank; 5 m³/h requires 200 L; 10 m³/h requires 300 L. Permanent stock is held in Portugal, with connection accessories, valves and adapters available in-line.
Frequently asked questions
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What is the difference between tanks with and without a membrane?
A tank with a membrane has an EPDM diaphragm that fully separates the water from the pressurised air, preventing water contact with the vessel walls. A membrane-free tank is a direct cylindrical vessel — simpler, but limited to applications where direct water contact is not an issue.
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How do I size the volume of a pressure tank?
It depends on pump flow, the pressure differential of the network and the maximum acceptable number of starts per hour (typically 15 to 20). As a rule for booster sets: 100 L for 2-3 m³/h, 200 L for 5 m³/h, 300 L for 10 m³/h.
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What should the air pre-charge be in a tank with a membrane?
The factory pre-charge is 2 bar. As a rule, adjust it to 0.2 to 0.3 bar below the pump start pressure to maximise the useful volume. The pre-charge must be checked every 3 months with the tank fully depressurised on the water side.
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What maximum pressure do JOVAL tanks support?
5, 6 or 8 bar depending on the model and version. The membrane tanks cover 5, 6 and 8 bar; the membrane-free tanks cover 6 and 8 bar. All models comply with the European PED directive for pressure equipment.
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Is the membrane replaceable without removing the tank?
Yes. The VIM-series tanks use replaceable EPDM membranes, which allows scheduled maintenance without having to replace the tank body or remove the vessel from the hydraulic line.
Can't find what you need?
Our technical team can help select the right equipment for your installation. Contact us with your project details — borehole depth, required flow rate and application.