Replacement bag - for AF/AFH/AFV - 35-50l; EPDM IVAR.NVEL

Product detailed description

Expansion tanks are essential components in closed-loop hydronic systems, ensuring pressure stability and system longevity. In residential, commercial and industrial buildings, these vessels accommodate thermal expansion of water in heating and hot water circuits. Over time, the internal membrane may degrade due to exposure to water, pressure fluctuations and temperature variations. When this occurs, the replacement bag becomes necessary to restore the tank’s functionality without requiring full vessel replacement.

Installers working on central heating systems, solar thermal loops or domestic hot water storage units frequently encounter the need for membrane replacement. This EPDM bag is specifically engineered for IVAR models AF, AFH and AFV with capacities between 35 and 50 litres. Its design allows for straightforward installation by trained technicians, ensuring the system maintains correct pre-charge pressure and hydraulic balance.

Technical parameters

Code	Q120034
Brand	IVAR

The bag is sized for vessels with a 35–50L total volume. The EPDM material is selected for its resistance to water and moderate temperatures typically found in heating systems. The correct fit ensures the membrane forms a tight seal against the tank shell, preventing cross-leakage between the water and air chambers. Sizing must match the original vessel specifications to maintain system performance and prevent over-pressurisation or under-expansion.

Installation and connection

Before replacing the membrane, ensure the system is depressurised and the tank is drained according to standard safety procedures. Remove the old bag carefully to avoid damaging the tank shell or internal fittings. The new EPDM bag should be inserted with the correct orientation, ensuring the sealing edges align with the tank flange. Reassemble the tank using the provided clamping ring or bolts, tightening evenly to avoid misalignment or leaks. After installation, re-pressurise the tank to the recommended pre-charge pressure level and check for any signs of leakage or improper seating.

Compatibility and accessories

This replacement bag is compatible with IVAR AF, AFH and AFV expansion tanks within the 35–50L size range. It is intended for use with standard water-based systems and is not suitable for chemical or glycol mixtures unless confirmed by the manufacturer. No additional accessories are required for installation, though tools such as wrenches and pressure gauges are recommended for accurate assembly and testing. Always verify the exact model and capacity of the vessel before ordering to ensure correct fit and function.

Technical background for designers

Expansion tanks operate on the principle of separating water and compressed air within a sealed chamber. The EPDM membrane acts as a flexible barrier, expanding and contracting with the thermal changes in the system. The material’s elasticity and resistance to water ensures long-term durability in typical hydronic applications. The size of the tank determines how much expansion can be accommodated without exceeding the system’s pressure limits. Proper sizing during design stages is crucial to avoid frequent pressure adjustments or system failures. The membrane’s integrity directly affects the tank’s ability to maintain pressure and prevent water ingress into the air chamber, which could lead to loss of pre-charge and system instability.

Service and operation

Periodic inspection of the membrane is recommended during routine system checks. Look for signs of wear, such as cracks, deformations or leakage. If the membrane fails, the tank must be removed from service and the bag replaced immediately. No specific service intervals are provided for this component; maintenance is performed as needed based on system performance and visual inspection results. After replacement, the tank should be re-pressurised to the correct level and tested for proper function before being returned to service.

Frequently asked questions

Can this EPDM bag be used in all IVAR expansion tanks?
This bag is specifically designed for AF, AFH and AFV models with a 35–50L capacity. It is not suitable for other models or capacities without confirmation from the manufacturer.

Is it possible to install the bag incorrectly?
Improper orientation or uneven tightening of the clamping ring can lead to leaks or membrane failure. Always follow the manufacturer’s installation instructions and verify the fit before re-pressurising the tank.

Does the EPDM material affect system performance?
EPDM is suitable for water-based systems and does not react with the fluid. As long as the membrane is correctly installed and undamaged, it will not impact system performance.

How do I know when to replace the membrane?
Signs of degradation include visible damage, loss of elasticity or leakage. If the tank is not maintaining pressure or shows signs of water ingress into the air chamber, the membrane should be inspected and replaced if necessary.