Ask to Mr. SOS

Are CIMM expansion vessels marked "CE"?

Yes, CIMM expansion vessels are built in compliance with the European PED Directive 2014/68 / EU (Pressure Equipment Directive) and according to EN 13831, therefore where required, they are provided with the "CE" mark.

Which expansion vessels must have the CE mark?

According to the European Directive PED 2014/68/EU, the "CE" mark must be affixed to all the vessels in which the product of the maximum working pressure (PS) indicated in the vessel’s label, and the volume (V) is more than 50 litres per bar. Vessels for which the product PSxV is equal to or less than 50 litres per bar are included in the category of vessels ruled by Article 4 par.3 of the Directive, which does not need the "CE" mark.

What documents are issued by the manufacturer?

According to the PED Directive 2014/68/EU, the pressure equipment manufacturer must issue the instruction manual and, where required, the Declaration of Conformity.

Download the Operating Instruction Manual - EC Workbook 


Is it necessary to check the air pre-charge pressure of the expansion vessels?

Yes, as written in the instruction manual, it is necessary to periodically check - at least once a year - the air pre-charge pressure of the expansion vessels, and if necessary charge them again to the value indicated on the label, to guarantee the correct functioning of the vessels in the plant.

Can the air pre-charge pressure of CIMM expansion vessels be modified?

Yes, it is possible to modify the air pre-charge pressure of CIMM expansion vessels with cautions. We suggest to ask to an expert and authorized personnel to carry out the operation. Being aware of the specific features of the system or plant where the vessel has to be or is installed, the pre-charge pressure of an empty CIMM vessel can be increased up to a maximum of 3.5 bar and can be reduced to a minimum of 0.5 bar.

How can you check if the internal membrane of an expansion vessel is broken?

All CIMM expansion vessels with membrane are pre-charged with air through an air valve. The rubber membrane inside the vessel keeps the water separated from the air. Therefore, in case of malfunction, to check if the membrane of the vessel is broken, you must act on the internal mechanism of the air valve, pressing it with a tool such as a screwdriver, and checking what comes out. If water leaks, it means the membrane is broken and the water has completely filled the vessel. Whereas, if air comes out, the membrane should still be intact and it is necessary to simply pre-charge the expansion vessel again to make it work.

Download the istructions to know how to change the membrane of an expansion vessel with interchangeable membrane.

In which CIMM expansion vessels can you directly install a manometer to check the air pressure?

On the interchangeable membrane expansion vessels with the upper tie rod, it is possible to install a manometer fixing it directly on the tie rod, after removing the cutting screw inside the tie rod itself.

When and why should you add a CIMM Intermediate Solar Tank to a CIMM Solar expansion vessel?

In solar energy systems, it is useful to provide a CIMM Intermediate Solar Tank – which is an additional tank without membrane - in order to protect the Solar expansion vessel from overheating in case of stagnant water. According to the VDI 6002 Directive, the use of an additional tank, such as CIMM Intermediate Solar Tank, is recommended when the fluid of the pipes placed between the solar collector battery and the expansion vessel is less than 50% of the correctly measured reception capacity of the expansion vessel.

What is the recommended volume for a CIMM Intermediate Solar Tank in solar systems?

Approximatively, the volume of a CIMM Intermediate Solar Tank should be at least 1/3 of the volume of the CIMM Solar expansion vessel to which it is combined.

Which CIMM expansion vessels are suitable for use with water and glycol? And in what percentage?

All the expansion vessels of the SOLAR range, manufactured by CIMM, can be utilized with water and glycol mixtures with a maximum glycol concentration of 49%.

Are CIMM fixed membrane expansion vessels suitable for use with drinking water?

NO, CIMM fixed membrane vessels, as indicated on the vessels label, CAN NOT be used in a sanitary water circuit and CAN NOT come in contact with drinking water.

What are the CIMM expansion vessels suitable for use with drinking water?

The CIMM expansion vessels suitable for use with drinking water are the ones with the interchangeable membrane that show the drinking water eligibility sign on the vessel label. In these vessels, the water is contained entirely inside a special bag shaped rubber membrane and never coming in contact with the metal body of the vessel.

Why does corrosion occur in expansion vessels in heating systems?

In heating systems expansion vessels corrosion is a known and widespread phenomenon, due essentially to the combined action of water and oxygen. Under correct operating conditions, in a closed heating system, oxygen is quickly eliminated during the first operating periods (vents) and should not lead to the formation of corrosive phenomena. Nevertheless, other external factors such as condensation, the presence of galvanic currents, high temperatures and undersized expansion vessels can cause or accelerate corrosion phenomena.

What information is required and how do you size CIMM expansion vessels?

Depending on the type of use (for boilers, heating systems, domestic hot water systems, hot and cold water systems, solar energy systems) it is possible to size the expansion vessel by consulting the CIMM CALCULATOR SOFTWARE FOR DIMENSIONING OF CIMM PRODUCTS at this link. For more information, contact our technical department.

How to avoid damages and malfunctions in expansion vessels and guarantee longevity to the installed product.

To avoid breakages and malfunctions, first consult the special label affixed to the expansion vessel and the instruction manual supplied by the manufacturer. Furthermore, it is necessary to:

  1. Perform a correct and periodic maintenance of the system in which the expansion vessel is installed
  2. Periodically check the pre-charge pressure of the vessel and if necessary restore it to the value indicated on the label
    (see question 4)
  3. Check the correct grounding of the system, in order to avoid galvanic currents
  4. Check the correct sizing of the expansion vessel
  5. Pay attention to excessive overpressure and water hammering phenomena in the system
  6. Avoid to install the expansion vessel in unsuitable environments or areas subjected to particularly aggressive climatic conditions
  7. Avoid the formation of condensation that leads to the development of corrosive phenomena (see question 13)
  8. Monitor the pH value of solutions containing glycols or other substances
  9. Avoid mixing different antifreeze products

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