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Ductwork Airtightness vs. Gasket Selection

Duct fittings with seals

Do you know that airtightness in ventilation systems is an important issue affecting the airflow and system effectiveness? A number of requirements and quality standards imposed by manufacturers determine the competitiveness of that solution.

To Seal or Not To Seal 

All gaskets should be fitted and held tight in the fitting's hemmed rim. Gaskets provide fully sealed and durable joints. If installed as recommended, gaskets provide superior air tightness class D (Certificate no. 0103/07 RISE according to PN-EN 12237). Using a gasket-free system and securing the connections with tape it is class B.

A very important aspect is the right choice for sealing material. Use several types of Alnor’s materials that are used in different operating conditions.

EPDM- ethylene propylene diene monomer

It is characterized by good resistance to many factors, such as:

  • Hot water and steam,
  • Organic and inorganic acids
  • Potassium and Sodium hydroxides, cleaning agents,
  • Hydraulic fluids based on phosphate esters,
  • Polar solvents as a ketons, esters, alcohols,
  • Ozone and UV radiation,
  • It does not discolour or dye other materials

EPDM Gasket has low elasticity as a result, it is also resistant to abrasion compared to other types of materials. EPDM- ethylene propylene diene monomer it is not resistant to

  • Products based on mineral oils, such as greases, oils and fuels.
  • Aliphatic, aromatic and chlorinated hydroxides.


Applications of EPDM gaskets in ventilation

  • Wherever an increased tightness class is required, but the air temperature doesn’t exceed 80◦ᴄ.
  • Hospitals, foundry and paper industries

The white coating on the EPDM gasket is a natural chemical phenomenon. After a few months of seasoning, talcum precipitates on the material surface.  It doesn’t change the material properties but makes the process of applying a gasket to the fitting easier.

NBR - acrylonitrile butadiene rubber

The content of acrylonitrile makes the NBR oils resistant. It has good mechanical properties such as high tensile strength, flexibility, low permanent deformation. Is the most universal material used for technical seals in contact with propane, butane, fuel, mineral oils (lubricating oils, hydraulic oils from groups H, H-L, H-LP)

Category H-L oils - refined mineral oils containing corrosion and oxidation inhibitors;

Category H-LP oils - deeply refined mineral oils together with oxidation inhibitors

Category H oils- rafined mineral oils without any improvers.

Chemical resistance of NBR gaskets:

  • Aliphatichydroxides : propane, butane, fuel, minerals oils (lubricating oil, hydraulic oils from groups H, H-L, H-LP)
  • Diluted acids hydroxides,
  • Non-flammable hydraulic fluids: HSA, HSB (oil-water emulsions) and HSC (polyglycol mixtures with water),
  • Oils of plant and animal origin light heater oils, diesel fuels.

Applications of NBR gaskets in ventilation

The system of pipes and fittings dedicated for general and technological ventilation with NBR gaskets is intended for places where there is contact with oils.

  • Home automation production plants
  • Automotive production plants,
  • Communications sector production plants.

Duct fittings with high-temperature seals

Silicone- the main chain of the macromolecule consists of silicon and oxygen atoms, the side chains are various organic groups.

It has the ability to small change physical properties in extremely wide temperature limits 80-200 ◦ᴄ.. The main properties of the material are:

  • Hydrophobicity,
  • resistance to gases such as : ozone, carbon monoxide, neon, nitrogen and helium,
  • resistance to ultraviolet rays

Applications of silicone gaskets in ventilation:

Especially recommended for places where there are higher temperatures of transported air and the risk of condensation.

  • in the food industry,

  • in the medical and pharmaceutical industry,

  • extractors of hot steams and gases, composting plants.

Leaks in the ventilation system cause interferences in the airflow. It makes the comfort of people staying in the building worse. The appearance of this type of phenomena also negatively affects on the construction of buildings and causes energy losses.

To prevent leaks in ventilation system it is important to realize yourself the sources of this problem.

  • leaks occur in places of longitudinal and transverse connections of ventilation ducts, places of ventilation grates, inspection elements
  • no gaskets used,
  • incorrectly selected sealing material.

You must remember that due to the diverse requirements for ventilation systems, it is important to choose the right solution which can meet these requirements!

Using systems with gaskets in the design, you will get the best possible ventilation system. It will guarantee you high tightness and quality, as well as compliance with standards for many years.
Spiral ductwork with factory-installed seals will increase energy efficiency, increase indoor climate comfort and reduce maintenance costs.

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