Nederlands 
Deutsch 
Français 
Italiano 
Español 
In dosing, centrifugal and positive displacement pumps, O-rings in pumps for corrosive media form the barrier between the medium and the mechanical components. They must prevent aggressive substances such as acids, alkaline solutions or chlorine-containing liquids from entering bearings or sealing faces. From a design standpoint, it is about an optimal balance between elastic deformation and chemical stability.
When the O-ring retains its shape while withstanding the medium’s pH value and temperature, the pump continues to operate leak-free. In this way, these seals play a decisive role in the operational reliability of installations in drinking water and wastewater treatment.
The choice of sealing material is crucial. O-rings in pumps for corrosive media are often made from EPDM, FKM (Viton®) or NBR, depending on the composition of the pumped medium. EPDM is ideal for aqueous solutions, weak acids and alkaline media, and meets drinking water standards such as WRAS and KTW. FKM, on the other hand, offers exceptional resistance to strong chemicals, oils and oxidative substances. For applications in sludge or wastewater plants, NBR remains popular because of its wear resistance and oil resistance. By selecting the right combination of elastomer, hardness and compression, these seals maintain their tightness even under varying pressures and temperatures, which is essential for long-term process reliability.
In the world of water treatment, strict requirements apply to safety, hygiene and sustainability. O-rings in pumps for corrosive media are therefore manufactured according to international standards such as ISO 3601. This standard specifies exact tolerances, surface roughness and dimensions, ensuring that seals are consistent and reliable in use. In addition, in drinking water installations, KIWA, WRAS, ACS or KTW certification is often requested, which ensures that the material does not release harmful substances into the water. By choosing O-rings with these certifications, pump installations not only comply with legal requirements but also minimize the risk of leakage, material ageing or microbial growth within the sealing zones.
In practice, many problems arise from incorrect material selection or improper assembly. O-rings in pumps for corrosive media can swell, crack or deteriorate when exposed to chemicals for which they are not designed. Excessive compression or incorrect groove dimensions often cause extrusion or deformation as well. For example, EPDM rings are regularly used incorrectly in applications with oils or chlorine-containing solvents, which significantly shortens their service life. By combining proper fitting and compatibility analysis with preventive maintenance, operators can prevent many of these problems and significantly extend the service life of the pump.
In modern treatment plants, O-rings in pumps for corrosive media are used in a wide range of conditions, from oxygen-rich aeration systems to aggressive sludge flows at high temperatures. FKM or Viton® is often chosen here because of its resistance to oxidation and chemicals, while EPDM remains suitable for neutral or slightly alkaline flows. Silicone seals are also used in dosing pumps for chlorine or ozone, where flexibility and purity are essential. In practice, it has been shown that the correct material combination, matched to the medium, pressure and temperature, can reduce maintenance frequency by up to 40%. In this way, high-quality O-rings directly contribute to the efficiency and sustainability of the installation.
|
Application type |
Medium/Environment | Recommended O-ring material | Key properties | Certifications |
| Drinking water pumps | Neutral to slightly alkaline water | EPDM O-ring water treatment | Excellent water and ozone resistance, suitable for drinking water | WRAS, KTW, ACS, KIWA |
| Dosing pumps | Chlorine or alkali solutions | Silicone O-ring drinking water | High purity, flexible at low pressure | FDA, WRAS |
| Wastewater pumps | Sludge, contaminated water with oils | NBR O-ring wastewater | Oil and wear resistant, suitable for mixed media | x |
| Chemical feed pumps | Acids, oxidizers, solvents | FKM O-ring / Viton O-ring | High chemical resistance, temperature resistant | x |
| Aeration systems | Oxygen-rich air, ozone | EPDM O-ring water treatment | Resistant to ozone and ageing | WRAS, KTW, KIWA |
| Hot water circulation | 70 - 90 °C process water | FKM O-ring corrosive liquids | Temperature resistant and durable | x |
EPDM, FKM (Viton®) and Silicone are the most commonly used materials due to their chemical resistance and temperature range.
Watch for deformation, sticky residues, or micro-cracks. These signs indicate ageing or incompatibility with the medium.
Yes, provided they comply with standards such as WRAS or KTW. EPDM is generally the best choice for this.
This standard ensures consistent dimensions, reducing leakage and assembly damage.
That depends on the medium, temperature and pressure, but preventive replacement after 12 to 18 months is common.