O-RING - NBR 70 25X3

Product description:

• O-Rings are closed-circuit seals, whose operation relies on the deformation of the cross section
• O-rings are produced endlessly from elastomeric materials, such as NBR, FKM (Viton), EPDM, etc., by vulcanisation in moulds
• The simple shape and reliability of the sealing function of O-rings is brilliant
• O-rings are therefore the most widely used seal
• Economical manufacturing and uncomplicated assembly make O-rings unsurpassed
• The description of the O-rings consists of the dimensions of the inner diameter and cord thickness in mm with the material designation and its hardness

Colour standard material:

• EPDM 70, black
• FKM 75, green
• FKM 75, brown
• FKM 80, green
• FKM 80, brown
• FKM 80, black
• FKM 90, green
• FKM 90, black
• HNBR 70, black
• NBR 70, black
• NBR 80, black
• NBR 90, black
• VMQ 70, red-brown
• FKM/FEP, transparent/black
• VMQ/FEP, transparent/reddish brown

Tolerances:

• According to DIN 3771 / ISO 3601

Operating parameters:

• Temperature EPDM 70 Sulphur: -45 °C to +130 °C
• Temperature EPDM 70 peroxide: -50 °C to +150 °C
• Temperature FKM: -15 °C to +200 °C
• Temperature HNBR: -30 °C to +150 °C
• Temperature NBR: -30 °C too +100 °C
• Temperature VMQ 70: -55 °C to +200 °C

Areas of application:

• O-rings are mainly used as seals of non-moving machine and plant parts (static application) against liquid and gaseous media, e.g. flange and lid seals, threaded connection of pipes and cylinder head and base on hydraulic cylinders
• Under certain conditions, O-rings can also be used for reciprocating and rotating movements (dynamic application)
• Pressure up to 1000 bar can be sealed if the installation space is properly designed and the materials are selected correctly
• Supporting rings may have to be used
• O-rings are used in numerous industries, e.g. hydraulics, pneumatics, vacuum applications, fittings industry, automotive industry as well as machine and plant construction

Installation spaces:

• The installation spaces (grooves) for O-rings should, if possible, be inserted rectangularly and carefully machined
• Burrs, scratches and nicks are to be avoided
• The dimensions for the required groove depth and width depend on the application situation and cord strength
• Construction tips and dimension tables can be found in our O-rings catalogue
• To facilitate assembly, we can offer you various surface treatments on request

Choice of groove depth and width:

• To achieve a good sealing function, you should select O-rings with the greatest possible cord strength
• The O-ring material hardness to be selected depends on the pressure, gap size, sealing method (static/dynamic) and surface quality of the machine parts
• For standard applications, we recommend a hardness of 70 Shore A when selecting the material.
• Furthermore, you should pay attention to the correct preload, elongation or butt and groove filling

Media:

• EPDM
  • EPDM materials generally have good resistance to hot water, water vapour, ageing and chemicals and allow many thermal applications
  • They are subdivided into sulphur and peroxide vulcanised types, with the peroxide mixtures able to withstand higher thermal loads and exhibit a significantly lower deformation residual
  • EPDM is highly resistant to hot water and water vapour, detergent, caustic soda, caustic potash, silicone oils and greases, many polar solvents, many dilute acids and chemicals
  • Special compounds must be used for glycol-based brake fluids
  • EPDM materials are absolutely not resistant to mineral oil-based products (lubricating oils, motor fuels)
  • Permissible temperatures range from -45°C to +130°C (-50°C to +150°C for peroxide mixtures)
• FKM
  • FKM materials are characterised by their good resistance to high temperatures and chemicals
  • It should also be noted that they are highly resistant to ageing and ozone, have low gas permeability (very suitable for vacuum applications) and an automatic extinguishing fire behaviour
  • The standard FKM material for O-rings is highly resistant to mineral oils and greases, aliphatic, aromatic and chlorinated hydrocarbons, motor fuels, the flammable liquids HFD and many organic solvents and chemicals
  • In addition to the standard materials FKM, several special compounds are available, which are extremely suitable for special applications due to different molecular structure compositions and varying fluorine contents (65% to 71%)
  • FKM is generally not resistant to hot water, water vapour, polar solvents, glycol-based brake fluids and low-molecular organic acids
• HNBR
  • HNBR is obtained by full or partial hydration of NBR.
  • This significantly improves the heat-, ozone- and ageing-resistant properties and achieves very good mechanical properties
  • The medium-resistant properties are similar to those of NBR
  • They are used at temperatures of approx. -30 °C bis +150 °C
• NBR
  • NBR is the most commonly used material for O-rings due to its good mechanical properties and resistance to mineral oil-based lubricants and greases
  • These properties are largely determined by the acrylonitrile content (ACN between 18% and 50%)
  • Low ACN content leads to good cold-temperature flexibility but limited resistance to oils and motor fuels; with increasing ACN content, cold-temperature flexibility decreases and resistance to oils and motor fuels increases
  • Dichtomatik's NBR standard material for O-rings has a medium ACN content, covering a wide range of applications
  • This material possesses good mechanical technology values, e.g. high wear resistance, low gas permeability and good resistance to mineral-based lubricating oils and greases, hydraulic oils H, H-L, H-LP, flammable liquids HFA, HFB, HFC, aliphatic hydrocarbons, silicone oils and greases, water up to approx. 80°C
  • NBR is generally not resistant to aromatic and chlorinated hydrocarbons, motor fuels with a high aromatic content, polar solvents, glycol-based brake fluids and the flammable liquids HFD
  • NBR is less resistant to ozone, weathering and ageing
  • In the vast majority of applications, however, this has no adverse effect
• VMQSilicone
  • compounds stand out for their great thermal application potential and the fact that they are highly resistant to ozone, weathering and ageingThe
  • mechanical properties of silicone are not as good compared to other elastomersIn
  • general, silicone materials are not harmful, i.e. they are used in the food and medical industries, among others.
  • used in the food and medical industriesThe
  • standard silicone material can be used at temperatures from -55°C to +200°C and is resistant to water (up to 100°C), aliphatic motor and cardanol oils, animal and vegetable oils and fatsSilicone
  • is generally not resistant to motor fuels, aromatic mineral oils, water vapour ( briefly up to 120°C possible), silicone oils and fats, acids and alkalis

Assembly:

• During assembly, any damage to the O-ring should be avoided, otherwise leaks may occur
• In addition, the following advice should be observed:
  • The O-ring must not be stretched to its elongation limit
  • The edges must be burr-free, round sections and bevelled edges must be seamless
  • Dust, dirt, metal splinters and other particles must be removed
  • Sharp points of the thread and installation spaces for other seals and guide elements should be covered with mounting sleeve
  • Mounting surfaces and O-rings should be coated with a suitable grease
  • Heating in oil or hot water to approx. 80°C makes elastomers more flexible. The O-ring can therefore be stretched more easily for assembly
  • Any assembly tools such as assembly mandrels or sleeves should be made of soft material (e.g. POM) and have no sharp edges
  • The O-ring must not be rolled over the mounting surfaces. When fitting in the groove, the O-ring must not twist