O-ring on Air Operated Double Diaphragm Pumps
O-Rings first became popular during World War II. One of the early standards, AN6227, contained only 88 sizes. As the usefulness and flexibility of the O-Ring became apparent, additional standards were developed to expand the sizes available to the engineers of the day. Today the choice of O-ring sizes and materials is unlimited.
Most common used standards in regards to O-ring sizes for the Diaphragm Pump industry are:
• AS-568 (American standard)
• BS1806 (British standard)
• DIN ISO 3601- 1 (European standard)
• JIS2401 (Japanese standard)
O-Ring Installation help
During repair or servicing your Air Operated Double Diaphragm pumps, any damage to the O-ring must be avoided, otherwise leaks may occur. The following instructions should also be observed:
- The O-ring must not be expanded up to the elongation limits.
- Edges must be free of burrs, radii and chamfers must be applied without transition.
- Dust, dirt, metal chips and other particles must be removed.
- Thread tips and installation spaces for other sealing and guide elements should be covered with the aid of a mounting sleeve.
- Assembly surfaces and O-rings should be provided with a suitable grease.
- Heating in oil or hot water to approx. +80 °C makes elastomers more pliable This makes it easier to expand the O-ring for assembly.
- Any assembly tools used, such as expanding mandrel or sleeves, should be made of soft material (e.g. POM) and be free of sharp edges.
- The O-ring should not be rolled over the mounting surfaces. When snapping into the groove, the O-ring are not used twisted
O-Ring Common Failures
For each O-Ring on an AODD pump, there is a matrix of system parameters—pressure, temperature, friction, environmental exposure and chemical exposure. All of these parameters must be considered together when designing the O-ring gland and selecting the O-Ring size and elastomer in order to ensure long-term seal reliability. Below you’ll find the most common failure modes seen with O-Rings in diaphragm pump applications.
1. Over Compression
The seal exhibits parallel flat surfaces corresponding to the sealing surfaces. It may also develop circumferential splits within the flattened surfaces.
- Excessive compression squeeze
- Poor compression set properties
- Elastomer with inadequate heat resistance
- Improperly cured part
- Volume swell due to system fluid
- Use smaller O-Ring or adjust gland design
- Select O-Ring with better compression set resistance
- Reduce system operating temperature
- Use more chemically resistant elastomer
- Check state of parts prior to installation
2. Spiral Failure
The seal surface exhibits a series of deep spiral 45 degrees angle cuts.
- Uneven surface finishing
- Elastomer too soft for the application
- Inadequate lubrication
- Wide clearances in combination with side loads
- Machine surface to correct finish (10-20 μinch)
- Consider higher durometer material
- Use external lubrication
- Decrease clearances
3. Installation Damage
The seal or parts of the seal may exhibit small cuts, nicks or gashes.
- Sharp surfaces on gland or components
- Inadequate lead-in chamfer
- Brake all sharp edges and cover threads with tubes or
tape during installation
- Use a higher-modulus/higher-harness material
- If possible provide 15° lead-in chamfer to guide the O-Ring properly
O-Ring Common Materials
O-rings used in AODD pumps are according one of the mentioned standards or metric sizes and different material options are available to meet your application requirements.
Thinqk Pump Parts supplies O-rings using one of the following materials:
A synthetic rubber with excellent oil resistance and fair to good chemical resistance.
A synthetic rubber providing excellent chemical resistance and heat resistance.
A synthetic rubber/elastomer providing excellent heat, oil, acid, weather and flame resistance.
An elastomer with excellent abrasion resistance and weather resistance, and good oil resistance.
A FDA approved TPE with excellent resistant against abrasion, tears, solvents and oil.
Excellent FEP chemical inert outer surface combined with a Viton inner core for optimal resilience.
Excellent FEP chemical inert outer surface combined with a Silicon inner core for optimal resilience.
Excellent chemical resistance to aggressive acids, bases, alcohols and oils. Good resistance on high and low temperatures.
Can we help you?
For questions on O-rings to service your AODD Pumps please contact our Team of professionals at Thinqk Pump Parts. We are more than happy to assist you with your o-ring needs. To reduce your downtime we stock most common O-ring sizes and materials used in the Diaphragm Pump industry. Parts ship worldwide from our semi-automated warehouse located in the Netherlands.
Thinqk O-Ring Pump Parts, original quality at a better price.