Frequently asked questions
Whenever possible, we recommend the use of the thinnest gasket possible, taking into account the gasket thickness that the system was designed to. Thinner gaskets seal tighter, which lowers emissions and product loss, increase blowout resistance, and typically cost less. Flange irregularities on older equipment can be difficult to seal for thin material, therefore a thicker material is often required.
Generally speaking, we never encourage or recommend the reuse of flanged gaskets, as their ability to seal decreases with each reuse. However, some gasket types such as door seals in the food industry, require repeated reuse cycles and are designed accordingly. In all cases, as temperatures increase, the gaskets’ ability to fully recover and then reseal become significantly more difficult.
For tongue and groove applications, it is extremely important for the fully compressed thickness of the gasket must be considered. With most sealing materials that are used in this type of application, they experience significant compression due to the load that is applied to them. As such, the compressed thickness must be greater than the groove depth or the space between the tongue and the groove when the flanges faces contact each other.
Our recommendation for circular flanges is for 30-35 serrations per inch in a concentric spiral pattern, cut with a 1/16” radius, round-nosed tool. For non-circular flanges or machined surfaces, we recommend a multi-directional lay and roughness of 125-250 micro-inch RMS.
No. The best solution is to install 2 thinner gaskets on either side of a serrated-face spacer ring of the same alloy as the piping. The thickness of the spacer ring and gaskets will depend on the size of the gap.
The number of expansion joints in your piping system depends on the length of pipe, the full piping run length, pressure, temperature, and pipe diameter. With this information in hand, we can help determine the optimal expansion joint configuration for your system.
There are a number of potential causes of expansion joint failure and our experience indicates that these are the most common contributors to failure:
- Excessive bellows deflection (lateral, axial, or angular deflections greater than design)
- Improper anchoring, guiding, and supporting of the system
- Bellows corrosion (internal or external)
- Installation errors
- Improper protection during installation
- System overpressure (hydrotest or in-service)
- Excessive vibration
- Damage from shipping (denting or gouging of bellows, improper stacking, insufficient protection from shipping environment conditions)
- Installation direction reversal (for joints with internal liners)
- Particulate matter packing in the bellows (preventing proper bellows movement)
Internal liners are used to protect the convolutions from direct flow impingement which can cause erosion and flow vibration. Liners extend the life of the joint.
Limit rods absorb pressure thrusts in the system by limiting axial compression and expansion which in turn prevents over-compression or over-expansion.
Some applications (mostly vertical ducting with vertical flow up) require an internal particulate deflector which is used to reduce airborne particulate from falling into the cavity of the expansion joint.
Universal expansion joints allow for lateral motion and are typically used in “Z-bend” or “L-bend” piping arrangements.
Generally speaking, metal expansion joints are far more popular than rubber joints, perhaps by 4:1, due to their resistance to temperatures and pressures. However, many applications can handle a rubber expansion joint, which can save users significant money. Where the application parameters warrant, rubber expansion joints perform better on:
- Lateral movements
- Spring rates
- Acoustical impedance
- Abrasion / Erosion Resistance
- Fatigue / Life Cycle
- Installation and Maintenance
Mechanical seals, when engineered for the system and installed correctly, will provide reliable operation for a very long time. Eventually they do wear out, but our experience indicates most seal failure is due to another issue in the system, such as:
- Contaminated lubricant
- Improper installation techniques
- Bearing wear
- Incorrect seal selection