1.0 Definitions of compensator characteristics
1.1 AXIAL COMPRESSION
Axial compression is the negative longitudinal dimensional variation (reduction) that occurs at the joint.
1.2 AXIAL EXTENSION
Axial extension is the positive longitudinal dimensional variation (extension) that occurs in the joint.
1.3 LATERAL OR TRANSVERSE MOVEMENT
It is the movement that occurs in the joint in the direction perpendicular to the longitudinal axis.
1.4 ANGULAR MOVEMENT
Angular movement is the angular displacement of the longitudinal axis of the expansion joint from its initial straight line position. This type of movement is measured in degrees.
1.5 TORSIONAL MOVEMENT
It is the rotation of one end of the expansion compensator with respect to the other end of the equipment. This type of movement is measured in degrees.
1.6 VIBRATION ABSORPTION
The ability of the expansion compensator to dampen mechanical oscillations or vibrations in the system.
2.0 Selection of rubber seals
In order to select the most suitable expansion compensator for each case or process, it will be convenient to study and analyze the following points:
2.1 SELECTION OF THE MODEL ACCORDING TO THE DIMENSIONAL VARIATIONS.
In order to select the expansion compensator model according to the dimensional variations, it will be necessary to take into account that the movements or vibrations to be compensated are compatible with the degrees of freedom allowed by the joint.
2.2 DETERMINATION OF THE DISPLACEMENTS TO BE COMPENSATED FOR
The displacements caused by expansion must be calculated from the corresponding expansion coefficients of the equipment material.
LINEAR DILATATION IN MILLIMETERS PER METER AND PER 100ºC
- Standard steel: 1.2
- Stainless steel: 1.6
- Aluminum: 2.2
- Plastics and other materials: Consult the manufacturer.
The coefficient between the total dilatation of the pipe and the length of the joint will determine the number of dilatation compensators to be installed. The temperature limits of the fluid and the environment must always be taken into account. The assembly tolerances and structure movements must be specified for each installation in order to avoid possible failures.
2.3 DETERMINATION OF PERMISSIBLE DISPLACEMENTS
In the case of combined displacements or dimensional variations, the geometric resultant of the deflections must be taken into account, which defines a triangle whose area indicates the field in which the expansion joint can work and allows the most suitable installation length to be determined.
2.4 SELECTION OF THE ELASTOMER
For the manufacturing of the expansion joint, it will be of vital importance to take into account the characteristics and properties of the process fluid that will be in contact with the expansion joint, as well as the operating temperatures and pressures, in order to select the appropriate materials that will make up the expansion joint:
| CODE | FLUIDS | ELASTOMER |
|---|---|---|
| Red | Acids and liquids of medium concentration max. temperature 110ºC | Butril |
| Green | Abrasive products max. temperature 110ºC | Natural |
| White-Yellow | Oils, hydrocarbons max. temperature 110ºC | Nitrilo |
| Yellow | Clean water 110º max. temperature 110ºC | Neopreno |
| Yellow-Yellow | Agua sucia, de calefacción, aire acondicionado, intemperie, t. máx. 110°C | EDPM |
| Verde-Verde | High concentration chemicals, high temperatures | Vitón |
| Red-Green | Strong acids and bases, and flame retardant environments Hypalon | Hipalón |
2.5 PRESSURE
Pressure ratings are given in the tables for each type of expansion joint and vary with operating temperature. The test pressure is set at 1.5 times the maximum operating pressure.
2.6 TEMPERATURE
Depending on the operating temperature, the most suitable type of elastomer or material should be selected according to the tables.
2.7 FLANGE STANDARDS
Define the drilling pattern.