1.0 Functional Capacities
1.1 AXIAL COMPRESSION
Axial compression is the loss of the length of the Joint measured along the longitudinal axis.
1.2 AXIAL EXTENSION
Axial extension is the increase of the Joint length measured along the longitudinal axis.
1.3 LATERAL OR TRANSVERSAL MOVEMENT
Lateral or transversal movement is the misalignment of the two ends of the expansion joint measured perpendicularly to the longitudinal axis.
1.4 ANGULAR MOVEMENT
Angular movement is the displacement, measured in degrees, of the longitudinal axis relative to its initial straight line position.
1.5 TORSIONAL MOVEMENT
Torsional movement is the rotatory movement of one end of the expansion joint in respect of the other end. As in the case of angular movement it is measured in degrees.
The capacity of the Flexible Joint to absorb the mechanical oscillations of the system.
2.0 Selection of rubber expansion joints
2.1 SELECTION OF THE MODEL BASED ON DIMENSIONAL VARIATIONS
In order to select the Joint model according to the dimensional variations, bear in mind that the movements to be compensated are compatible with the displacements allowed by the expansion joint.
2.2 DETERMINATION OF DISPLACEMENTS TO BE COMPENSATED
Only the displacements produced by temperature variations can be calculated. The following expansion coefficients can be used for calculation.
LINEAL EXPANSION IN MILLIMETRES PER METRE AND PER INTERVAL OF 100°C:
- Normal steel: 1.2
- Stainless steel: 1.6
- Aluminium: 2.2
- Plastics and other materials: Please consult the manufacturer
The number of expansion joints to be installed is determined by the coefficient of the total expansion of the pipeline and the maximum allowed displacement of the expansion joint. The maximum ambient and fluid temperatures should always be taken into account. The assembly tolerances and movements of the structure, should be specified for each installation.
2.3 DETERMINATION OF THE DISPLACEMENTS ALLOWED
In the case of existing combined displacements, the geometric resultant of the deflections must be used. This resultant defines a triangle whose area indicates the working area of the joint and also permits determining the most suitable length of the assembly.
2.4 SELECTION OF ELASTOMER
Elastomers show excellent corrosion resistance to a wide range of fluids. The table below shows some general characteristics. Contact Safetech for a specific elastomer recommendation.
|Red||Acids and liquids of a medium concentration. Max. temperature 110ºC||Butyl|
|Green||Abrasive products. Max. temperature 80ºC||Natural|
|White||Oils, hydrocarbons. Max. temperature 110ºC||Nitrile|
|Yellow||Clean water. Max. temperature 110ºC||Neoprene|
|Yellow - Yellow||Waste water, hot heating water, air conditioning. Max. temperature 140°C||EPDM|
|Green - Green||Chemical products of high concentration, high temperatures.||Viton|
|Green - Red||Strong acids and bases, fire-resistant environments||Hypalon|
Pressure resistance is indicated in the tables corresponding to each type of Expansion Joint and vary with temperature. The pressure is established at 1.5 times the design pressure.
The selection of the elastomer depends of the working temperature. For choosing the most appropriate material refers to the tables.
2.7 FLANGE STANDARDS
Drilling norm should be specified.