EXPANSION JOINTS · CUSTOM DESIGNS
Custom expansion jointsSelection and design for installation parameters
Not every installation fits within the parameters of a standard catalogue variant. Differences may concern face-to-face length, diameters, medium, temperature, pressure, required movements, pipeline routing or connection configuration.
At Metal-Gum, selection starts with the operating conditions of the installation. On this basis, we check whether an appropriate configuration from an existing product family is sufficient or whether an individually engineered design is required. For non-standard projects, the solution can also be verified using FEA/CAE calculations.
A custom-made expansion joint is not an “unrestricted” component. Every change in geometry, material or design must remain consistent with the process parameters and required operating range.
01 / NON-STANDARD CONDITIONS
When may a standard variant be insufficient?
An individual configuration is considered primarily when the actual installation conditions go beyond a typical product configuration or when several requirements occur simultaneously.
- non-standard face-to-face length
- different diameters on the two sides
- specific connection requirements
- larger or combined movement range
- operation under vacuum
- specific process-contact material requirements
- elevated temperature
- limited installation space
- matching a new expansion joint to an existing installation
Not every such case requires a design from scratch. Often, a suitable configuration of an existing variant is sufficient. The scope of changes results from the complete technical data, not from the phrase “non-standard design” alone.
02 / INPUT DATA
What data do we start selection from?
The basis is the actual operating conditions. The more accurately the process and installation geometry are described, the faster it is possible to determine the correct configuration and assess whether an individual design is required.
For preliminary selection, we primarily need:
- 01type of medium;
- 02composition and concentration of the medium, where relevant to material resistance;
- 03operating temperature and minimum and maximum values;
- 04working pressure and possible pressure surges;
- 05information about vacuum, if it may occur;
- 06DN on both sides of the installation;
- 07PN and connection standard;
- 08available face-to-face length;
- 09required axial, lateral and angular movements;
- 10pipeline routing and the location of anchors and guides;
- 11external conditions at the installation location;
- 12drawing, sketch or photographs of the existing installation.
If the installation operates in several process states, the parameters should include all conditions relevant to expansion-joint durability – including start-up, shutdown, flushing or cleaning where they differ from normal operation.
03 / GEOMETRY
Dimensions and face-to-face length
Installation geometry is one of the most common reasons for preparing a non-standard configuration. The expansion joint must match not only the nominal diameter, but also the face-to-face length, connection position and available installation space.
We do not assume that the expansion joint will be made to fit the pipeline by forced extension, compression or misalignment. Such installation uses part of the available movement range before the system starts operating and changes the conditions for which the component was selected.
If a new expansion joint is to replace an existing component, it is worth providing its documentation, basic dimensions and photographs of the installation. If documentation is unavailable, a simple dimensioned sketch is often sufficient to recreate the installation conditions for further analysis.
04 / MATERIALS
Medium and material selection
The material of parts in contact with the medium is selected according to the actual process composition and temperature. Our portfolio includes separate families of rubber expansion joints, PTFE expansion joints, rubber-PTFE expansion joints and conical expansion joints. Each has its own design and its own operating parameter range.
We do not automatically transfer temperature, pressure or chemical-resistance ranges between different product families. Material compatibility is assessed for the specific medium and operating conditions and then related to the complete expansion-joint configuration.
Particularly important for material selection:
- exact medium name;
- composition and concentration;
- temperature;
- pressure;
- contact time;
- installation washing and flushing conditions;
- presence of solid particles or abrasive properties.
05 / CONNECTIONS
Connections and flanges
For custom-made configurations, the connections are part of the complete structural system. Our product families use flanged connections, and rubber expansion joints are available, among other options, with galvanised carbon-steel or stainless-steel flanges.
To assess feasibility, we need:
- DN;
- PN;
- connection standard and bolt-hole pattern;
- required flange material, if specified;
- flange type or mounting method where relevant;
- available installation space.
A non-standard termination or connection is always treated as an element requiring technical confirmation for the specific design.
06 / MOVEMENTS
Axial, lateral and angular movements
The movement range of an expansion joint is selected for the movements that actually occur in the installation. Axial, lateral and angular values should be specified separately, together with movement direction and the operating states in which they occur.
Maximum values for individual movement types are not treated as independent parameters simultaneously available at their full values. For combined movements, their mutual share is analysed for the specific configuration.
For more complex systems, the most useful input is a pipeline sketch showing movement directions, anchors, guides and adjacent equipment. See also axial, lateral and angular expansion-joint movements.
07 / DESIGN VARIANTS
Reducing, conical and multi-convolution configurations
The rubber expansion-joint family includes, among other options, reducing, multi-convolution and vacuum configurations, while conical expansion joints form a separate design group. Such solutions can provide a starting point where there is a difference in diameters, increased movement requirements or specific installation conditions.
However, simply changing the number of convolutions or the geometry is not an independent way of increasing operating range. Dimensions, material, reinforcement, pressure, temperature and required movements must be assessed together.
08 / VACUUM
Operation under vacuum
If vacuum can occur in the installation, we need this information at the beginning of the selection process. The rubber expansion-joint family includes vacuum configurations and anti-vacuum rings that reduce the risk of collapse of the flexible part.
The analysis should include the actual vacuum level and the conditions under which it occurs, including temperature and the remaining process parameters. The design and any reinforcement are confirmed for the specific configuration.
09 / ENGINEERING
Made-to-measure design and FEA/CAE validation
We can design non-standard configurations and prototypes to specific dimensions. If the design or operating conditions require additional verification, the solution can be analysed using FEA/CAE calculations.
This does not mean that every non-standard expansion joint requires the same scope of calculations. The scope of analysis is selected for the specific task – geometry, materials, loads and operating conditions.
This allows a non-standard case to be treated as an engineering task rather than simply choosing the closest variant from a table.
10 / ENQUIRY
How should an enquiry be prepared?
It is best to include a drawing, diagram or photographs of the installation location with the enquiry. If the expansion joint is to replace an existing component, its designation, available documentation and basic installation dimensions are also useful.
Any specific requirements concerning acceptance documentation, installation conditions or other system constraints should be stated at the outset. This makes it possible to assess the complete configuration during selection instead of correcting assumptions later.
11 / COMMON MISTAKES
Common mistakes when ordering a non-standard expansion joint
- selecting solely by DN;
- providing a general medium name without concentration and temperature;
- omitting vacuum conditions;
- failing to provide actual movement values;
- attempting to fit the expansion joint by forced extension, compression or misalignment;
- assuming that the parameters of one product family also apply to another;
- treating a custom-made configuration as a design without material and mechanical limits.
12 / FAQ
Frequently asked questions
Do you manufacture made-to-measure expansion joints?
Yes. We design and manufacture non-standard solutions for the parameters of a specific installation. Feasibility and the final design depend on the technical data supplied for selection.
Can I order an expansion joint with a non-standard face-to-face length?
Such a configuration can be considered individually. The specific length is checked together with the required movements, material, pressure and flexible-element design.
Does a non-standard configuration always mean a design from scratch?
No. In many cases, modifying an existing variant or selecting an appropriate configuration from an available product family is sufficient. The scope of changes results from the geometry, materials and operating conditions.
Can a custom-made expansion joint be reducing or conical?
Our portfolio includes reducing configurations and a separate family of conical expansion joints. The feasibility of a specific geometry is confirmed on the basis of the installation data.
Do you analyse every non-standard project using FEA/CAE?
No. FEA/CAE calculations are used when the nature of the design or the operating conditions justify additional verification. The scope of analysis depends on the specific project.
13 / FROM DATA TO DESIGN
Custom expansion joints – from data to a specific configuration
A non-standard configuration starts with complete installation data: medium, temperature, pressure, geometry, connections and required movements. On this basis, we determine whether an appropriate configuration of an existing product is sufficient or whether an individually engineered design is required.
If you are planning a modernisation or have an installation for which a standard variant does not meet the requirements, send us the process data together with a drawing or photographs of the installation location. This allows us to begin selecting the appropriate solution.