Thermal expansion is one of the most significant challenges in the operation of industrial conveyor systems, particularly in processes operating at high temperatures. As materials expand when the temperature rises, conveyor systems face mechanical stresses that can lead to premature wear, deformations, and unexpected downtimes. Link conveyor chains In design, thermal expansion must be taken into account at an early stage.
Maintenance managers know the situation: conveyor chains need to be replaced more often than expected, even though they are dimensioned to withstand the process conditions. The reason is often thermal expansion and its secondary effects, which have not been sufficiently considered in the system design or component selection.
Thermal expansion is the tendency of matter to change its volume in response to temperature changes. It affects conveyor chains because materials expand when heated and contract when cooled. As a conveyor chain is exposed to varying temperatures, these expansions and contractions can alter its length, tension, and overall performance. This can lead to issues such as slackening, increased wear, or even breakage if not properly accounted for in the design and maintenance of the system.
Thermal expansion is a physical phenomenon where materials increase in volume as temperature rises. In conveyor chains, this means that chain links, shafts, and housing structures expand in different ways depending on the material and temperature, causing mechanical stresses and alignment problems.
The coefficient of thermal expansion of metals varies depending on the material. Steel expands by approximately 12 micrometres per metre for every degree Celsius. This means that a 10-metre conveyor structure can expand by up to 48 millimetres when the temperature rises by 400 degrees Celsius. In a conveyor chain, this expansion is not distributed evenly but is concentrated at specific points, causing uneven loading.
Thermal expansion affects the operation of conveyor chains in several ways. The distance between chain links changes, the alignment of the sprockets can be compromised, and the tension of the chain varies with temperature. These changes increase wear and can lead to chain breakage or deformation, particularly when the transported material includes large and irregularly shaped items.
How do temperature fluctuations cause problems in a conveyor system?
Temperature fluctuations cause cyclical stresses in the conveyor system, which weaken the mechanical properties of components and cause fatigue fractures. Repeated expansion and contraction alter the chain's geometry and increase friction between moving parts.
High temperatures significantly weaken steel's tensile strength and surface hardness. When the temperature rises above 250 degrees Celsius, the mechanical properties of ordinary manganese steel begin to deteriorate rapidly. At the same time, hot material lumps can cause thermal shock to the chain, leading to permanent deformation.
Another significant problem arises when the internal temperature of the conveyor drops too low. If the temperature falls below the acid dew point, sulfuric acid can form from the process gases, which dramatically accelerates corrosion. For this reason, the optimal operating temperature range is 250–400 degrees Celsius, where the mechanical properties of the chain are maintained and the risk of internal corrosion is minimised.
Temperature fluctuations also affect the conveyor's seal. When structures expand unevenly, gaps and dust leaks occur. This not only compromises process safety but also increases material loss and maintenance requirements.
The behaviour of materials at different temperatures
Different chain materials behave differently under the influence of temperature. Manganese steel (20MnCr5) functions well in lighter applications and at temperatures below 200 degrees Celsius. Boron steel (27MnCrB5), on the other hand, retains its mechanical properties better at high temperatures, up to 400 degrees Celsius.
The surface hardness of boron steel at room temperature is approximately 30 per cent higher than that of manganese steel. At high temperatures, this difference is further accentuated, increasing to as much as 70 per cent. Furthermore, the hardness of boron steel does not change with surface wear in the same way as manganese steel.
How can thermal expansion be compensated for in conveyor design?
Thermal expansion is compensated for in conveyor design by taking into account the thermal movements of the structure, selecting appropriate materials, and using expansion joints at critical points. The design is based on calculated thermal movements and their controlled management.
The first step is a precise thermal analysis. The conveyor structure is designed so that thermal movements are anticipated and controlled. This means careful placement of fixed points and expansion joints, as well as leaving sufficient clearances between components.
Material selection is crucial. For conveyor chains designed for high temperatures, boron steel is recommended due to its superior heat resistance. Stainless steel towing chain withstand continuous thermal load excellently and retain their mechanical properties for a long time.
Insulation design is critical for temperature management. Careful insulation ensures that the internal temperature of the conveyor remains within the optimal range and temperature fluctuations are controlled. At the same time, insulation protects the chain from sudden thermal shock.
Structural solutions
The conveyor structure is designed so that the chain is protected from both radiant heat and collisions with material pieces. The protected structure reduces deformation and evens out the load applied to the chain.
The placement of the chain sprockets and the selection of bearings are made with thermal expansion in mind. The bearings must be positioned so that they can compensate for the axial length changes without introducing additional stress.
Optimising the transport speed is an important factor. Chain wear increases exponentially as the transport speed rises, so the slowest possible transport speed will significantly extend the chain's service life.
Practical implementation
In practice, thermal expansion is compensated for using several methods simultaneously. Compensators are used at the ends of the conveyor, allowing for controlled movement. The chain tension is adjusted according to the average operating temperature, not room temperature.
The maintenance program considers temperature cycles and their effects on components. Regular inspections focus on the impacts of thermal expansion, such as chain alignment and tension.
In demanding industrial conditions, such as metallurgical smelters, controlling thermal expansion requires deep expertise and experience. A correctly designed and implemented system can double the chain's service life compared to traditional solutions. If you are wondering whether your process conveyor chains could last longer than they currently do, Get in touch And let's find out together.
You have a challenge that needs solving?
Let us help! Contact us for more information about our products and services.