CHAMBER EXPANSION JOINTS PREVENTING MEDIA FROM PACKING UP
An asphalt manufacturer from France contacted Belman due to problems in the plant with repeated failures of the built-in Expansion Joints. Therefore, the manufacturer asked Belman to find a functional solution to the problem.
The construction of Expansion Joints for operational plants where the medium has a relatively high viscosity (that is, the medium is very thick, e.g. asphalt) poses a special challenge to the designer. With a thick medium the flow is more sluggish due to the inner friction of the medium and this poses the risk that the medium will settle in the convolutions of the compensator and block the flow. In the worst case the flow is completely cut off. This phenomenon is often referred to as ”packing up”, ”cooking” and/or ”caking”. As the fluidity of the liquid – its ability to flow – generally increases with higher temperature, the solution to the problem of the asphalt manufacturer was a Chamber Expansion Joint, which makes it possible to increase the temperature of the asphalt in the Expansion Joint and thus ease the flow.
In principal, a Chamber Expansion Joint is a compensator with another, larger Expansion Joint mounted around it, whereby a chamber is formed between the two. The medium flows through the inner bellow as usual, while a heating medium, in this case oil, flows in the chamber between the bellows. The oil is heated and flows through the chamber through an inlet and an outlet respectively. On its way through the chamber the oil emits heat to the inner bellow, thus maintaining/increasing the temperature of the asphalt. This increases the fluidity of the asphalt and eliminates the risk of ”packing up”. Following the installation of Chamber Expansion Joint, the asphalt manufacturer has experienced no failing bellows.
Is it possible to solve the problem through insulation?
LInsulating around the Expansion Joint would merely postpone the problem with flow cut-off/”packing up”. The insulation would reduce the heat loss, but not sufficiently so. The Chamber Expansion Joint supplies heat to the medium and this is not possible through insulation alone, as the insulation only retains the existing heat. This heat is not sufficient to minimise the viscosity, nor is it sufficient to avoid a cooling and settling of the medium in the convolutions of the Expansion Joint. Therefore, the Chamber Expansion Joint is to be preferred for sluggish mediums.
Chamber Expansion Joints and materials
Chamber Expansion Joints have many areas of application and are therefore manufactured in all types of materials according to the intended use. Usually the material is determined by the temperature as well as the type and consistency of the medium. If the medium is very corrosive, usually high-alloy materials are used. The surroundings of the Expansion Joint may also influence the choice of material.