Each process water cistern is important
Process water in industry accounts for about 60% of all water use in Sweden. The management of process water must be safe. It is necessary to keep production running and to protect our nature. Cisterns containing process water should be able to deliver what is expected - the right water quality at the expected capacity. A leaking process water cistern could compromise both production capacity and product quality. During production, the process water can become contaminated. To provide good protection for both people and the environment, process water tanks must be of a high standard
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Process water cisterns can look different
Process water is stored in different ways. The solution chosen depends on the amount of water to be stored, how it will be used and the quality of the water. Here are some of the most common solutions: Process water cistern/process water tank: Process water is often stored in large cisterns or tanks. They can be installed either above or below ground. They can be made of steel, concrete or plastic (PE or GAP). The material used depends on the water quality requirements of the production and whether the process water contains chemicals or contaminants. Dam systems: In the mining or power industry, concrete dam systems are common.
Common problems with process water tanks
Water is highly reactive. Together with various chemicals and substances, water can form compounds that can damage the cistern.
Corrosion is one of the most common problems. Water that is high in salt (chlorides or sulphates), has a low pH value or contains aggressive chemicals can cause corrosion. Oxygen dissolving in the water can cause corrosion. Corrosion breaks down the walls of the tank. Initially, the damage is microscopic but if not addressed, cracks will form and the tank will leak. In the worst case, the tank may collapse.
Cracks can occur due to corrosion but there are also other causes. Cracking is more common in tanks that are exposed to changes in temperature and pressure. The changes in temperature and pressure can weaken joints and seams, causing cracks to form. A tank with cracks will leak. The leak may mean that there is not enough process water for production. More water will have to be added and energy consumption will also be higher.
Sediment forms when rust and other deposits come off the walls of the tank. Sediment can clog pipes and valves, resulting in reduced flow rates and increased pressure. It can also contaminate the process water. Another problem is the growth of micro-organisms, which can occur when water is stored for long periods and exposed to sunlight. The problem is particularly troublesome in the food and pharmaceutical industries where purity requirements are high.
Avoid problems with inspection
As process water can affect both people and the environment, the authorities have developed rules on how often cisterns should be inspected. The regulations vary depending on the industry and circumstances. If the tank contains flammable liquids, such as solvents, inspection of the installation must by law be carried out by accredited bodies. The intervals are 6 or 12 years. More information on what applies to cisterns can be found here
>> (internal link) By inspecting frequently, preferably more often than the intervals required by the authorities, you can detect and address deficiencies at an early stage. You can find more arguments for frequent inspections on our website.