The paper machines used in the paper factories of Technocell Dekor in Titisee-Neustadt are technically good production plants. These machines perform to a high level 24 hours a day for 350 days of the year. High machine availability must be ensured all year round, as a failure of machinery means high financial losses.
Reiner Lippert, Technical Manager of Technocell, was on an inspection round through the paper production halls with the new testo 880 thermal imager. The inspection of electrical installations, production processes and mechanical components was of particular interest.
For more than 110 years, the Felix Schoeller Group has concentrated on the production of high-quality special papers. Technocell Dekor is part of the Felix Schoeller Group and with an annual output of 200,000 tons is a producer of decorative papers on the international market.
Regular maintenance inspections and accurate analysis of damage encompassing all areas of the production machinery in the Technocell plant prevent expensive system failures. Thermography has become a useful tool in industrial maintenance, as it offers many advantages: Thermographic images can locate potential sources of interference without contact, and quickly and reliably help to initiate corrective measures in good time before there is a costly shutdown of production.
On an inspection round through the halls of the paper production plant, the testo 880 thermal imager helps the maintenance engineer look for any possible sources of interference. The testo 880 thermal imager also soon makes causes of faults that are usually not visible to the human eye.
Electrical maintenance work
The German Insurance Association (VdS) recommends that Technocell carries out a thermographic inspection of electrical equipment once a year as a fire prevention measure.
When inspecting electrical installations in accordance with clause 3602 and testing guidelines VDS 2871, the VdS expert inspects the mains distribution box and switchgears for impermissible heating. Technocell has been using thermographic inspection as a key tool for maintenance to great effect for approximately 15 years.
Firstly, this regular inspection reliably minimises the risk of fire. This not only increases safety in production but also reduces the risk deduction for the insurance. Secondly, thermographic inspections enable Technocell to keep its machine availability high, thereby ensuring constant production.
During the inspection round with the testo 880 thermal imager, critical heating was discovered in a temporary power cable connection. The maximum temperature of power cables is normally 60°C. If the temperature increases to more than 100°C, the cables pose a potential fire hazard which must be dealt with immediately through appropriate measures.
At the time of inspection, the temperature of the detected faulty cable was 75°C. There may be several reasons for the cable being this hot: poor insulation, overload, loose connections. These factors can increase the resistances, which bundle the energy in the cable and push up the temperature.
As the consequences of an overheated power cable can be serious, regular inspection with the testo 880 thermal imager is worthwhile, as discrepancies in temperature can quickly be detected with thermographic images. The critical temperature situation of the cable will be observed carefully and closely over the next few weeks and the reason for the heating examined. Without the use of the testo 880 thermal imager, the problem would not have been discovered until much later, perhaps not even until the consequences of the heating could no longer be averted.
A digital camera built into the testo 880 thermal imager offers the possibility during inspection of producing a corresponding real image in addition to the infrared image. The comparison of the real and infrared image makes it easier to locate the damage and also provides more information for the final documentation and reporting.
In addition to the inspection of the power cable, the analysis of what is referred to as the motor circuit breakers is also informative. The circuit breakers monitor different motors. If one of the motors is overloaded, the switch responsible is tripped and the motors are stopped before they run too hot.
The temperature of the motor circuit breaker gives a clue as to the load of the motor. The more power a motor has to provide, the stronger the load that is placed on the motor circuit breaker and the more energy that runs through the switch. No irregularities were detected on the motor circuit breakers in the routine inspection with the testo 880 thermal imager.
In order to service and inspect high-voltage components such as the transformers, looking through a testo 880 thermal imager can also be informative. Transformers transmit electrical energy to another electrical voltage level. Transmission resistances can cause serious damage. Servicing high-voltage plants is dangerous and can only be done from a safe distance.
However, how then can electrical connections be inspected reliably and safely? An anecdote from earlier times shows how inventive the industrial inspectors had to be in those days in order to inspect and service their installations: as electrical parts get very hot before they finally fail, it was clear from an early stage that the condition of the transformers can be assessed accurately on the basis of their temperature.
To check the temperature of the transformer connections, the inspectors attached a wax candle to a long insulating rod and held it directly at the connections. If the wax melted, they could say straight away that the temperature of the transformer was so critical that immediate countermeasures had to be taken.
Today a thermal imager can be used to help service and inspect high-voltage networks. Even from a safe distance, it measures the temperature distributions reliably and shows the inspector at a glance how hot the connections are and how critical their condition is.
It is necessary for this application to have the possibility of changing the lens. Using a telephoto lens that automatically comes in the professional set for the testo 880 thermal imager, it is possible to zoom into the parts of the transformer to be examined. The inspection of the transformers at Technocell Dekor confirmed that they were in good condition.
Mechanical maintenance/production control
The use of thermographic images is not only effective for electrical maintenance work, but is also helpful for servicing mechanical installations in production. A high level of heat emissions from mechanical components may indicate an elevated level of stress. This is caused, for example, by friction due to faulty adjustment, component tolerances or a lack of lubricant.
Thermography is an effective measuring method for early detection and prevention of defects on mechanical components. High consequential costs or even a complete shutdown of production due to machine failures can be avoided with consistent and targeted use of a testo 880 thermal imager, as this detects problems long before a fault occurs and, by displaying the exact temperature distributions, helps to immediately assess the urgency of possible repairs.
An important end process in the production of decorative paper is the finishing of raw paper. The smoothness and gloss of the paper required by the processing industry for better printability is achieved using a special kind of smoothing in a glazing machine with what is known as calendaring. The paper goes through a three-roller calendar, the middle one of which is heated and evinces high temperatures. During this process, it is important that the heating of the mating rollers does not exceed the maximum temperature of 130°C and that the difference in temperature between two neighbouring measuring points does not rise above 30°C.
To create this uniformity of temperature, the mating rollers are controlled with cooling air over several air zones. These nozzles can fail and as a consequence the rollers are no longer sufficiently cooled. Using a testo 880 thermal imager, it is possible to check at regular intervals how hot the rollers are and whether the air nozzles are still working properly.
However, thermography also has its pitfalls and does not always work accurately or reliably. If the objects to be measured are made from a shiny, bare metal, measurement may be problematic due to the low emissivity and the high reflectiveness of the metal. The measurement may then not produce any clear result. However, a prospective thermographer learns about these problems with the use of a testo 880 thermal imager in special training courses. In addition to operating the testo 880 thermal imager, the training seminars also address the difficulties of thermography.
Level control
Level control in sealed fluid tanks has also proved to be a useful tool for avoiding machine damage and therefore production losses. If, for example, the fluid in coolant tanks falls to a dangerously low level, machines may no longer be cooled correctly. They run hot and may fail.
Normally, an automatic level control regulates the level of the water and issues an alarm if the level is too low. However, this automatic control can also fail. In this case, a regular look through a testo 880 thermal imager will also help. The water level produces different temperature distributions in the water tank. The testo 880 thermal imager sees and measures these different temperatures and provides information about the fluid level.
Conclusion
Thermography is a good tool for preventive and active industrial maintenance. Not only in paper production but equally in any other production plant, a large number of unscheduled production shutdowns can be prevented with a thermographic analysis. Use of the testo 880 thermal imager is uncomplicated and operation is easy and intuitive.
“Images are taken quickly, although interpretation of these images requires a certain specialist knowledge and is not easy“, as Lippert knows from his own experience. “Without the appropriate training, I would not be able to use the thermal imager correctly. How else would I know which materials can reliably be thermographed and what the emissivity of metal is, for example?” Fortunately, however, the Testo Academy, for example, or the German Association for Applied Thermography offers user-oriented training courses.
Background: what is decorative paper?
The decorative papers produced by Technocell Dekor in Neustadt are high-tech special papers and serve as a basis for the surface finishing of wood materials such as chipboards or MDF boards. As there are any number of possible colour designs for decorative papers, designers are constantly adding to their scope for designing our domestic and working worlds.
A large number of new areas of application for decorative papers were opened up in the 1960s, with the result that decorative papers now finish off kitchen worktops, furniture, doors, wall panels or laminate floors.