Illustration 1: Oven during the test run
Illustration 1: Oven during the test run

A look behind the scenes: factory acceptance test of a calcination oven

Drying and heat treatment units are employed in many industrial production processes and therefore also to be found in the ceramic industry.

If drying units for roofing tiles, tempering ovens for refractory bricks or large conveyor ovens for different ceramic materials the drying or thermal treatment process is almost one of the most important steps in the production process and essential for the quality of the product. Standard solutions such as simple chamber or standard continuous flow dryers exist for many thermal applications. With larger production lines or the modernisation of existing units a customer and project-specific design and development is often the preferred solution.

The advantages of a customised unit are for example a greater degree of freedom in the design and development, introducing modern production processes, savings of costs and energy or that optimised dimensions can be achieved. Along with these advantages the development and building of a special unit contains increased risks. The customer's confidence in the plant manufacturer must be evident so that major projects can be successfully implemented.

The following article, using the experience gained of a current project, describes which challenges can arise with a customer-specific design and development, how the customer's risk can be reduced and how the plant manufacturer can react in the event of upcoming problems.

Special requirements for factory acceptance tests of large industrial production plants – Based on the example of a calcination oven for technical ceramics

This project concerns a new production line of automobile catalytic converters. The base of the catalytic converters or diesel filters are temperature-stabling elements, so-called honeycomb bodies made of ceramic or metal foils, which have a multitude of small thin walled channels. The surface of the channels is coated with a reactive film, which later serves as the actual catalyst during the purification of exhaust gases. Depending on the production process the coated honeycomb bodies have first to be pre-dried before passing through a calcination step. The coated honeycomb bodies are then fitted into the appropriate housing in a later production process. Some ceramic elements can be seen in Illustration 2.

Parts of the new production line are amongst other things two belt dryers and a continuous flow oven for calcination, which heats up the coated ceramic elements up to 500 °C. The handling of the ceramic elements inside, outside and between the plants is also an important part of the project. Münstermann has many years of experience with thermal processing units for the production of catalytic converters and supplies all well-known producers in Europe. In the past, together with the project customers, joint projects were undertaken however with another range of products and with smaller thermo processing units.

Hot test in the Münstermann production halls

The production line is part of an extension to an existing factory. Due to the unsatisfactory experiences with a former supplier the customer insisted on a Factory Acceptance Test (FAT) consisting of a heat up of the system in the production halls of the supplier before delivery to the final installation site. The test was more or less a preliminary start-up. The purpose of this complete acceptance test is to ensure the specific values such as the heating-up curve, maximum temperatures, airflow velocities, temperature tolerances and peripheral parameters such as the noise levels of the unit lie within the predefined parameters. This is carried out before the oven is later assembled and taken into operation in the customer's production halls.

It is customary practice that individual sub-sections or function blocks are tested during the assembly according to an agreed acceptance protocol. To completely heat up a plant of this size and take it in into operation under actual production conditions, if only for a few days, constitutes a major, large-scale project on its own. The electrical power requirement alone to run the large continuous oven at over 500°C would overload the local power supply. Specifically for the heating up phase diesel generators with an overall performance of 4 MW were rented, with which the oven could be operated. Illustration 3 shows the aggregates in front of one of the Münstermann production halls.

Collective acceptance tests

The test conditions for the oven were clearly defined jointly with the customer at the placement of the order. As the test procedures were to be as realistic as possible a number of different product types and size variations were made available. The samples were uncoated ceramic objects like the ones that would be later heated up in the oven. Both the size and the shape of the samples correspond to the subsequent production conditions such as the airflow velocity and temperature curve that change according to the dimensioning of the test samples. Temperatures and airflow were measured by a large number of sensors. A whole week was estimated for the different tests. Only one test run of a representative quantity of honeycomb bodies through the oven followed by a data evaluation of the measurement results lasted several hours. Illustration 1 shows the oven shortly before the first test run.

The initial test runs were carried out together with customers' employees and showed that the oven could not be operated under the required specific parameters. The airflow velocity of the air circulation in the oven was too low. This just shows that an acceptance test run even when very elaborate, as in the present case, and although very time-consuming is good sense. This is especially true for projects with new partners and with new types of plants. Computer aided air flow simulations and the following verification in a test oven in the company's own Technical Centre proved that with a few mechanical modifications the required specifications could be achieved. Together with the customer's experts the methods of resolution of the problems could be thoroughly discussed and successfully implemented. During the actual commissioning when under time pressure and at the final location in Eastern Europe modifications to the oven would have been certainly more protracted, complicated and expensive.

Future prospects

Special plant engineering projects always involve risks for the producers of goods but also for the suppliers. If and when working together with new partners, elaborate acceptance tests at the supplier's location can lead to confidence-building measures. Small problems and adjustments to the unit during the acceptance test are routine. In the case in question it even was an advantage that not everything functioned at first go. The customer became involved with the professional problem solving at every step and communication was always transparent and open. The actual situation and even initial problem solving failures were discussed between the partners at regularly held meetings or videoconferences. The complete execution of the acceptance test became, for this reason, a trust-building exercise. A series of tests, for example, when a complete acceptance test is carried out, is time consuming but provides the opportunity for employees of the different companies to get to know each other better. At the end the additional effort has definitely been worthwhile for both partners.