Explosion Risk Assessment for the Design Stage of a Plant as Exampled by the Company Lajkonik Snacks Sp. z o.o.

Grupa WOLFF

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Karolina Pyrek | GRUPA WOLFF

When choosing the company to carry out the work related to explosive safety, we laid a strong emphasis on experience. On that basis, we selected GRUPA WOLFF and we have been cooperating with them for many years now. I admit that I knew the company from my previous job and already then, they proved themselves as a reliable partner who knows their business.

Michała Dunal
Engineering Design Specialist
Lajkonik Snacks Sp. z o.o.

This is how it began

In 1910, merchant Henry Franck founded the “Henry Franck and Sons” Coffee Substitutes Factory in Skawina near Cracow. Initially, the plant dealt with drying, grinding and roasting of chicory, but as soon as a year after the start of the production, the assortment was extended by coffee substitute.

In 1939, the plant already employed 658 people and the annual production of coffee and chicory reached ca. 7.5 thousand tonnes. After the war, the factory was nationalized and adopted the name “Coffee Substitute Factory”. In the 1950s, the name was changed once again to “Coffee Substitute and Pasta Factory”. However, if the name were to take into account the full range of the company’s offer, it should have also included “concentrated soups and prepared meals, spices, canned meat, fruit and vegetables, baking powder, powdered soups, jelly desserts, Worcester sauce…etc.”.

In 1961, a period of intensive growth began that lasted unceasingly till 1974. In 1970, the production of food concentrates was discontinued and the focus was put on salty sticks. At that time, there was launched the production of another “iconic” product, namely coffee Inka. In the early 1980s., products from Skawina were sent to the USSR, the USA, Germany, Canada, England, Australia, Kuwait, Malaysia, New Zealand, Saudi Arabia, and Belgium. Lajkonik’s products even found their way to Cuba, Island, and the Kingdom of Bahrain! In 1993, the most important event for today’s position of the Lajkonik brand occurred: the “Skawina Food Concentrates” works were privatised. The production increased, the factory was expanded and modernised, and “Lajkonik” snacks landed on tables all around Poland. A number of new products occurred, including Cracow Slices or Junior Sticks. At that time, Lajkonik products won numerous awards and distinctions. A new era in the company’s history began.

New times and explosive safety

The present time is the period of continuous development of the manufacturing plant. One of the most important investment project in this area was the construction of an installation for unloading, storage and pneumatic transport of flour to the process equipment of production lines. The new installation allowed to increase the production capacity of the plant by another 14%. However, due explosive safety regulations in force both in Poland and throughout the European Union, the capital investment required a detailed analysis from the point of view of the explosion risk and safety condition.

Explosion risk assessment at the design stage

In order to eliminate any errors and costly modifications in relation to the finished installation, the investor decided that the explosion risk assessment should be conducted still at the design stage. Thereby, it was possible to verify the assumptions and implement necessary changes and modifications to the design. An important element of the work was to determine explosion hazard zones and, in consequence, to select properly the equipment and tooling intended for work in the area where the so called explosive atmospheres occur. At that stage, a concept of an anti-explosive system was also implemented, i.e. the legally required ultimate form of protection against explosions. In this case, due to the technological conditions, the plant was equipped with an explosion suppression and decoupling system in the form of HRD cylinders and rotary valves in the design resistant to breakthrough of the pressure wave and flames.

The explosion risk assessment that the plant design had been submitted to revealed a number of risks that may occur within the plant. As a result, the authors of the document worked out some recommendations of varying weight which helped minimize both the risk of an explosion and its possible consequences to a safe level.

Although the applicable law does not require the implementation of a risk assessment for the design, but only for existing plants, this solution has many advantages from the practical point of view. The most important of them is improvement of the safety of the plant and reduction of its construction costs.

The design assessment allows to eliminate potential errors and, in consequence, costly changes in a completed plant (e.g. replacement of equipment incorrectly selected in relation to the determined hazard zones). It also happens that the design offices, having no experience in the field of explosive safety, excessively tighten the safety conditions, which results in an increase in the cost of the equipment purchased. Other frequent errors concern an incorrect application, or total absence, of explosion protections (too small surface of explosion relief panels or installation of the panels in a closed room, the lack of explosion decoupling systems, etc.). All of this can have a negative impact on investment costs, as well as the plant acceptance and, consequently, the time limit for completion of the work.

In the case of workplaces where there is a possibility of explosive atmosphere occurrence, i.e. a mixture of flammable substances in the form of gases, vapours, mists or dusts mixed with air, the employer is obliged to carry out an explosion risk assessment. The obligation follows directly from the Regulation of the Minister of Economy of 8 July, 2010 on minimum occupational safety and health requirements as related to the possibility of occurrence of explosive atmosphere in the work area – (Journal of Laws 2010 No. 138 item 931).

Implementation of recommendations

After taking into account in the design the guidelines and recommendations resulting from the risk assessment document, the plant was erected and secured in accordance with the previously developed concept. The last stage of the investment project from the point of view of explosive safety was formulation of an Explosion Protection Document (EPD) for the existing plant. This document was created on the basis of the explosion risk assessment for the design stage, which allowed to shorten significantly the project implementation time and thereby reduce the costs.

Now let us have a look at the completed plant with a particular focus on the solutions that are essential for explosive safety.

Flour for the Skawina plant is supplied with road tankers and then transported to silos with capacity of 98 m3 each. Tests of explosion parameters revealed, among other things, a very low ignition energy of the cloud of flour dust and, in consequence, an ignition of the explosive atmosphere could have occurred even as a result of an electrostatic discharge. For this reason, the unloading station was equipped with a certified earthing system with earthing correctness control which allows for attaching a compressor only when the road tanker is properly earthed (the system reduces the risk of ignition of an explosive atmosphere from an electrostatic discharge). On the pipelines supplying the silos with flour, there were installed explosion decoupling systems in the form of HRD cylinders (which prevent explosion from spreading to the remaining part of the plant). The same pipelines were also equipped with magnetic separators that protect them against penetration of ferromagnetic contaminants to the inside of the silos and to a further part of the process plant (the system reduces the risk of ignition of an explosive atmosphere from sparks resulting from ferromagnetic elements hitting the walls of equipment and pipelines, moreover, the solution protects the final product from an influx of unwanted impurities). The silos are equipped with minimum and maximum filling sensors and a weighing system. A bag filter was installed on the roof of each of the silos. On the system for unloading flour from the silos, rotary valves were mounted in the design allowing them to work as an explosion decoupling system (they form a protective system designed to stop the pressure wave and flame and prevent the explosion from spreading to the remaining part of the plant). Each silo has a vibrating bottom to facilitate pouring the flour to unloading systems. The unloading systems of the silos transport the flour to the pneumatic transport system which further carries it to the production line equipment.

Who should carry out an Explosion Risk Assessment

According to the existing regulations, the employer is required to perform an explosion risk assessment and prepare an explosion protection document. In practice, however, the employer often lacks resources or expertise in the field of explosive safety. In such situations, the work is outsourced.

However, at present, there are no provisions that would regulate the verification of knowledge, skills and experience of the companies operating in the area of broadly defined explosive safety. So we have decided to ask Mr. Michał Dunal, an engineering project specialist in the Lajkonik company, what criteria were applied for selection of the company responsible for carrying out of that phase of the investment project.

“When choosing the company to carry put the work related to explosive safety, we laid a strong emphasis on experience. On that basis, we selected GRUPA WOLFF and we have been cooperating with them for many years now. I admit that I knew the company from my previous job and already then, they proved themselves as a reliable partner who knows their business” – Mr Michał Dunal said.

Summary

After completion of the project, engineers from the Grupa Wolff affirmed that technical and organizational safety measures had been ensured within the plant. Another analysis was carried and it ultimately showed that thanks to the technical solutions applied, the probability of occurrence of effective ignition sources that could ignite the flour dust and cause an explosion was very small. Moreover, in the event of an explosion in one of the silos, the solutions adopted provide the highest technically available level of explosion safety.

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