What should be paid attention to when installing stainless steel welded ventilation pipes in food processing workshops?

What matters should be paid attention to when installing stainless steel welded ventilation pipes in food processing workshops?

Food processing workshops have strict requirements on hygiene, cleanliness and cross-contamination prevention. As the core carrier of environmental protection ventilation project, stainless steel welded ventilation pipes should not only meet the transportation requirements of waste gas, odor and hot and humid air, but also conform to the hygiene standards of food industry, and be strictly controlled in terms of material selection, pipe structure, welding technology, installation layout, cleaning and maintenance, safety and compliance, so as to avoid the pipes from becoming pollution sources for microbial growth and oil accumulation.

Material selection is the primary control point, 304 stainless steel is preferred in food workshops, and 316L stainless steel is recommended for processing scenes with high salt, high water vapor and acid materials. It is forbidden to use common galvanized sheet and color steel duct, which are easy to rust and peel off, and rust will fall into the production area and cause food pollution. The thickness of the plate should match the wind pressure of the ventilation system to avoid the deformation of the pipe wall under negative pressure; Check that there are no scratches, oil stains and trachoma on the surface of the plate when it enters the site, and keep the material certificate of the raw materials for food safety and environmental protection verification. All supporting fittings, elbows, tees, reducers, flanges, elevators, etc., must be made of the same material as the main body of the pipeline to prevent electrochemical corrosion caused by contact of dissimilar metals.

The welding process must meet the requirements of food hygiene. The pipeline shall be fully welded by argon arc welding, and the weld shall be polished and polished. The weld on the inner wall shall be smooth without flash, pit and burr. There are no gaps and dead corners in the inner wall of the pipeline, and water vapor, food crumbs and grease are easily left in the gaps, which breed bacteria and molds. Passivation treatment is needed after welding is completed to remove the oxide layer produced by welding high temperature and improve the corrosion resistance. Welds must be tested for air tightness, so as to prevent air leakage from causing odor overflow in the workshop or unclean air from the outside from infiltrating into the clean production area. It is forbidden to use ordinary sealant inside the pipeline, and food-grade high-temperature resistant sealing materials should be used to avoid the aging and falling off of the rubber compound and polluting the products.

Pipeline layout and installation design should give consideration to clean partition and airflow organization. Food workshops are generally divided into clean areas, quasi-clean areas and non-clean areas, and ventilation pipes cannot cross regions at will to prevent cross-contamination of air in different areas. The gas collecting hood of the production line should be close to the point where odor, oil fume and steam are generated, and the wind speed should be controlled reasonably to avoid the dust of food raw materials caused by airflow disturbance. The horizontal long-distance laying of the pipeline shall be reduced as far as possible, and the horizontal pipe section shall be provided with a reasonable slope, and the drainage outlet shall be provided to discharge the condensed water in time, so as to prevent the accumulated water in the pipe from being stranded for a long time and breeding microorganisms. Spacers are added between the hanger, the bracket and the pipeline to avoid condensation corrosion caused by direct contact of the bracket with the pipe wall. Try to reduce elbows, reducing diameter and other resistance parts in the pipeline, reduce wind resistance, and ensure the stability of system air volume.

The structural design of cleaning and operation and maintenance can't be ignored. Food oil mist and water vapor residue will adhere to the inner wall of the air duct in the food workshop. Sufficient inspection ports and cleaning ports must be reserved for the pipeline. The inspection ports adopt food-grade sealed cover plates to facilitate regular washing and wiping. The inner wall of the pipeline shall be kept smooth, and there shall be no structures that are easy to accumulate dirt, such as raised rivets and flange lining. The external surface of the pipeline is smooth, which is convenient for daily wiping and disinfection in the workshop. System fans, filters and other supporting equipment, to support differential pressure monitoring, timely grasp the filter plug situation, to prevent pollutants from flowing back to the workshop.

Health and epidemic prevention, environmental protection and safety standards are implemented simultaneously. Ventilation engineering should distinguish between process exhaust, workshop ventilation and clean fresh air, and the fresh air pipeline must be equipped with primary and intermediate filter devices to filter external dust and mosquitoes. The exhaust system containing oil fume and steam is equipped with oil fume purification and gas-liquid separation device at the front end to prevent oil pollution from directly entering the air duct, causing oil accumulation in the pipeline and reducing the fire risk. Electrical appliances and fans shall be protected against explosion, and the wet areas shall be protected against leakage. After the completion of the project, air volume test and air leakage detection should be carried out, the exhaust emission index should meet the requirements of environmental protection, and the overall scheme should meet the hygienic standard of food production.

In the construction stage, site control should be done well, and the pipeline prefabrication should be completed as far as possible outside the workshop. Before entering the food workshop for installation, the inside and outside of the pipeline should be thoroughly cleaned and degreased to remove oil stains and metal chips. During installation, dust protection shall be done, and the pipe opening shall be temporarily blocked to prevent construction dust and sundries from entering the pipe. After the construction is completed, the whole system shall be purged and cleaned, and it can be put into use only after passing the acceptance.

To sum up, the core of stainless steel welding ventilation pipeline project in food processing workshop is to give consideration to environmental ventilation performance and food hygiene and safety, strictly control the material, welding, structure, cleaning and zoning airflow, prevent the pipeline from fouling, corrosion and cross-contamination, ensure the air environment in the workshop to meet the standards, and meet the requirements of environmental protection and food safety inspection.