A Preventive Maintenance Checklist for Industrial Ovens
Safety in production means, for ovens, following the correct safety measures and proper equipment-specific instructions. Experts from Haas-Meincke (Buhler), Koenig, and Reading Bakery Systems share their preventive maintenance priorities, steps for periodic inspections, and insights into troubleshooting possible oven malfunctions.
Oven operations are best performed under recommended parameters, from baking to cleaning and maintenance downtimes. A new industrial baking oven installation comes with a set of safety instructions according to the characteristics of the oven. This also helps avoid possible hazards. At Reading Bakery Systems (RBS), all ovens include “operation and maintenance procedure manuals that identify potential hazards and explain how to avoid them, while working on or around the oven. These hazards include exposure to high temperatures, automatic movement of components like belts and take up system, and the shock hazard inherent in any machine powered by electricity,” the company tells us.
Oven-specific guides
Teflon, stone plate, mesh belt ovens – what are equipment-specific safety precautions?
Specific hazards may vary based on the type of heat source used in the baking environment. “Fossil fuel and electric ovens would have the same hot surface and fire concerns. However, a fossil fuel oven would have an additional potential explosion hazard,” RBS explains. “RBS uses – and highly recommends using – a real time data recording system to determine the actual and ongoing environmental conditions within the oven chamber. This should include recording temperature, air flow, humidity, and heat flux, and should be done in a way that provides an accurate picture of those characteristics across the width of the oven. RBS uses the Reading Thermal Scorpion System, which includes sensors for measuring these key parameters and can train plant staff on their use and implementation for maintenance and troubleshooting.”
The safety instructions are very similar for all Koenig industrial ovens, says Benedikt Christian, oven design group leader with Austrian specialist. “One difference is, for example, whether the oven has safety fence doors. Maintenance instructions vary for different kinds of ovens – e.g. stone plate ovens are more sensitive than steel plates,” adds Christian.
As ovens will always be product dependent, Indirect Fired Convection ovens (used for biscuits, cookies, cakes, pizzas, etc.) can be heated by gas, oil, or electricity.
“The flame from the burner heats up the burner chamber and the tube bundle of the heat exchanger. The flue system removes the combustion gases. Therefore, there is no risk of contact with the products in the oven, securing a clean oven environment. A fan blows the air around the heat exchanger room and circulates the air around the heat exchanger. A temperature sensor controls the burner in order to secure a constant and correct baking temperature,” explains Haas-Meincke’s team. The benefits of Direct Fired Convection ovens are short heating-up and recovery times, low energy consumption, easy operation, USDA approvable, and full moisture control.
DGF ovens, suitable for products including hard biscuits, crackers or pita breads, feature “integrated cable trays, recipe-controlled burner systems, easy access to the inside of the baking chamber through cleaning doors for every two meters”, Haas-Meincke says. In the case of cyclothermic ovens, “the air is regulated through dampers for more or less top or bottom heat. For uniform baking of the products the heat distribution can be regulated across the baking room by dampers in the tubes. The regulation will be done at the commissioning of the oven. A damper system controls the amount of humid process air which is sent out and the amount of dry fresh air which is taken into the oven. In this way it is possible to control the humidity in each heating zone. Via suction dampers, the air is sucked from the oven chamber to the exhaust duct. If required, some of the air can be regulated by dampers and recirculated to the oven chamber through nozzles in a duct across the oven chamber creating turbulence in the whole oven chamber.”
Periodic Inspections Explained by Koenig
Koenig lists some examples for periodic inspections. “These are only general assumptions, since specifics depend on the oven, in which periods maintenance inspections need to be carried out.
The general recommendation is to exchange certain parts if they are damaged or show strong wearing or any sign of leakage.
DAILY: Control of toothed belt discs for contamination
WEEKLY: Control of motor temperature (on display of touch panel, average of all motors should be 50°C)
MONTHLY: Check for deposits on the chains and wearing; Control of short and long toothed belt for dirt or wear; Control of drive unit for tight fit of all components, no deposits on the shafts and rotating parts; Circle reverse control and rails: check screws for tight fit, contamination of the tooth gaps; Baking plates – check plates if they are damaged or warped; Humidity sensors: control on display panels for irregularities, recalibration recommended every two years.
YEARLY: Heat exchanger: sight control; Sealings and sealing rings: check for wearing or damage
Maintenance Checklist Explained by RBS
Periodic maintenance procedures that RBS provides instruction on include:
DAILY: Conveyor Belt Condition, Belt Carrying Rollers & Supports Condition, Take-Up System Parameters, Zone Temperature Range throughout production
WEEKLY: Belt Drive System, Oven Interior Condition, Combustion blower filters
MONTHLY: Bearing and gearbox Lubrication levels, Oven Belt condition and tracking, Combustion and Exhaust Blowers, Valve Motor and Valve Maintenance
QUARTERLY: Air Cylinder condition, Gas Supply Lines and Gas Trains, Burners, Burner Safety Shut-Off Circuit, Start-up and Oven Temperature Switches,
YEARLY: Drain and refill all Motors and Gearboxes with fresh food grade oil, check the conveyor bed guides underneath the belt for wear.
You can read additional information in our print magazine European Baker & Biscuit (Jan/Feb 2018)!