Safety in Heat Treatment By David Pye
Safety in heat Treatment touches each and every one who works in either a captive or a commercial heat treatment shop. We all have a responsibility to each other to minimize the risk of accidents and injuries (no matter how minimal or extensive that injury might be). The two area’s that this presentation will address are shown below;
Housekeeping is a relatively easy subject to address and attend to. It is suggested that you consider a daily routine for floor cleaning. The following could then be considered;
- Painting of demarcation lines around the furnace equipment plus demarcation lines for stacking area’s for baskets, trays and load preparation and unload areas.
- Demarcation lines around process enrichment gas bottles.
- Demarcation lines around external bulk gas storage area’s for easy access for bulk gas delivery vehicles.
- Defining the receiving area as dispatch/pickup area.
- If you are operating salt baths, ensure that the salt storage area is a very secure area and under lock and key.
- Quenching medium should also be stored in a secure area and (if quench oil) well away from any heat source.
- No entry and emergency exits should be clearly identified as well as notices to follow to the nearest emergency exit.
Quite a large number of both captive and commercial plants have as their processing equipment, the integral quench furnace. That are used for atmosphere heat treatment procedures such as Carburizing, Carbonitriding, and neutral hardening procedures. The furnaces are more often than not, filled with combustible atmospheres as well an internal quench tank of specialty quench oil.
Shown below is an integral quench furnace. Once the furnace is gassed up, it can be likened to a ‘fire breathing dragon’ once the furnace is gassed up. The atmosphere concern and consideration apply also to continuous furnace systems, shaker hearth furnaces, 2 to 4 row pusher furnaces
Fig 1 An integral quench furnace filled with the process gas.
Fig 2. The fire breathing Dragon!!
The safety rules are really quite simple; however, one should follow (implicitly) the furnace builder’s safety and handling of atmosphere introduction into the furnace. This will be found in the Manufacturers Operational and Maintenance manual.
- DO NOT INTRODUCE THE COMBUSTIBLE ATMOSPHERE INTO THE FURNACE BELOW 1400°F!!!
- Never stand directly in front of the furnace door once the furnace is gassed up with a combustible gas. If an explosion should occur there is the potential for the explosion to blow off the furnace door.
- The integral quench furnace will have an internal oil quench built into the unit. Ensure that the set point oil quench medium temperature is maintained. In other words, ensure that the oil quench agitators are functional and most importantly, that the quench oil heat exchanger is functional and operating within the quench medium temperature set point.
- Ensure that the oil quench filters (usually on the external side of the furnace). This is because when the quenching procedure is in operation, fine particles resulting from microscopic debris quenching from both the work load and atmosphere are recirculating through the filters. It is recommended that a weekly filter clean is part of the weekly maintenance routine.
- Check monthly the functionality of the explosion caps.
- Ensure that all pilot light sensors are lightly brushed to remove any soot build up that will have deposited onto the sensors. (This applies to the main flame curtain as well as explosion caps).
- Ensure that Operating and Maintenance manuals are kept. It is suggested that a master copy be held in a secure location, and that one is kept in maintenance department and the final one on the shop floor in a safe and secure location.
- If operating an atmosphere generator, ensure that the air to gas is correct and not to forget to consider potential variances in atmosphere moisture content, (Particularly during both humid and rainy weather).
- Wear eye protection (goggle or full-face mask) If operating a salt bath wear the face mask with complete head protection against salt splashes.
- Wear a full heat resisting jacket with long sleeves for arm protection.
- Wear also long-sleeved heat resistant gloves.
- Wear appropriate foot protection with safety boots or shoes.
- Wear appropriate ear protection against excessive noise.
- Develop a personnel list of specialized heat treaters who can monitor the safety aspects of the department.
- Develop a first aid team or individual who has at least been trained in FIRST AID. The first aider should at least be able to deal with burns that may occur in the department.
- Develop a good first aid kit. Ask the local Dr for assistance in developing a first aid kit.
- Know the local first responders’ access telephone numbers. (Including hospital, ambulance, fire department)
- Do not use water to extinguish an oil fire. It can make the fire spread even further. If possible, starve the fire of oxygen by covering with a heat resistant blanket.
- Have CO₂ and gas detectors at strategic locations within the heat treatment shop.
- DO NOT enter a CONFINEDSPACE WITHOUT CONDUCTING A CONFINED SPACE ENTRY MEETING SO THAT ALL PARTY’S FULLY UNDERSTAND THEIR FUNCTION.
- Confined space entry by a single individual with out back is a recipe for a serious potential accident.
Regular furnace maintenance must be mandatory in any heat treatment shop. Without the furnace, and its control systems need to be regularly maintained. Without the furnace and its associated equipment, nothing is treated!!Your furnace equipment are your assets! People are also your assets. Ensure that employee safety is mandatory. The writer suggests a regular meeting of a formed safety committee within your organization to address with management to discuss potential safety issues. Have all of the appropriate and emergency telephone contact number available and located in a Manual of Corporate Standard Operating Procedures (SOP).