Flue Fire Prevention Awareness

Transcription

1 Flue Fire Document_R1 Page 1 of (C) Recommendations Version: 1 Flue Fire Prevention Awareness Introduction Beech Ovens are one of the leading manufacturers of stone hearth ovens in the world. Stone Hearth Ovens are simple to operate and virtually maintenance free however dangerous situations can occur if the ductwork is not cleaned regularly and/or the Spray Filter (wet scrubber) system (if installed) is not maintained. Beech Ovens is the only company that has developed innovative exhaust solutions to address this potential fire hazard. Recently there have been a number of flue fires which in our opinion resulted from incorrect façade installation and inadequate cleaning of grease laden ductwork. These fires could have been prevented if the installers/operators had adhered to the guidelines contained in our Installation and Operation Manual. Pages 3 to 8 of this document highlight the 3 most common errors which can cause an exhaust fire and how they can be prevented. Pages 9 & 10 identify additional safety options available to our clients to further reduce the risk of fire hazard. In December 2007, we released a revised Installation and Operational Manual containing detailed illustrations which comprehensively addresses all aspects of the installation and operation of our stone hearth oven range. A PDF copy is attached or a hard copy is available by contacting our office. To ensure the safe operation of a stone hearth oven, it is critical that Designers, Installers and Operators read and follow the advice outlined in our Installation and Operation Manual. For further information on any of the issues mentioned in this document, please contact the Beech Ovens support team at; technical@beechovens.com.au or by visiting our website at;

2 Flue Fire Document_R1.doc Page 2 of (C) Overview Fires have occurred for 3 main reasons: Fire in flue/duct above oven door Potential cause As described in the diagram on page 3, grease fires have occurred here due to a build-up of grease in the spigot before the spray filter. This build-up of grease is ignited by a flash fire off the grill and/or sparks/embers from wood fire, igniting the contaminates in the duct above. Solution: Clean the oven spigot daily or weekly (as required) to eliminate grease build-up. Fire behind the façade Potential cause As described in the diagram on page 5, poor sealing between the façade and the oven lintel (spigot) leading to grease contamination between the façade and outer spigot wall. This grease contamination is then ignited (as in 1 above) by a flash fire off the grill and/or sparks/embers from wood fire. Solution: Ensure that the area above the oven door and façade is fully sealed with a fire proof material (refer diagram on page 6) Excessive flue temperatures Potential cause Excessive flue temperatures can potentially lead to combustion within the flue/duct system. The diagram on page 7 outlines the potential causes of high flue temperatures and the diagram on page 8 identifies the normal operating temperatures of the Spray Filter system. Solution: Ensure that the duct damper is correctly adjusted, the fan is correctly sized and that the cool air make-up unit is functioning correctly. Potential Improvements Pages 9 and 10 outline two (2) potential improvements to the ducting system to address the above mentioned issues. These improvements are recommendations only. Contact Beech Ovens head office for further information.

3 Flue Fire Document_R1.doc Page 3 of (C) 1. Potential cause of Flue fire Flue fires are primarily due to poor maintenance and the lack of a rigid cleaning schedule. Most flue fires can be prevented by implementing a regular and thorough maintenance schedule as outlined in the Beech Spray Filter maintenance schedule document. The illustration below outlines the most common cause of a flue fire and highlights the most vulnerable area which requires regular cleaning and maintenance. C. The fire, fuelled by a residual build up of grease, fat and creosote, is drawn through the Spray Filter and into the main Exhaust duct. REGULAR DUCT MAINTENANCE IS ESSENTIAL. REFER TO THE MAINTENANCE SCHEDULE IN THE INSTALLATION AND OPERATION MANUAL. B. NOTE: Flames will pass directly through the Spray Filter misting spray as it is only designed to remove pollutants. The Spray Filter is NOT designed to extinguish flames. FIRE A. Grease build up on spigot walls ignites from flash fire on Char Grill THE SPIGOT WALLS MUST BE CLEANED DAILY OR WEEKLY DEPENDING ON THE GREASE BUILD UP

4 Flue Fire Document_R1.doc Page 4 of (C) 1. (A). Wood Fired Oven - Direct Connect Exhaust The illustration below outlines the most common cause of a flue fire with a wood fired oven at the oven spigot directly connected to the exhaust ducting system. This also highlights the most vulnerable area which requires regular cleaning and maintenance. B. The fire, fuelled by a residual build up of grease, fat and creosote, is drawn into the main Exhaust duct. REGULAR DUCT MAINTENANCE IS ESSENTIAL. REFER TO THE MAINTENANCE SCHEDULE IN THE INSTALLATION AND OPERATION MANUAL. FIRE A. Grease, soot and creosote build up on spigot walls ignites due to spark from wood fire The spigot walls need to be cleaned daily or weekly depending on the build up Sparks from the Wood Fire Wood Fire

5 Flue Fire Document_R1.doc Page 5 of (C) Spigot Maintenance IMPORTANT: Be sure to follow the Maintenance instructions as outlined in the Installation and Operation Manual. Daily Checks 1. Cleanliness: No debris or rubbish left around, under or in the oven area. 2. For ovens equipped with a Spray Filter, the tundish drain should be checked daily to ensure that water is flowing at a trickle rate (15-35lts/hr). 3. Draft at the spigot above the oven mouth should be noticed when the exhaust fan is operating. For simple airflow measurement advice refer to A4 Paper Test in the Installation and Operation Manual or from the Pre-Fire Checklist document on the Beech Ovens website For ovens with a Char Grill, the grill, spigot and surrounding area should be cleaned of grease build up daily (See below). More regular cleaning of the flue and oven spigot area may be required depending on the amount of grease produced. Weekly Checks 1. The Spigot area of the oven, above the mouth or door of the oven, should be cleaned of build-up at least once per week (7 days). Spigot cleaning brush Be sure to clean the spigot thoroughly, all the way to the top of the spigot adapter

6 Flue Fire Document_R1.doc Page 6 of (C) 2. Potential cause of fire behind the façade Poor sealing between the façade and oven door leads to grease contamination between façade and oven wall. This grease contamination is then ignited by a flash fire off the grill. Solution: Ensure that the area above the oven door and façade is fully sealed with a fire proof material as shown on page 7. B. The fire, fuelled by a residual build up of grease, is drawn into the area above the oven igniting any flammable material in this area. IT IS ESSENTIAL THAT THE OVEN IS INSTALLED CORRECTLY IN ACCORDANCE WITH THE INSTALLATION MANUAL PROVIDED FIRE Oven Facade A. Grease build up between the façade and spigot ignites from flash fire on Char Grill THE AREA BETWEEN THE SPIGOT AND THE FAÇADE MUST BE SEALED WITH A FIREPROOF MATERIAL E.g. METAL STRIP

7 Flue Fire Document_R1.doc Page 7 of (C) Façade Installation Warning An important area to be aware of is directly in front of the exhaust spigot of the oven. If the facade protrudes from the spigot there may be an area between the spigot/lintel and the facade which is left uncovered and vulnerable to soot and grease build-up. This area is commonly overlooked when constructing the oven facade and if not sufficiently sealed creates a fire hazard. Exhaust Spigot Insulation between spigot and facade face Be sure to sufficiently seal the area between the exhaust spigot and the facade with a metal infill to ensure high temperatures and flame do not enter the facade cavity Facade face

8 Flue Fire Document_R1.doc Page 8 of (C) 3. Potential cause of high flue temperatures after Spray Filter In order to achieve above normal temperatures after the Spray filter, (i.e. above 85 C) one (1) or more of the following situations exists; 1. Fan incorrectly sized (too small) 2. Fan failure 3. Cool air make-up blocked or restricted 4. Ductwork blocked/restricted 5. Duct damper (if installed) incorrectly adjusted (in semi-closed position) All of the above mentioned situations relate to a insufficient air-flow duct environment allowing ductwork to have excessive heat & 2. 3.

9 Flue Fire Document_R1.doc Page 9 of (C) Spray Filter normal operating Temperatures and Air flow volumes The diagram below identifies the normal operating temperatures for the Spray filter System. Exhaust Exit temperature less than 100 C (@700l/sec 1000l/sec for 2 door oven) Exhaust Temperature entering Spray filter approx C (@ approx 150l/sec) Cool Air make-up unit. Approx 30 C (@ approx 550 l/sec) Spray Filter helps to removes pollutants (Creosote, ash, etc) Fresh air (approx 22 C) mixes with hot air from oven cavity Oven Temperature approx 350 C Oven Facade

10 Flue Fire Document_R1.doc Page 10 of (C) Potential Improvement 1 (Recommended) The installation of a canopy has several benefits. 1. Easy access to filters for regular cleaning 2. Visible break between spigot and canopy to alert if flash fire should occur 3. Better access to oven spigot to allow for regular cleaning 4. Allowance for an independent Tyco/Wormald/Ansul wet chemical fire protection system to be fitted 5. Options such as an Automatic Water Wash and Misting Spray System for high use applications (Contact Beech Ovens for detailed information) Optional Tyco/Wormald/Ansul fire protection system Canopy filter consisting of Cyclonic and Mesh filter to remove grease, fat and creosote and help to prevent embers entering ductwork Optional Auto Water Wash and/or Misting Spray

11 Flue Fire Document_R1.doc Page 11 of (C) Potential Improvement 2 The installation of a Beech Ovens Spray Filter can be beneficial in many applications, though proper routine maintenance is essential. Listed below are some added safety features that can be fitted to a standard Spray Filter. 1. Weekly alarm/warning light to advise maintenance staff to clean spigot area 2. 3 monthly alarm/warning light to advise maintenance staff to clean all ductwork 3. Water Supply Sensor to ensure water is always on during operation 4. Independent Tyco/Wormald/Ansul wet chemical fire protection system 5. Maintain System in accordance with Beech Ovens Installation and Operation manual 4. Optional Tyco/Wormald/Ansul fire protection system 3. Water Supply Sensor 1, 2 & 3. Alarms to advise maintenance staff