Kitchen suppression systems are designed, tested, and approved to provide fire protection for commercial kitchen cooking appliances, hoods, and ducts. The suppression systems consist of an agent storage tank, manual release station, an automatic releasing mechanism, and supply piping that directs the agent to nozzles strategically positioned at heat sources in the kitchen.
NFPA 17 requires that every 12 years the agent-holding tank, whether it is a pressurized or non-pressurized system tank, must be pulled out of service to be tested.
For all systems, the agent storage tank must be pressure tested to ensure the integrity of the cylinder. There are many types and manufactures of kitchen commercial wet chemical systems, each one has different test pressures for the cylinder, which are set by the manufacturer. Once filled with water, and sometimes oil, the cylinder is capped off, then pressurized to the manufacture test pressure and held at that pressure for no less than 1 minute. These systems are often tested to almost two times the service pressure.
On a non-pressurized system, there is a cartridge that pushes the agent out of the cylinder. This cartridge is replaced every 12 years. In some instances, these systems can have a burst disc that would need to be replaced before the 12-year hydrostatic test is scheduled.
Pressurized systems have valve stems, O-rings, and pins that need to be replaced. This is called a rebuild kit.
Once all of the cylinders are tested, dried, and documented they get filled back up with the proper wet chemical agent and put back into service if there is not any issues with the test pressures. All systems, both pressurized and non-pressurized, get new agent during a 12-year hydrostatic test. For certain suppression systems, hoses will need to be replaced at the 12-year hydrostatic test.
According to the National Fire Protection Association (NFPA), more than half of the 8,160 structure fires involving commercial cooking equipment or ventilation components that occur annually begin in kitchens or cooking areas. Between 2004 and 2008, these cooking fires caused three deaths, 100 injuries, and $229 million in director property damage each year.
A kitchen hood is important fire protection at it eliminates air contaminants and toxic chemicals from the air, which are released when cooking. The filters in the kitchen hood capture grease and debris in these fumes and prevents them from entering your exhaust system.
Kitchen hood grease filters are an important fire prevention device. With grease or debris in your exhaust ducts, a fire could occur within the hood system. Duct fires can be intense, difficult to extinguish, and are susceptible to re-ignition.
No cook likes to clean the grease filters, however, regular cleaning of your grease filters is critical to maintaining proper function. Let your kitchen staff focus on their real job functions and remove this risk of worker compensation claims by collaborating with a knowledgeable partner to clean your filters. Having your Life Safety Partner perform this service will save you money while also keeping your employees safe, and your kitchen in compliance.
A filter exchange program can be a real benefit to any food service company or restaurant. At the intervals required for your kitchen, based on cooking methods, appliances, and volume of operation, your filters will be scheduled for automatic replacement.
Not only are the dirty filters removed and replaced with clean filters, but also the dirty filters are taken off-site to be cleaned. By not cleaning the grease filters at your restaurant you can reduce the amount of grease going down your drain by up to 70%, and the grease will be disposed of in an environmentally friendly manner. This offsite cleaning will save you money by reducing chemical costs, water usage, and the amount of grease in your traps.
Kitchen Hood systems are one of the most widely used fire protection systems given the fire source and fuel load. Kitchen Hood systems include the hood, exhaust, and ducting systems over your cooking appliances. This system vents airborne grease, combustion products, fumes, smoke, odors, heat, and steam.
These systems are customized for the kitchen layout as well as each appliance. Kitchen Hood systems require regular maintenance and inspections as grease build-up, damage to the hood, or moved appliances can cause the Hood system, along with any interconnected fire suppression system, not to function properly. You can read A1’s blog for more information on the kitchen hood suppression system.
The required schedule for cleaning a Hood system varies based on the type of cooking appliances, methods, and amount of use. According to NFPA 96, general guidelines for cleaning a Kitchen Hood system are as follows:
- Kitchens with solid fuel such as wood or charcoal must have the kitchen hood system cleaned every month.
- Kitchens with a high volume, 24 hour operations, charbroiling, or wok cooking must have the kitchen hood system cleaned every 3 months.
- Kitchens with moderate volume operations must have the kitchen hood system cleaned every 6 months.
- Kitchens with low volume operations, such as churches, day camps, seasonal business, or senior centers, must have their kitchen hood system cleaned once a year.
Because the Kitchen Hood system is cleaned in areas you will not be able to see on a daily basis, such as inside the ducts and vents, it is important that you are provided with before and after pictures of your system such as the ones shown here. You also want to be sure that all areas of your Kitchen Hood system are being cleaned – this includes fans, vertical duct, horizontal duct, plenum, inside and outside of the hood system and cleaning inside access panels.
Most of these areas are not ones that are not regularly visible. However, grease buildups occur throughout the system and it is critical that the full hood system is cleaned to bare metal in order to ensure proper function and continued safety.
It has been established that replacing the Oxygen in your sprinkler pipes with Nitrogen will reduce, or even stop, corrosion; thus, significantly extending the service life of your sprinkler pipes, and reducing maintenance and repair costs.
Since the solution to corrosion is nitrogen, the question becomes how to produce and inject Nitrogen into your fire sprinkler system. There are two methods for Nitrogen generation, Membrane technology and PSA technology.
Nitrogen generating membranes line the fire sprinkler pipes and generates gaseous Nitrogen on-site. The polymeric hollow fiber, which makes up the membrane, permeates oxygen, water vapor, and impurities out of sidewalls, allowing Nitrogen to flow through its center. Membranes require a minimum of 125 PSI of clean, dry compressed air. A refrigerated air dryer will ensure clean and dry air is reaching the membranes. This is important for increasing the lifespan of the membrane, as properly designed and maintained membranes can have a lifespan of 8 to 13 years.
Pressure Swing Absorption (PSA) technology has vessels full of Carbon Molecular Sieve (CMS). Under high pressure, CMS absorbs impurities, allowing Nitrogen to pass through and into the Nitrogen receiver tank. This is an efficient way to generate nitrogen as it has an air to nitrogen ratio of 2:1, while the ratio for membranes is 3:1. It has a greater longevity and performance as the lifecycle before re-nourishment is 20-25 years. It holds 98%+ purity for longer and outputs 39% more nitrogen production. PSA technology also requires 46% less air compressor load, which will significantly increase the life of your air compressor.
Complimentary Technology for Corrosion Protection
High purity Nitrogen must be equally distributed throughout the entire sprinkler piping system in order to effectively inhibit corrosion. An automatic, pneumatic vent should be installed at each riser of your fire sprinkler system to provide a low volume, constant purge of Nitrogen throughout each fire protection system. This vent also provides a testing point for monitoring Nitrogen levels in the system.
A portable, nitrogen purity sensor is a hand-held device that can be connected to your pneumatic vent or at any system sampling port to verify the desired levels of Nitrogen are being achieved throughout the sprinkler system piping.
For large systems, or systems that are monitored offsite, you have the option of utilizing an electronic manifold that can monitor each Zone of your system and track a daily sampling of Nitrogen levels. If purity does not meet specifications during a sampling phase, the manifold will cause the Nitrogen vents to remain open for a continual purge until the next sampling phase. You Nitrogen generator will provide the Zone with more Nitrogen until purity specifications are met.
Fire sprinkler systems experience corrosion due to the interaction of oxygen, an unprotected metal, and moisture. In 25 years, 35% of wet fire sprinkler systems have significant corrosion issues. In only 12.5 years, 73% of dry and pre-action systems have significant corrosion issues.
Corrosion will cause leaks in your sprinkler pipes, resulting in costly repairs which may include replacing piping, fittings, or even the entire system, facility or equipment damage from water leaks, and sprinkler head blockages.
To combat corrosion, fire sprinkler systems utilize either galvanized steel or black steel for pipes, as each type of steel has corrosion resistant properties.
Galvanized and Black Steel
Galvanized steel pipe is hot-dipped in zinc to have a protective coating on the walls of the pipe. The zinc coating, or galvanizing, acts as a sacrificial anode to reduce the corrosion of steel pipe. However, galvanized steel pipe does corrode in any pitted area or space where the galvanized coating is damaged or missing.
Black steel pipe has little to no protective coating. This is the most commonly used steel pipe for sprinkler systems. The oxygen within the water is quickly dissipated, thus reducing the corrosion potential. However, black steel pipe does corrode in a uniform thinning of the walls.
Since neither type of steel is able to stop corrosion, one of the other agents in corrosion, either oxygen or moisture, must be addressed in order to stop the problem. While water is inevitable in sprinkler pipes (even dry system pipes will have condensation), Oxygen can be replaced with Nitrogen – effectively breaking the corrosion triangle.
Dry and Pre-Action systems can be pressurized with Nitrogen, instead of air. Wet systems can have the pipes charged with Nitrogen before being flushed with water, so that any “air” pockets are actually pockets of Nitrogen. Read more about corrosion solutions specifically for Dry/Pre-Action Systems and Wet Systems.
Testing Corrosion Rates in Steel Pipes
An independent lab has been conducting ongoing, long-term exposure tests to compare the performance of Nitrogen vs Oxygen, in both black steel (schedule 10) and galvanized pipe, and the effects on corrosion. Each pipe segment is subjected to compressed air or supervisory nitrogen, as they would be in a practical application of a dry pipe fire sprinkler. At regular intervals, the pipes are opened and the amount of corrosion is measured so that the rate of corrosion can be calculated.
The images below show pipe segments that have been exposed to either compressed air or 98% Nitrogen for 6.5 years, and in both the state the pipe was received and then that pipe segment cleaned. At the rate of corrosion found, the Black Steel Pipes would last 19.8 years with compressed air and 60.9 years with 98% Nitrogen. The Galvanized Steel Pipes would last 9.2 years with compressed air and 162.3 years with 98% Nitrogen. The results clearly show that a significant cost savings can be realized by using black steel pipe in combination with Nitrogen supervision.
Corrosion is a problem that must be addressed in both dry pipe and wet pipe sprinkler systems. In this article, we will discuss pipe corrosion in wet sprinkler systems and methods of preventing the corrosion.
The water that fills wet sprinkler pipes contains approximately 10 parts per million (ppm) of dissolved oxygen. All wet systems experience initial corrosion because of this dissolved oxygen. However, this corrosion is self-limiting as some of that dissolved oxygen will be consumed until the system is refilled with fresh, oxygenated water.
The primary catalyst of pipe corrosion in a wet system is air that has been trapped in air pockets of the pipes. These air pockets exist frequently within wet system pipes at high points of the piping. These trapped air pockets contain 20.9% oxygen, which can fully sustain electrochemical corrosion. As a result, pinhole leaks eventually develop at the location of the air pockets. These leaks have costly results including property and equipment damage, ongoing repairs to pipes or full system replacement, sprinkler head blockages, and an inoperable fire protection system that puts your people and assets at risk.
In order to prevent pinhole leaks, there must be less than 2% oxygen in the trapped space (reduced from the 20.9% that would typically be present). There are several preventative actions that can be taken: wet air vents, auto inert with nitrogen, and remove oxygen from the water. While each action can be taken individually, the best results occur when they are combined.
Wet Air Vents
Installing wet air vents is the most basic step you can take to reduce oxygen corrosion in your wet sprinkler pipes. Your Life Safety Partner will install the wet air vents at high points and other potential areas where air can be trapped, in order to provide a vent to remove the air. There are two types of wet air vents, single and dual. Both types remove the oxygen from the pipe, venting it outside the sprinkler pipe. A single vent removes the air and closes the valve when water reaches it, this water then drains back into the sprinkler pipe. The single vent will discharge any overflow so it should not be used in areas that are water sensitive. A dual vent will not discharge water so it is safe to install in water sensitive areas. As the pressure from the sprinkler pipe drops, any collected water in the air vents will automatically drain back to the sprinkler pipe through the secondary valve. The dual valve also creates redundancy, eliminating any failure concerns.
Auto Inert with Nitrogen
Filling the sprinkler pipes with high purity nitrogen gas prior to charging the system with water can ensure that corrosion in all trapped air locations is slowed. To do this to a wet sprinkler pipe system, you must first drain the fire protection system of all water and install an auto inert system. The fire sprinkler system is then filled with 98% pure nitrogen through the inert system. By displacing the trapped air with high-purity nitrogen, you minimize the source of oxygen to sustain electrochemical corrosion and corrosion cells have less chance of propagating.
You can use this technique in place of wet air vents, as installation of wet air vents may not always be possible due to lack of headroom or varying elevations, which make identification of trapped air pockets challenging or impossible. However, the best results for slowing corrosion occur when you combine the two solutions.
Removing Oxygen from a Wet Pipe Sprinkler System
Removing oxygen from a wet pipe sprinkler system is the best option to slow, or eliminate, internal wet system corrosion. In addition to the wet air vents, this method removes the oxygen from the trapped air pockets and reduces the dissolved oxygen in water to 1.0 ppm or less.
First, the wet pipe system is pre-purged with nitrogen. This changes the pockets of trapped air to pockets of trapped nitrogen gas, which does not act as a catalyst for corrosion like oxygen does. The sprinkler pipe is filled with deoxygenated water, 1.0 ppm or less of dissolved oxygen. This deoxygenated water, which is below the threshold of oxygen known to cause corrosion, stays in constant contact with the sprinkler piping. There is now not enough oxygen in the water to dissipate into the trapped nitrogen gas pockets, which protects the areas of pipe that would have corroded under normal circumstances.
Understanding the correct cause can help you to slow or stop dry sprinkler pipe corrosion.
Microbiologically influenced corrosion (MIC) was once thought to be the primary threat to sprinkler pipe longevity. However, further research has found that oxygen is the primary factory in sprinkler pipe corrosion for both wet and dry pipe systems. In this article, we will discuss how corrosion occurs in a dry sprinkler system and the options for preventing or slowing this corrosion in order to maintain your system and extend the life of your sprinkler piping.
The corrosion triangle illustrates the three factors necessary for corrosion to take place: an unprotected metal, electrochemical potential in the form of oxygen, and electrolyte in the form of moisture. When all three factors are present, there interaction results in corrosion of the unprotected metal. To prevent corrosion, you must remove one factor in the corrosion triangle.
Removing the Unprotected Metal from the Equation
Galvanized steel prevents corrosion by having a protective surface between the metal and the water or air; Black steel pipe has little to no protective coating. However, both galvanized steel and black steel pipes present opportunities for corrosion – an issue we will go into further in a future blog.
Removing Water from the Equation
The definition of a dry sprinkler pipe system says that the sprinkler pipes are dry – without water. And this is true, the purpose of a dry sprinkler system is to provide piping without water in sensitive areas, such as areas where the water in sprinkler pipes would freeze or locations where any water leakage could cause serious damage. (Although, if your sprinkler system is located in an area where any water can cause serious damage to the facility or equipment, it is best to look at other fire suppression options such as aerosol based or clean agents.)
However, dry sprinkler pipes will still collect trace amounts of water due to hydrotesting, flow testing, and condensation. Even when you properly drain the system on a regular basis (read more on how to drain your dry system pipes here – drip drum blog), the water is present and can react with the pipe and oxygen to create corrosion. The remaining option is to remove the oxygen from the dry pipe system in order to prevent corrosion.
Removing Oxygen from the Equation
Dry sprinkler and pre-action system pipes are pressurized with air until the system is alerted that a fire is occurring, at which time the sprinklers activate releasing the air from the system and filling the pipes with water. Instead of pressurizing these pipes with air, however, you can pressurize them with nitrogen, which does not react with the water or pipes to create corrosion.
Ongoing, long-term exposure tests have been conducted, and have shown that nitrogen filled sprinkler pipes slow or stop corrosion and extend the life of the sprinkler pipes significantly. This preventative measure for your dry sprinkler system can save you money in costly repairs due to corrosion including property and equipment damage, ongoing repairs to pipes or full system replacement, sprinkler head blockages, and an inoperable fire protection system that puts your people and assets at risk.
Nitrogen arrests electrochemical, galvanic and MIC corrosion. The nitrogen also prevents ice plugs by ensuring a -40F to -70F dew point within the sprinkler system. As high purity nitrogen enters the sprinkler piping, corrosive oxygen is displaced – preventing corrosion, slowing corrosion that may already have occurred, and maintaining your sprinkler system for a longer life span.
What are Drum Drips?
Drum drips are drains on dry sprinkler systems, which are used to empty the dry sprinkler pipe of any water that has collected due to condensation or water draining within the system. Since dry pipe systems are utilized in areas where water may freeze, it is important to regularly remove any condensed water to prevent freezing and damage to the pipes.
Drum drips can also be called auxiliary drains, drip legs, and condensate drains. No matter what they are called, a drum drip consists of two, 1-inch valves with a short section of two-inch pipe between them. These are normally located at the lower points of the system or where piping elevation changes may occur.
Locating and Labeling Drum Drips
Systems may have multiple drum drips and it is important that each be drained on a regular basis to prevent costly damage from freezing water. NFPA standards require that drum drips within buildings be identified so that they are easier to maintain. You must also have an informational sign at the system’s control riser that includes the location of all drum drips.
When to Perform Drum Drip Maintenance
All drum drips should be operated weekly during the fall and winter months, even if no water is found on a regular basis. When preparing for cold weather, you should operate the drum drips daily and may decrease the operation based on the amount of water discharged.
After a dry sprinkler system operation, you should perform drum drip maintenance on a daily basis until several days pass with no discharge of water from the drain valve. At that time, you can decrease the frequency to weekly or longer intervals depending on the volume of water discharged.
In many cases, frequency of drum drip maintenance can decrease if the system is shown to be dry.
How to Perform Drum Drip Maintenance
- Locate all drum drips throughout the property.
- If a quick opening device is installed, temporarily remove it from service.
- At the drum drip, ensure both valves on the drum drip are closed.
- To catch any water that may discharge from the drum drip, place a container underneath the bottom valve. For interior locations, remove the plug from the bottom valve. (Exterior locations may not have a plug.)
- Slowly open the top valve to full open position and maintain this position for 10 seconds.
- Close the top valve. **You should never open both the top and bottom valve at the same time as this may activate your system.**
- Slowly open the bottom valve to discharge any water. If you cannot see the discharge point, allow water to drain for 10 seconds.
- Close the bottom valve.
- If water discharged when you opened the bottom valve, repeat steps 5 through 8 until no water appears when you open the bottom valve. This will ensure you have removed all water from the system.
- When the system has been completely drained, meaning no water appears when the bottom valve is opened, close the bottom valve. Then slowly open the top valve and, if applicable, replace the plug. This will return the drum drip to service.
- If you removed a quick opening device from service before beginning drum drip maintenance, re-install it at this time.
If your drum drip discharges to a location you cannot see, you can use a second person to watch the drain and notify you when there is no more water draining from the system. Another option to identify when all water has been removed from the system is to place a bucket under the drain and empty the bucket after each discharge.
If you are discharging water without using a bucket to collect it, be sure the water will not cause a safety hazard in traffic areas, or damage any surrounding areas or equipment.
Need more help? Check out A1’s video on how to perform drum drip maintenance.