Combustible Dust… Elements of Dust Hazard Assessment

July 3, 2013

Old Factory - Conditions were bleak

Combustible dust assessments are performed to assist management in identifying and defining hazardous conditions and risks so they may be eliminated or controlled. The analysis should examine the process, systems, subsystems, components, actions (or lack of actions), and their interrelationships.

The assessment and review of what can go wrong may not be an easy task. Many dust losses are not the result of a single cause. Rather, it is the confluence of multiple events which occur simultaneously or in a chain of events. Systems should be designed using methods considered to create a “safe” situation. The reliability of the components and assemblies must also be considered. When components or assemblies fail the initial design parameters are compromised. The compromised system is outside of the normal scope of design, and a loss is much more likely to occur.

A dust hazard analysis may be used wherever a dust condition exists. It may be a process which involves drying a liquid sprayed into a drying chamber. It may involve grinding, sifting, screening, or other manipulation of a product. The dust may be released from the process of pouring ingredients from a bag into a vessel. It may be dust within a conveying system. The dust may be tramp dust emissions, or escape material from process leakage points in a manufacturing situation. Dust may also be present from inadequate housekeeping. Dust hazards may exist where large pieces of material are handled, but in the manufacturing process, dusts are created in small amounts and allowed to accumulate over time.

A Look Back in Time

In the grand scheme of the Industrial Revolution, systemized educational curriculums for safety and hazard analysis are relatively recent. Only a few decades ago, finding a college curriculum majoring in safety, fire protection, or process hazard safety were limited. Fortunately, today, such programs are more available and have sprung up at several colleges and universities around the country. Even in universities without dedicated safety programs, safety courses are offered, and even required, in many engineering curriculums. Safety is a topic of discussion in all aspects of engineering.

Early systematic processes were identified in aviation and military applications. Equipment or system failure at 20,000 ft. is not always a survivable event. Moving into the space age, NASA learned through failures that a systematic process must be followed to identify points of failure in each system installed and implemented into the space vehicles launched into outer space.

In the 1960’s, the process and chemical industries embraced Process Hazard Analysis. Calling it HAZOP, for Hazard and Operability Method, it became better identified and published in the 1970’s. Its introduction into process safety regulations in the 1980’s and 1990’s caused a dramatic increase in the implementation of the process. Industries performing high hazard operations have incorporated process hazard analysis into their design and analysis procedures.

Sometimes, product liability drives the need for safety analysis. Today, auto makers perform hazard analysis for each vehicle they make, but this was not always so. Prior to the 1970’s, safety hazard analysis studies were not routinely performed on new car designs. One prominent example was the Ford Pinto. Its gas tank had a tendency to explode into flames upon rear impact. According to some accounts, Ford Motor Company performed cost benefit analysis and identified that the cost to make changes to the vehicle would be greater than the cost of anticipated legal claims. The legal battles over occupant deaths and injuries of the Ford Pinto changed the auto industry’s attitude toward safety analysis on their auto designs. Today, auto makers routinely analyze their vehicles for failure in an attempt to identify weaknesses. The industry has changed over the last 40 years and vehicle safety is a major selling point.

Today, the practice of performing hazard analysis is spreading across general industry. Hazard analysis and safety assessments are provided for many reasons. Companies are concerned with product liability, safety of a hazardous process, property conservation, business continuity, and worker safety. While many corporations have concerned management, there are some who will be dragged into the process through losses, government fines, and litigation.

Preventing Dust Explosions

Unfortunately, there is no easy answer to preventing explosions. NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids discusses many aspects of preventing dust explosions. One of the primary items is designing the processes and facilities that handle combustible particulate solids appropriately. The design must take into account the physical and chemical properties that establish the hazardous characteristics of the materials. The building and processes should undergo a thorough hazard analysis study. The study should look at equipment design, process procedures, worker training, inerting and other protection means. The process system should be designed to limit fugitive dust emissions to a minimum. Any changes, additions, or modifications to the system or process should be reviewed in a management of change evaluation. The major objectives in the review should be life and property conservation. The structural integrity and damage limiting construction is an important aspect. Mitigation for the spread of fire and explosion should be designed into the system. The design should adhere to existing codes, and be of sound, proven technology and technique. NFPA 654 provides a number of sound methods for the design of dust related occupancies, and references several other NFPA codes and standards for specific concerns.

Additional Information – ASSE Safety 2013 Proceedings / Presentation June 25, 2013

For additional information, CLICK HERE see the Proceedings Paper submitted to ASSE for Safety 2013!

Storage Of Pressurized Gas Cylinders

March 16, 2013

I run across a lot of improperly secured pressurized compressed gas cylinders. There are correct and incorrect ways to maintain and store compressed gas cylinders.

Although chains and eyelet rings are provided, they are not being used. bottles are not secure. They are in direct sunlight.

Although chains and eyelet rings are provided, they are not being used. bottles are not secure. They are in direct sunlight.

improper storage2-BEATTIE

Although chains and eyelet rings are provided, they are not being used. bottles are not secure. They are stored in direct sunlight.

There are three main types of gas cylinders.

Liquefied gases are gases that become liquids when they are pressurized. They exist in a liquid-vapor state within the cylinders. Examples are anhydrous ammonia, propane, chlorine, nitrous oxide and carbon dioxide.

Non-liquefied gases are gases which remain in the gaseous state when pressurized. Examples are oxygen, nitrogen, helium, and argon.

Dissolved gases are gases which are dissolved into another material. Acetylene is the most common gas and it is dissolved in acetone. Acetylene is very unstable and can explode under pressure. It is commonly used and people may become complacent in its use.

Pressure cylinders have an incredible amount of stored energy. Cylinders may have over 2,000 psig of pressure. Even empty, a cylinder may have over 100 psi of pressure, more than the pressure in your automobile tires. A regulator or other assembly is placed on the cylinder head before opening the valve. This safely controls the pressure release.  The cylinder should not be opened without a proper assembly to control the pressure. Opening a cylinder will allow full pressure of the cylinder to escape. Uncontrolled pressure may pierce the skin, break an eardrum, or damage the eyes. Uncontrolled release of pressure from accidentally breaking off the head can be extremely damaging. The cylinder may fly like a rocket with enough power to blast through concrete block walls. uncontrolled pressure releases may allow the cylinder to fly may hundreds of yards, even after blasting through walls. the cylinder may ricochet around inside an enclosure or spin uncontrolled, causing significant damage.

Many of the gases used in industry are flammable or support combustion, such as oxygen. Some are asphyxiates, others are poisons. Each cylinder should be properly identified as to its contents. Most are color coded. Do not paint bottles a different color. Many cylinders have a special or left hand thread to prevent improper hoses from being attached. Some gases are reactive with other materials. For instance, do not allow grease to contaminate oxygen cylinders. Provide proper signage for compressed gas cylinders at the storage area and point of use.

Storage Of Compressed Gas Cylinders

Cylinders should be stored in accordance with “Compressed Gas Association (CGA) Pamphlet P-1-1965.”

Cylinders should be stored in accordance with all local, state, municipal, and federal regulations. Cylinder storage areas should be provided with signage to identify the products being stored. Gases of different types should be grouped by type. incompatible gases must be separated from one another. Proper signage should be provided.

Charged and empty cylinders should be stored separately. The layout of the operation should be such that empty cylinders may be removed easily with a minimum of handling. The area should be open to allow for dollies and handling equipment to be used in an unobstructed manner.

Storage rooms should be controlled environmentally. They should be dry, cool and have adequate ventilation. Substantial, noncombustible, and fire rated construction should be used. Cylinders should be stored at grade or above, not in depressions such as basements or on ledges when they could fall and become damaged. Heavier than air gases will lay in the low levels and accumulate. The storage area should be away from heat producing equipment, out of the direct sunlight from the warming sun, and ideally below 125°F. The storage area should be away from highly flammable and combustible materials such as oils, fuels, and waste materials. The area should be secure and protected from damage and vandalism.

Cylinders should be protected from corrosion. Corrosion may be from excess water, acids, salt, chemicals, or chemical fumes such as from industrial processes.

When in use, the regulator should be attached and in a protected area.

Cylinders should be stored in an upright position. They should be stored with their protective caps screwed in place and be individually secured. Cylinders should be chained individually. The chain should be above the tip point of the cylinder, about 2/3 of the way up the bottle. I recommend heavy metal chain for securing bottles. In the event of a fire, polyester, nylon, and fabric straps will fail much earlier into a fire. Even if you have gotten out of the building by that time, your emergency response team and firefighters are subject to injury from a falling bottle. I see web strapping in laboratories, and discuss the security of fabric under fire conditions. in Construction sites, I see a group of cylinders with a rope around them – an unsafe condition and an inappropriate method of storing pressure cylinders. Oxidizers and flammable gases should be stored in separate areas,  separated by concrete walls or adequate separation (at least 20 feet). NEVER PLACE ACETYLENE CYLINDERS ON THEIR SIDE.

proper storage1-BEATTIE

Cylinders are protected from the sun and weather by a canopy. Individual slots are provided for cylinders and a chain is used for securing each cylinder.

proper storage2-BEATTIE

Cylinders are protected from the sun and weather by a canopy. Individual slots are provided for cylinders and a chain is used for securing each cylinder. Even short cylinders are provided with caps and chains.

Speaking of laboratories, it is many times safer to provide a dedicated properly designed, ventilated cabinet outside of the lab and piping to the work station. Changing bottles is easier, cylinders do not need to be moved within the lab, and they are out of the way and less subject to damage. Flame impingement onto a tank is extremely dangerous as it heats the gas, increases the pressure, and weakens the cylinder shell. Also, remember that steel cylinders will conduct electricity. They may become part of an electrical circuit if allowed.

Empty cylinders should have the regulators removed and the cap should be screwed onto the top. Empty cylinders should be stored separately from full cylinders. Mark the cylinder as empty or place a distinguishing tag on it. Unless proper provisions and training are provided bottles should be refilled only by the supplier. Never release the gas totally. At least 25 psi of gas should remain in the cylinder to prevent air from entering the cylinder and potentially contaminating the next refill. Totally emptying the cylinder will require the distributor to go to extra expense to purge the cylinder, then refill it. Treat every cylinder as though it is under full pressure. Discounting the hazards because a cylinder is almost empty is a dangerous practice.

When moving cylinders, special carriers or dollies should be used. The carrier should secure the cylinder and prevent it from rolling off. Regulators should be removed and caps replaced.

Employee training should be provided for all employees using or working in the proximity of pressure cylinders. Emergency response plans should be developed, implemented, and updated at least annually.

Additional information may be found at,

–  OSHA Standard Number 1910.101, Compressed gases (general requirements).

–  OSHA Standard1926.350(a), construction standard for storing compressed gas cylinders (for welding).

–  OSHA Subpart Q, Welding, Cutting, and Brazing, Standard 1910.253, Oxygen-fuel gas welding and cutting.

–  OSHA Subpart H, Hazardous Materials, Standard 1910.102, Acetylene.

–  OSHA Subpart H, Hazardous Materials, Standard 1910.103, Hydrogen

–  NFPA 55, Compressed Gases and Cryogenic Fluids Code. Chapter 2 has a list of other referenced publications which may also provide good information.

Star Sprinkler Model B 165°F manufactured in 1946

December 16, 2012

Star 1946 B Upright 1-BEATTIE

Star Sprinkler Model B 165°F manufactured in 1946

Star Sprinkler Model B 165°F manufactured in 1946

Star Sprinkler Model B 165°F manufactured in 1946

Star Sprinkler Model B 165°F manufactured in 1946

Star Sprinkler Model B 165°F manufactured in 1946. This is an upright 1/2 inch, K=5.6

Sprinkler heads manufactured prior to 1953 have a smaller sprinkler deflector and are called “old-style” or “conventional” sprinklers. These heads were smaller, and approximately 40% of the water was directed upward.

Christmas 2012

December 14, 2012

Christmas 2012

Dry Christmas Trees Can be a DISASTER!

November 24, 2012

The Holidays are upon us. Where has the year gone? I would like to remind everyone to keep their Christmas trees well watered and fully hydrated. If you need visual proof, watch them burn HERE!

Trees used indoors for the holidays account for approximately 400 fires annually, resulting in 10 deaths, 80 injuries and more than $15 million in property damage. These videos demonstrate how quickly the fire can develop when a DRY tree is exposed to an open flame.

Properly maintain your cut Christmas tree to maintain a high moisture content in the needles of the tree. This will help to limit accidental ignition and prevent a rapid flame spread fire from developing in your home.  A tree which has dry needles can readily ignite and generate heat release rates that are capable of causing flashover in residential sized rooms. Watch the videos to see just how rapidly the fire spreads!

Storage tank implosion

June 2, 2012

The tank to the right has a huge dent, likely from a depressurization

Partial tank implosion

The fuel oil and chemical storage tanks you see at the major refineries can hold hundreds of thousands of gallons of liquid. Some oil storage tanks may hold from 500,000 to 1,000,000 gallons (1,893 to 3,785 cu m) or more. These are big tanks. They are made of heavy steel plates, capable of taking the pressure and weight exerted by the liquid inside. hey are not designed to withstand the force of a vacuum condition.

When a tank is filled, the liquid entering the tank must displace the air in the tank. The air exhausts from the tank through a vent on the top of the tank. The vent also permits air to escape and be drawn into the tank when the tank heats and cools due to atmospheric temperature fluctuations. Even the effects of solar heating during the day and subsequent cooling at night have an impact on maintaining normal atmospheric pressure.

Think back to your basic chemistry classes in high school. Do you remember Charles’ and Boyle’s Laws? These are examples of empirical gas laws. If I recall, Boyle discovered that the larger the volume gets, the lower the pressure of the gas (in this case air) becomes. If there was no vent and there was no air exchange into or out of the tank, when liquid is drawn out of the tank, the volume of the air cavity increases, and the pressure decreases. Without a vent to allow additional air into the tank, the pressure will decrease.

Charles’ Law takes temperature into account. As the temperature of a gas increases, the molecules become more active and move faster. As they move faster, the pressure in a fixed volume will increase. Likewise, when the volume cools, the pressure will decrease.

While driving one day, I happened to notice this tank and had to get a couple quick snapshots of it. This tank has a dent in it. I have no idea what caused the dent, but short of a very, very, large truck backing into it, or a crane wrecking ball taking an errant swing, I can only presume this was caused by a plugged or malfunctioning vent valve. Vent valves are critical pieces of operational equipment for the tank. Even a plastic tarp laid over the vent is enough to cause a tank implosion. the forces of the pressure are tremendous.

Using Charles’ and Boyle’s Laws, there might be two logical ideas. I might presume the tank was drawn down (emptied) at too great a rate for the vent valve to compensate and the pressure decreased to the pont where the tank partially failed by implosion. Or, the temperature within the tank decreased at night, the vent became stuck, the pressure within the tank decreased, and the tank failed by implosion.

San Francisco Earthquake – April 18, 1906

April 18, 2012

San Francisco Today

April 18, 1906 5:12 AM

The California earthquake of April 18, 1906 is one of the most significant earthquakes of all time. The earthquake ruptured approximately 296 miles of the San Andreas earthquake fault from Northwest of San Juan Bautista to the triple junction at Cape Mendocino. At 5:12 AM local time, a shock brand throughout the San Francisco Bay area. Approximately 20 to 25 seconds later, violent shocks shook the city. The epicenter of the earthquake was right near San Francisco. The earthquake was recorded in Gottingen, Germany, 91 km away!

The casualty accounts vary widely, but it is generally accepted that more than 3000 people died in the event. A 1906 U.S. Army report recorded 498 deaths in San Francisco, 64 in Santa Rosa, and 102 deaths near San Jose. The population of San Francisco in 1906 was approximately 400,000. 225,000 people were left homeless, over one half of the population. 28,000 buildings were destroyed, and tent cities became the abode for many.

Fires ravaged the city of San Francisco for more than three days causing more damage then realized by the earthquake. The burned area covered approximately 4.7 square miles. Based on a NOAA report,

– Wood buildings lost = 24,671 (photo)
– Brick buildings lost = 3,168 (photos)
– Total buildings lost = 28,188 (photos)
– Monetary Loss – More than $400 million

Broken and leaking gas lines were the predominant cause of fires in the city. The fire department was at a disadvantage in fighting the fire. Fire Chief Dennis T. Sullivan died in the earthquake, leaving the city’s firefighters without effective leadership. It is reported that the firefighters used dynamite to destroy selected houses in an effort to stop the spread of the conflagration. Unfortunately, the explosions created more damage. Water mains below the city streets were rendered useless because the earthquake ruptured the pipes, causing the water pressure to drop to unusable levels.

It is also believed that some people set their own houses on fire in hopes of insurance compensation for fire. Insurance companies at the time did not indemnify policyholders in the event of an earthquake, but did for fire.

Many experts claimed that 90% of the damage in San Francisco was as a result of the ensuing fires. Approximately 490 city blocks were destroyed! The city was in a state of disarray with thousands homeless, tent cities springing up, and lawlessness running rampant. Eventually, the U.S. Army was activated to assist with the cleanup and control of the city.

San Francisco began rebuilding immediately. Reconstruction was mostly completed by 1915, nine years later.

Dry Pipe Sprinkler Systems – Inspection, Testing & Maintenance

April 14, 2012
Dry Pipe Valve

A differential Dry Pipe Sprinkler System

The next article in a series discussing fire sprinkler system inspection testing and maintenance is published in ASSE Fireline.

Inspection, testing and maintenance of dry pipe valves and dry pipe systems are critical to maintaining effective fire protection. Dry pipe valves are used in areas subject to freezing temperatures.

This article focuses on Chapter 13, Valves, Valve Components and Trim, and assumes that all items discussed in previous articles regarding valve inspection and testing, records plans and calculations and impairments to the fire system have been completed. This article discusses items that apply specifically to dry pipe valves.

A dry pipe sprinkler valve is a special valve that prevents the pressurized water in the fire mains from entering the sprinkler system piping. Normally, this is accomplished by filling the system with air. Most valves use a differential method of keeping the valve shut, and generally, the differential is 5:1 or 6:1. This means that 5 or 6 psi of water pressure is held back by 1 psi of air pressure. In the event of a fire in which a sprinkler head actuates, the air pressure in the system decreases until the valve trips. The trip pressure in a 5:1 dry pipe valve at 60 psi of water pressure is 12 psi. As the air pressure dips below 12 psi, the valve will trip, allowing water to enter the sprinkler piping and eventually exit through the open sprinkler head. A safety factor, usually about 20 to 25 psi, is maintained above the trip pressure to help prevent false trips. An air compressor, or other means of maintaining pressure in the system, is arranged to automatically maintain adequate air pressure.

Components of dry pipe valves are discussed, described, and explained. Testing procedures for properly tripping a dry valve is outlined, as well as an explanation of how to reset typical differential dry valves.

Find the article here – Dry Pipe Sprinkler Systems – Inspection, Testing & Maintenance

Find additional articles at my Articles & Presentations Page

Backflow Preventers on Fire Protection Systems

January 29, 2012

Most municipalities require UL listed or FM Global approved backflow preventers on the incoming water line feeding fire protection systems. A backflow preventer does just what the name implies, it prevents water from the fire system from flowing back into the water system.

Backflow preventers may be created in a number of ways. One way is to install a fire pump and water storage tank. The tank has a float valve which opens a fill valve on the public water supply. The water flows like a faucet into a bathtub, and the water passes through the air before filling the tank. When the tank is full, the float shuts the valve and the flow of water from the public water supply. The public water fill pipe is above the level of the water, so once the flow of water stops, there is no way to flow back into the system. This system is referred to as an air break.

Single wing-check valves have been used for a hundred years as a means to prevent backflow. Unfortunately, a simple check valve is not leak proof, and conditions were found where the single check valve was allowing water to back up into the public system. Then double swing-check valves were used, doubling the reliability of backflow prevention.

An improvement in the swing-check valve was the addition of weight inside the valve body and hung on the downstream face of the check valve. The additional weight prevented the swing check from floating open and allowing seepage backwards through the valve and into the public side of the piping. A down side to the design of many older check valves is the inability to actually test the valves to verify that the valves are seating positively.

Today, the design of the check valves for fire systems has improved significantly. Many newer backflow prevention check valve assemblies do not rely on a swing check system. They use a more sophisticated spring loaded system in which the seat moves perpendicular to the valve seat. Other valves which are of the swing design have a spring loaded cam arm to maintain positive seating force against the top of the clapper. Most valves have means of testing the valves to verify that the seats are definitely holding. Most of the valves available today are on an angled seat that create a greater differential over the face of the clapper to help hold the valve closed. Many are weighted or spring loaded.

Reduced pressure zone valves are considered more reliable at backflow prevention. The assembly has two check valves in series. The volume between the check valves is monitored for pressure differential. If the differential is not great enough, water from the section between the valves will discharge to create a greater differential pressure. Constant or frequent discharge from the differential drain may indicate that the check valve seat is not holding and allowing water to flow backwards into the reduced pressure zone of the valve.

These devices must be maintained and tested on an annual basis. This inspection is usually accomplished by shutting the valves on both side of the assembly. The housing is opened and the clappers removed. Some styles have an access port which is held closed by a rubber gasket and flanges that are paired to create a full circle around the gasket and lid and are bolted together. There may be a screw type housing for the clappers. The clapper assemblies are unscrewed from the seat housing and removed from the maintenance port. The spring or spring loaded cam arm is disarmed, the clapper is cleaned, inspected, and tested. The manufacturers specifications must be closely followed, and most municipalities require the servicing technician to be trained, certified, and sometimes licensed.

For more information and to actually see videos on how the assemblies work, are disassembled and reassembled, and maintained, look on the manufacturers’ websites. Watts Water Technologies, Inc. is one company that provides videos of the inner workings of the devices. Watts is the owner of Watts, Ames, Mueller, Febco, and other brands very familiar to those in the fire protection field.

The major disadvantage of backflow prevention devices is the additional friction loss. The head loss as a result of water friction loss is substantial and becomes greater as the flow increases. If a backflow preventer is added to a fire protection system which was not originally designed for one, the friction losses across the backflow preventer assembly may be so great as to make the sprinkler system(s) inadequately supplied with pressure and volume.

ASSE Helps Provide Fire Prevention Training for Students

January 21, 2012
Campus Fire Safety

Campus Fire Training - Demo burn of a dorm room

Each year, college students are injured and killed in preventable campus-related fires. To prevent injuries and fatalities caused by fires that occur in college residence halls, off-campus housing and fraternity/sorority houses and to raise awareness about life-saving fire prevention knowledge as students head back to school, ASSE, West Virginia University (WVU), RA Fire Academy and the Morgantown Fire Department are providing key fire prevention information and demonstrations.

According to NFPA, from 2000 to the present, 146 students have died in a combination of off-campus, residence hall and fraternity/sorority fires. The majority of campus-related fatal fires occur in off-campus housing. According to the U.S. Fire Administration, of the 146 campus-related fire fatalities that occurred from January 2000 to the present, 85% happened off campus. Today, more than two-thirds of the U.S. student population lives in off-campus housing.

WVU’s Department of Environmental Health and Safety (EH&S) recognized the importance of having a strong, vibrant fire safety program. The RA Fire Academy evolved out of several training sessions the department offered for the students, campus community and local high schools in the area. By working collaboratively with various university departments, administrators, student staff and the Morgantown Fire Department, the RA Fire Academy was created. Some form of this fire safety training has been offered since 2003 to students in the campus community. WVU EH&S envisions offering this fire academy training to all first-year students.

All student RAs are required to participate in the RA Fire Academy in a variety of hands-on training scenarios. The RAs then share the information they learn with the students on their respective floors. Activities include:

•  smoke-filled hallway

•  hands-on fire extinguisher training

•  quizdom training

•  movie/lecture

•  competition games [Skeet Shoot Frisbee (shoot Frisbee from the air) and Medicine Ball Push (push ball with fire hose to a designated distance)]

•  live burn (A mock dormitory room is constructed with the appropriate early warning fire protection. The room is then set ablaze. Students observe how quickly a room is engulfed with smoke and flames; and, they learn the importance of smoke detectors, evacuation and sprinkler systems. Additionally, the importance of using open flames with caution is discussed.).

Each RA rotates through each training station. The training culminates in the sixth station where a dorm room mockup is lit, and students are able to see just how quickly a dorm room fire can spread. The overall goal is to provide each RA a rounded training session.

The RA Fire Academy is intended to provide student leaders with the necessary knowledge and skills to better enable them to assist others in the event of an actual fire emergency on campus. The goal is to give them some real life hands-on experience in a safe and controlled setting so if they are ever faced with a real fire emergency, they will have the confidence to make the right decisions in a quick, calm way and hopefully save lives.

See the article by John A. Principe III CSP, CHCM & Walter S. Beattie, CSP, CFPS, CSHM: ASSE Helps Provide Fire Prevention Training for Students