Preventing Unintended Chemical Injection


Aquatic venues are fun, but complex systems. They’re a delicate balance of lifeguards, water… …sunscreen, pool treatment equipment, and chemicals. When the operation is running smoothly and effectively, behind the scenes systems are rarely a thought until they fail. Malfunction is to blame for a chlorine leak after several people were sickened. Several ambulances were called around noon on Saturday after several people reported difficulty breathing. And the effects can be serious. We ended up transporting 35 patients away from the scene after decontaminating them. The sickest of them had difficulty breathing and were vomiting. The chemicals involved were muriatic acid and chlorine. There was an accident that occurred. Somehow the muriatic acid and chlorine undiluted got mixed together inside the Pump Room. It created a visible yellow cloud and that drifted across the pool deck. What that can do is cause the lungs to start leaking… …fluid, and fill the lungs up with that fluid and you end up drowning in your own fluid. Pools of all sizes are complex systems of pipes, pumps, filters, and injectors. Water must be clean, free of debris, and… …chemically treated to make it safe for swimmers, and it must be constantly flowing through the system in order for the treatment to work. Most times minor problems pose no serious risk… …like if the pH is slightly off or if there’s minor debris in the pool. But when there’s a problem with the critical process of circulation and chemical injection.. …the risk to swimmers can become life-threatening. Here’s how it’s supposed to work… Pool water is constantly circulated by a pump. The water is filtered and a chlorine-based disinfectant and acid are added to make the pool water sanitary. As long as water continues to circulate there is no cause for concern. In the incidents shown at the beginning of this program something went wrong. Remember that the system is safe as long as water is circulating. If circulation stops but the chemicals continue to be injected, serious problems can occur. Chlorine based disinfectants and acid react to produce chlorine gas. When the circulation pump is off… …and the chemical feeders continue to pump… …dangerous levels of chlorine gas can build up in the pipes. When circulation resumes… …the gas is pushed out of the pipes and into the pool, endangering people in and around the pool. To protect people… …chemical feeders should automatically shut off when there’s no water flow in the circulation system at the point of chemical injection. In order for this automatic shutdown to work, all components should be electrically interlocked together… …so they function as one system. There are essentially two ways to electrically interlock a system. Either conceptually through circuit breaker design… …or directly through the use of a master electrical interlock box, also referred to as a safety switch. It’s important to note that basic interlock designs only react to electrical incidents such as loss of power… …and not to an inherent loss of flow, which might be caused by something else. The basic level of interlock protection is to ensure… …electrical connections to the circulation pump and the chemical controller or feeders are on the same circuit. If the circuit powering the pump is tripped, power to the chemical feeders is also lost and chlorine-based… …disinfectants and acid will not be injected. A more advanced level of interlock protection would be to… …incorporate a flow or float switch in the sample stream of the chemical controller. When the sample stream loses flow, the switch signals the controller to stop the chemical feed. However, this method is dependent upon where the sample stream is installed in the circulation system. The highest level of protection is to incorporate an interlock box or safety switch that monitors and controls the… …circulation pump and the chemical feeders from the point of injection. The individual components are truly interlocked or dependent upon each other for proper operation For example, if the circulation pump stops, the interlock automatically shuts the chemical feeders down. So if these systems are designed to protect people in the event of a failure, why do people get hurt? The answer is simple, mechanical failure or human factors. A flow switch could fail and send a false indication of water flow when there is none. And the chemical injectors would still feed chlorine disinfectant and acid into the system. Additionally, a maintenance operator can bypass these safety methods… …by plugging the chemical feeders into another circuit. As shown in this video, many incidents occur as a result of human error that led to a situation that endangered swimmers. These incidents arise not out of maliciousness, but from a desire to keep the pool open. Unfortunately, they may have acted without an understanding of the consequences of their actions. The more barriers in place, the less likely all are able to fail or be bypassed at the same time. First and foremost the aquatic venue should be closed and all bathers removed from the pool and deck anytime… …there is maintenance work to be performed on the circulation and chemical systems. The pool and deck area should be cleared immediately any time a flow sensor detects no flow in the system… …or when there is an unexpected or manual deactivation of the circulation pump… …or when the interlock system is activated indicating a problem with the flow system. Bathers should not be allowed back into the aquatic venue until the cause of the interruption is understood and the condition is corrected. The system should operate correctly for at least 5 minutes and the water… …tested to ensure proper pH and free chlorine levels before allowing bathers into the pool and deck areas. The circulation and chemical feeder system, as well as the electrical interlock system, should be working properly. The safety switch system and the electrical interlock should be installed and maintained according to the manufacturer’s instructions. It should not be modified or bypassed in any way. You should not use an alternate source of electrical power to the feeders. This defeats the purpose of the interlock. An alarm or other indicator should be activated whenever the chemical feeder is… …disabled through the safety switch or electrical interlock system to alert staff to evacuate the pool area. An initial challenge test should be conducted upon installation of the system and… …regular challenge tests… …including a backwash cycle at least once a month should be conducted to ensure the proper operation of the interlock system safety switch… …sensors and alarms. There should be proper labeling of all components including tanks… …feeders… …pipes, and direction of flow. Keep all signs, labels, and placards up-to-date and legible. Consider using safety signs as reminders to take actions, such as evacuate the pool area under certain conditions. Staff should be trained on recognizing high-risk scenarios that could lead to chlorine gas exposure… …including when circulation ceases and when the electrical interlock and safety switch failure alert system is activated. It’s best to prevent emergencies before they happen. OSHA hazard communication plan requirements should be followed including developing an emergency action plan. Aquatic venues of all sizes are complex systems, but with a few precautions and adherence to critical safety measures… …they can be extremely fun and safe!

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