Safe working condition inside confined spaces at power plants

Safe working condition inside confined spaces at power plants, by Deepak Pahwa, Director, Technical Drying Services (Asia) | | June 2022

Working in a power plant inherently arises a lot of concern around the safe working conditions inside confined spaces. A certain sense of uneasiness continuously lingers for the safety of the workers. Such industries innately have a dangerous setting and possess a confined space where all the major risky and instrumental operations take place.

Studies have emphatically elucidated the perils of working in a confined spaces and have even brought to light that an estimated 60% of fatalities occur while working in a confined space every year. As a result, carrying out maintenance work in confined spaces mandates taking added measures and precautions to render the space environmentally in harmony with the outside ambient conditions that are conducive for the humans to work efficiently while being relieved of the comfortable environment inside.

A confined space by virtue is a fully or partially enclosed area and can be found in any workplace. It includes tanks, boiler, drum, economizer, condenser water box, cooling water duct, furnace, DM Water tanks, columns, spheres, boilers, drums, chimneys, pipelines, cyclones, coker drums, ESP areas, kiln, and other similar spaces. The place is generally predominated by the presence of harmful gases, fumes, or vapors. There is also a high probability of flammable or explosive atmosphere with the added danger of excess oxygen worsening the situation. The environment inside is threatening given to the excessively high temperatures which sometimes is coupled with the unforeseeable lack of oxygen. Hence, the operations going on inside the confined spaces harbor conditions that arouse the risks of accidents, harm, or injury requiring emergency action.

Additionally, there are various factors that cumulatively account for poor air quality. The insufficiency of oxygens makes it difficult for the workers to breathe and gives rise to symptoms such as rapid breathing, rapid heart rate, clumsiness, emotional upset, and fatigue. In worst cases, there can be instances of nausea and vomiting, collapse, convulsions, coma which can even lead to death. The toxic gases present can potentially make workers ill and in serious conditions, one can also lose consciousness.

Such places also run the risk of fire hazards where flammable liquids and gases and combustible dust account for the explosive or flammable atmosphere which if ignited would lead to fire or explosion. Most of the time even visibility can be impaired given to the smoke particles suspended in the air. In addition to the already existing hazardous conditions, the presence of viruses, bacteria from fecal matter and sludge, fungi, or molds can further add to the misery.

Hence, the unhealthy and hazardous air inside makes it difficult for workers to carry out maintenance and repair works like welding, fabrication, riveting job, strip lining, nozzle replacement, trays replacement. Moreover, the presence of many people during maintenance work contributes to the soaring temperature which can touch as high as 48-50 degrees Celsius accompanied by high relative humidity.

Therefore, before setting off to work in a confined space there should be thorough air quality testing. Fresh air must be mediated to purge out the toxic gases with the correct amount of air change. Oxygen levels must be maintained within safe limits and it should be ensured that the ventilation equipment is working properly. It is strictly advisable to maintain the temperature between 32-35 degrees Celsius and ensure that the relative humidity is below 60%.

To achieve the above stated conducive environment the power plants are shut down to cool down the furnaces. But relying solely on natural ventilation to cool down the space is generally not reliable and is also not sufficient to achieve the optimum air quality. It takes a lot of time that incessantly affects the completion of the project and amount for the wasted time, productivity and revenue. For which external dehumidification, temperature control, and ventilation systems are required to render comfortable working conditions within the confined spaces. They provide engineered solutions for humidity control, drying, temperature control, and ventilation.

The dehumidifiers, condensing units, blowers, and ducts together help in achieving the required temperature and relative humidity levels. They play an instrumental role in faster cooling of the furnace and substantially reduce the shutdown time. To cool down the furnace, dehumidified cool conditioned air is forced inside the confined space which creates a positive pressure to remove the contaminated air. By bringing in fresh, dry, and cool air the desired temperature is achieved at a much faster rate as compared to natural cooling. It also removes the toxic gases which pose a potential threat for the workers. Along with this, the desiccant-based dehumidifiers effectively adsorb the excess moisture present in the air and ensure that the relative humidity remains below 60%. On the other hand, the condensing unit side by side maintains the temperature between 25-26 degrees Celsius.

The application of such solutions reduces the shutdown time and consequently adds to the productivity of the workers. It contributes to the timely completion of the project and makes up for the revenues which otherwise would have been lost to the long shutdown periods. At the same time, the health and safety of the workers are also not compromised.

Considering the complexity of operations taking place in power plants giving rise to hazardous conditions, it is important to regulate the environment within the confined spaces before starting the maintenance or repair jobs. Deploying mechanical ventilation and temperature systems for the task plays a very crucial role in achieving comfortable and safe working environmental inside the confined spaces for the health and safety of the workers and ensures optimum and quality work.

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