【HaiChuan Safety Discussion】Hidden Dangers Around Us – The Use of Submersible Long-Shaft Pumps for Oil-Containing Sewage Pumps in Tank Farm Areas

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Walk every day, and fear not even ten thousand miles； Do it often, and you won’t fear a thousand things. Learn one safety in production knowledge point every day, continuously strengthen memory, and improve professional skills in safety in production. As a worker, the more vigilant you are, the greater your chances of survival ； As a business manager, more strictness means less risk. Only by treating every detail with professionalism can the safety goal of \"zero accidents\" be truly achieved. Safety is never a \"choice question\" but a \"must-answer question.\" There is no such thing as “more or less” when it comes to safety; only “100%”. A little more careful inspection today means fewer risks of accidents tomorrow. Security management is never a matter of focusing on the big issues while ignoring the small ones. The significance of identifying potential hazards lies in turning \"invisible risks\" into \"visible actions for correction.\" We firmly believe that every improvement in safety awareness and every enhancement in protective capabilities serves to build a stronger barrier for lives and ensure safety for businesses. Keep hidden dangers in sight and have safety by your side at all times! --------------------------------------------------------------------- All members of the community are welcome to participate in the discussion and share their insights on this thread: [HaiChuan Safety Discussion] – A compilation of potential hazards around us. https://bbs.hcbbs.com/thread-5705518-1-1.html HaiChuan becomes even better with you here! ------------------------------------------------------------------------------------------------------ I. Basis for inspection: \"Safety Management Standards for Atmospheric Storage Tanks of Flammable Liquids in Chemical Enterprises\" A3063-2025, 5.2.2.5. Pumps used for handling oily wastewater in storage tank areas should be surface-mounted pumps with self-priming capabilities; submersible long-shaft pumps should not be used. II. Hazard Analysis 1. The long shaft is prone to wear and significant oscillation, resulting in poor operational stability. Submersible long-shaft pumps have slender shafts with large spans; over time, shaft bending and wear of bearings/shaft sleeves can occur, leading to increased vibration and seal failure. Oil-containing wastewater can leak along the shaft, creating a risk of leakage of flammable liquids. 2. The risk of mechanical seal/failure is high; leakage of the medium can occur. Oil-containing wastewater, along with impurities, sediment, and corrosive substances, can accelerate the wear of the mechanical seal ； Once the seal fails, the oily wastewater leaks directly onto the ground, and in the presence of an ignition source, it can cause fires and flash explosions, as well as lead to environmental pollution. 3. The submersed components are immersed in wastewater, making maintenance difficult. The pump body, impeller, and bearings are all below the water surface; therefore, maintenance requires emptying the wastewater tank and setting up a working platform. This constitutes work in a confined space, which can lead to delayed maintenance and the persistence of potential hazards. 4. Cavitation and vacuum conditions are likely to occur, leading to damage to the pump body and leakage. Fluctuations in the liquid level in the sewage tank, along with the presence of debris, can also cause vacuum conditions and cavitation, damaging the impeller and pump casing and resulting in leaks ； At the same time, a sudden shutdown of the pump may cause sewage to spill over. 5. There are no effective measures for preventing leaks; submersible pumps often lack trays, bunds, or collection ditches to contain leaks. When a leak occurs, oily wastewater flows directly onto the ground and enters the rainwater system, damaging the fire dikes and rainwater isolation systems in the tank area and violating the environmental and fire safety requirements for such areas. 6. Electrical explosion protection and static electricity risks: The tank area is a flammable and explosive zone. If the explosion protection rating of the pump motors and junction boxes is insufficient, or if grounding is inadequate, friction and sparks can ignite any leaked oil or gas, creating a risk of explosion. 7. Entanglement and blockage by debris can cause the pump to stick or overheat and burn out. Oil-containing wastewater often contains flocs, silt, and other debris, which can entangle the impeller and block the inlet, leading to the pump sticking or the motor overheating and burning out. This can result in power outages, shutdowns, and various secondary risks. III. Rectification suggestions: 1. Replace the pump type – stop using submersible long-shaft pumps and opt instead for self-priming pumps, magnetic pumps, shielded pumps, or surface-mounted centrifugal pumps. By avoiding long shafts and submersible sealing mechanisms, leakage and maintenance risks can be reduced at the source. 2. Install additional leakage collection facilities: set up liquid collection trays, diversion channels, and collection tanks to ensure that any leaked substances are collected uniformly; they must not fall to the ground directly or enter the rainwater system. 3. Improve shutdown and isolation measures: Install shut-off valves and check valves at the pump’s inlet and outlet to facilitate maintenance and isolation ； The oil-containing wastewater pipes are installed separately; it is strictly prohibited to connect them with rainwater pipes. 4. Enhance explosion protection and static grounding: The explosion protection rating of motors and junction boxes should be no lower than Ex d IIB T4; the pump body and pipelines must be properly grounded against static electricity, with the grounding resistance meeting the specified requirements. 5. Add level and operation protection: Install high and low level alarms in the sewage tank, as well as a interlock system to stop the pump when the liquid level is low, thereby preventing vacuum conditions, cavitation, and dry grinding that could damage the seals. 6. Implement anti-clogging measures: Install grids and filters at the pump inlet, and clean them regularly ； If necessary, add mixing or recirculation devices to prevent sludge deposition and entanglement of debris. 7. Standardize maintenance management: If it is necessary to continue using the submersible pump, a regular maintenance record should be kept, and the shaft, bearings, and seals should be replaced periodically ； Before maintenance, permits for confined space work, hot work, and blind plate removal/installation must be strictly obtained. 8. Improve labeling and record-keeping: Label the pump bodies and pipes with the name of the medium and the flow direction, and install safety warning signs ； Establish ledgers for equipment operation, maintenance, and rectification of potential hazards.