Centrifugal pumps are one of the most popular types of pumps used both domestically and in industrial settings. There are various designs of centrifugal pumps (Figure 1), and they all work in a similar manner at high velocity and pressure. To avoid accidents when using such pumps, as well as avoid damage to a pump, here are 12 safety tips that should be followed.
Read and Follow Instruction Manual. Ensure you read the instruction manual that comes with your pump before you install, operate, or perform maintenance on it or its related equipment. Always check for the recommended specifications for pump components in the manual before making adjustments.
For instance, you should check for the recommended limit for the clearance between the pump’s impeller and the wear plate. Going beyond or less than the recommended limit will reduce the pump efficiency and cause the components to wear out quickly.
Avoid Overheating. When a centrifugal pump overheats, it not only can damage internal components but also could cause severe burns and injuries to anyone servicing the pump. It’s important to ensure pumps do not overheat; to avoid the problem, always leave the suction and discharge line open during operations.
However, if overheating occurs, stop the pump immediately and allow it to cool to the air temperature. Then vent the pump at the drain plug, slowly and cautiously, before restarting. Also, always allow an overheated pump to cool to air temperature before removing the cover plate, gauge port plug, or fill port cap.
Check for and Replace Worn-out Components. Check for worn-out components (Figure 2) and replace them immediately to avoid catastrophic damage to your centrifugal pump. For instance, when the bearing is worn out, the pump shaft begins to wobble, and the pump becomes noisy and eventually will overheat. You should also check for worn suction line fittings and pipe plugs, and ensure there are no solids such as sand that may cause scratches and rapid wear of seal faces.
Check for Air Leaks. When worn out, suction line fittings and pipe plugs begin to have air leaks, which can cause the pump to lose its static lift. Make sure the suction line is airtight by regularly checking for air leaks using a vacuum gauge.
Usually, when a centrifugal pump is shut down, the vacuum gauge reading will display the vertical distance from the product level to the gauge tap. However, if the suction pipe is not airtight, and atmospheric pressure is entering, the vacuum will fall off after shutting down. The vacuum gauge will give erratic or fluctuating readings, which are an indication that the suction flap valve, seals, or hose are worn out and need replacement.
Check for Suction Line Blockage. Partial blocking of the suction line, which may lead to a blockage of the suction flow, can occur when the rubber lining in a suction hose pulls away from its fabric. This blockage of flow may cause the centrifugal pump to develop a high vacuum and a low discharge pressure.
Check for this suction hose problem by using a vacuum gauge to take readings during operations. Readings that are higher than normal are an indication that the rubber lining has pulled away from the suction hose, and the hose needs replacement.
Perform Routine Maintenance. Always carry out routine maintenance to check the pump’s engine or motor, to ensure the engine is getting the power it needs to operate efficiently and to check whether it needs tuning or servicing. Maintenance of the pump’s components, such as the volute casing, the wear plates, and impeller vanes, is also important.
A maintenance check (Figure 3) should be performed at least every six months, or more often depending on the pump’s usage. Inspection and cleaning of the suction strainer should also be done frequently as the accumulation of debris may cause clogging of the strainer, and obstruct the flow through the strainer.
Perform a Shut-off Test. This test is done to inspect the components and measure the internal wear of the centrifugal pump. To perform the test, start the pump and allow it to achieve full flow. Then slowly close the discharge valve and record the discharge and suction gauge reading. Under normal circumstances, the reading should be equal to the pump performance maximum pressure noted at zero flow.
Check Discharge Lines. Always check the operating condition of your discharge line, as old discharge lines may begin to rust internally, causing friction losses and reduction in flow. Therefore, it is important to check all the components in the discharge line, including the valve, check valves, release devices, and shock control devices, for normal operations.
Be Cautious. Before starting operations, always ensure all the guards and shields of the pump are in place. When the pump is in operation, approach it with caution to avoid accidents.
Make the Pump Accessible. Make sure the centrifugal pump is accessible (Figure 4) by locating it as close as safely possible to the liquid being pumped. However, do not place the pump within three feet of other equipment. Ensure the pump is in place and will not move during operation by adequately securing it to the ground or other surface.
Use the Pump for Its Designated Use. Do not use a centrifugal pump to pump liquid that it’s not designed to pump. For instance, do not pump flammable or corrosive liquids, such as gasoline or acid, with pumps designed for pumping water. Never operate pumps in flammable or explosive environments, unless the pump is designed for such service.
Experienced Personnel Only. Only experienced personnel should be allowed to operate a centrifugal pump and do not remove warning tags or labels from the machinery. Also, authorized personnel should not wear loose clothing around the machinery and must be provided with appropriate safety gear.
Additional Safety Tips. If the centrifugal pump has an electric motor or panel, always make sure the pump is locked out before performing maintenance. If the pump is fuel-driven, do not overfill the tank or spill fuel when refueling.
If the pump is located underground, make sure there is adequate ventilation, and always follow confined space entry procedures. When lifting a pump, use only lift equipment with adequate lifting capacity.
Centrifugal pumps utilize high velocity and pressure during operation. Therefore, irrespective of the type of centrifugal pump being used, it is important to observe safety precautions, as well as maintain pumps to avoid accidents. It is advised to always refer to the owner’s manual for instruction before installing, using, and maintaining a centrifugal pump. ■
—David Holland is vice president of Mahan’s Thermal Products.