Explosion Proof Submersible Sump Pump
Explosion Proof Submersible Sump Pump
What is an explosion-proof submersible sump pump?
An explosion proof submersible sump pump is a type of pump with an explosion-proof structure built to be fully submerged in the sump. The pump encloses the motor and pump as a single unit, which is insulated to prevent vapors from igniting and causing the explosion of the pumped fluid. An explosion-proof submersible sump pump is manufactured following the standards set by the National Electric Code (NEC) and National Fire Protection Association (NPFA). Explosion-proof submersible sump pumps are meant to pump water contaminated with various CSA, UL listed pollutants. They are also suitable for operations in potentially hazardous environments, such as chemical plants, coal mines, oil rigs, etc. They sit submerged and closed inside sumps in oil refinery basements, helping to detect the elevating liquid level and pressure levels to ensure it does not rise too high. When the rising liquid level activates the pump’s switch, the pump turns on and directs the liquid to the designated area through the delivery pipe.
Figure: Showing an explosion-proof submersible sump pump
Components of an explosion-proof submersible sump pump
Figure: Components of a explosion-proof submersible sump pump
The pump housing contains the pump’s internal components such as the impeller, shafts, and bearings housing. The housing also acts as a pressure containment vessel and has suction and discharge ports to direct the fluid into and out of the pump ports. The explosion-proof submersible sump pump manufacturers design the edge cutting units with durable housing, typically from castings that are hydrostatically tested to withstand the forces of an internal explosion. The pump housing is also designed to mitigate the creation of sparks through the use of non-sparking materials such as copper-aluminum alloys, stainless steel, silver, aluminum, and galvanized steel. Such materials are also less prone to corrosion, allowing the pump to last longer.
The impeller is a rotor that serves the role of increasing the kinetic energy and pressure of the fluid. It is fitted with a series of backward-curved vanes. It is usually mounted on the pump shaft and housed in the pump casing.
The shaft is a rotary mechanical component supported on bearings. Its main functions are to carry the impeller. It is usually coupled with the prime mover.
The motor is the source of mechanical energy to run the pump. It works by converting electrical energy into mechanical torque output which is transmitted to the pump head via coupling and pump shaft.
Explosion-proof submersible pumps consist of a long exhaust path built into their construction. The function of the exhaust path is to force any released gases to travel an extended distance, reducing their exhaust temperature to a value considered safe for the immediate area.
The explosion-proof submersible sump pump manufacturers design the pump to operate at a lower temperature than comparable standard pumps. To achieve this, the manufacturers fit the explosion-proof submersible sump pump with a pilot thermal sensor in the stator windings to monitor the operating temperature. The thermal sensor helps to keep the surface temperature below the safe temperature threshold, thereby preventing the potential detonation of environmental gases. The explosion-proof submersible sump pump can withstand a maximum temperature of 115 degrees Fahrenheit.
The pump switch allows the pump to turn on and off independently. The explosion-proof submersible sump pump’ switch can be a pressure switch, float switch, diaphragm switch, or electronic switch, depending on the mechanism of operation. A vertical float switch is the most common and of float that slides up and down a rod. When the pumped liquid level rise, the float ascends, switching the pump on. When the level descends, the float lowers, and the turning off pump.
Figure: Showing a vertical float switch
How does an explosion-proof submersible sump pump work
The explosion-proof submersible sump pump sits inside the sump and has a mechanism to detect the rising water level. When the switch is activated by the rising water level, the motor turns on and rotates the pump impeller at a high speed. The centrifugal effect of the rotating pump impeller creates a vacuum inside the pump casing, which allows water to enter through the pump inlet. When the water strikes the impeller blades, the centrifugal force moves it radially and axially outwards while imparting great kinetic energy until it enters into the volute chamber at a very high velocity. In the volute chamber, the extreme kinetic energy is converted into a high-pressure head and then the water is directed into the discharge pipe where it flows to the designed location.
Types of explosion-proof submersible sump pumps
Positive displacement pump
The explosion-proof submersible sump pumps in this category use contracting and expanding cavities to move fluid.
Dynamic explosion-proof submersible sump pumps
These types of pumps combine fluid velocity and momentum to generate pressure. They can generate variable flow and high flow rates with low-viscosity fluids.
Single suction explosion-proof submersible sump pump
In a single suction explosion-proof submersible sump pump, the fluid enters the impeller from one side and exits from the other side. the single suction type provides smooth operation and easy maintenance.
Figure: Showing a single suction explosion-proof submersible sump pump.
Double suction explosion-proof submersible sump pump
In this pump, the pumped liquid enters from either side of the impeller and exits from the middle section. The pump is less likely to experience cavitation because of reduced inlet flow. They can also manage higher discharge pressure than the single suction pump.
Figure: Showing a double suction explosion-proof submersible sump pump.
Applications of explosion-proof submersible sump pumps
The explosion-proof submersible sump pump manufacturers design them to excellently cater to a wide range of potentially hazardous industrial applications such as chemical plants, coal mines, oil/gas refineries, petrochemicals, and municipal works. They are suitable for any operation involving flammable liquids or an environment containing combustible gas or vapors. The following are some of the typical uses of explosion-proof submersible sump pumps:
- Explosion-proof submersible sump pumps are used for pumping flammable liquids in gas refineries
- They are used for Class 1, Division 1, and Group D hazardous locations. This is the UL classification for environments containing highly combustible materials, vapors, and/or flammable liquids, such as Acetone, alcohol, benzene, benzol, butane, gasoline, natural gas propane and equivalent hazardous materials, etc.
- They are used in wastewater treatment because explosive gases are a byproduct of the treatment process.
- They used for drainage operations in coal mines
- They are used for handling industrial wastewater containing explosive materials such as oil, chemical, and cleaning products
- They are used in municipal works to pump water contaminated with various pollutants
- They are used to discharge groundwater and water containing suspended pulverized coal grains of up to 2 inches in size.
- They are also used for petrochemical drainage because the explosion-proof submersible sump pump manufacturers fit them with an explosion-proof structure.
- They are also used for pumping effluents from industrial and commercial premises.
Advantages of an explosion-proof submersible sump pump
- Explosion-proof submersible sump pumps are quiet in operation they are completely submerged in pumped liquid during operation.
- They are perfect for transferring flammable liquid without putting life and property at risk.
- They provide cavitation-free operation because there is no spike in pressure as the pumped liquid flows through the pump.
- Explosion-proof submersible sump pumps are self-priming because they operate under the surface of the pumped liquid.
- They have a long service life because their construction materials are less prone to corrosion and wear.
- They can handle solid material with sizes of up to 2 inches.
- They are space-saving, energy-efficient, and reliable in operation.
Disadvantages of an explosion-proof submersible sump pump
- The explosion-proof submersible pump is a bit expensive because its design is much more technical and complex as compared to the conventional pump designs
- The pump seal may corrode with time causing water seepage into the motor, ultimately leading to motor failure.
- The mechanical seals make the motor difficult to access for repairs
- The pump must be fully submerged because it used the pumped liquid for cooling. If not submerged the motor can overheat and fail.
- The explosion-proof submersible sump pump can be located in a truly deep and difficult-to-reach sump. As result, the pump is left to operate without regular inspection of its condition and status.
Troubleshooting explosion-proof submersible pump
The motor fails to start
- The pump cable is broken. Inspect and change the cable if necessary.
- The motor is burned out. Consult a qualified technician to inspect the motor’s conditions and replace it if necessary.
- There is no power supply to control the Panel. Check that the power cables are connected per the explosion-proof submersible sump pump manufacturers’ guide. Check the main input panel.
- The fuse has failed. Inspect and replace the fuse if necessary.
The pump does not shut-off
- The switch is in the hand position. turn the explosion-proof submersible sump pump switch to auto position.
- Fault in pump wiring. Check for correct wiring or loose wires in the control panel and correct them.
- The contact is sticking. Replace contactor.
- There is insufficient liquid level in the sump. Check the level of liquid input to the sump.
- The motor operation is reversed. Ensure that the motor rotation direction matches the direction indicated by the explosion-proof submersible pump manufacturer. Reverse the motor polarities.
- Impeller seized. Inspect the impeller for blockage and remove it.
- The discharge pipe is blocked. Inspect and clean the discharge pipe.
Pump cycles frequently
- Shortcomings in the pump wiring. Inspect the control pane or junction box for correct wiring and correct any shortcomings.
- Some discharge valves are not open. Ensure all discharge valves are open.
- The float is set too close or the pump switch is defective. Reposition the float or replace the pump switch if necessary.
The pump experiences a thermal trip
- The density or viscosity of the pumped liquid is too high. Ensure the pump is suited for the applications. Open the pump valves.
- The stop level is too low. Ensure that the stop switch level is set according to the specification of explosion-proof submersible sump pump manufacturers.
- The pump head is too low. Adjust the pump head or install a control valve to detect and interpret the back pressure explosion in line with the value set by the explosion-proof submersible sump pump manufacturer.
The pump capacity is too low
- The pump working in reverse. Reverse the motor polarities.
- The discharge pipe is blocked. Inspect and remove any blockage from the discharge pipe.
- The impeller of the pump casing is partially clogged. Disassemble and clean the pump interiors.
The leakage detector is activated
- The detector cable is compromised either through wear, damage, or contact with oils. Inspect the status of the detector cable and replace it if necessary.
An explosion-proof submersible sump pump is a type of pump design with an explosion-proof structure that is completely immersed in a sump during operation. The pump consists of a motor and pumps enclosed in a single unit, which is insulated to prevent combustible elements from igniting and causing an explosion. Explosion-proof submersible sump pump manufacturers design edge-cutting units to mitigate the creation of sparks through the use of non-sparking materials such as copper-aluminum alloys, stainless steel, silver, aluminum, and galvanized steel. The pump casing is mainly made through the casting process and is hydrostatically tested to overcome the forces of an internal explosion. Explosion-proof submersible sump pumps are widely used for pumping contaminated water, such as wastewater containing explosive materials such as oil, chemical, and cleaning products. They excellently cater to pumping operations in potentially hazardous environments, such as chemical plants, coal mines, oil/gas refineries, and petrochemicals. Explosion-proof submersible sump pumps have many advantages such as safe, quiet, reliable, resistant to corrosion, and cavitation-free operation.