How to Choose an Explosion-Proof Submersible Pump

A pump installed in a coal mine, petrochemical plant or other hazardous location cannot be selected in the same way as an ordinary drainage pump. The hydraulic duty still matters, but the pump must also be suitable for the explosive atmosphere, electrical system and installation rules of the project.

The words “explosion-proof” alone are not enough. Before placing an order, the buyer should confirm the hazardous-area classification, required protection marking, certification system, liquid properties and operating conditions. A pump that is suitable for one mine or industrial site may not be approved for another.

This guide explains what information a supplier needs and how to avoid the most common purchasing mistakes.

The first step is not choosing a motor power. It is identifying the environment in which the pump will operate.

An explosive atmosphere can be created by flammable gas, vapour, mist or combustible dust mixed with air. The site owner or qualified engineer should classify the area and define the required equipment protection level. The assessment should identify whether the application is an underground mine or a surface industrial location, because these environments can use different equipment groups and protection requirements.

The buyer should provide the supplier with the complete required marking, not simply ask for an “ATEX pump” or an “explosion-proof motor.” Important details may include the equipment group, zone or category, type of protection, gas or dust group, temperature class and equipment protection level.

If the project has not yet been classified, the pump manufacturer should not guess the classification. This decision belongs to the responsible hazardous-area engineer or local authority.

Certification requirements depend on where the equipment will be installed. IECEx is an international conformity assessment system for equipment used in explosive atmospheres. In the European Union, equipment placed on the market for potentially explosive atmospheres is covered by ATEX Directive 2014/34/EU. Other countries may require national mining approval, local certification or a North American Class/Division or Zone listing.

These systems are related, but they are not automatically interchangeable.

Ask the supplier to provide the certificate for the exact proposed model and configuration. Check the certificate number, issuing body, marking, scope, permitted operating conditions and any special conditions of use. The pump nameplate should agree with the certificate.

A catalogue statement or a photograph of another model’s nameplate is not proof that the pump being quoted is approved for your project.

Explosion protection does not determine hydraulic suitability. The pump still has to handle the actual liquid without rapid blockage, corrosion or wear.

Provide information about:

• Water temperature

• pH and density

• Sand or solids concentration

• Maximum particle size

• Fibres, rags or other debris

• Chloride content and corrosive chemicals

• Whether the liquid is sewage, mine water or process water

The SLAPK BQS catalogue describes mining explosion-proof drainage pumps for water containing permitted solids and abrasive material. It also offers different structural arrangements and optional materials. However, allowable solids and liquid limits depend on the selected model and project requirements.

A pump that can pass a particle is not necessarily resistant to continuous abrasion. High sand concentration can wear impellers, pump casings, diffusers and seals. For severe slurry service, a dedicated slurry pump or another hydraulic design may be more suitable.

For more guidance, read How Much Sand Can a Deep Well Submersible Pump Handle?.

Select the pump at the required operating point, not from motor power or outlet size alone.

The required flow should come from the expected water inflow, storage volume and allowable drainage time. Total dynamic head should include vertical lift, discharge pressure, pipe friction and losses through valves and fittings.

In mine drainage, the discharge line may be long and steep. Ignoring friction can cause the selected pump to deliver much less water than expected. It can also move the operating point away from the pump’s efficient range.

The BQS catalogue covers a broad range of flows, heads and motor powers across many configurations. Those family limits should not be treated as the performance of one pump. Request the curve for the exact model and confirm the operating point, efficiency, absorbed power and allowable range.

See Deep Well Pump Sizing Guide: How to Calculate Flow Rate and Total Dynamic Head for the complete calculation method.

Mining and industrial projects may use different voltages from standard commercial installations. Confirm the available voltage, frequency, phase and permitted starting method before production.

The cable is part of the explosion-protected installation. It must meet the required flame-retardant or hazardous-area specification, withstand continuous immersion and have enough conductor area for the motor current and complete route length. Cable entries, joints and glands must preserve the approved protection concept.

Also confirm whether the pump will use direct-on-line starting, star-delta starting, a soft starter or a variable-frequency drive. A VFD should only be used when the motor, cable, protection system and certificate permit it. Long motor cables can create additional electrical stress and may require filters or reactors.

The control panel, starter and local isolator must also be suitable for their installation locations. An approved pump does not make an ordinary control cabinet safe inside a classified area.

A submersible motor normally depends on the surrounding or pumped liquid for cooling. Some BQS configurations use a cooling jacket and pumped-water circulation, which may support operation at a lower surrounding water level. The permissible minimum level still depends on the exact design.

Do not assume that an explosion-proof submersible pump can run dry. Loss of cooling can raise surface and winding temperatures, damage seals and create an unsafe operating condition.

Ask the supplier to state the minimum operating level, permitted installation position and any limit on partial submergence. The control system should stop the pump before unstable flow or inadequate cooling occurs. Thermal protection, level control and dry-running protection should be coordinated with the certified design.

Mine water may contain sediment, gravel or corrosive substances. Review the materials used for the impeller, casing, shaft and fasteners. Ask whether wear-resistant surface treatment, stainless steel or another material is available for the liquid.

Mechanical seals are equally important. The catalogue shows different sealing arrangements, including double-end and series mechanical seals. The appropriate arrangement depends on pressure, submersion depth, solids and expected operating hours.

Maintenance planning should begin before installation. Confirm the lifting points, pump weight, cable handling method, pipe connection and space needed for removal. Hazardous-area equipment should be inspected and repaired by competent personnel using approved parts and procedures. An unauthorized modification to a cable entry, enclosure or flame path can invalidate the protection.

Before approving the quotation, ask the supplier to confirm:

• Exact pump and motor model

• Duty point and performance curve

• Maximum absorbed power

• Explosion-protection marking

• Certificate number and issuing body

• Suitability for the project’s area classification

• Permitted liquid and solids limits

• Minimum operating water level

• Cable type, size and length

• Starting method and protection requirements

• Pump materials and sealing arrangement

• Overall dimensions, weight and outlet connection

• Included accessories and recommended spare parts

The quotation should clearly separate standard features from optional or project-specific items.

The most serious mistake is selecting a pump only because a supplier describes it as explosion-proof. Other common problems include using a mining-certified model in an unrelated industrial zone without checking its marking, ignoring the temperature class, selecting from maximum catalogue data, underestimating abrasive solids and installing non-approved cables or controls.

Another mistake is ordering the pump before confirming the site voltage and control method. Changing the motor, cable entry or starting arrangement later may require a different design or certificate.

Clear technical information at the inquiry stage is faster and less expensive than correcting a compliance problem after delivery.

An explosion-proof submersible pump must satisfy three requirements at the same time: hazardous-area compliance, hydraulic performance and reliable operation in the actual liquid.

Begin with the site classification and destination-market requirements. Then calculate the flow and total dynamic head, check solids and corrosion, and confirm the motor, cable, cooling and control system. Finally, verify the certificate and nameplate for the exact model being purchased.

Send SLAPK your required flow and head, water analysis, solids information, installation drawing, voltage, cable length and complete explosion-protection requirement. Our engineers can review whether a BQS mining pump or another configuration is appropriate for the project.

Contact SLAPK for an explosion-proof pump selection