Table of Contents

1. definition">Definition of Explosion Proof Submersible Pumps
2. hazard-zones">Hazardous Area Classifications and Standards
3. energy-challenges">Energy Challenges in Hazardous-Area Pumping
4. benefits">Benefits of Energy Saving Practices
5. design-considerations">Energy Efficient Design Considerations
6. selection">Pump Selection for Energy Efficiency
7. motor-efficiency">High-Efficiency Explosion Proof Motors
8. vfd-control">Variable Frequency Drives and Intelligent Control
9. installation">Installation and System Design Best Practices
10. operation">Operational Strategies for Energy Saving
11. maintenance">Maintenance and Condition Monitoring
12. monitoring-metrics">Key Energy Performance Indicators
13. specs-tables">Typical Specifications and Comparison Tables
14. applications">Common Applications and Use Cases
15. checklist">Energy Saving Checklist for Explosion Proof Submersible Pumps
16. conclusion">Conclusion

1. Definition of Explosion Proof Submersible Pumps

Explosion proof submersible pumps are electrically driven pumping units designed to operate fully or

partially submerged in liquids within hazardous locations where explosive gas, vapor, or dust atmospheres

may be present. These pumps combine submersible hydraulic performance with explosion proof motor and cable

designs to prevent ignition of surrounding flammable atmospheres.

An explosion proof submersible pump typically consists of:

• A submersible electric motor with explosion proof or flameproof enclosure
• Hydraulic pump end (impeller, casing, diffuser or volute)
• Sealing system (mechanical seals, shaft sleeves, oil chambers)
• Power cable with Ex-rated glands and terminations
• Integrated sensors such as temperature, moisture, and vibration monitors

The term “explosion proof” generally refers to equipment that:

• Withstands an internal explosion of a flammable mixture
• Prevents the transmission of flame or hot gases to the external atmosphere
• Operates within specified surface temperature limits (e.g., T1–T6 temperature classes)

In the context of energy saving practices for explosion proof submersible pumps, the explosion protection

measures must always take priority. Any efficiency improvement must fully comply with relevant standards

while reducing power usage, heat losses, and hydraulic inefficiencies.

2. Hazardous Area Classifications and Standards

Energy saving practices for explosion proof submersible pumps must align with hazardous area standards.

Pump selection, motor design, control systems, and monitoring equipment must be certified for the intended

zone or division.

2.1 Zone and Division Systems

The most common hazardous area classification systems are:

• IEC / ATEX Zone System:

  • Zone 0: Continuous or long-period presence of explosive gas atmosphere
  • Zone 1: Likely presence during normal operation
  • Zone 2: Not likely in normal operation, if present then infrequently and briefly
  • Zone 20/21/22: For combustible dust atmospheres

• NEC / CEC Division System:

  • Class I Div 1: Gases or vapors normally present
  • Class I Div 2: Gases or vapors present only under abnormal conditions
  • Class II and III: Dust and fibers

2.2 Explosion Protection Concepts Relevant to Submersible Pumps

Common protection types used in explosion proof submersible pumps include:

• Flameproof / Explosion Proof (Ex d / XP) motor enclosures
• Increased Safety (Ex e) terminal boxes and connection chambers
• Encapsulation (Ex m) for sensors and electronics
• Intrinsic Safety (Ex i) for low-power control and monitoring circuits

2.3 Standards and Directives

When implementing energy saving practices for explosion proof submersible pumps, plant operators should

reference:

• ATEX Directive 2014/34/EU for equipment in explosive atmospheres
• IECEx certification scheme
• IEC 60079 series for explosive atmospheres
• NEC Articles 500–505 (North America)
• Relevant pump standards such as ISO 5199, ISO 9906 for performance testing

3. Energy Challenges in Hazardous-Area Pumping

Explosion proof submersible pumps often operate in environments with demanding process conditions, which

directly influence energy consumption and efficiency. Understanding these challenges is essential for

applying effective energy saving practices.

• High safety margins: Extra safety factors in design and operation can lead to

  oversizing of pumps and motors, increasing energy use.

• Harsh media: Abrasive, corrosive, or viscous liquids can reduce hydraulic efficiency,

  causing higher power draw.

• Variable operating conditions: Level changes, fluctuating inflow, and intermittent

  duty can keep pumps away from their best efficiency point (BEP).

• Thermal constraints: Explosion proof motors must limit surface temperature, sometimes

  at the expense of higher internal losses.

• Access limitations: Submerged and confined installations make inspection and

  maintenance more difficult, reducing the likelihood of timely efficiency improvements.

Addressing these challenges requires a systematic energy management approach that respects explosion

protection requirements while optimizing hydraulic and electrical performance.

4. Benefits of Energy Saving Practices for Explosion Proof Submersible Pumps

Implementing energy saving practices for explosion proof submersible pumps offers multiple benefits across

safety, operational, and financial dimensions.

4.1 Reduced Operating Costs

• Lower electricity consumption across the pump’s lifecycle
• Reduced demand charges in facilities subject to peak tariffs
• Decreased need for backup capacity due to more stable operation

4.2 Improved Reliability and Availability

• Operation closer to BEP reduces vibration, wear, and seal failures
• Optimized motor loads decrease thermal stress in explosion proof motors
• Energy-focused maintenance often overlaps with reliability-centered maintenance

4.3 Enhanced Safety

• Lower operating temperatures reduce ignition risks in hazardous atmospheres
• Stable operation minimizes unplanned stops and restarts in explosive zones
• Reduced cavitation and mechanical impact lower the risk of damage and leaks

4.4 Environmental and Regulatory Benefits

• Lower CO₂ emissions associated with energy use
• Support for corporate sustainability and energy management programs
• Improved compliance with efficiency-related regulations and standards

5. Energy Efficient Design Considerations

The foundation of energy saving practices for explosion proof submersible pumps lies in the initial system

and equipment design. Early decisions often determine most of the lifetime energy consumption.

5.1 Hydraulic Design for High Efficiency

• Impeller type: Choose the appropriate impeller style (closed, semi-open, vortex,

  channel) balancing energy efficiency with solids handling and clogging risk.

• Hydraulic optimization: Use designs with optimized flow passages to minimize

  recirculation and turbulence losses.

• BEP alignment: Select hydraulic design where the duty point is close to the BEP of the

  pump curve.

5.2 Materials and Wear Resistance

Wear and corrosion reduce efficiency over time. Energy saving practices emphasize:

• Appropriate material selection (e.g., duplex stainless steel, high chrome iron)
• Coatings or surface treatments to maintain smooth hydraulic surfaces
• Wear rings and replaceable liners to restore clearances economically

5.3 Motor Design in Explosion Proof Execution

While explosion proof designs can introduce additional losses, high efficiency is still achievable:

• Use high-efficiency motor designs (e.g., IE3 or IE4 efficiency levels where permitted)
• Optimize stator design and copper fill for lower I2R losses
• Use efficient bearing systems and low-loss seals between motor and pump
• Ensure adequate cooling via surrounding liquid or internal circulation

5.4 Cable and Power Supply

• Size cables to limit voltage drop and I2R losses, especially with long cable runs
• Use Ex-rated cables compatible with the hazardous area classification
• Ensure power quality (voltage balance, harmonic distortion) to reduce motor losses

6. Pump Selection for Energy Efficiency

Proper pump selection is one of the most powerful energy saving practices for explosion proof submersible

pumps. Oversizing or misapplication can lock facilities into high energy costs for years.

6.1 Matching Pump Curve to System Curve

The selected pump must operate close to its BEP under typical conditions. To achieve this:

• Estimate realistic flow and head requirements, including friction and static components
• Avoid excessive safety margins that move the duty point far from BEP
• Consider multiple duty points if operation will vary significantly

6.2 Avoiding Oversizing

Oversized explosion proof submersible pumps:

• Operate at reduced efficiency and higher recirculation losses
• Require throttling, which wastes energy as pressure loss
• May experience more starts and stops, reducing reliability

Right-sizing or using multiple smaller pumps in parallel can offer better energy performance.

6.3 NPSH and Cavitation Considerations

While submersible pumps are generally favored for good NPSH conditions (due to immersion), specific

applications may still be at risk of cavitation. Energy saving practices recommend:

• Select pumps with adequate NPSH margin under all expected operating conditions
• Avoid high suction velocities that increase losses at the pump inlet
• Ensure inlet screens or strainers do not cause excessive pressure drop

6.4 Efficiency Classes and Labels

When available and compatible with explosion proof requirements, select pumps and motors with:

• High hydraulic efficiency rating (documented per ISO 9906)
• High-efficiency motor classes (IE2, IE3, IE4), considering Ex requirements
• System-level efficiency evaluation, not just component-level

7. High-Efficiency Explosion Proof Motors

The motor is a critical component in energy saving practices for explosion proof submersible pumps. Motor

efficiency directly impacts overall system energy consumption.

7.1 Motor Efficiency Levels

Typical efficiency classes for submersible motors may include:

• Standard efficiency (legacy designs)
• High efficiency (equivalent to IE2)
• Premium efficiency (equivalent to IE3)

In explosion proof execution, achieving higher efficiency levels may require more advanced designs and

materials.

7.2 Design Features for Efficient Ex Motors

• Optimized lamination materials with low core losses
• High-grade copper conductors and optimized slot geometry
• Reduced air gap while maintaining mechanical safety margins
• Efficient rotor designs tuned for the application’s speed and load profile

7.3 Thermal Management in Hazardous Areas

Explosion proof motors must limit external surface temperature, which can complicate heat dissipation. Energy saving

strategies include:

• Operating within recommended load range to avoid overheating
• Ensuring proper cooling via surrounding fluid without blockage
• Monitoring winding temperature with embedded sensors

8. Variable Frequency Drives and Intelligent Control

Variable frequency drives (VFDs), also called variable speed drives (VSDs), are central to many energy

saving practices for explosion proof submersible pumps. Adjusting pump speed to match demand eliminates

throttling losses and enables smooth control.

8.1 Benefits of VFDs in Hazardous-Area Pumping

• Energy savings: For centrifugal pumps, power is roughly proportional to the cube of

  speed; reducing speed by 20% can cut power consumption by nearly 50% in ideal conditions.

• Process optimization: Maintain stable levels, pressures, and flows with less

  oscillation.

• Reduced mechanical stress: Soft starts and stops minimize torque shocks and water

  hammer.

8.2 Explosion Protection for VFD Systems

The pump motor is submersible and explosion proof, but the VFD is usually installed in a safe or protected

area. Energy saving practices must ensure:

• Compatibility of motor insulation system with VFD output waveforms
• Proper grounding and shielding of long submersible cables
• Use of Ex-rated control and signal circuits between hazardous and safe areas

8.3 Advanced Control Strategies

Intelligent control strategies can maximize energy savings and extend equipment life:

• Level-based control: Adjust pump speed to maintain liquid levels within a target

  band, avoiding frequent on/off cycling.

• Pressure or flow control: Maintain constant discharge pressure or flow, adapting to

  process demand.

• Multi-pump optimization: Sequence multiple pumps for best combined efficiency and

  redundancy.

• Energy-optimized setpoints: Use algorithms that minimize kWh per cubic meter pumped.

9. Installation and System Design Best Practices

Proper installation is a fundamental energy saving practice for explosion proof submersible pumps. Even a

high-efficiency pump can waste energy if installed poorly.

9.1 Hydraulic System Layout

• Minimize pipe length and fittings that introduce friction losses
• Use appropriate pipe diameters to balance friction losses and material costs
• Design smooth transitions and avoid sudden enlargements or contractions

9.2 Sump and Intake Design

Efficient intake conditions help maintain high pump efficiency and prevent cavitation:

• Provide sufficient submergence depth to avoid vortex formation
• Design sumps with proper geometry to prevent swirling and air entrainment
• Install suitable screens or strainers with low pressure drop and easy cleaning access

9.3 Electrical Installation

• Ensure correct phase sequence and voltage at the motor terminals
• Use Ex-approved junction boxes, cable glands, and conduits
• Verify insulation resistance and continuity before commissioning

9.4 Instrumentation and Monitoring

Monitoring is a key enabler of energy saving practices for explosion proof submersible pumps:

• Install level sensors, pressure transmitters, and flow meters rated for hazardous areas
• Use temperature and leakage sensors integrated into the pump for condition monitoring
• Route signals through appropriate intrinsic safety barriers or Ex interfaces

10. Operational Strategies for Energy Saving

Day-to-day operating practices strongly influence the real-world energy performance of explosion proof

submersible pumps.

10.1 Operating Near Best Efficiency Point (BEP)

Running the pump near its BEP minimizes hydraulic losses, vibration, and noise. Operators can:

• Adjust system valves and setpoints to move duty closer to BEP
• Use VFDs to shift the pump curve for an optimal match
• Review performance periodically as system conditions change

10.2 Minimizing Throttling Losses

Control valves used for throttling create significant energy losses as heat. Energy saving practices

recommend:

• Use speed control via VFDs instead of throttling whenever feasible
• Eliminate unnecessary restrictions, partially closed valves, and undersized components
• Evaluate the potential for two-speed or multi-pump operation rather than heavy throttling

10.3 Optimizing Start/Stop Strategy

Excessive starting and stopping increases wear and reduces efficiency:

• Set level control hysteresis bands to avoid short cycling
• Coordinate multiple pumps in lead/lag arrangements
• Use soft starters or VFDs to reduce inrush current and mechanical stress

10.4 Seasonal and Process Adjustments

Process conditions such as fluid temperature, viscosity, and production rate may vary throughout the year.

Energy saving practices for explosion proof submersible pumps include:

• Adjusting control setpoints to match seasonal patterns
• Reducing pump speed during low-demand periods
• Scheduling non-critical pumping tasks during off-peak energy tariffs when possible

11. Maintenance and Condition Monitoring

Maintenance has a direct impact on energy consumption. Worn or damaged components increase friction and

hydraulic losses, causing higher power draw for the same flow rate.

11.1 Preventive Maintenance Practices

• Periodic inspection of motor insulation, cable condition, and junction boxes
• Wear ring and impeller clearance checks and adjustments
• Seal condition monitoring to prevent leakage into the motor
• Sump cleaning to reduce sediment build-up around the pump

11.2 Condition-Based Maintenance (CBM)

Condition monitoring supports both reliability and energy savings:

• Use vibration monitoring to detect imbalance, misalignment, and bearing issues
• Analyze power consumption trends to detect hydraulic deterioration
• Monitor motor winding temperature and leakage sensors for early warning

11.3 Cleaning and Fouling Control

Fouling on impeller surfaces and pump casing significantly reduces hydraulic efficiency. Energy conscious

maintenance should include:

• Regular cleaning schedules appropriate to the pumped fluid
• Inspection of inlet screens and suction bells for blockages
• Corrective actions when unusual noise or reduced flow is observed

12. Monitoring and Energy Performance Metrics

Measuring performance is essential to manage and improve energy efficiency of explosion proof submersible

pumps over time.

12.1 Key Metrics

12.2 Data Collection Methods

• Installing power meters with Ex-appropriate transducers
• Using SCADA or DCS systems to log flow, level, and energy data
• Periodic portable measurements for smaller installations

Analysis of these metrics supports continuous improvement in energy saving practices for explosion proof

submersible pumps.

13. Typical Specifications and Comparison Tables

While exact specifications depend on manufacturer and application, the following generic tables illustrate

the types of parameters commonly considered when evaluating energy saving practices for explosion proof

submersible pumps.

13.1 Typical Performance Data for Explosion Proof Submersible Pumps

13.2 Example Comparison: Standard vs Energy-Optimized Ex Submersible Pump

13.3 Example Specification Summary for an Energy-Efficient Ex Submersible Pump

14. Common Applications and Use Cases

Energy saving practices for explosion proof submersible pumps can be applied across many hazardous-area

industries and processes.

14.1 Oil and Gas Industry

• Crude oil storage tank drainage and transfer
• Produced water handling and injection systems
• Refinery sump and pit dewatering

In these applications, uptime and safety are critical. Energy optimization reduces heat load on motors and

lowers operational costs at remote and offshore locations.

14.2 Chemical and Petrochemical Plants

• Hazardous effluent pumping
• Solvent and flammable liquid transfer
• Neutralization and treatment pits in explosive atmospheres

Stable flow and minimized leakage are essential, and speed control with Ex-compliant monitoring provides

both process control and energy savings.

14.3 Mining and Mineral Processing

• Underground dewatering in gassy mines
• Slurry and tailings handling in hazardous zones

Abrasive fluids accelerate wear, so materials and maintenance are central to long-term efficiency.

14.4 Wastewater and Sewage in Hazardous Areas

• Pumping stations where flammable gases such as methane may accumulate
• Industrial wastewater with explosive vapors

Energy saving practices are particularly impactful in continuous-duty wastewater systems, where pumps run

many hours per year.

15. Energy Saving Checklist for Explosion Proof Submersible Pumps

The following checklist summarizes practical energy saving practices for explosion proof submersible pumps.

It can be used during design, audit, or optimization projects.

• Confirm hazardous area classification and select appropriate Ex rating
• Size pumps based on realistic flow and head requirements with minimal oversizing
• Select high-efficiency hydraulic designs and materials resistant to wear and corrosion
• Choose high-efficiency explosion proof motors where applicable standards permit
• Evaluate VFD or variable speed control to match pump output with system demand
• Optimize piping, valves, and sump design to reduce hydraulic losses
• Install accurate level, flow, and pressure instrumentation for control and monitoring
• Implement control strategies that minimize throttling and operate near BEP
• Monitor key energy performance metrics such as kWh/m3 and system efficiency
• Apply preventive and condition-based maintenance to preserve efficiency over time
• Train operators on how their actions influence pump energy consumption and safety
• Review performance periodically and adjust control parameters to changing conditions

16. Conclusion

Energy saving practices for explosion proof submersible pumps combine careful equipment selection, smart

control strategies, robust installation, and disciplined maintenance. In hazardous area applications where

reliability and safety are non-negotiable, these practices not only reduce operational costs and emissions

but also support safer, more stable pump operation.

By viewing the explosion proof submersible pump as part of an integrated pumping system, and by monitoring

performance through relevant energy and reliability metrics, plant operators can realize substantial and

sustainable energy savings while fully complying with ATEX, IECEx, NEC, and other hazardous-area standards.

Applying these industry-wide, manufacturer-neutral principles enables optimization of explosion proof

submersible pump systems in oil and gas, chemical processing, mining, wastewater treatment, and other

sectors where hazardous atmospheres and demanding duty cycles make efficient, safe pumping an essential

requirement.