Table of Contents

1. intro">1. Introduction to Explosion Proof Submersible Pumps
2. hazardous-areas">2. Hazardous Area Basics and Classification Systems
3. benefits">3. Key Advantages of Explosion Proof Submersible Pumps
4. common-mistakes">4. Top Explosion Proof Submersible Pump Installation Mistakes to Avoid
5. selection-mistakes">5. Selection and Sizing Mistakes
6. electrical-mistakes">6. Electrical and Grounding Mistakes
7. mechanical-mistakes">7. Mechanical, Piping and Sealing Mistakes
8. commissioning-mistakes">8. Commissioning, Testing and Documentation Mistakes
9. maintenance-mistakes">9. Maintenance and Operation Mistakes
10. specs">10. Typical Explosion Proof Submersible Pump Specifications (Example Tables)
11. checklist">11. Installation Checklist for Explosion Proof Submersible Pumps
12. faq">12. Frequently Asked Questions
13. conclusion">13. Conclusion

1. Introduction to Explosion Proof Submersible Pumps

An explosion proof submersible pump (often called an EX-proof submersible pump or flameproof

submersible pump) is a pump designed to operate fully submerged in a liquid while being safe for use in

potentially explosive atmospheres. These pumps are specifically engineered to prevent the ignition of

surrounding flammable gases, vapors or dust.

Explosion proof submersible pumps are widely used in:

• Oil and gas production, refineries, and petrochemical plants
• Fuel depots, tank farms and loading terminals
• Chemical processing and pharmaceutical manufacturing
• Paint, coating, ink and solvent handling facilities
• Mining operations and underground fuel storage
• Wastewater treatment plants with explosive gas risks (e.g., methane, hydrogen sulfide)
• Food and beverage plants that handle alcohols or flammable cleaning chemicals

Because these pumps operate directly inside sumps, tanks, pits, or wells that may contain explosive mixtures,

correct installation is essential. Even a certified explosion proof pump can become unsafe

if installed incorrectly. Incorrect wiring, poor sealing, or ignoring hazardous area classifications can

negate the explosion protection design.

The goal of this article is to highlight the most important

explosion proof submersible pump installation mistakes to avoid and provide clear, SEO-friendly,

industry-wide guidance that can be applied to most brands and models.

2. Hazardous Area Basics and Classification Systems

Understanding hazardous area classifications is the foundation of safe explosion proof submersible pump

installation. The explosion protection concept only works if the pump, cables, junction boxes, and all

accessories are appropriate for the specific classified area.

2.1 What is a Hazardous Area?

A hazardous area is any location where flammable gases, vapors, mists, or combustible dusts may be present

in quantities that could lead to an explosion if an ignition source is present. Submersible pumps are

frequently installed in:

• Sumps that collect hydrocarbon or solvent mixtures
• Wastewater pits with biogas formation
• Underground tanks containing fuels like gasoline or diesel
• Process vessels containing volatile chemicals

2.2 Zone and Class/Division Systems

Two main classification systems are commonly used worldwide:

• IEC / ATEX Zone system (Europe and many international regions)
• NEC Class/Division system (primarily North America)

When installing any explosion proof submersible pump, the first question is:

Which Zone / Class / Division applies to the sump, tank or pit?

Installing a pump certified for Zone 2 in a Zone 0 environment, for example, is a critical mistake.

2.3 Gas Groups and Temperature Classes

Gas group and temperature class determine whether an explosion proof submersible pump is safe for a specific

flammable substance.

A common installation mistake is ignoring the gas group and temperature class stamped on the pump nameplate.

The pump, cables, junction boxes, and level switches must all be compatible with the same hazardous area

classification.

3. Key Advantages of Explosion Proof Submersible Pumps

Understanding the benefits of explosion proof submersible pumps also helps clarify why correct installation is

so important. If the pump is installed incorrectly, these advantages can be lost.

• Enhanced safety in explosive atmospheres – The motor, cable entry, and terminal chamber

  are designed to prevent sparks and limit surface temperature.

• Space saving – As submersible units, they are installed inside the fluid, freeing up

  surface space and eliminating the need for complex above-ground pump houses.

• Reduced noise and vibration – Being submerged dampens noise and allows for smoother operation.

• Self-priming operation – Submersible pumps do not require separate priming systems, which

  eliminates a common source of installation mistakes.

• Lower risk of leakage above ground – As most pipework is underground or contained,

  spill risk can be reduced when properly installed.

• Wide range of applications – From transfer and drainage to process circulation and

  emergency pumping in hazardous environments.

To realize these benefits, installers must avoid the critical explosion proof submersible pump

installation mistakes described in the following sections.

4. Top Explosion Proof Submersible Pump Installation Mistakes to Avoid

Many problems occur repeatedly in the field, regardless of region or industry. Below is an overview of

common categories of mistakes:

The following sections detail these mistakes and provide practical tips to avoid them in real installations.

5. Selection and Sizing Mistakes

5.1 Choosing the Wrong Explosion Proof Rating

One of the most serious explosion proof submersible pump installation mistakes is selecting

a pump with an incorrect rating for the hazardous area.

• Installing a Zone 2 rated pump in a Zone 1 or Zone 0 area
• Using a pump certified for gas group IIA in a IIB or IIC atmosphere
• Ignoring temperature class requirements when fluids have low auto-ignition temperatures

Always cross-check the hazardous area classification drawing, the fluid data sheet and the pump nameplate

before installation.

5.2 Incorrect Hydraulic Sizing (Flow and Head)

Oversizing or undersizing an explosion proof submersible pump can cause:

• Excessive current draw and motor overheating
• Operation far from the best efficiency point (BEP)
• Unstable operation, vibration and cavitation

Mis-sized pumps are more likely to overheat, which increases surface temperature and can compromise the

explosion proof rating. Thermal protection may trip often, leading to nuisance shutdowns and unsafe bypasses.

5.3 Inadequate Material and Seal Selection

The pumped liquid may contain corrosive chemicals, solids, or abrasives. Common mistakes include:

• Using standard cast iron pumps in corrosive chemical pits without coating or stainless steel
• Specifying unsuitable elastomers in the mechanical seal for solvents or hydrocarbons
• Ignoring solids size and choosing an impeller design prone to clogging

5.4 Ignoring Ambient and Fluid Temperature Limits

Explosion proof submersible pumps are certified for specific ambient and fluid temperature ranges. Exceeding

these limits can:

• Reduce motor cooling efficiency
• Push the motor surface temperature beyond the certified T-class
• Accelerate insulation ageing and shorten motor life

Verify maximum fluid and ambient temperatures and ensure they remain within the pump’s certified limits

during all operating conditions.

6. Electrical and Grounding Mistakes

Electrical errors are some of the most dangerous explosion proof submersible pump installation

mistakes because they can directly create ignition sources.

6.1 Using Non-Certified Cable Glands and Junction Boxes

An explosion proof submersible pump is usually supplied with a certified EX-rated cable. A common mistake is:

• Terminating the pump cable in a non-EX junction box located in a hazardous area
• Using generic cable glands instead of certified EX cable glands
• Failing to maintain the integrity of the sheath, conductors and armor (if applicable)

All terminations and accessories within the classified area must have appropriate certifications for the same

Zone/Class and gas group.

6.2 Incorrect Grounding and Bonding

Proper grounding and bonding are essential for explosion proof pump safety. Typical mistakes:

• Not connecting the pump’s grounding terminal to the facility grounding system
• Failing to bond metallic piping, guide rails and structures
• Relying only on the cable shield without a dedicated ground conductor

Poor grounding can lead to static discharge or stray currents, which may ignite explosive atmospheres.

6.3 Ignoring Required Protection Devices

Explosion proof submersible pumps often require specific protective devices:

• Thermal overload relays or integral thermal switches
• Motor protection relays with phase loss, phase imbalance and locked-rotor protection
• Seal leak detectors and moisture sensors
• Level controls with fail-safe logic

Bypassing or not wiring these devices is a common mistake that removes layers of protection designed to

prevent overheating and ignition.

6.4 Wrong Voltage, Frequency, or Connection

Installing the pump on an incorrect supply voltage or frequency can quickly overheat the motor. Typical issues:

• Connecting a 60 Hz pump to a 50 Hz supply without derating
• Wrong star/delta wiring on three-phase motors
• Unbalanced line voltage causing excess current in one phase

Always compare the pump nameplate data with the site electrical supply and follow the manufacturer’s wiring

diagram exactly.

6.5 Improper Use of Variable Frequency Drives (VFDs)

VFDs are increasingly used to control pump speed, but in hazardous areas they introduce additional risks:

• Increased motor heating at low speed due to reduced cooling
• Voltage spikes damaging insulation and compromising EX integrity
• Harmonics affecting protective device operation

When using VFDs with an explosion proof submersible pump, verify that:

• The motor is approved or suitable for inverter duty
• The EX certificate permits speed control (some do not)
• Additional temperature monitoring or derating is applied as required

7. Mechanical, Piping and Sealing Mistakes

7.1 Poor Guide Rail and Lifting System Installation

Many explosion proof submersible pumps are installed in pits using guide rails. Mistakes include:

• Misaligned guide rails causing the pump to jam during installation or removal
• Unsupported or weak upper rail brackets
• Improperly sized lifting chains or hooks not rated for the pump weight

In hazardous areas, safe and quick removal of the pump is critical. A stuck or jammed pump often leads to

unsafe improvisation during maintenance.

7.2 Incorrect Discharge Piping Design

Common discharge line mistakes that affect explosion proof submersible pumps:

• Lack of a check valve, causing reverse flow and water hammer
• No isolation valve, making maintenance difficult
• Excessive elbows and restrictions increasing head losses
• Unsupported vertical or long horizontal runs that stress the pump outlet

These mistakes can increase starting torque, overload the motor, or cause repetitive failures that compromise safety.

7.3 Incorrect Pump Orientation and Depth

Explosion proof submersible pumps must remain fully or sufficiently submerged to ensure proper cooling. Mistakes:

• Installing the pump too close to the liquid surface, leading to vortexing and air entrainment
• Placing the pump directly on sludge or debris that blocks the suction
• Insufficient submergence during low-level operation

Always follow the manufacturer’s minimum submergence and clearance recommendations.

7.4 Inadequate Sealing Around Cables and Penetrations

Cable entries into pits, tanks or bunds must be sealed to prevent vapor migration. Mistakes include:

• Running cables through unsealed conduits into non-hazardous areas
• Using foam or non-certified sealing compounds
• Ignoring the compatibility between sealing material and the fluid or vapors

Poor sealing can spread explosive atmospheres into safe areas, complicating classification and increasing risk.

7.5 Ignoring Mechanical Seal Support Requirements

Some explosion proof submersible pumps include:

• Double mechanical seals with an oil-filled chamber
• Seal flushing or cooling arrangements
• Seal monitoring probes

Failing to fill the seal oil chamber correctly, not venting air, or ignoring seal monitoring leads to early seal

failure and increases the risk of explosive fluid ingress into the motor housing.

8. Commissioning, Testing and Documentation Mistakes

8.1 Skipping Pre-Start Checks

Rushing to start an explosion proof submersible pump without basic checks is a frequent installation mistake.

Essential checks include:

• Insulation resistance and continuity tests
• Verification of EX labels, nameplate data and certification
• Correct rotation direction for three-phase motors
• Proper functioning of floats, level sensors and interlocks

8.2 No Functional Testing of Protection Systems

Protection devices are often installed but not tested under real conditions. For safe operation:

• Simulate high temperature to verify thermal trip
• Test seal leakage alarms
• Check that level control stops the pump when liquid is too low
• Confirm that emergency stop and lock-out systems function correctly

8.3 Incomplete Documentation and Labelling

Documentation is essential for long-term safety and regulatory compliance. Mistakes include:

• No as-built drawings showing cable routes and junction box locations
• Missing hazardous area classification maps
• Unlabelled disconnects, panels and protection devices

Comprehensive documentation helps ensure any future maintenance or modification does not undermine explosion protection.

9. Maintenance and Operation Mistakes

9.1 Performing Hot Work Near the Pump Without Controls

Welding, grinding, or hot cutting in or near hazardous areas without proper permits and gas testing is a

significant risk. Even if the pump is explosion proof, the surrounding atmosphere may ignite.

9.2 Ignoring Early Warning Signs

Operators often ignore warning signs that the pump is not operating correctly:

• Frequent tripping of thermal protection
• Unusual noise or vibration
• Leaks around cable glands or seal failure alarms
• Reduced flow or fluctuating discharge pressure

In hazardous areas, these symptoms should trigger immediate investigation, not repeated resets.

9.3 Using Non-Original or Non-Certified Spare Parts

Explosion proof submersible pumps are certified as complete assemblies. Replacing:

• Mechanical seals with non-equivalent parts
• Cable glands with non-EX certified components
• Fasteners with incorrect materials or grades

can invalidate the EX certification and compromise safety.

9.4 Operating the Pump Outside the Design Envelope

Running the pump continuously at very low flow, against a closed valve, or with excessive solids beyond

design limits leads to overheating and premature wear. In an explosion proof context, this can push the

motor beyond its safe temperature class.

9.5 Lack of Periodic Inspection in Hazardous Areas

Many standards require periodic inspection of equipment in explosive atmospheres. Typical tasks include:

• Checking cable condition, glands and junction boxes
• Inspecting for corrosion, damage or loose hardware
• Verifying that labels and EX markings remain legible
• Confirming that seals and gaskets are intact

10. Typical Explosion Proof Submersible Pump Specifications (Example Tables)

The following tables illustrate typical specification ranges for explosion proof submersible pumps. They are

generic and may vary by manufacturer, but they highlight the main parameters to review before installation.

10.1 Typical Hydraulic and Motor Data

10.2 Typical Explosion Protection Data

10.3 Typical Construction Materials

11. Installation Checklist for Explosion Proof Submersible Pumps

The following concise checklist helps avoid the most common explosion proof submersible pump

installation mistakes. It can be used as a guideline during planning and on-site work.

12. Frequently Asked Questions

12.1 Why is correct installation more critical for explosion proof submersible pumps than standard pumps?

Standard pumps may fail without directly creating an explosion hazard. Explosion proof submersible pumps

operate inside potentially explosive atmospheres. Incorrect installation can bypass the protection concepts

and create ignition sources such as overheating, arcing or static discharge in an environment filled with

flammable gases or vapors.

12.2 Can any submersible pump be used in a hazardous area if it is installed carefully?

No. Only pumps with valid, appropriate explosion proof certification (such as ATEX, IECEx

or NEC/CEC approvals) should be used in hazardous areas. Careful installation does not compensate for the

lack of certified explosion protection features.

12.3 Are all explosion proof submersible pumps suitable for Zone 0?

No. Most EX submersible pumps are designed for Zone 1 or Zone 2. Zone 0 has the highest hazard level and

often requires special designs and certifications. Always check the zone suitability on the pump nameplate

and documentation.

12.4 What is the most common explosion proof submersible pump installation mistake?

One of the most common mistakes is using non-certified cable glands, junction boxes, or level sensors in a

hazardous area. Even if the pump is correctly certified, using non-EX accessories can introduce ignition

sources and invalidate the entire installation.

12.5 How often should explosion proof submersible pumps be inspected?

Inspection frequency depends on local regulations, standards, and the operating environment. However, many

facilities perform at least annual inspections of EX equipment, with more frequent checks in harsh or critical

applications. Follow both regulatory and manufacturer recommendations.

12.6 Can a VFD be used with an explosion proof submersible pump?

Yes, but only if the motor is suitable for VFD operation and the EX certification allows its use with

frequency inverters. Additional temperature monitoring, derating, or restrictions on speed range may apply.

Improper use of VFDs is a frequent cause of overheating and failure.

12.7 What documentation should be kept for an explosion proof submersible pump installation?

Recommended documentation includes:

• Pump data sheet and performance curves
• EX certificates, declarations of conformity and nameplate photos
• Hazardous area classification drawings
• Wiring diagrams and protection device settings
• Commissioning and test reports
• Maintenance and inspection records

13. Conclusion

Explosion proof submersible pumps provide safe and reliable pumping in hazardous areas when they are

correctly selected, installed and maintained. Many incidents arise not from equipment design flaws but from

avoidable explosion proof submersible pump installation mistakes such as:

• Using pumps or accessories with incorrect EX ratings for the classified area
• Poor electrical practices, including non-certified glands and inadequate grounding
• Incorrect hydraulic sizing, leading to overheating and unstable operation
• Mechanical and sealing errors that compromise cooling and containment
• Inadequate commissioning, testing, and continuous inspection

By understanding hazardous area concepts, verifying certification data, following industry standards and

applying the practical checklist above, installers and operators can significantly reduce risk, extend pump

life and ensure compliance. Treat the explosion proof submersible pump as part of an integrated hazardous

area system, rather than an isolated component, and always avoid shortcuts that undermine its explosion

protection design.