An explosion-proof pump (ATEX pump) is a pump-and-motor assembly designed to operate safely in environments containing flammable vapors or gases, by containing internal sparks, heat, and faults so they cannot escape and trigger an ignition. When pumping solvents, fuels, paints, acetone, or other low-flash-point liquids, an ATEX/IECEx-certified explosion-proof motor paired with a static-electricity-eliminating grounding system is a mandatory requirement to remove ignition sources. This article explains how to read Ex classification codes, how to select the appropriate temperature class, and key technical considerations when deploying in a factory.
A pump assembly is considered “explosion-proof” when both the motor and the grounding path are certified for the specific hazardous area. The following are the key parameters to verify before placing an order.
- Ex db IIB T5 Gb — ATEX/IECEx code describing the protection type, gas group, and surface temperature class.
- Class 1 Div 1 Group D — North American (NEC) hazardous area classification for flammable gases/vapors.
- T3 / T4 / T5 — maximum surface temperature class of the motor; select based on the auto-ignition temperature of the chemical.
- Grounding lug — integrated grounding terminal to bond the motor, pump tube, and container, eliminating static electricity.
- CE · ATEX · IECEx · QPS — applicable certification systems depending on market and inspection requirements.
What Is an Explosion-Proof Pump and Why Is It Necessary?
Controlling the Ignition Source, Not Resisting External Fire
Many people mistakenly believe “explosion-proof” means an external fire-resistant housing. In reality, an explosion-proof motor is designed to contain all internal faults — sparks from carbon brushes, heat generated under overload — preventing them from escaping and becoming an ignition source for flammable vapors in the surrounding air. This is the principle of the “flameproof enclosure” (protection type Ex d), the core of all ATEX-compliant equipment.
When drawing flammable chemicals from a drum using a corrosion-resistant chemical pump or a standard drum pump, three hazards arise simultaneously: solvent vapors accumulate around the drum opening, flow friction generates static electricity, and the electric motor may produce sparks. A single sufficient heat source is enough to ignite a vapor-air mixture within the flammable concentration range.
!A standard electric motor (without Ex certification) placed beside an open solvent container is a serious safety violation — commutator sparks or winding heat can ignite acetone, ethanol, or toluene vapors in an instant.
How to Read ATEX/IECEx and Class/Division Classification Codes
Decoding “II 2G Ex db IIB T5 Gb”
The nameplate classification code precisely indicates the zones in which the motor is permitted to operate. Breaking down the code II 2G Ex db IIB T5 Gb:
- II — equipment group for surface industries (not mining).
- 2G — category 2, Gas environment where explosive vapors may be present during normal operation.
- Ex db — “flameproof enclosure” protection type (explosion-proof housing), containing internal combustion.
- IIB — gas group (includes ethylene and many industrial solvents).
- T5 — maximum surface temperature 100°C; T4 corresponds to 135°C, T3 to 200°C.
- Gb — high Equipment Protection Level (EPL), suitable for Zone 1.
Two parallel classification systems exist: the North American (NEC) system uses Class / Division / Group, while the European-international (ATEX/IECEx) system uses Zone / Group / Temperature Class. When importing equipment into Vietnam, both systems are accepted provided the corresponding valid certification is available.
| Criterion | North American System (NEC) | ATEX / IECEx System |
|---|---|---|
| Hazardous Area | Class 1, Division 1 | Zone 0 / Zone 1 |
| Typical Gas Group | Group D | IIB |
| Temperature Class | T3 (200°C) | T4 (135°C) / T5 (100°C) |
| Example Certification | QPS | CE, ATEX, IECEx |
Selecting the Temperature Class and Grounding Based on the Chemical
The Temperature Class Must Be Below the Fluid’s Auto-Ignition Temperature
The principle for selecting the temperature class is straightforward: the maximum surface temperature of the motor (T-class) must be lower than the auto-ignition temperature of the chemical being pumped. For example, for a solvent with an auto-ignition temperature of around 200°C, a T5 motor (≤100°C) provides a wider safety margin than a T3 (≤200°C). In high-ambient-temperature environments, a high-temperature version rated T4 should be selected to maintain the safety margin.
Beyond the temperature class, grounding and bonding is a factor that is often overlooked. When liquid flows through the pump tube, friction generates static charges that can produce sparks between isolated conductors. An integrated grounding lug allows the motor, pump tube, and container to be bonded into a single equipotential unit, eliminating static charge accumulation.
- Identify the flash point and auto-ignition temperature of the chemical from its MSDS sheet.
- Select a T-class with a safety margin below the auto-ignition temperature.
- Ensure motor–tube–container bonding before operation.
- Verify that the gas group (IIB / Group D) matches the solvent type.
!The rated flow rate of an explosion-proof pump is typically reduced when pumping flammable substances to lower flow velocity and static generation. Do not use the flow rate specifications for non-flammable substances as the design basis for a solvent pumping system.
Finish Thompson Solution: SX Series Explosion-Proof Motors
FINISH THOMPSON · USA SX Motor for Chemical Drum Pumps
Finish Thompson (USA) offers the SX series explosion-proof motors for drum pumps, a suitable option when transferring flammable chemicals from containers. The SX motor features a dual-speed design, weighs approximately 3 kg (6.6 lb), and comes equipped with an integrated grounding lug for bonding the motor–pump tube–container to eliminate static electricity.
The SX series is available in different certification configurations depending on the market and installation environment:
| Model | Enclosure | Certification | Classification |
|---|---|---|---|
| S1X | IP55 / TEFC | QPS | Class 1, Div 1, Group D · T3 |
| S2X | IP55 / TEFC | CE, ATEX, IECEx | II 2G Ex db IIB T5 Gb |
| S2X-HT | IP55 / TEFC | CE, ATEX, IECEx | II 2G Ex db IIB T4 Gb (high ambient temperature) |
In terms of flow rate, the SX motor delivers approximately 64.4 lpm (17 gpm) at high speed and 26.5 lpm (7 gpm) at low speed with non-flammable liquids; when pumping flammable substances, the flow rate is reduced to approximately 15.1 lpm (4 gpm) to minimize static generation. These configurations are suitable for many industries: aerospace, automotive, cosmetics, electronics, food and beverage, oil and gas, coatings, and pharmaceuticals.
Considerations for Deployment in Vietnamese Factories
From Equipment Selection to Safe Operation
An explosion-proof pump system is only safe when the entire chain — motor, pump tube, fittings, and grounding cable — is compliant. For continuous solvent applications, consider combining with sealless magnetic drive pump technology to eliminate the leakage point at the mechanical seal — where flammable vapors can escape. Refer to industrial chemical pump solutions to select wetted materials compatible with each chemical.
- Require the supplier to present the original ATEX/IECEx or QPS certificate and verify that the certificate number matches the nameplate.
- Cross-reference the T-class against the auto-ignition temperature of the chemicals used in the plant.
- Install and inspect the grounding–bonding system before each operating shift.
- Select wetted tube materials (PP, PVDF, ETFE, SS316) compatible with the chemical to prevent corrosion-induced leakage.
- Train operators on grounding procedures and flow rate limits for flammable substances.
TKT Pumps is the authorized distributor of Finish Thompson in Vietnam, with over 19 years of experience, more than 12,000 projects, and a warehouse of over 5,000 spare parts, providing 24/7 technical support to advise on explosion-proof configurations that meet your factory’s safety standards.
Frequently Asked Questions
What is an ATEX explosion-proof pump?
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An ATEX explosion-proof pump is a pump-and-motor assembly certified to operate safely in environments containing flammable vapors or gases. The motor is designed to contain internal sparks and heat (protection type Ex d), combined with a grounding system to eliminate static electricity, so it does not become an ignition source when pumping solvents, fuels, paints, or low-flash-point chemicals.
What does the code “Ex db IIB T5 Gb” mean?
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This is the ATEX/IECEx classification code: “Ex db” is the flameproof enclosure protection type, “IIB” is the gas group (covering many industrial solvents), “T5” is the maximum surface temperature of 100°C, and “Gb” is the high protection level suitable for Zone 1. This code indicates the hazardous zones in which the motor is permitted to operate.
How do I select between temperature class T3, T4, or T5?
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The maximum surface temperature of the motor must be lower than the auto-ignition temperature of the chemical: T3 ≤ 200°C, T4 ≤ 135°C, T5 ≤ 100°C. A higher class number (T5) means a lower surface temperature and a wider safety margin. In high-temperature environments, a high-temperature version rated T4 is recommended.
Why must the flow rate be reduced when pumping flammable substances?
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Higher flow velocity produces greater friction and static electricity, increasing the risk of sparking. Therefore, the rated flow rate when pumping flammable substances is reduced compared to non-flammable ones. For example, the SX motor delivers approximately 26.5 lpm with non-flammable substances but is reduced to approximately 15.1 lpm when pumping flammable substances.
Why is grounding required when pumping chemicals?
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As liquid flows through the tube, friction accumulates static charges that can produce sparks between isolated conductors. An integrated grounding lug allows the motor, pump tube, and container to be bonded into a single equipotential unit, eliminating static electricity before it can cause ignition.
What applications is the Finish Thompson SX motor suitable for?
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The SX series explosion-proof motor is designed for drum pumps and is suitable for the aerospace, automotive, cosmetics, electronics, food and beverage, oil and gas, coatings, and pharmaceutical industries. Three configurations are available: S1X (QPS), S2X (CE/ATEX/IECEx T5), and S2X-HT (T4, high ambient temperature).
Need advice on ATEX explosion-proof pump configurations for flammable chemicals? The TKT Pumps technical team assists in selecting the temperature class, gas group, and wetted materials appropriate for your factory’s safety standards.
Submit a Consultation Request or hotline 0941.400.488
Technical source: Finish Thompson Inc. product documentation (SX series explosion-proof motors for drum pumps). Compiled and localized by TKT Pumps for operating conditions in Vietnam.
