QDX Submersible Clean Water Pump for Home, Farm & Drainage

Introduction: The Benchmark in Portable Submersible Pumping

The QDX series submersible clean water pump is a compact, integrated pump-motor unit engineered for shallow-water extraction, drainage, and irrigation where portability, simplicity, and economic efficiency are paramount. Designed in accordance with JB/T 10179-2016 and IEC 60034-1 standards, the QDX series features a dry-type motor architecture with the motor cavity hermetically sealed from the pumped fluid, distinguishing it from oil-filled (QY) or water-filled alternatives.

With power ratings from 0.37 kW to 2.2 kW, flow capacities from 1.5 m³/h to 65 m³/h, and heads up to 60 meters, the QDX series serves the complete spectrum of household water supply, garden irrigation, agricultural drainage, and light industrial dewatering requirements.

1. Motor Architecture: Dry-Type Design & Thermal Performance

1.1 Dry-Type Motor Principle

The defining engineering characteristic of the QDX series is its dry-type motor construction. Unlike oil-immersed (QY) or water-filled submersible motors, the QDX motor cavity contains only air and is hermetically isolated from the external pumped fluid by a dual mechanical seal system. This architecture provides:

• Simplified maintenance: No oil replacement or water-circuit flushing required
• Reduced weight: Elimination of oil mass enables lighter, more portable units
• Direct cooling: Motor heat is dissipated through the external motor housing to the surrounding water bath

The thermal equilibrium of the dry-type motor is governed by convective heat transfer from the stator windings to the motor housing:

Q_thermal = h_water × A × (T_housing − T_fluid)

Where: 
Q_thermal = Heat dissipation rate (W) 
h_water = Convective heat transfer coefficient in water (~500–1500 W/m²·K) 
A = External motor housing surface area (m²) 
T_housing = Motor housing surface temperature (°C) 
T_fluid = Ambient fluid temperature (°C)

Critical Design Constraint: The dry-type motor requires continuous submersion to maintain adequate cooling. Operation above the water surface or in partially exposed conditions will result in rapid temperature rise and thermal protector activation.

1.2 Built-In Thermal Protection

QDX series single-phase motors incorporate a thermal overload protector embedded directly in the motor winding. This bimetallic device monitors winding temperature in real-time, automatically disconnects power when temperature exceeds safe thresholds, and self-resets after the motor cools to acceptable levels.

The thermal protection activation temperature is calibrated to Class B insulation limits (130°C maximum), providing a safety margin against insulation degradation per the Arrhenius degradation model:

Insulation Life ∝ e^{(−E_a / (k × T))}

Where: 
E_a = Activation energy for insulation degradation 
k = Boltzmann constant 
T = Absolute winding temperature (K)

This exponential relationship underscores why thermal protection is critical: every 10°C increase above rated temperature approximately halves insulation life.

2. Hydraulic Fundamentals: Pump Performance Equations

2.1 Hydraulic Power & Pump Efficiency

P_hydraulic = (ρ × g × Q × H) / (1000 × η_p)

Where: 
ρ = Fluid density (kg/m³); 1000 kg/m³ for clean water 
g = 9.81 m/s² 
Q = Flow rate (m³/s) 
H = Total dynamic head (m) 
η_p = Pump hydraulic efficiency (decimal)

Practical Calculation Example: 
For a QDX1.5-32-0.75 pump operating at rated conditions (Q=1.5 m³/h = 0.000417 m³/s, H=32 m), with estimated η_p=0.45: 
P_hydraulic = (1000 × 9.81 × 0.000417 × 32) / (1000 × 0.45) ≈ 0.29 kW 
The installed 0.75 kW motor provides a service factor of ~2.6, ensuring reliable startup under voltage fluctuation and wear-induced efficiency degradation.

2.2 System Head Calculation

H_total = H_static + H_friction + H_velocity

Darcy-Weisbach Friction Loss:

H_f = f × (L / D) × (v² / (2g))

Velocity Head:

H_v = v² / (2g)

For QDX series applications, recommended discharge velocities range from 0.5 to 2.0 m/s to balance hydraulic efficiency against noise and erosion considerations.

2.3 Specific Speed & Impeller Classification

N_s = n × √Q / H^0.75

Where: 
N_s = Specific speed (metric units) 
n = Rotational speed (RPM); QDX series operates at 2860 RPM (2-pole, 50 Hz) 
Q = Flow at Best Efficiency Point (m³/s) 
H = Head at Best Efficiency Point (m)

For the QDX series, typical N_s values range from 300 to 2500, indicating single-suction, radial-to-mixed-flow impellers optimized for the low-power, moderate-head application space.

3. QDX Series Technical Specifications

3.1 General Operating Parameters

3.2 Model Nomenclature

The QDX series model designation follows a systematic coding convention: 
QDX [Flow]-[Head]-[Power]

Example: QDX1.5-32-0.75 
QDX: Single-phase dry-type submersible pump 
1.5: Rated flow = 1.5 m³/h 
32: Rated head = 32 m 
0.75: Motor power = 0.75 kW

QX [Flow]-[Head]-[Power]: Three-phase dry-type submersible pump (380 V)

Suffix Codes:

• F: Float switch equipped (automatic level control)
• T: Thermal protector enhanced version
• S: Stainless steel construction
• TF: Float switch with thermal protection

4. Performance Data Tables

4.1 Single-Phase QDX Series: 0.37 kW – 0.75 kW

The most commonly specified range for household water supply, garden irrigation, and small-scale drainage.

4.2 Single-Phase QDX Series: 1.1 kW – 1.5 kW

Suitable for medium-scale irrigation, water tower supply, and construction dewatering.

4.3 Three-Phase QX Series: 0.75 kW – 2.2 kW

Engineered for agricultural cooperatives, small industrial processes, and three-phase power installations.

Note: All performance data represents nominal values at rated voltage, frequency, and clean water conditions (ρ = 1000 kg/m³, 20°C). Actual field performance varies with fluid properties, system geometry, and wear state. Head range indicates the recommended operating envelope for optimal efficiency and reliability.

5. Structural Design & Sealing Technology

5.1 Integrated Pump-Motor Architecture

The QDX series features a vertically integrated "pump-over-motor" design:

• Pump section (lower): Single-stage centrifugal impeller with volute casing; positioned below the motor to ensure priming and prevent air locking
• Motor section (upper): Dry-type single-phase or three-phase asynchronous motor with sealed stator cavity
• Seal interface: Dual mechanical seal assembly separating the pump hydraulic chamber from the motor dry cavity

5.2 Mechanical Seal System

5.3 Impeller & Hydraulic Design

Impeller geometry is optimized for the low-specific-speed regime, delivering stable head-flow curves with minimal hysteresis, non-overloading power characteristics across the recommended operating range, and reduced NPSH requirements for shallow submergence applications.

6. Application Engineering & Selection Guidelines

6.1 Duty Point Selection

The optimal pump selection positions the system operating point within the recommended head range specified for each model. The recommended operating range is defined as:

H_min ≈ 0.7 × H_rated to H_max ≈ 1.2 × H_rated

Critical Warning: If the actual operating head is significantly below the rated head (e.g., using a QDX1.5-32-0.75 in a system requiring only 5 m head), the pump will operate at excessive flow, causing motor overload and thermal protector tripping, cavitation at the impeller inlet, and accelerated mechanical seal wear. Conversely, if the actual head exceeds the rated head, flow will be insufficient for the application requirement.

6.2 NPSH & Cavitation Assessment

NPSH_a = (P_atm - P_vapor) / (ρg) + H_submergence - H_{friction,suction}

NPSH_a ≥ NPSH_r + 0.5 m (minimum safety margin)

For QDX series pumps operating in shallow sumps or wells: 
Minimum submergence: 0.5 m above pump base to prevent vortex formation 
Maximum submergence: 5 m (limited by cable length and motor pressure rating) 
Clearance from bottom: ≥0.5 m to prevent silt ingestion

6.3 Typical Application Scenarios

7. Material Selection & Corrosion Resistance

7.1 Standard & Optional Material Configurations

Special Execution Codes: 
S suffix: Full stainless steel construction (wetted parts in 304/316 SS) 
F suffix: Float switch equipped for automatic level control 
T suffix: Enhanced thermal protection for high-duty-cycle applications

8. Installation, Operation & Maintenance

8.1 Installation Requirements

8.2 Float Switch Operation (F Suffix Models)

Float switch equipped models enable automatic level control:

The float switch differential (hysteresis) is typically 150–300 mm, preventing rapid cycling and extending contactor life.

8.3 Maintenance Protocol

9. Ordering Information & Custom Engineering

9.1 Required Specification Data

9.2 Custom Engineering Options

• Special voltage/frequency: 110 V, 127 V, 240 V; 60 Hz designs for export markets
• Extended cable: Custom lengths up to 30 m with submersible-rated H07RN-F insulation
• Stainless steel construction: Full 304/316 SS wetted parts for potable water and corrosive applications
• High-temperature execution: Up to 60°C fluid temperature with Class F insulation
• Abrasive-resistant impeller: Hardened aluminum or cast iron for sandy water conditions
• Double mechanical seal: Enhanced seal arrangement for extended MTBF in critical applications

10. Why Choose QDX Series for Your Water Management Needs?

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