High Head Dewatering Pump — CDW Series | 40–140 M Head

What is a CDW High Head Dewatering Pump?

The CDW High Head is a submersible dewatering pump rated 5–75 HP with shut-off heads of 40–140 M and flow rates of 350–2,200 LPM. It is designed for mine dewatering, tunnel construction, and high-head building projects where the standard CDW series (max 86.5 M) is insufficient.

Where a conventional submersible dewatering pump reaches its pressure limit at moderate pit depths, the CDW High Head’s 2-stage impeller design sustains discharge pressure across significantly deeper sumps — making it the correct selection for open-cast mines, hydro-civil tunnels, and deep basement excavations that exceed 80 M depth. For a complete overview of the full submersible dewatering pump range, see the category page.

CDW High Head — At a Glance

Where CDW High Head Fits in the Submersible Dewatering Range

The CDW series is structured as three distinct head bands to allow precise motor sizing without over-specifying for shallow sites:

• CDW Standard (1.5–50 HP, up to 86.5 M): General construction, basements, and infrastructure sites where TDH does not exceed 80 M.
• CDW High Head (5–75 HP, 40–140 M): Mine pits, railway tunnels, highway underpasses, and high-head civil structures where TDH falls between 80 M and 140 M.
• CDW Ultra High Head (50–120 HP, 90–200 M): Very deep underground mines, hydroelectric shafts, and long-run tunnel drainage where TDH exceeds 140 M.

Specifying the correct band prevents the two most common site failures: under-specifying head (causing the pump to dead-head and overheat) and over-specifying HP (inflating power costs and reducing flow-curve efficiency at normal operating points). The CDW High Head is the correct selection when the site TDH falls reliably above the standard CDW’s 86.5 M ceiling.

The CDW High Head is part of the broader dewatering pump guide which covers the complete selection hierarchy from standard head through to ultra high head models.

CDW High Head HP Selection — Complete Range

The table below covers the full CDW High Head range from 5 HP to 75 HP. Select the model whose maximum head comfortably exceeds your calculated Total Dynamic Head (TDH) — see the calculation guide in the next section.

Note: For dewatering heads above 140 M, the CDW Ultra High Head (50–120 HP, 90–200 M) is the correct upgrade path. Both series use SS316 impellers and CI FG 300 motor bodies for compatibility in abrasive site conditions.

How to Calculate Dewatering Head for Mine & Tunnel

Correct pump selection depends on calculating the Total Dynamic Head (TDH) before specifying motor HP. Under-sizing the head leads to pump overload and premature seal failure; over-sizing wastes capital and energy. The three-component TDH formula below aligns with the HowTo steps in the structured data for this page.

Step 1 — Calculate Total Dynamic Head (TDH)

The TDH formula for submersible mine and tunnel dewatering is:

TDH = Static Head + Friction Losses + Velocity Head

• Static Head: Vertical distance (metres) from the pump inlet (lowest sump level) to the discharge outlet at surface or drainage channel level.
• Friction Losses: Pressure drop due to pipe diameter, length, bends, and fittings. For 50–100 M discharge runs with 100–150 mm pipe, budget 15–20% of static head. Use the Darcy-Weisbach equation for precise projects.
• Velocity Head: Typically 1–3 M for submersible dewatering applications. Use 2 M as a conservative default.

Step 2 — Estimate Peak Inflow Rate

Head alone does not determine pump selection — the dewatering pump must also move sufficient volume to keep pace with groundwater inflow. Calculate peak inflow Q (litres per minute) using the rational method:

Q = C × I × A / 6

• C — Runoff coefficient (dimensionless): 0.9 for hard rock mine floor; 0.6–0.7 for fractured rock or exposed clay; 0.3–0.5 for stable overburden
• I — Rainfall intensity (mm/hour): Use 50-year return period for permanent dewatering sumps; 10-year for temporary construction
• A — Catchment area (hectares): The plan area draining to the sump, including open pit benches and any surface runoff paths
• The factor 6 converts the result from m³/hour to LPM (× 1,000 / 6)

Select a CDW High Head model with a rated flow at the required TDH that is ≥ 110% of peak inflow Q. The 10% buffer accounts for impeller wear over a 12-month operating cycle and minor calculation uncertainty. For mines with multiple independent sump levels, calculate Q per sump and size each pump individually — do not aggregate catchment areas across separate drainage zones.

Step 3 — Apply Safety Factor to TDH

Always multiply the calculated TDH by a safety factor of 1.10–1.15 to account for:

• Sediment accumulation reducing effective pipe bore over time
• Variation in peak inflow during monsoon or high-water events
• Actual pump curve deviation from rated performance at elevated temperatures
• Future bench deepening or tunnel extension increasing static head mid-contract

Step 3 — Select HP from the CDW High Head Range

Match the safety-factored TDH and required flow rate to the CDW High Head table. Select the model whose rated maximum head exceeds your TDH by at least 10–15 M to keep the pump operating in the efficient mid-curve zone rather than near shut-off.

Worked Example: 80 M Open-Cast Mine Pit

Selection outcome: At 108 M design TDH, the CDW HH 50 HP (max head 125 M) is the correct selection — it covers the required head with a 17 M operating margin, keeping the pump well within its efficient curve range. If peak inflow exceeds 1,800 LPM, deploy two CDW HH 40 HP units in parallel to match flow without compromising head capacity.

For deeper dewatering above 140 M TDH, see the CDW Ultra High Head (90–200 M).

CDW High Head vs CDW Ultra High Head — When to Use Each

Both series are submersible dewatering pumps engineered for demanding mine and tunnel conditions, but they serve distinct depth and flow envelopes. Use the table below to determine the correct series for your project TDH.

Decision rule: If your design TDH falls between 40 M and 140 M, specify the CDW High Head. If TDH exceeds 140 M or your project requires flows above 2,200 LPM at high head, the CDW Ultra High Head (90–200 M) is the appropriate upgrade. Both series use the same SS316 impeller material, CI FG 300 motor body, and SiC mechanical seals — reducing spare-part inventory complexity on multi-series sites.

CDW High Head Applications

The CDW High Head is deployed across a range of high-head civil and industrial dewatering scenarios. The matrix below maps typical Total Dynamic Head requirements to recommended HP for each primary application sector. For detailed project-level support across mine dewatering applications, consult the application engineering team.

For rental deployment across mine and tunnel projects, the CDW High Head is available through the dewatering pump rental fleet — covering short-duration mobilisations, standby hire, and emergency response deployments.

CDW High Head Technical Features

The CDW High Head is engineered to sustain continuous operation in abrasive, high-pressure dewatering environments. Each specification below directly addresses a failure mode common in under-specified high-head submersible pumps.

Hydraulic Assembly

• 2-Stage SS316 Impeller: Dual-stage impeller stack generates the pressure differential required for 40–140 M head without cavitation at operating point. SS316 grade resists abrasion from suspended solids (4–12 mm) and mild saline groundwater.
• Anti-Corrosive SS316 Strainer: Prevents oversized solids from entering the impeller while resisting chemical attack in acidic mine water (pH 5–8).

Motor & Mechanical Construction

• CI FG 300 Motor Body & Wetted Parts: High-grade cast iron provides structural rigidity and thermal mass for sustained deep-submersion operation.
• SS431 High-Torsional-Strength Shaft: Designed to transmit the elevated torque loads generated by 2-stage impellers at 50–75 HP without shaft deflection or fatigue failure during surges.
• Class H Insulation (180°C rated): Motor windings tolerate the elevated temperatures generated during continuous high-head pumping, with thermal sensor for overload protection.
• Naturally Cooled Motor: The motor is cooled by the surrounding pumped fluid, eliminating the need for an external cooling jacket and simplifying installation in confined sumps.

Sealing System

• Dual SiC vs SiC Mechanical Seals: Silicon carbide face seals on both primary and secondary positions provide superior abrasion resistance compared to TC vs TC seals in mineral-laden water. Dual arrangement ensures motor protection if the primary seal is compromised.
• Viton Rubber Parts: Fluoroelastomer O-rings and gaskets tolerate saline groundwater, mild chemical contamination, and coastal construction environments where standard EPDM rubber degrades.

Installation & Connectivity

• 20 m Power Cable: Heavy-duty submersible-rated cable provides sufficient reach for typical mine sump configurations without requiring cable extensions that introduce connection risk.
• Vertical + Horizontal Installation: The motor’s natural cooling design and balanced shaft assembly support both vertical and horizontal mounting — critical for inclined tunnel floors and restricted-geometry sumps.

Pre-Start Commissioning Checklist

The following site checks should be completed before starting any CDW High Head unit for the first time or after extended storage:

1. Megger test motor insulation resistance — Must read ≥ 1 MΩ at 500 V DC before energising. Values below 0.5 MΩ indicate moisture ingress or damaged cable insulation; dry out or replace before use.
2. Check rotation direction — Momentarily start the pump and verify impeller rotation matches the direction arrow cast on the motor body. Reversed rotation reduces head by approximately 30% and causes premature bearing load.
3. Verify sump depth > 0.5 m above pump inlet — Minimum submersion prevents air entrainment and vortexing, which destabilises pressure at the 2-stage impeller. For high-sediment sumps, raise pump 0.3 m off the floor using the discharge stand.
4. Confirm cable entry gland integrity — Visually inspect the cable gland compression ring before lowering. A weeping gland is the primary cause of motor winding failure in submersible dewatering pumps on long-duration mine sites.
5. Record baseline amperage — Log full-load current at start-up against the nameplate full-load amps (FLA). A reading > 10% above FLA indicates pump deadheading against closed valve, excess head, or blocked strainer.

For planned maintenance schedules and spare-part kits (seal kit, wear part kit, instant service pack), contact the application engineering team or request through the dewatering pump rental service desk.

Size Your CDW High Head Pump with iDEWA

iDEWA is an AI-powered dewatering advisor that takes your project parameters — pit depth, inflow rate, pipe layout, and water type — and returns a validated CDW High Head model recommendation with TDH calculation and sizing rationale. It is available at no cost for qualifying infrastructure, mining, and tunnelling projects.

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Frequently Asked Questions

What is the maximum head for the CDW High Head pump?

The CDW High Head series reaches a shut-off head of 140 M at 75 HP, compared to 86.5 M for the standard CDW series. For dewatering depths above 140 M, the CDW Ultra High Head (90–200 M) is the correct choice.

Can CDW High Head pumps be used for mine dewatering?

Yes. The CDW High Head is specifically engineered for mine dewatering pits up to approximately 120 M deep. It handles dirty, muddy water with suspended solids up to 12 mm at specific gravities up to 1.1, which covers most open-cast and underground mine sumps. For comprehensive information on mine-specific applications, see mine dewatering applications.

What is the difference between CDW and CDW High Head?

The standard CDW covers 1.5–50 HP with max head of 86.5 M. The CDW High Head covers 5–75 HP with max head of 140 M. Both handle the same water types (dirty, muddy, SG ≤ 1.1, solids ≤ 12 mm), but the CDW High Head uses a higher-pressure 2-stage impeller design for deeper applications. Use the standard CDW for construction sites and basements where TDH is below 80 M; upgrade to the CDW High Head where TDH exceeds 80 M.

How deep can the CDW High Head pump from a mine pit?

With a maximum shut-off head of 140 M (at 75 HP), the CDW High Head suits mines and tunnels up to approximately 120 M deep, accounting for friction losses and safety margins in the TDH calculation. For pits exceeding 120 M effective depth, the CDW Ultra High Head (max 200 M) is recommended.

Does the CDW High Head work for tunnel dewatering?

Yes. Tunnel dewatering typically requires 60–140 M TDH depending on tunnel depth and pipe routing. The CDW High Head range (40–140 M, 5–75 HP) covers most road, railway, and metro tunnel dewatering applications. The 2-stage impeller and SS431 shaft provide the sustained pressure required for continuous tunnel pumping over multi-month construction schedules.

Is the CDW High Head suitable for saline groundwater?

The CDW High Head uses SS316 impellers, Viton rubber parts, and an anti-corrosive SS316 strainer, making it suitable for mildly saline groundwater encountered in coastal construction sites, land reclamation projects, and near-shore tunnels. For highly corrosive or chemical-bearing effluents, contact the application engineering team for material-of-construction recommendations.