Cosmos Pumps supplied 8 CDW High Head submersible dewatering units to a civil contractor working on an underground metro corridor in North India, where groundwater ingress at excavation depths of 18 metres required continuous dewatering at heads up to 24 metres to keep excavation faces operational. The project ran for 16 months without a single excavation shutdown attributable to pump failure, removing a total of 52,000 cubic metres of groundwater from active excavation points across the corridor.
Written by Cosmos Pumps Engineering Team
The Challenge
Underground metro corridor construction in North India placed civil contractors below the water table from the first weeks of excavation. At depths of 18 metres below grade, groundwater inflow is continuous and does not pause for equipment changes or shift changes. Each excavation face requires dedicated dewatering capacity — a gap in coverage floods the face within hours and sets the project back by at least a day of recovery pumping before work can resume.
The contractor’s selection criteria came down to three requirements. First, head range: with excavation depths at 18 metres and discharge points at ground level, pumps needed to sustain flow at working heads between 18–28 metres across the different stations. Standard-head submersible pumps — those rated to 86 metres maximum — could not cover the deeper excavation stations. Second, solids handling: groundwater entering the excavation carried fine construction silt with suspended solids up to 12 mm, putting abrasive wear on impellers from the first hour of operation. Cast iron impellers on comparable projects had required replacement at intervals that drove unplanned downtime. Third, site maintainability: on a multi-station excavation, a pump returned to the workshop for repair leaves an excavation face at risk for the duration. The contractor needed pumps their own site team could service at the pit head.
The CDW High Head range met all three requirements.
Our Solution
Cosmos Pumps supplied 8 CDW High Head units deployed across 5 active excavation stations on the metro corridor. The CDW High Head operates at shut-off heads of 40 to 140 metres, covering the full range of the site’s excavation depths within a single pump model — no secondary units needed for deeper stations.
Before the first unit went down, the Cosmos technical team adjusted the wear plate gap on each pump to the specific particle size of the site’s silt load. This calibration, which takes under 30 minutes per unit, reduces abrasive impeller wear by allowing the correct clearance between the wear plate and impeller face. The nitride-hardened SS-410 impellers — hardened to HRC 52–55 — were the primary reason Cosmos was specified over alternatives using cast iron impellers. Cast iron at the same hardness number runs approximately one-third the wear life of nitride-hardened stainless steel in silt-laden water; on a project of this duration, that difference directly drives unplanned downtime.
A site parts depot was established with spare seal kits, wear plates, and impeller assemblies, enabling the contractor’s maintenance team to complete field service without transport back to Faridabad. Cosmos stationed a support technician on site for the first 3 weeks of deployment to certify the site team on service procedures.
CosmoSmart IoT monitoring was installed on 4 primary units at the deepest excavation stations. The project dewatering supervisor received real-time running data and automatic service alerts, reducing physical site inspections at excavation depth to planned intervals rather than reactive checks.
Pump Specification
| Parameter | Value |
|---|
| Pump model | Cosmos CDW High Head Submersible Dewatering Pump |
| Units deployed | 8 |
| Working head at site | 24 metres |
| Flow rate per unit at working head | 1,400 LPM |
| Shut-off head capacity | 40 M – 140 M |
| HP per unit | 15 HP |
| Impeller material | Nitride-hardened SS-410 (HRC 52–55) |
| Insulation | Class H (180°C) |
| Solid handling | Up to 12 mm suspended solids |
| Special features | Adjustable wear plate gap, CosmoSmart IoT monitoring |
Results
Over 16 months of continuous operation, the CDW High Head units dewatered 52,000 cubic metres of groundwater from the active excavation corridor. Key outcomes:
- Excavation shutdowns attributable to pump failure: 0
- Total groundwater removed: 52,000 m³
- Wear part replacement interval achieved: 1,200 hours — approximately three times the cast iron baseline the contractor had planned for
- Unplanned downtime events: 0
Impeller wear inspection at the 1,200-hour service mark showed less than 0.25 mm of impeller face wear — approximately one-third of the wear profile the contractor had budgeted for based on prior experience with cast iron impellers at comparable dewatering heads.
“The field-serviceable design and the pre-positioned parts depot let our site team keep multiple excavation faces running simultaneously without specialist pump support on call at each station — that was the difference between hitting our programme and losing weeks to recovery pumping.”
— Project Dewatering Engineer, Civil Contractor, North India
For CDW High Head specifications and flow/head curves, see the CDW High Head product page.
For metro and tunnel dewatering project enquiries: +91 99333 22238 | cosmos@cosmospumps.com
