Ebara DRD Wastewater Lift Pump

The Ebara DRD is a submersible wastewater pump for soiled liquids and sewage in civil and industrial systems. Ebara also puts it on liquids with filamentary substances or solid particles, on emptying tanks, and in its manual on mud and light agricultural sewage. The range is metric and 50 Hz throughout, with flanges to EN 1092-2 and voltage at 400/690 V.

The width of the range is the reason to look at it. Sizes from the 65DRD to the 350DRD, motors from 2.7 kW to 85 kW, and four pole counts. That last one matters more than the catalogue makes it look. Abrasive media want pumping slowly, and a slow pump is a selection constraint that never shows up on a performance curve. Where grit is doing the damage, the 6-pole and 8-pole builds at 950 rpm and 750 rpm are the reason to be looking at a DRD rather than something that only comes at 1,450 rpm.

There is a real limit on the other side of the curve, and Ebara states it plainly. The DRD cannot be run at heads below the lowest point on its published characteristic curve, because the motor overloads there. This is the mirror image of the sizing mistake that lands on the desk most often. Everyone in the chain adds a little margin, the pump is specified far bigger than the duty, and it then runs off the end of its curve. On a DRD the penalty is not just poor efficiency. It is an overloaded motor.

Cast iron sets the chemistry. Casing, suction cover and motor frame are EN-GJL-250 cast iron, the impeller EN-GJS-250, the shaft AISI 420B stainless. Ebara's manual also rules the DRD out of environments with a risk of explosion and out of flammable liquids. If your sump is a classified hazardous area, ask us for a pump certified for the zone instead.

A multi-channel impeller is not a macerator. It passes what fits through the channel and it binds on what does not. Where a station is putting more rag through than the free passage can take, the answer is screening or maceration upstream, not a larger pump. That is a system change rather than a pump change, and it is the one that holds.

The Ebara DRD draws through a flanged suction, works the medium with a two- or three-channel cast iron impeller, and discharges through a second flange. Both connections are to EN 1092-2. Ebara tests the range to ISO 9906 Annex A.

Sizes, poles and speed

Ebara publishes a separate specification and selection chart for each DRD size, each with its own pole options and power band. Speed follows the pole count directly: 2 poles gives 2,850 rpm, 4 poles 1,450 rpm, 6 poles 950 rpm and 8 poles 750 rpm.

Designations look like 150DRD530T4BG. The 5 in that string is Ebara's frequency digit for 50 Hz across the D Series. If you are matching an existing pump, send us the whole designation and the serial number off the nameplate rather than the size.

The motor

The DRD motor is an asynchronous squirrel cage machine, insulation class H at 180°C, IP68, dry and cooled by the liquid around it. Supply is three-phase 400/690 V ±10% at 50 Hz, with the frequency tolerance given as -5/+3%. Starting is direct on line or star-delta. Ebara allows a maximum of 5% voltage unbalance between phases, in line with CEI EN 60034-1, and rates the motor for a maximum of 15 starts an hour at regular intervals. Overload protection and a humidity probe are fitted across most of the range. Cable is 10 m of neoprene H07RN/F.

A cooling jacket version is available. Ebara's manual is specific about what that buys you: with the jacket the pump can work continuously at full load in a dry installation, or with the diffuser completely submerged. Without it, the liquid level has to stay above the midpoint of the stator housing for continuous full-load running.

Seal, oil and bearings

The DRD runs an oil-lubricated single spring single mechanical seal with a lip seal behind it. Faces are silicon carbide against silicon carbide on the pump side, carbon against ceramic on the motor side, with nitrile o-rings and lip seal. Bearings are oversized and life-lubricated; the 4-pole builds and some of the slower ones use an oversized double ball bearing with greasers.

The oil chamber carries a water infiltration detector. It reports when water in the oil passes 30%, which is your early warning that the seal is going. Change the oil at that point. If it trips again shortly afterwards, replace the mechanical seal rather than the oil, because the seal is what is letting the water in.

Installation and upkeep

Ebara catalogues two installation arrangements for the DRD. The lowering device drops the pump onto a coupling foot fitted with two guide tubes, so it can be lifted for inspection without breaking into the pipework. The support foot version takes a flexible hose, a handle and a supporting foot for portable use. Where more than one pump shares a sump, Ebara requires an automatic alternating system, which is the duty and standby arrangement a UK station runs anyway. Maximum immersion depth is 20 m. Ebara asks for an inspection at least once a year, more often on hard duties, and a full overhaul by a qualified mechanic every three years under normal working conditions.