Ebara 3S series Coupled Stainless End Suction Pump

Buy the Ebara 3S when the motor matters more than the footprint. Ebara builds its stainless 3 series in three drive arrangements, and the hydraulics are identical across all of them. The 3M is the monobloc, the 3S runs a rigid coupling to an IEC standard motor, and the 3P an elastic coupling. Nothing about that choice changes the duty the pump will do.

What it changes is the motor. On a 3S the motor is an ordinary IEC frame, flange-mounted IM B5 up to 2.2 kW and IM B35 from 3 kW. A 160M is a 160M whoever built it, so a failed motor is a stock replacement or a local rewind instead of a pump-specific order with a lead time on it. On plant where the pump has to be back on line the same week, that is usually the whole argument.

The second argument is the one that ends the discussion. Ebara offers an ATEX version of the 3S and the 3P and of nothing else in the range. If any part of the duty sits in a classified area, the monobloc is out and you are choosing between the 3SF and the 3PF.

Both of those come at a price, and it is alignment. A coupling has to be aligned when the set is installed and checked again after anything that separates it, including a seal change. A monobloc has no coupling and nothing to get wrong. If nobody on site is going to check alignment, you will get a longer life out of a 3M, however much better the 3S looks on paper.

Two more things before you order. Ebara rates the 3 series for clean water and moderately aggressive fluids, but AISI 304 and AISI 316L are different steels and the 3L series exists because of it, so tell us what is in the medium rather than what it is called. And send the real duty point. Ebara says not to run the pump below 10% of best efficiency point flow because of the overheating risk, and oversizing does the quieter damage: an oversized motor stays oversized, and you pay for it every hour it runs.

The Ebara 3S takes liquid in axially at the suction flange, throws it out through a closed impeller and discharges radially at the top of the casing. A single mechanical seal keeps the liquid off the shaft and sealed ball bearings carry it. The motor drives through a rigid coupling, and the whole set sits on a baseplate. Ebara tests the curves to ISO 9906:2012 Grade 3B with clean water at 20°C and a kinematic viscosity of 1 cSt, at about 2,900 rpm on the two-pole motor.

The motor is a standard IEC frame

The 3S drives through a rigid coupling to an ordinary IEC motor, flange-mounted IM B5 up to 2.2 kW and IM B35 from 3 kW. Ebara publishes the frame size against every model, so you know what you are buying before it arrives.

That is the practical difference from the monobloc: a 3M carries an Ebara motor, and a 3S carries a frame anyone makes. It also runs quieter, because the motor and its fan sit away from the hydraulics. A 40-200/11 is 74 dB(A) as a 3S and 80 dB(A) as a 3M, and a 32-200/7.5 is 72 dB(A) against 75 dB(A), measured as a mean of several readings at 1 m with a ±2.5 dB tolerance.

The cost is alignment. Ebara publishes coupling dimensions for every model, down to the set screw, which tells you this is a joint somebody has to set up properly. Get it wrong and the bearings and the seal pay for it, and the seal is what usually goes first.

The ATEX build is the 3SF

The standard 3S is not an ATEX pump. The ATEX build is a separate version, the 3SF, and Ebara publishes a separate data book and instruction manual for it. Ebara's own wording is that the 3(L)S series and 3(L)P series are available with ATEX certified hydraulics and motor.

The marking is II 2G Ex h IIC T3 to T4 Gb. That is Group II, Category 2G equipment for gas atmospheres, protected to EN 80079-36 and EN 80079-37 and certified for use in Zone 1 and Zone 2. Ebara deposited the technical file for type 3(L)SF and 3(L)PF with TÜV CYPRUS Ltd, notified body 2261, under ATEX Directive 2014/34/EU, on deposit 0205991 Rev.01. The 3SF is built in the same twelve sizes as the 3S.

The temperature class follows the medium, not the pump.

Two conditions come with it. Ebara specifies an ambient of -20°C to +40°C and atmospheric pressure of 0.8 to 1.1 bar for explosion-proof pumps. And the set only complies as a unit when the pump and its motor are both ATEX approved, so an ATEX pump on an ordinary motor is not an ATEX pump set. Tell us the zone and the gas group at enquiry and we will specify both halves.

The seal sets the temperature

Temperature limits on this pump belong to the mechanical seal, not the hydraulics. The standard ceramic, carbon and NBR seal runs -10°C to +90°C. The H, HS, HW and HSW builds, which put graphite, silicon carbide or tungsten carbide faces on FPM elastomers, take it to +110°C. The E build with EPDM runs -20°C to +120°C, and the Q1AEGG, U3U3EGG, Q1Q1EGG, Q1U3EGG and U3CEGG special sets reach +120°C.

One caveat is worth more than the ceiling. Where the medium is water and the elastomers are FPM, Ebara recommends holding the fluid to 75°C for a reasonable life out of the sealing parts. On a 3SF that ceiling matters twice over, because the fluid temperature is what fixes the temperature class.

Motors and efficiency

Motors are three-phase only and IE3 under Regulation 1781/2019, IP55, insulation class F with a class B temperature rise. Supply is 230/400 V ±10% up to 4 kW and 400/690 V ±10% from 5.5 kW. Two-pole and four-pole versions are catalogued; the two-pole runs at about 2,900 rpm. There is no single-phase 3S. Ebara offers single-phase on the monobloc 3M only, up to 2.2 kW.

The minimum efficiency index (MEI) is ≥0.7 on every size except 32-125 and 50-125 at ≥0.4 and 32-200 at ≥0.6. Those figures match the 3M and beat the 3P, which drops to ≥0.6 on the 40-125, 50-160, 65-160 and 65-200 and to ≥0.5 on the 32-200. If you are choosing between the two coupled builds on running cost, the 3S is the better of them.

Drinking water approvals

The 3S in its EPDM E build is approved for contact with drinking water under Italian Ministerial Decree 174/2004, on ICIM certificate ICIM-CAP-052120-00, covering the 3 series in sizes 32, 40 and 50 and running to the end of 2030.

For a UK potable duty, the approval you want is WRAS, and Ebara publishes that one for the 3ME, meaning the monobloc built with the E seal. A potable specification therefore points at the 3M rather than the 3S. Say so at enquiry and we will quote the right build.

Reading the designation

A 3S 65-200/22 is an AISI 304 rigid-coupling pump with a DN65 discharge, the 200 impeller and a 22 kW motor. An L before the version letter, as in 3LS, means the pump is built in AISI 316L instead, and the F suffix marks the ATEX version. Letters between the version and the size give the seal option: H, HS, HW, HSW or E. If you are matching an existing pump, send that string and the serial number off the nameplate.