Iwaki EHN Model Code Explained: Reading Every Position

EHN-BN11VCMKR-NAE-HC. That is the example Iwaki prints in its EHN brochure, and it looks like noise until you know the rules. Every Iwaki EHN model number is built position by position, and once you split it up you can read off the drive power, flow step, wetted materials, controller and any special version.

A lot of the enquiries we get are copied off an old nameplate. Dropping a character, or writing VS where it should say VC, happens all the time. Get the material wrong and the seals arrive unable to handle the chemical. Learning the rules beats memorizing part numbers.

Iwaki EHN Model Code for Standard Liquid Ends: Nine Positions

On the five standard liquid ends, VC, VS, PC, PS and PP, an Iwaki EHN model code runs to as many as nine positions.

Positions 1 to 3: series, drive, diaphragm size

• Position 1, EHN: the series, Iwaki's EHN electromagnetic metering pump.
• Position 2, BN or CN: the drive unit, defined by average power. BN is 20 W, CN is 24 W.
• Position 3, a number: effective diaphragm diameter. 11 means 10 mm, 16 means 15 mm, 21 means 20 mm, 31 means 30 mm and 36 means 35 mm.

A bigger diaphragm moves more liquid per stroke but holds less pressure. The BN11 tops out at 38 mL/min and 1.0 MPa, while the BN31 reaches 230 mL/min but only 0.20 MPa. With the same 16 or 21 diaphragm, CN pumps a bit more and holds a step more pressure. The CN16 is 80 mL/min at 1.0 MPa, the BN16 65 mL/min at 0.70 MPa.

Position 4: liquid end material, the one people copy wrong

In an Iwaki EHN model, the five material codes differ mainly in head, ball and seal materials:

1. VC: PVC head, alumina ceramic balls, FKM seats and O-rings;
2. VS: PVC head, balls equivalent to SUS316, EPDM seats and O-rings;
3. PC: GFRPP head, alumina ceramic balls, FKM seals;
4. PS: GFRPP head, balls equivalent to SUS316, EPDM seals;
5. PP: GFRPP head, alumina ceramic balls, PCTFE seats, FKM O-rings.

All of them use a PTFE+EPDM diaphragm, with the EPDM kept out of contact with the liquid. VC and VS differ by one letter, but one means FKM and the other EPDM, and their chemical resistance is completely different. Check this position against the chemical every time. Also note that PP isn't offered on every size, so check the model list first.

Positions 5 to 7: connection, vent valve, controller

Position 5, M, means multi-hose connection. Hose size follows the diaphragm: small diaphragms take thin tubing, 31 and 36 take thicker tubing, and the exact sizes are in the brochure. If the position reads 1/2 instead, that is the connection used only on the H high-pressure type, with different tube sizes on the outlet and inlet, so don't fit ordinary tubing.

In position 6, no code means a vent valve is fitted and K means none. The brochure limits K to 31 and 36 sizes in VC/VS with the R controller. Position 7 of the Iwaki EHN model code is the controller: R is standard, YN is advanced.

Positions 8 and 9: special versions

Position 8 only shows up on a special Iwaki EHN model: NAE for auto-degassing, 55 for high compression ratio and H for high pressure. Position 9 only applies to NAE and gives the separator rod material: no code is titanium, HC is equivalent to Hastelloy C276, and S6 is SUS316. The last two are only for the BN11VC-NAE.

Read in order, the opening example is a 20 W drive, 10 mm diaphragm, VC materials, multi-hose connection, K, standard controller, auto-degassing type and Hastelloy separator rod. Iwaki built that example to show all nine positions, so restrictions like the one on K still need checking when you order a real Iwaki EHN model.

The Shorter Iwaki EHN Model Code for FC and SH

FC and SH liquid ends follow a separate six-position code, for example EHN-BN11FC2R. Diaphragm size comes in only 11, 21, 31 and 36. Position 5 is the connection: for FC, 2 means Ø4×Ø6 and 6 means Ø10×Ø12; for SH, 9 means Rc 1/4. Position 6 is again R or YN.

FC is a PVDF head with alumina ceramic balls and PCTFE seats. SH is a SUS316 head with balls equivalent to Hastelloy C276. One trap: the CN36 in FC/SH form is rated 410 mL/min, a little below the 450 mL/min of the standard liquid end, so don't carry the figure across.

Copying an Iwaki EHN Model Off Site: Common Traps

Nameplates fade after a few years of chemical splash, and some customers just send a blurry phone photo. When that happens we ask for three things: is the head transparent, is the tubing thin or thick, and how many keys does the control panel have? Iwaki's PVC is transparent PVC, so a clear head points to VC or VS, and an opaque one sends you to the GFRPP options. That narrows things down fast.

The controller is the second trap. Many projects later want to connect a current signal from the control system. The R standard controller only takes pulse and stop inputs, and analog input is only on the YN advanced version. Don't write R in position 7 just because it's quicker, or changing it later becomes a headache.

Some people also copy only the front half of an Iwaki EHN model number and lose the NAE at the end. A standard head and an auto-degassing head are built differently, so liquid end parts ordered for a standard pump may not fit.

After the Iwaki EHN Model Code, Check the Ratings

The maximum output in the brochure is measured at maximum discharge pressure, rated voltage and room temperature, at 100% stroke length and 360 spm, pumping clean water. Viscous chemicals and long lines will cut into it.

Two more points get missed. Discharge pressure needs to be 0.12 MPa or more (0.05 MPa or more for the BN31 and CN36), otherwise fit a check valve or back pressure valve to stop over-feeding. Liquid temperature is generally 0–60℃, and 0–40℃ for VC.

Conclusion

Reading an Iwaki EHN model code comes down to one order: BN/CN and diaphragm size for the flow and pressure step, then the liquid end material against your chemical, then the controller and any special version. The one-letter material codes like VC and VS matter most, so check them twice.

FAQ

Is BN vs CN only a power difference?

No. With the same diaphragm size, CN delivers somewhat more flow and pressure than BN.

The old nameplate is unreadable. What now?

Confirm the head material and tubing size, then count the keys on the panel. Three keys means the R standard controller, four keys means YN advanced. That narrows down the Iwaki EHN model quickly.

VC or VS for sodium hypochlorite?

It depends on concentration and conditions, and the material code must be checked against the chemical. For gassing sodium hypochlorite, Iwaki also points to the NAE auto-degassing and 55 high compression versions.

Without NAE in the code, can the pump still vent?

Yes. The five standard liquid ends generally have a manual vent valve, and turning the knob lets the air out of the pump chamber. It just doesn't vent continuously on its own.

Why is there no voltage in the Iwaki EHN model code?

The whole EHN series runs on AC100–240V, 50/60Hz single phase, so the code doesn't need a power position.

Send us a photo of the old nameplate or your chemical data through our contact page and we'll check the code position by position.