SEKO Mechanical Diaphragm Pump Selection: Kosmo, MS1 and MSA by Flow and Head Material

Once a dose climbs into tens or hundreds of liters an hour, a solenoid pump starts to struggle and most buyers move to a motor-driven unit. If you are choosing a SEKO mechanical diaphragm pump, the catalog gives you four practical series: MSA, MS1, and the MM1 and MM2 under the SEKO Kosmo name. Their flow bands overlap and their head materials differ, so a wrong pick leaves you short on pressure or with the wrong material.

Below we line the four series up by flow, then cover head and seal choices, and finish with the mistakes we see most on site.

Flow Bands of Each SEKO Mechanical Diaphragm Pump Series

Start with the limits to get a rough picture:

• MSA: 10–120 L/h, up to 5 bar;
• MS1: 5.5–1200 L/h, up to 10 bar;
• Kosmo MM1: 3–530 L/h, up to 12 bar;
• Kosmo MM2: 80–2300 L/h, up to 10 bar.

Every SEKO mechanical diaphragm pump in this group keeps the chemical in contact only with the head, diaphragm and valves, and the diaphragm is always PTFE. The differences lie in the return mechanism and housing: MSA uses spring return in a PPS housing, MS1 uses spring return in an aluminum housing, and SEKO Kosmo uses a mechanical return.

Matching a SEKO Mechanical Diaphragm Pump to Flow and Pressure

As with solenoid pumps, the higher the flow within a series, the lower the pressure, so always check the injection pressure against a specific model.

MSA: The Compact Unit Around a Hundred Liters

The MSA SEKO mechanical diaphragm pump uses a single 70 mm diaphragm. The first five models run from 10 L/h to 90 L/h, all at 5 bar, and the largest, MSAH070R, gives 120 L/h at 3 bar. It has a built-in double-cam mechanism, which the catalog says keeps running smooth and quiet, and the whole pump is rated IP55. The motor is only 0.06 kW, available for three-phase or single-phase supply. Heads come only in PVC and SS316L, with no PVDF option, so rule that out early.

MS1: The Widest Flow Span

MS1 runs from 5.5 L/h all the way to 1200 L/h. Pressure falls in steps: models at 120 L/h and below are rated 10 bar; the three MS1C138 sizes are 7 bar; MS1C165 is 5 bar at 230 and 330 L/h and 4 bar at 530 L/h; and the fastest-stroking Q models give 4.5 bar at 750 L/h and only 2 bar at 1200 L/h.

So although MS1 is listed at 10 bar, the larger models lose pressure quickly.

The Last Letter Is Stroke Frequency

The A, B, C and Q at the end of an MS1 model mean 58, 78, 116 and 232 strokes per minute, and the number before it is the diaphragm diameter. With the same diaphragm, higher frequency means more flow. When we size a SEKO mechanical diaphragm pump, we generally suggest the lower frequency option as long as flow is sufficient: the pump runs more smoothly and valves and diaphragm wear more slowly. With slightly viscous chemicals the low-frequency advantage is even clearer, since suction fills better and dosing is steadier.

SEKO Kosmo: A Little More Pressure Headroom

MM1 reaches 12 bar up to 22 L/h, 10 bar at 53 L/h, 7 bar from 85–340 L/h, and 5 bar at 400 and 530 L/h. For two or three hundred liters an hour, MM1 leaves a bit more pressure margin than MS1.

MM2 handles large flows: 10 bar from 80–450 L/h, 7 bar at 500 and 600 L/h, 3.5 bar from 750–1200 L/h, and 3 bar at 1600 and 2300 L/h. Motor power goes up to 1.1 kW.

One more point: SEKO Kosmo flows are measured on water at 20℃ with a 50Hz motor. At 60Hz, multiply flow by 1.2. If the site chemical is thicker than water, real flow will be lower, so allow for that in your margin.

SEKO Mechanical Diaphragm Pump Head Material and Seals

MS1 and SEKO Kosmo use the same head codes: 21/24 for SS316L, 31/34 for PVC and 41/44 for PVDF. Valve seats are PTFE throughout; plastic heads use ceramic balls and stainless heads use SS316L balls.

Seals come in FPM or EPDM. The catalog puts it plainly: EPDM suits alkaline fluids and FPM suits acidic fluids. Alkaline chemicals such as sodium hypochlorite or sodium hydroxide and acids such as hydrochloric or sulfuric acid need different seals, so don't use one configuration for everything. When concentration and temperature are uncertain, send the chemical data to the supplier.

All four series list a maximum fluid temperature of 40℃, even with stainless heads. For hot chemicals this is the first limit to check, and anything above it needs confirming with the manufacturer.

SEKO Mechanical Diaphragm Pump Model Code and Options

Taking MS1 as the example, the catalog code is M S1 A 064 B 31 A4 080: diaphragm pump, drive type, stroke length, diaphragm diameter, stroke frequency, head material, motor and optional items. In the motor position, A4 is standard, CS is variable frequency and CX is explosion-proof.

Besides VFD and explosion-proof motors, MS1 can take a 4–20mA electronic stroke controller. SEKO Kosmo can also be ordered with a VFD or explosion-proof motor. If flow has to follow a DCS signal, settle this at order time.

Common Site Mistakes

1. Selecting on the series maximum alone. MS1 says 10 bar, but the model above a thousand liters gives only 2 bar, nowhere near enough for a pressurized line.
2. Using an FPM seal on an alkaline chemical, which tends to cause seal trouble after a while.
3. Being too optimistic about suction lift. Even a SEKO mechanical diaphragm pump is best fed by gravity, with the tank level above the head and a strainer on the inlet.
4. Leaving out a back-pressure valve on low-pressure injection, so flow surges when there is no discharge pressure.

These look obvious, yet they are where most site problems start. Put injection pressure, chemical and temperature into the inquiry, and choosing a SEKO mechanical diaphragm pump gets much easier.

If the project has no brand requirement, domestic mechanical diaphragm pumps covering the same flow band are worth comparing too, such as the NEWDOSE NDJ, NDWS, NDWL, ND1000 and ND2000 series.

Conclusion

A simple path: around a hundred liters at modest pressure, look at MSA; anything from a few liters to over a thousand, look at MS1; the same flow with more pressure, look at SEKO Kosmo MM1; over a thousand liters, look at Kosmo MM2. Choose the head from SS316L, PVC or PVDF by chemical, use FPM for acids and EPDM for alkalis, then check the 40℃ limit and injection pressure, and your SEKO mechanical diaphragm pump should be right first time.

FAQ

Can an MSA SEKO mechanical diaphragm pump take a PVDF head?

The catalog lists only PVC and SS316L heads for MSA. If you need PVDF, look at MS1 or SEKO Kosmo.

Can I pump a hot chemical?

Not without checking. All these series list a maximum fluid temperature of 40℃, so confirm with the manufacturer before going above it.

Which SEKO mechanical diaphragm pump handles over a thousand liters an hour?

For 1200 L/h, look at MS1C165Q or Kosmo MM2: the former gives only 2 bar, while the MM2 model gives 3.5 bar. Up to 2300 L/h, only MM2 covers it.

Can flow be adjusted remotely?

Yes. Choose a VFD motor, and MS1 can also take a 4–20mA electronic stroke controller. Decide at order time.

Can a SEKO mechanical diaphragm pump be used in a hazardous area?

MS1 and SEKO Kosmo can both be fitted with explosion-proof motors. Confirm the exact protection rating and certification with the supplier.

Not sure which series and head suit your flow and chemical? Send your duty through our contact page and we will go through the SEKO data with you.