SEKO Hydraulic Diaphragm Pump Guide: Where Nexa and Nyva Fit

A buyer sends over the SEKO catalog and asks a fair question: both lines are hydraulic, so what actually separates Nexa from Nyva, and which row of the table should I be reading? If you are sizing a SEKO hydraulic diaphragm pump, the answer comes down to diaphragm count, head material and the exact plunger and stroke speed you order.

Short version first. If your SEKO hydraulic diaphragm pump needs high flow, high pressure, zero leakage and a pump that keeps running when one diaphragm fails, look at Nexa. If your duty sits within a few hundred liters per hour and the chemical doesn't call for double diaphragm protection, Nyva usually does the job. Both are built to API675, and both are rated for fluid temperatures from -10℃ to 70℃.

Hydraulic vs Mechanical Diaphragm: Why It Matters

In a mechanical diaphragm pump, a rod pushes the diaphragm directly. Push hard enough and the diaphragm takes uneven stress and fatigues. In a hydraulic design, the plunger pushes oil and the oil pushes the diaphragm, so the load on both sides stays balanced. That is why a SEKO hydraulic diaphragm pump can reach far higher pressures with steady metering. The trade-off is an oil system you need to keep an eye on during maintenance.

Nexa vs Nyva: Double or Single Diaphragm

Nexa is the double diaphragm SEKO hydraulic diaphragm pump line, split into the YN, TN and HN sub-series. The feature page quotes up to 9000 L/h per head and up to 200 bar, with SS316L, PVC or PVDF heads. A rupture detection system raises an alarm if one diaphragm breaks, while the second one keeps the pump running until a planned shutdown.

Nyva is the single diaphragm version, split into CB0 and CB1, with a maximum of 660 L/h and 124 bar. Head materials are again SS316L, PVDF and PVC.

Every SEKO hydraulic diaphragm pump in these two lines has a mechanical automatic oil refill system. It holds the oil level steady, which supports linear and repeatability accuracy and limits diaphragm deformation for longer life. The drives use a built-in worm gear in an oil bath, with explosion-proof and variable-speed motors as options.

Reading the SEKO Hydraulic Diaphragm Pump Table: Start With Material

Most people scan for flow first. Start with head material instead, because the same plunger can lose most of its pressure rating once you switch from steel to plastic.

Nexa YN: the widest flow range

YN is the SEKO hydraulic diaphragm pump range most buyers end up in, covering N0 through N4. N0 runs 2.8 to 97.3 L/h; with PP or PVC heads it is rated 12 bar, PVDF with a small plunger reaches 20 bar, and SS316L with a small plunger reaches 40 bar. N1 goes up to 1258 L/h. N2 spans 865 to 2610 L/h, and pressure falls as plunger size grows, down to 6 bar on the largest plunger.

N3 and N4 come only in SS316L at 10 bar. N3 offers 2600 or 3900 L/h, N4 offers 6000 or 7500 L/h on an 18.5 kW motor. Note the gap: the feature page says 9000 L/h, but the data table stops at 7500 L/h. If you need more, confirm it with SEKO directly.

Valves and venting

Nexa vents gas automatically in operation and has manual venting to help at start-up. A relief valve protects against overpressure. For low flows you can choose double or triple ball valves with precision seats, and the valves can be changed without removing them from the line. SS316L heads use metal seals, plastic heads use FPM seals.

TN and HN: SS316L only, higher pressure

If your SEKO hydraulic diaphragm pump has to beat serious line pressure, look here. TN reaches 120 bar. The N0 with a 12 mm plunger delivers 4.5 L/h, while the largest N2 plunger at 202 L/h drops to 80 bar. HN is listed at 200 bar with flows of 10 to 67 L/h, the low-flow, very-high-pressure end of the range.

Nyva CB0 and CB1

On the Nyva side, the SEKO hydraulic diaphragm pump rows follow a clean pattern: PVC heads 15 bar, PVDF heads 20 bar, and only SS316L goes high. CB0 covers 3 to 97 L/h, with the 12 mm SS316L plunger at 124 bar. CB1 covers 18 to 660 L/h; small SS316L plungers also reach 124 bar, but the 50 mm plunger at 660 L/h is down to 24 bar.

Where Nexa Earns Its Place

The Nexa double diaphragm head is the zero-leak SEKO hydraulic diaphragm pump option for toxic, corrosive or otherwise hazardous fluids that simply cannot escape. Its diaphragm limiting system avoids a perforated plate on the process side, so it can handle suspensions with solids of a certain size.

SEKO lists chemicals, oil and gas, petrochemicals, power generation, pharmaceuticals, paper and textiles among its industries. The line carries ATEX certification for hazardous areas. On continuous processes where an unplanned stop is a problem, the rupture alarm is the feature that sells it.

When a Nyva SEKO Hydraulic Diaphragm Pump Is Enough

For routine municipal, wastewater and chemical dosing, where flow is moderate and double diaphragm protection isn't needed, Nyva keeps things simpler. The single diaphragm head is still zero-leak and also keeps outside contaminants from entering the pumped fluid, which is why it shows up in food and beverage and detergent work.

Common Mistakes on the Data Sheet

1. Stroke speed sets the flow. One plunger size often appears with two or three stroke speeds and very different flows. Specify the exact row on your order.
2. Don't size pressure from the series maximum. CB1 is quoted at 124 bar, yet its large plungers sit in the twenties.
3. Don't forget the accessories. SEKO offers calibration columns, pulsation dampers, safety valves and back pressure valves, and a low-pressure injection point needs that back pressure valve.

For remote flow control, the AKTUA electronic actuator replaces the manual adjuster, sets stroke length remotely, can be calibrated while running and comes in an ATEX version.

Bottom Line

Read a SEKO hydraulic diaphragm pump table in this order: series, then material, then plunger and stroke speed. Nexa suits high flow, high pressure, hazardous fluids and processes that can't stop. Nyva covers routine dosing within 660 L/h and 124 bar with one less layer of protection, which is fine for ordinary chemicals. Plastic heads sit around 12 to 20 bar, and anything high-pressure means SS316L.

FAQ

Will a Nexa keep running if one diaphragm breaks?

Yes. The protection system alarms immediately and the second diaphragm keeps the pump working. Schedule the repair soon.

Can a PVC head handle 50 bar?

No. Per the tables, Nyva PVC heads are rated 15 bar and Nexa YN PP/PVC heads 12 bar. High pressure means SS316L.

Can a SEKO hydraulic diaphragm pump handle a few solids?

Nexa's diaphragm limiting design allows suspensions with solids of a certain size. Send your fluid details to SEKO to confirm what particle size is acceptable.

What about a fluid at 80℃?

Both series are rated for -10℃ to 70℃. Anything outside that range should be cleared with the manufacturer first.

Can I install one in an explosion-proof area?

Nexa carries ATEX certification and can take an explosion-proof motor. The AKTUA actuator for automatic stroke control also has an ATEX version.

Not sure which SEKO hydraulic diaphragm pump row matches your duty? Send us the fluid, flow, pressure and temperature through our contact page. We can also compare it against a NEWDOSE option for the same conditions.