Cheonsei Dosing Pump Liquid Ends: PTC, FTC and STS Explained

Look at any Cheonsei dosing pump model, say KDV-33H-PTC, and there are always three letters near the end. Plenty of buyers treat them as an internal reference and copy whatever was on the last order. Then the pump arrives, the chemical is a fairly strong acid, and the head is plastic. Those three letters are the wetted material, and they deserve more attention than any other part of the code.

How to Read the Three Letters on a Cheonsei Dosing Pump

In the KD series model code, the liquid end section has three positions in a fixed order:

1. Head: P is PP or PVC, F is PVDF, S is STS304, 6 is STS316.
2. Diaphragm: T is PTFE, E is EPDM.
3. Check ball: C is ceramic, S is STS304, 6 is STS316.

Put together, PTC means plastic head, PTFE diaphragm and ceramic balls. FTC is a PVDF head with PTFE diaphragm and ceramic balls. STS is a stainless head with stainless balls, and 6T6 moves the head and balls up to 316.

The Four Standard Combinations

The letters don't tell the whole story, because seats, ball guides, joints and O-rings change with them. Here is what the standard material table in the Cheonsei dosing pump literature says.

PTC

On small sizes 21H–82H, the head, ball guide and joint are PP. From 13H up they switch to PVC. The diaphragm is PTFE as standard, with EPDM as an option, and the balls are ceramic. Ball seats are FKM on small sizes (EPDM optional) and PVC from 13H up. O-rings and packing are FKM, with EPDM available. PTC is the first standard Cheonsei dosing pump option in the catalog, and for sodium hypochlorite or dilute acids and alkalis in water treatment it's usually the first one to check.

FTC

Head, ball guide and joint move to PVDF, and on large sizes 14H–54L the head can be PVDF or PTFE. The diaphragm stays PTFE, balls stay ceramic, seats are PTFE (PVDF on some sizes), and O-rings and packing become PTFE. When a chemical is too aggressive for PVC, FTC is the usual step up for a Cheonsei dosing pump.

STS and 6T6

The head is a stainless casting: 304 grade on STS, 316 grade on 6T6. Diaphragm and seals stay PTFE and the balls are stainless. Seats depend on size: PTFE on 21H–82H, stainless from 13H up. A stainless Cheonsei dosing pump suits liquids that plastics can't handle and that don't attack stainless, and it's common where temperature runs higher.

For special materials such as Hastelloy, the literature says to contact the supplier. They aren't in the standard table.

Reading a Full Model Against the Cheonsei Dosing Pump Spec Table

The catalog's example code is KDV-33H-PTC-FWS. V is vertical. 33 reads as 3×10³, so nominal capacity is 3000 mL/min. H is the high pressure rank. PTC is plastic head, PTFE diaphragm, ceramic balls. F is flange, W is standard viscosity, and the last letter is the power supply.

Now find 33H in the specification table: 2900 mL/min maximum at 50 Hz, 10 bar maximum, 0.4 kW motor, KS10K25A flange. Nominal and tested maximum flow differ a little, which is normal. Size your margin from the table figure, not the round number in the model code.

Don't Skip the Temperature Limits

Right material, wrong temperature, and you still have a problem. Plastic liquid ends such as PVC and PVDF are rated for liquid at 0–50°C. Stainless liquid ends are rated 0–80°C. Ambient temperature is 0–40°C for all of them.

A typical trap: a chemical is fine in a PTC Cheonsei dosing pump at room temperature, but part of the process heats it, or the tank sits in summer sun. Once the temperature climbs, a plastic head starts to deform and weep. Either cool the liquid or go straight to stainless.

Connection and Viscosity Codes

After the material letters come a few more. Connection: F is flange, H is hose, X is special. Viscosity: W is standard and V is high viscosity. The Chinese catalog puts standard at under 500 cp and high viscosity at 500–3000 cp.

Small models mostly use hose connections, with different sizes for PVC and PTFE hose. Flanges run from KS10K15A to KS10K50A by model size. The English manual also notes that thread connections are only available on P-type plastic liquid ends, so ask separately if you want threaded ports on a stainless head.

Common Material Selection Mistakes

1. Asking only about the head and not the seats and O-rings. The head survives, the O-ring swells, and the pump leaks anyway.
2. Copying the old Cheonsei dosing pump model code. If the chemical, concentration or temperature changed, recheck the materials.
3. Assuming a stainless Cheonsei dosing pump handles everything. The manual's first caution says never pump a liquid that corrodes the wetted materials. With high-chloride chemicals, stainless isn't automatically better than plastic.

If in doubt, send the factory the liquid name, ingredients, concentration, temperature and viscosity. That's exactly what the catalog asks for at ordering.

Wear Parts and Inspection

Liquid end parts on any Cheonsei dosing pump wear. For continuous duty the manual suggests replacing balls, ball guides, seats, O-rings and the oil seal at about 1 year and the diaphragm at about 4000 hours, noting that actual life depends on conditions. Valves should be inspected every 6 months and the diaphragm usually every 1–2 months.

When ordering spares, give the full model, especially the material letters. PTC and FTC seats and O-rings look similar but are different materials, and a mixed assembly won't last.

When reassembling a check valve, keep the order: ball guide on top, ball in the middle, seat at the bottom. Get it backwards and the liquid flows the wrong way, which can damage the pump.

Conclusion

On a Cheonsei dosing pump, the three letters at the end of the code are the material spec, so don't copy them blindly. PTC is plastic with ceramic balls and covers most water treatment chemicals. FTC uses PVDF for stronger chemicals. STS and 6T6 are stainless and take liquid up to 80°C. Check seats, seals, temperature and viscosity together, and ask the factory about special liquids.

FAQ

How do PEC and PES relate to PTC?

Using the same letter logic, PEC swaps the diaphragm to EPDM, and PES swaps the diaphragm to EPDM and the balls to stainless. The literature lists them in brackets after PTC as optional combinations.

Which material for sodium hypochlorite?

Start with PTC or FTC. Concentration and temperature still matter, so send the chemical data to the factory rather than assuming.

Can FTC handle liquid at 60°C?

Not according to the literature. Plastic liquid ends top out at 50°C, so at 60°C look at STS or 6T6, provided the chemical does not attack stainless.

How often should the diaphragm be replaced?

The reference figure is about 4000 hours of continuous duty, but conditions vary. Check it every 1–2 months and replace it as soon as you see damage.

Which code for a viscous chemical?

Choose V in the viscosity position. The Chinese catalog gives 500–3000 cp for high viscosity. Above that, ask the factory first.

To double-check the materials on a Cheonsei dosing pump, or see how a comparable Chinese-made pump would be configured, send us your chemical data through our contact page.