Pneumatic PTFE Piston Cup Seals for Nordson®-Type Dispensing Pumps

Nordson® is a registered trademark of Nordson Corporation. XHH Seals is an independent manufacturer of compatible replacement parts.

1. Role of the Piston Cup Seal in a Dispensing Pump

In many adhesive lines, a small piston cup seal decides if production is stable or not.

The seal is mounted on the piston inside the pump or cylinder.

It generates the dynamic seal between the piston outer diameter and the cylinder bore.

In Nordson®-type dispensing pumps and jet valves, compressed air moves the piston.

The piston cup seal must:

• seal the air chamber,
• convert air pressure into linear force,
• guide the piston, and
• withstand continuous cycling at high frequency.

If the cup seal leaks, the air pressure drops.

Pump stroke becomes irregular.

Outlet pressure and shot volume start to drift.

Compared with an O-ring, a piston cup seal has:

• a larger contact area,
• a defined sealing lip, and
• better stability under dry or low-lubrication conditions.

This makes it a good choice for compact air cylinders in dispensing and hot-melt systems.

2. Why PTFE-Based Cup Seals Are Used in Jet Dispensing

Many older pumps used rubber cup seals.

They work well at low cycle rates and moderate temperatures.

However, jet dispensing and modern coating lines push the limits.

Typical requirements are:

• very high cycle rate,
• long maintenance intervals,
• dry or almost dry compressed air,
• contact with reactive adhesives or solvents.

For this duty, PTFE-based materials are often a better choice.

Key advantages of PTFE piston cup seals

• Low friction – PTFE has a very low coefficient of friction.

           It reduces stick-slip at start-up and allows fast piston movement.

• Good wear resistance – especially when filled with PI or other fillers.

           This supports long life under high cycle counts.

• Broad chemical resistance – PTFE resists many adhesives, solvents and cleaning agents.

           It is suitable for epoxy, UV adhesives, some hot melts and other fluids used in electronics and packaging.

• Wide temperature range – PTFE keeps its properties over a wide temperature window.

           This is useful near heaters, manifolds, or when the pump handles hot melt material.

Many cup seals for dispensing pumps use PTFE + PI (polyimide) composite.

The PTFE provides low friction and chemical resistance.

The PI filler increases wear resistance and reduces creep under load.

3. How Cup Seal Condition Affects Process Quality

The piston cup seal is not only a spare part.

It directly influences the quality of every dispensed shot.

3.1 Air leakage and pressure stability

When the sealing lip wears, air leaks across the cup seal.

The pump still runs, but pressure in the chamber becomes unstable.

You may see:

• pressure overshoot at start-up,
• slow pressure build-up, or
• pressure drop during long runs.

For jet valves and spray modules, this instability translates into variable stroke and speed.

3.2 Shot volume and bead quality

Stroke variation leads to:

• changing shot volume,
• bead width variation,
• satellites or stringing for jets, and
• poor edge definition in coating applications.

Operators often try to correct this with parameter changes.

They adjust pressure, stroke time, or temperature.

In many cases, the root cause is only a worn piston cup seal.

3.3 Energy consumption and noise

A leaking cup seal also increases air consumption.

Compressors run longer to keep system pressure.

Noise levels rise.

Over time, this adds cost and reduces overall equipment efficiency.

4. Key Design Points When Selecting a Piston Cup Seal

When you select a piston cup seal for a dispensing pump, you should review several technical points.

4.1 Cylinder geometry

• Cylinder bore diameter.
• Piston design (single cup, double cup, or cup + backup washer).
• Stroke length.

Tolerance and surface finish of the bore are also important.

A smoother bore gives lower wear and better sealing.

4.2 Operating conditions

• Air supply pressure and regulation range.
• Maximum cycle rate (shots per second or cycles per minute).
• Duty cycle (continuous operation vs. intermittent).
• Presence of vacuum phases in the same chamber.

Higher speed and high pressure place more stress on the lip and on the backing section of the cup.

4.3 Environment and media

• Compressed air quality (dry, lubricated, or with residual oil).
• Process temperature near the pump.
• Possible contact with adhesive fumes, solvents or cleaning fluids.

For aggressive environments, PTFE with PI or other high-performance fillers is recommended.

For mild conditions, a simpler PTFE grade may be sufficient.

4.4 Material selection

Typical options include:

• PTFE with polyimide filler,
• PTFE with glass or carbon filler,
• high-performance elastomers for special cases.

Each material has a different balance of:

• friction,
• wear rate,
• creep resistance, and
• chemical compatibility.

Your application data should guide the final choice.

A simple material upgrade at the cup seal often brings a clear improvement in pump life.

5. Replacement and Maintenance Best Practices

5.1 Typical wear signs

You should consider replacing the piston cup seal when you see:

• rounded or thinned sealing lip,
• small cracks or chips at the lip edge,
• visible deformation or flattening of the cup,
• shiny spots or scratches on the sealing surface,
• increased noise and air consumption,
• first signs of pressure or shot instability.

Visual inspection during scheduled maintenance is usually enough.

5.2 Handling and installation

PTFE cup seals are rigid compared with rubber parts.

Correct handling is important.

• Avoid bending the cup too much during installation.
• Use suitable tools or sleeves to guide the cup into the bore.
• Keep the sealing surfaces clean and free from sharp edges.
• Apply a thin film of compatible lubricant if allowed by the process.

Incorrect installation can create small nicks in the lip.

These defects quickly become leak paths.

5.3 Preventive replacement strategy

For high-value production lines, a preventive strategy is better than running to failure.

• Track operation hours or cycle count of each pump.
• Replace piston cup seals at a defined interval, together with O-rings and other critical seals.
• Keep a small stock of validated cup seals on site to avoid long downtime.

A simple maintenance standard based on cup seal life can sharply reduce unplanned stoppages.

6. XHH PTFE Piston Cup Seals for Dispensing Pumps and Jet Valves

XHH designs and manufactures PTFE-based piston cup seals for demanding dispensing applications.

We focus on compatible and custom solutions for:

• adhesive and sealant dispensing pumps,
• hot melt coating systems,
• jet valves and micro-dispensing modules,
• electronics assembly and packaging equipment.

What we can offer

• PTFE and PTFE-composite piston cup seals for small-bore air cylinders.
• Material options optimized for low friction, high wear resistance, and good chemical resistance.
• Engineering support to match cup seal design to your piston and cylinder.
• Custom production based on drawings or physical samples.

We can also supply complete seal kits that include:

• piston cup seals,
• dynamic O-rings,
• static gaskets and backup rings.

These kits are suitable for maintenance teams that need fast replacement of all critical sealing parts in one operation.

7. FAQ – Pneumatic Piston Cup Seals in Dispensing Pumps

Q1. How often should I replace the piston cup seal in my dispensing pump?

Replacement interval depends on cycle rate, pressure, and environment.

In a clean plant with moderate speed, many users inspect the pump every few million cycles or every few months.

If you already track preventive maintenance for your plant, you can add the cup seal as one more line item.

If you are not sure, we can review your process data and suggest a starting interval.

Q2. Can I upgrade from a rubber cup seal to a PTFE cup seal?

In many cases, yes.

If the piston and cylinder design are compatible, a PTFE or PTFE-composite cup seal can replace a rubber cup seal and give longer life.

We will need at least the piston drawing, cylinder bore tolerance, and operating conditions.

Based on this, our engineers can propose a suitable material and lip design.

Q3. Will a PTFE piston cup seal work with my adhesive or solvent?

PTFE has very broad chemical resistance.

It works with many epoxies, UV adhesives, anaerobic adhesives, and some hot melts.

However, there are always exceptions.

If you send us the Material Safety Data Sheet (MSDS) of your fluid or the trade name, we can check compatibility and, if needed, suggest a different material.

Q4. I use Nordson®-type pumps. Can you supply compatible piston cup seals?

Yes.

XHH designs and produces compatible replacement piston cup seals for many common dispensing pumps and jet valves used in the market.

You can send us the OEM part number, a used sample, or a dimensioned sketch.

We will not copy the OEM design, but we will engineer a functionally compatible seal that fits your equipment.

Note: Nordson® is a registered trademark of Nordson Corporation. We are an independent manufacturer and not affiliated with or endorsed by Nordson.

Q5. What information do you need for a custom cup seal?

For a new design or a direct replacement, we usually ask for:

cylinder bore diameter and tolerance,

piston design and available groove depth,

stroke length and maximum pressure,

approximate cycle rate and duty cycle,

operating temperature and fluid / adhesive type,

any previous seal problems you want to solve.

The more information you provide, the faster we can propose a robust design.

8. Next Steps – Work with XHH on Your Dispensing Pump Seals

If you see unstable pressure, changing shot volume, or frequent maintenance on your dispensing pumps, the piston cup seal may be the real cause.

A well-designed PTFE piston cup seal can:

• stabilise pump behaviour,
• extend service intervals, and
• reduce total cost of ownership for your line.

You can send us:

• photos of your pump and current seals,
• a small drawing or sketch with key dimensions, or
• an OEM kit or used cup seal as a reference sample.

Our engineering team will review your case and suggest a practical sealing solution.

Contact XHH Seals

For technical support or a quotation, please email: xhh@xhh-smartech.com

We are glad to help you turn a small seal into a big improvement in your dispensing process.