Q1. What are the two PU materials? How do Ester and Ether differ?

Ester-based and Ether-based PU differ primarily in moisture-related behavior and typical operating environments.

Ester-based PU is commonly used in dry pneumatic systems and is often evaluated where abrasion, friction, or lubricated air (oil mist) is present. Ether-based PU has low moisture absorption and strong hydrolysis resistance, and is typically evaluated where humidity, condensation, wet compressed air, or outdoor exposure may affect long-term material behavior.

Humidity / wet compressed air / outdoor exposure → Ether-based PU
Dry environments with oil mist (lubricated air) → Ester-based PU

Q2. Do PU tubes absorb moisture? Will it shorten service life?

Moisture response differs by PU type: Ester-based PU is more sensitive to long-term moisture exposure, while Ether-based PU typically shows minimal moisture absorption.

Prolonged moisture exposure can trigger hydrolysis in Ester-based PU over time, which may gradually change flexibility and mechanical strength. Ether-based PU resists water absorption and tends to maintain more stable long-term material behavior in humid or wet-air conditions.

Controlled dry compressed air → commonly evaluated Ester-based PU
Humid environments / wet compressed air / condensation risk → typically evaluated Ether-based PU

Q3. Can PU tubes burst because of moisture in pneumatic air?

Moisture alone typically does not cause sudden failure; risk is more often associated with long-term material degradation combined with pressure or mechanical stress.

The primary moisture-related concern is long-term hydrolysis in Ester-based PU. If mechanical strength is reduced over time, pressure spikes, vibration, or fitting pull-out may increase the likelihood of rupture depending on installation quality and system duty cycle.

Humid conditions / wet compressed air → typically evaluate Ether-based PU.
For additional isolation and maintenance convenience, consider shut-off fittings where appropriate for the system design.

Q4. What is the typical service life of PU tubing?

Service life is application-dependent and is strongly influenced by operating environment and duty cycle.

Humidity, UV exposure, temperature, and cycling stress all influence long-term aging behavior. Ether-based PU is typically evaluated where moisture stability is a dominant factor; Ester-based PU is commonly used in dry conditions where routing includes movement, friction, or oil mist exposure.

Plan periodic inspection based on duty cycle. Typical aging indicators include whitening, haze, hardening, cracking, or permanent deformation.

Q5. How do PU, Nylon 6 (PA6) and Nylon 12 (PA12) compare?

PU is commonly selected for routing flexibility; PA6 is commonly used for fixed routing in dry environments; PA12 is typically evaluated where higher pressure capability and moisture stability are required.

Each material addresses a different tubing role in pneumatic systems (dynamic routing vs. fixed routing, pressure requirements, and moisture response). Always confirm ratings against the specific OD/ID and operating temperature.

Full comparison:

Tight bending / dynamic routing → PU
Fixed routing → PA6
Higher pressure / main lines → PA12

Q6. Can PU be used in food-processing equipment?

Food-contact applications require certified food-grade materials; Ether-based PU is commonly evaluated where moisture stability is also required.

Moisture stability can be relevant in washdown or humid environments, but food-contact use depends on meeting the required food-contact compliance and certification for the target market and process.

Confirm the required food-contact compliance, then request food-grade Ether-based PU if moisture stability is a key operating factor.

Q7. Can PU tubes transport liquids?

Ester-based PU is typically evaluated for air service; Ether-based PU is commonly evaluated for water service. Chemical media requires chemical compatibility verification.

Ester-based PU may hydrolyze in water over time. Ether-based PU is more stable in water, but chemical compatibility varies widely by chemical type, concentration, temperature, and exposure duration.

Water → typically evaluate Ether-based PU
Oils / chemicals → request SHPI chemical compatibility verification

Q8. Which PU type is better for oil-mist environments?

Ester-based PU is commonly selected for lubricated air or oil-mist environments.

Ester-based PU is typically evaluated for oil-mist exposure where swelling or mechanical property changes must be managed. Ether-based PU is primarily evaluated for moisture-driven stability.

Oil-mist / lubricated air → Ester-based PU

Q9. How is working pressure determined for PU tubes?

PU tubing pressure ratings are defined by tube size, wall thickness, hardness, and temperature; published working pressure should be applied with appropriate derating.

Working pressure is affected by wall thickness, hardness, OD/ID, and operating temperature. Higher temperature generally reduces pressure capability.

Example:

Follow SHPI W.P. ratings and apply temperature derating where applicable.

Q10. Does tube hardness affect performance?

Tube hardness affects stiffness, routing behavior, and pressure capability; selection should match the installation role and bending requirements.

Higher hardness generally increases stiffness and pressure capability but reduces flexibility. Lower hardness improves routing and bending behavior but can reduce pressure capability depending on tube geometry and temperature.

• High-pressure fixed lines → commonly evaluate higher hardness
• Tight bends / movement → commonly evaluate lower hardness

SHPI PU tubes are engineered with a balanced hardness window commonly used for automation and pneumatic tools. This balance supports:

• Good abrasion resistance
• Ease of routing and installation
• Stable pressure performance
• Elastic recovery with low permanent deformation

Q11. Can PU tubes be used outdoors?

Ether-based PU is commonly evaluated for outdoor use where humidity and moisture exposure are key operating factors.

Outdoor conditions can include humidity, condensation, temperature cycling, and UV exposure. Ether-based PU typically maintains more stable behavior under moisture exposure. UV performance depends on formulation and color selection.

Outdoor with humidity exposure → typically evaluate Ether-based PU (darker colors are commonly used for additional UV screening depending on formulation)

Q12. Will PU tubes deform when over-bent?

Yes — bending below the minimum bend radius can cause deformation and increased flow restriction.

Over-bending can flatten the tube, increase pressure loss, and introduce stress concentration. Typical indicators include whitening, haze, or cracking initiation depending on duty cycle and environment.

Follow SHPI bend-radius guidance and avoid routing that forces the tube below its minimum bend radius during operation.

Q13. What fittings are compatible with PU tubes?

PU tubes are widely compatible with standard pneumatic fittings; fit and retention depend on OD tolerance, cut quality, and correct insertion depth.

PU elasticity supports sealing and retention in push-in fittings, valves, and shut-off fittings, provided that tube OD tolerance and installation practice are controlled.

For consistent installation feel → SHPI one-touch fittings

Q14. When should PU tubes be replaced?

Replacement timing is typically based on observed aging indicators and the system’s risk level rather than a fixed calendar interval.

Whitening, cracks, hardening, haze, or deformation can indicate loss of mechanical integrity and increased failure risk, especially under pressure cycling or vibration.

Replace when aging indicators appear. Use batch tracking and maintenance records where controlled replacement practice is required.

Q15. How do I choose between Ester and Ether if I am unsure?

Selection is typically driven by the dominant operating factor: moisture exposure versus oil-mist/abrasion exposure.

Ether-based PU is typically evaluated for humidity, condensation, or wet compressed air where hydrolysis risk must be managed. Ester-based PU is commonly used in dry pneumatic systems, and is often evaluated where abrasion and lubricated air (oil mist) are present.

Humidity / wet compressed air → Ether-based PU
Wear / oil mist exposure → Ester-based PU
Share operating conditions (humidity, pressure, temperature, bending profile, and media exposure) with SHPI for a selection check.