Process Valves

PTT (polytrimethylene terephthalate) polymerisation involves three critical challenges for process valves:

• High temperature: process temperatures reach 250–270°C; valve bodies and seals must maintain dimensional stability and sealing integrity at these temperatures.
• High-viscosity melt: molten PTT has extremely high viscosity; valve cavities must be designed to prevent polymer pooling and degradation in dead zones.
• Clean switching: fast, clean cut-off is required to prevent melt stringing, dripping, or fibre breakage. BONAFEI valves use a precisely ground knife-gate mechanism to shear the melt cleanly.
• Corrosion resistance: 1,3-propanediol (PDO) and terephthalic acid (TPA) intermediates require stainless steel or special alloy wetted parts.

BONAFEI PA6 extraction knife gate valves are rated as follows:

• Operating temperature: –10°C to +200°C (continuous); short excursions to 220°C
• Operating pressure: up to 1.6 MPa (16 bar)
• Blade material: 316L stainless steel with hard-chrome or tungsten carbide coating for abrasion resistance against the caprolactam/water slurry.

All ratings are verified through factory hydro-static and pneumatic tests; material certificates and test reports are supplied as standard.

Under normal operating conditions, a planned preventive maintenance interval of 6–12 months is typical for PTT/PA6 valves. Factors that extend service life:

• Temperature management: avoid thermal cycling beyond design range; use steam tracing or electric heat to keep the valve at operating temperature.
• Clean media: filter out particulates upstream to protect the blade and seat surface.
• Correct actuation speed: use the appropriate actuator speed — too slow causes melt freezing; too fast causes water hammer.
• Spare-parts stock: maintain a set of blade/seat/seal spares to enable rapid field replacement and minimise downtime.

Yes, with appropriate material selection. The core rotor-stator and knife-gate designs are adaptable to other melt-phase polymer processes:

• PET: operating temperatures 270–290°C; requires higher-temperature body materials and seals — available as a configured variant.
• Nylon 66: temperatures up to 290°C and higher melt viscosity than PA6; blade geometry and actuator force must be recalculated — BONAFEI provides application engineering support.

Please provide process temperature, pressure, viscosity, and corrosive species data when enquiring so that the correct specification can be confirmed.