Technical Details

PTFE Lined Pipe & Fittings

LinedPipe.Com offers ½ inch through 12 inch PTFE lined pipe and fittings in both carbon steel and stainless steel in standard and special configurations. PTFE liners are produced using a proprietary technology and the highest quality resins. This process creates free sintered liners with superior properties for strength and resistance to permeation.

Pipe liners are ram paste extruded or isostatically molded and have consistent, dimensional accuracy for excellent performance in service. The liners are installed in A587, A106 and A53 steel pipe with rotating A395 ductile iron or A105 forged steel flanges.

We invite you to bring us your toughest plastic lined pipe problems. Have a specific pipe or fitting need that you don't see addressed here? Get in touch with us.

LinedPipe.Com Liner Data

LinedPipe.Com liners meet or exceed the ASTM F1545 minimum at every size. PP and PVDF liners are listed through 6"; larger sizes on request.

All fittings conform dimensionally to ANSI B16.5

All fittings conform dimensionally to ANSI B16.5

• All lined pipe, fittings and flanges comply with ASTM F1545 Standard Specification for Plastic Lined Ferrous Metal Pipe, Fittings and Flanges.
• The lined fittings we supply are welded in compliance with ASME B31.3 by welders certified to Section IX of the ASME Boiler and Pressure Vessel Code. Lined pipe spools are assembled with rotating flanges over a flared liner and need little welding.
• Carbon steel components are primed with rust preventative gray primer and are suitable for top coating in the field. Special coatings are available on request.
• All lined spools and fittings are subjected to a minimum 10,000 volt spark test to detect liner defects. Any audible or visible spark is cause for rejection of the liner.
• All flared surfaces are protected by wooden end covers to insure their integrity during shipping and handling. Covers must remain in place prior to installation.
• Lined fittings carry identifying markings on their flanges in accordance with ASTM F1545. Spools fabricated by Marspec are stamped with the Marspec M on the flange.

A = outside diameter · B = thickness · C = bolt circle. Metric flanges are also available.

* Including a flat washer on each side.

Recommended Bolt Torque (ft·lb)

The maximum recommended torque values are suggested for lined systems operating at or near the maximum recommended pressures and temperatures. Systems operating under less severe conditions can in general experience leak-free performance using lower torque values. Any time gaskets or spring type washers are used, we suggest using the minimum recommended torque value and increasing only to obtain satisfactory sealing. For systems that will require frequent disassembly, start at the minimum recommended torque to avoid distortion of the plastic face.

The same general techniques used to install flanged carbon steel piping systems can be applied to plastic lined piping systems.

When assembling flange connections, always use a full complement of clean, new high strength A193 B7 bolting. If using stainless steel bolting, use A193 (or A320) Grade B8M Class 2 bolts with A194 Grade 8M nuts. If other bolting materials are used, the end user must ensure that the new bolting material strength properties exceed the calculated bolt stress values to be generated in making the piping connection.

• Always use flat washers on both sides of the connection.
• Tighten the flange bolts with a calibrated torque wrench to the specified bolt torques. NOTE: if using anti-seize compounds, the torque values will be different.
• Tighten the flange bolts with a torque wrench using a crisscross pattern that alternately tightens the bolts located 180° apart.
• Using this pattern, tighten the bolts in 20% increments of the final bolt torque until 80% of the final bolt torque has been achieved.
• For tightening to the final torque values, tighten the bolts sequentially clockwise once around the flange. This will help insure that the bolts are evenly stressed.
• Care should be taken to prevent over-torqueing, which will cause damage to the sealing surfaces.

NOTE: when bolting together dissimilar materials, always tighten to the lowest recommended torque of the components in the joint. Using higher torques may cause excessive deformation of the "softer" material in the joint. Install a ½" thick spacer between plastic lined pipe or fittings and other plastic lined components, particularly valves, if the diameters of the raised faces are different. Belleville washers are not recommended for use with PTFE lined products.

Re-torqueing

A re-torque should be applied a minimum of 24 hours after the initial torque or after the first thermal cycle. This allows for seating of the plastic and for relaxation of the bolts. Torqueing should only be done on the system in the ambient, cooled state, never while the process is at elevated temperature or excessive force could be applied to the plastic faces. Never disassemble a flange joint in a hot system. Wait until the system has cooled to ambient temperature.

Hydrotesting

Normally, after initial torque and re-torque, a hydrotest should be performed following ANSI requirements. If a flange leaks, first check the torque values and then tighten in 10% increments over the specified bolt torques until sealed. However, if 150% of the specified torque value is reached and the flange joint still leaks, stop and disassemble the flange joint. Something else is likely wrong such as a scratched plastic face. Only after the hydrotest has been successfully completed and any leaks corrected can the pipeline be signed off and commissioned.

Annual Re-torqueing

Re-torqueing should be done at least annually thereafter, especially if the process line experiences elevated temperatures or thermal cycling. Torqueing should only be done on the system in the ambient, cooled state and never while the process is at an elevated temperature; excessive force will likely be applied to the plastic faces.