A. Scope
In most of the Chemicals, Petrochemicals, Food Industries, Pharmaceuticals, and almost every company handling highly corrosive and hazardous acids and solvents for their processing requirements the lined pipes systems find their application. Many a times, these chemicals are to be conveyed from storage vessels to the mixing tanks or reactors where they form an intermediate product. Being highly acidic and corrosive in nature, these chemicals have a tendency to corrode and eat away the steel piping which are used as conveyors, leaving the system useless and unsafe for use.

To avoid depleting the material and arrest the growth of corrosion inside the conveying system, a long sleeve or tube made of PTFE is inserted inside the Steel pipes, bends, tees, reducers, spacers, valves and all such fittings installed in the whole pipeline. Due to the inertness of PTFE to almost all chemicals and solvents, it acts as a effective barrier between the chemical and steel, thus not only protecting the conveying system, but also safe guarding working environment. Enveloping steel tube from inside with PTFE has proved to be economical in the long run as the structural cost for the conveying system, the losses occurring due to leakages, and the downtime for repairing and maintenance is reduced to a significant extent.

The advantages of using lined pipe systems are as follows:

1) The life of pipeline systems increases due to absence of rust formation.
2) PTFE lining safeguards and enhances better working conditions as leakages does not occur and subsequent harmful gases and vapors do not evaporate in the atmosphere.
3) The cost incurred in maintenance & repairing and time lost can be minimized.
4) A wide variety of chemicals can be used through a PTFE lined system, making it more flexible and economical.

B. MATERIAL SPECIFICATION:
LINING MATERIAL SPECIFICATION

C. STEEL:
1. CARBON STEEL PIPES:
Pipes material used are according to ASTM A 106 Gr-B Seamless,
Sizes 25 NB to 200 NB in sch 40.
Sizes 250NB to 350NB in sch 30.
Above 350NB schedule 20.

2. FLANGES:
Flanges used are Slip-on (SOFF/SORF) as per ANSI B 16.5 Class 150.
Generally flanges supplied are from plate material IS2062 Gr-A/B, however if specifically required A105 material of flanges are also supplied if requests are made during the offer or for special requirements.

3. PIPE FITTINGS:
 Elbows and reducers are as per ASTM A 234 WPB made from specially bending pipe specifications as given above. Flanges are fixed welded at both the ends. For special requirement if any both side loose flanges can be supplied.
 Housing material for tee is made from pipes. Tees are generally made with flanges welded at all the ends, however loose flanged tee’s can also be supplied upto size 150NB.
 Housing material for Reducing flanges are DI as per ASTM A395 for sizes upto 150NB (for specific sizes), whereas material IS 2062 Gr-A/B for others.
 Housing material for Lined spacers are from plate material IS 2062 Gr-A/B only.

D. DIMENSIONAL STANDARD:
 Lined piping are according to ANSI B 31.3.
 Lined fittings dimensions are as per ANSI B 16.5 fabricated fittings, 150#.
 Tolerances are as per ASTM F 1545.

E. CONSTRUCTION:
The PTFE lined pipeline systems can be made in any of the following ways:

• INSERTED & FLARED PTFE LINING:
Ram Extruded / Paste Extruded tubes of required thickness being inserted into steel pipes of pre-determined lengths and flared on the either ends of the flanges. The insertion of PTFE tube into steel pipe can either be loose, shrink-fit or interference fit. For best results interference fit is the most ideal method.

• ISOSTATIC MOLDING:
In-situ fitting of PTFE by using isostatic pressing followed by sintering. This process compresses the PTFE resin under high pressure, so as to result in a uniform lining of PTFE along the length of steel pipe and flange. The material has uniform grain strength giving least possibility of seepage of corrosive fluids.
 Due to the careful processing method, sensitive properties like impact resistance, bending stress, tensile stress and the crystallinity are preserved to a high degree.
 The strength of the PTFE pipes is practically identical in the circumferential direction and in the longitudinal direction irrespective of the method of safety, which results in vacuum resistance and protection against stresses due to pressure changes.
 The high density and high crystallinity of the PTFE used, and the generous dimensions of the wall thickness give rise to a favorable vacuum resistance and at the same time give minimal permeability to gases and steam.
 The homogeneous formation of the lining, also in places not easily accessible, rules out any weakening of the structure or reduction of the wall thickness.
 A small constant shrinkage minimizes the changes in shape during the sintering process.

F. VENTING:
Venting shall as a minimum meet the requirements of ASTM F 1545 for the indicated liner material. Pipe is vented on the housing by means of small vent holes (1”-4” =3/32”, 6”-8”= 5/32”) allowing permeates vapors to escape. Pipe spools up to 18” length receive 1 vent hole in the center of the pipe. Pipe spools greater than that receive 2 vent holes, one at each end 180° apart. For special requirements venting boss are welded to vent holes, if the pipe line to be installed is insulated. Boss is internally threaded CS A106 pipe of ½” size and 1” long.

G. TESTING:
• HYDROSTATIC TEST:
In this test all pipes and fittings are subjected to 29Bar (425psig) for hydro pressure test at room temperature. The test is carried out according to ASTM F 1545. In this test vent holes and the pressure gauge are observed for any leakage in the pipeline which may cause the rejection.

• ELECTROSTATIC TEST
In this test all the pipes and fittings are subjected to 25KV non destructive spark test. The test is carried out as specified in ASTM F 1545. This test is carried to detect any defects, cracks pin holes in the liner. Spark occurs which is audible and visible if there is any defect in the lined part.

H. MARKING:
All the items are marked with permanent paint marker. The marking are applied in such a manner that it remains legible after installation and inspection have been completed. Markings include:
Markings: ASTM Designation/ Nominal Pipe Size /Pressure Class Manufacturer's Name /Traceability Number/Your TAG #

I. CERTIFICATES
Following Certificates shall show for each piece:
Manufacturer, Traceability Number, FI-Tag-No., Manufacturing Date, Inspector's Name, ASTM-Designation, Component Type, Pressure Rating, Pipe Size, Pipe Schedule, Housing Material, Flange Material, Liner Material, Test Pressure, Pipe Spool Length. The request for a Test certificate must be made while ordering for PTFE lined pipe systems.

J. PACKAGING
Packaging shall be in accordance with ASTM F 1545. The Flare face of each spool or fitting shall be protected by end plates of wooden or plastic covers.

K. STORAGE AND HANDLING REQUIREMENT
Straight pipes are packed in wooden crates on specific request. Protective caps are provided on the flange joining areas, which have to be removed only before installation.
The center of gravity of the pipe can be very deceptive. Use extra care in handling, transfer, and storage of the product to avoid sudden load shifting causing possible personal injury and/or product damage.