Requirements of RTRP Piping Design and its Advantages

RTRP (Reinforced Thermosetting Resin Pipe) is a non-metallic piping system widely used in process industries for various applications. FRP, GRP, GRE, RTP, RTPR and GRV are different abbreviations for specific types of RTR pipes based on the resin systems used in the manufacturing of the piping system. It comprises thermosetting plastic resins, glass-fiber reinforcements & addictive. RTRP establishes strength from the fiberglass reinforcement and corrosion resistance property from the resin.

Applications

The usage of reinforced thermosetting resin pressure piping has increased significantly in chemical plants, oil & gas facilities, water and sewage system. It is because of its corrosion resistance, strength & durability features. 

RTRP Piping Advantages

• Provides corrosion resistance for numerous services including seawater pipeline, acids.
• Fiberglass piping is lighter compared to steel. So, it doesn’t require heavy lifting equipment for site erection and installation.
• Fiberglass piping has a smoother internal surface that lowers the frictional losses and energy requirements for pumping.
• The RTRP piping does not corrode from naturally changing soil and groundwater conditions.

Manufacturing Process

There are three different types of manufacturing processes as follows:

Filament Winding Process: ASTM D2996 covers RTRP pipe manufactured by the filament winding process up to 24 inches. Then the glass fiber roving or roving tape is wetted through resin and wrapped in a particular pattern until the required structural thickness is obtained. The recommended angle for winding angle is 54º ± 2°. It provides optimum axial and hoop strength to the RTR pipe. This method of manufacturing results in a higher glass fiber to resin ratio and lower wall thickness. The internal diameter of the pipe remains fixed while the external diameter varies with the wall thickness of the pipe. The filament winding process provides higher tensile strength and a uniform glass pattern. However, for corrosion-resistant applications which require a resin-rich (90% +) inner layer, fabrication generally starts through the hand lay-up process.

Centrifugal Casting Process: The ASTM D2997 specification covers machine-made glass-fiber-reinforced thermosetting-resin pressure pipe manufactured by the centrifugal casting process. In this process, the resin and glass fiber reinforcement is applied to the internal side of a mold so the outside diameter remains constant. And the inside pipe diameter changes as per the wall thickness of the reinforcement. It provides the most consistent mechanical properties and close tolerance on dimensions.

Different types of RTRP Piping Joining Systems

• Adhesive Bonded Joint or Cemented Joints
• Mechanical Joints or Rubber Seal Joint
• Laminated Joint 
• Threaded Joint
• Flanged Joint

RTRP Performance Qualification Testing 

• Hydrostatic Design Stress: ASTM D2992 standard defines two procedures for determining the hydrostatic design basis (HDB) or pressure design basis (PDB) of fiberglass piping. It includes Procedure A (cyclic) and Procedure B (static).
• Stiffness Testing: It is considered following ASTM D2412 standard. There should be no visual indication of cracking or structural damage at 10% deflection.
• Beam Strength Test: This test is carried out following ASTM D2925 standard. The apparent elastic pipe modulus gets calculated using the total maximum measured deflection which shall not be less than 6900 MPa (1,000,000 psi). 
• Hydrostatic Strength: It includes testing of the complete piping system. The components shall be tested under ASTM D1599 standard.
• Joint Integrity Test: All restrained gasket joints shall be tested per ASTM D4161 standard.
• Flange Pressure Rating: It is following ASTM D4024 standard.

RTRP Piping Applicable Standards

Let’s have a look at the comprehensive list of standards applicable to the design, manufacturing, inspection & testing of fiberglass piping.

ISO 14692-1: Glass-reinforced plastics (GRP) piping for petroleum and natural gas industries – Part 1: Vocabulary, symbols, applications and materials
ISO 14692-2: Qualification and manufacturing of GRP piping and fittings 
ISO 14692-3: Provides guidelines for the GRP piping systems design
ISO 14692-4: Provides requirements and recommendations for the fabrication, installation, operation, inspection and maintenance of GRP piping systems
ASTM C581: Standard practice for determining thermosetting resins chemical resistance used in Glass-Fiber-Reinforced structures intended for liquid service
ASTM C582: Standard specification for contact-molded reinforced thermosetting plastic (RTP) laminates for corrosion-resistant equipment
ASTM D543: Evaluates the resistance of plastics to chemical reagents
ASTM D2992: Standard practice for obtaining hydrostatic or pressure design basis for “Fiberglass” pipe and fittings
ASTM D2996: Standard specification for filament-wound fiberglass pipe
ASTM D2997: Centrifugally cast “Fiberglass” (Glass-Fiber-Reinforced Thermosetting-Resin) Pipe
ASTM D3262: Standard Specification for “Fiberglass” Sewer Pipe
ASTM D5421: Standard Specification for Contact Molded "Fiberglass" Flanges
ASTM D5685: Standard Specification for "Fiberglass" Pressure Pipe Fittings
ASTM D3517: Standard Specification for "Fiberglass" Pressure Pipe
ASTM D4024: Standard Specification for Machine Made "Fiberglass" Flanges

Hence, the list mentioned above of piping standards helps to reduce significant costs by providing optimum piping design. If you’re looking for piping design and engineering services for your next project, consider outsourcing a reliable team having an in-depth understanding of modern piping design industry codes and standards.