Product Design
General
Pipeline and piping systems shall be designed so that mechanical integrity is maintained under all coincident loading conditions and process temperatures to which these systems can be exposed, and shall represent the most severe anticipated conditions experienced during installation and within the service life of the system.
GRP pipe systems are more sensitive to mechanical overloading, surge, and water hammer effects than steel systems and this requires special care when designing GRP pipe systems.
Triplet designers are actively involved throughout the entire project from start to finish, including late installation changes, system hydro testing, up to commissioning.
Jointing System
Triplet is offering various types of bonded and mechanical joints for GRP piping system. These tend to be proprietary in nature but can generally be categorized into the following types:
Adhesive-bonded joints, (conical bell & spigot)- Laminated joints (butt & wrap joint)
- Mechanical O-ring bell-and-spigot elastomeric seal joints (key lock joint)
- Flanged joints;
- Threaded joints
- Metallic/GRP interfaces.
Adhesive-bonded joints
The adhesive-bonded joint is a rigid type of joint, which consists of a slightly conical (tapered) bell end and a machined tapered spigot end Adhesive joints have the lowest material cost of all joints, and are structurally efficient when made up correctly. Make-up of the adhesive joint tends to become more difficult for larger sizes, particularly for pipe above 600 mm diameter. Triplet recommends using adhesive bonded joint up to 600 diameter and up to 65 bar design pressure.
Typical adhesive-bonded joint
Key
| 1 Design and failure envelope of GRE pipes and fittings | 2 Adhesives | 3 Finishing fillet | 4 Pipes with spigot end |
Laminated joints
The laminated joint consists of plain-ended pipe and fittings, prepared, aligned and laminated with reinforcing fibres and resin/hardener mixture as shown in Figure. There are two types of laminated joint: the outer surface of the pipe can be either lightly abraded leaving a cylindrical surface, or else abraded to provide a taper.
Typical laminated joint
Key
| 1 laminate overlay | 2 pipe laminate | 3 laminate lengths | 4 tapers not steeper than 1 in 6 | 5 pipe center line |
Threaded connections
Thread joints are normally use for high pressure piping system. Threaded end connections which conform to API standards should meet the requirements of API 15HR. Threaded end connections which are the design of the manufacturer should meet the specification.
Triplet recommends using threaded joints for high design pressure (more than 70 bar).
Threaded joint
Key
| 1 Standard API threads | 2 Pipe body male end | 3 Pipe body female end | 4 Pipes center line |
Flanged joints
Flanged joints facilitate connections with steel piping and allow easy assembly and disassembly of piping systems. The outside diameter and hole spacing of flanges should meet the requirements of ASME B16.5/ASME B16.47. GRP flanges are always flat-faced and, accordingly, matching flanges should also be flat-faced in order to avoid the crack.
Typical Sketch of GRE Flange to CS Flange Connection using Gasket & Spacer Ring
Mechanical O-ring elastomeric bell-and-spigot seal lock joints (Key-lock joint)
Elastomeric bell-and-spigot seal lock joints are made up of a spigot end and a socket end with O sealing rings. The socket will be an integrated part of the pipe. If a tensile-resistant joint is required, a locking strip can be incorporated as shown in Figure
These are the simplest joints to assemble, and they can be designed to enable a small amount of axial and angular movement within the joint. They are cheaper and generally structurally more efficient than flanged joints, but more expensive than adhesive joints. They are more bulky than adhesive joints but have the advantage that they can be quickly assembled in poor working conditions and are the preferred joint for concrete gravity-base system piping and ballast transfer piping in ships.
Typical elastomeric bell-and-spigot sealed joints (locking type)
Key
| 1 Pipe with integral socket end | 2 Elastomeric rings | 3 Locking strips | 4 Pipes with spigot end | 5 insert hole for locking strip |
