GRP AND FRP PIPELINE

INTRODUCTION

DEFINATION A complex non-isotropic material, in which two or

more distinct, structurally complementary substances, glass fiber and thermoset polymer resin, combine to produce structural or functional properties not present in the individual component

GLASS FIBERS :- strength and stiffnessRESIN :- impact resistance, compressive strength,

and corrosion resistance

TYPES OF FRP PIPE

GRP-GLASS REINFORCE POLYEASTER GRV-GLASS REINFORCE VENYLEASTER GRE-GLASS REINFORCE EPOXY

RESINS-will provide the thermal and chemical properties such as glass transition temperature, resistance to heat, chemical resistance etc. required for the finished product.

GRP PIPE

GRP Pipes are made from the dual helical winding technology. The major raw materials used for this are fiber glass, Iso-phtahlic resin and sand (certain cases).

Inner liner consists of surface tissue and vinyl ester resin for maximum chemical resistance and will enhance abrasion resistance.

The structural layer consists of E- glass and Iso- pthalic resin.

Outer Liner is a thinl layer with structure similar to the structural layer.Diameters of pipes produced range from 25mm to 2000mm currently.

GRV PIPE

GRV Pipes are made from the dual helical winding technology. The major raw materials used for this are fiber glass, Vinyl Ester resin and sand (certain cases).

Inner liner consists of surface tissue and Vinyl ester resin for maximum chemical resistance and will enhance abrasion resistance.

The structural layer consists of E- glass and Vinyl Ester resin.

Outer Liner is a thin layer with structure similar to the structural layer.

GRVE Pipes have better mechanical and chemical Properties when compared to GRP Pipes. Diameters of pipes produced range from 25mm to 2000mm currently.

GRE PIPE

GRE Pipes are made from the dual helical winding technology. The major raw materials used for this are fiber glass, Amine Cured Epoxy resin and sand (certain cases).

Inner liner consists of surface tissue and Amine Cured Epoxy resin for maximum chemical resistance and will enhance abrasion resistance.

The structural layer consists of E- glass and Amine Cured Epoxy resin.

Outer Liner is a small layer with structure similar to the structural layer. Diameters of pipes produced range from 25mm to 2000mm currently.

RAW MATERIAL GLASS FIBERS REINFORCEMNENT (IN THE

FORM OF VAIL) THERMOSETTING RESIN CHOPPED STRANDS WOVEN ROVING AUXILIARY COMPONENT 1) CATALYST FOR POLYESTER RESIN 2) ACCELERATOR 3) INHIBITOR 4) SILICA SAND

PIPE COMPOSITION

GRP pipe wall consists of three layers perfectly adherent to each other and having different characteristics and properties in relation to their function.

Inner Liner Structural Wall External Liner

PIPE COMPOSITION

GRP pipe wall consists of three layers perfectly adherent to each other and having different characteristics and properties in relation to their function

1) Inner Liner2) Structural Wall3) External Liner

INNER LINER

Liner or chemically resistant layer is the internal layer of the pipe. It is in direct contact with the conveyed fluid. This layer has the function to guarantee the resistance to the chemical corrosion and the impermeability to the pipe. Liner has the internal surface, namely be one in contact with the conveyed fluid, particularly smooth. This characteristic of smoothness reduces the fluid head losses to the minimum and opposes the growth of mineral deposits and algae. The liner is made of two monolithic sub layers. The inner one, in direct contact with the fluid, is reinforced with glass veil, with a resin content of 90% and the outer one is reinforced with CSM glass, with a resin content of 70% by weight. The standard liner thickness, is about 0.5 to 1.5 mm, higher thickness can be produced on request.

STRUCTURAL WALL

Glass reinforced layers guarantee the mechanical resistance of the whole pipe against stresses due to internal and external pressure, external loads and thermal loads. For GRP/GRV pipes, this layer is obtained by applying on the previous partly cured liner, continuous roving of glass wetted with resin, under controlled tension. For GRE pipes, the structural wall is wound directly on a wet liner. This layer can contain aggregates like silica sand. Thickness of the mechanical layer depends on the design condition. .

EXTERNAL LINEAR

Top coat or external liner is the outer layer of the pipe which consists of pure resin added with UV protectors to protect the pipe from sun exposure. In case of severe exposure condition like aggressive soils or very corrosive environment, the external liner can be reinforced with a surfacing veil or added with fillers or pigments

WALL CONSTRUCTIONPERCENTAGE OF DIFFERENT TYPE OF MATERIAL IN FRP PIPE

WITH RESPECT TO LAYERS

METHOD OF CONSTRUCTON

HAND LAY-UP OPERATION

SPRAY LAY-UP OPERATION

PULTRUSION OPERATION

CHOPPED STRAND MAT

FILAMENT WINDING

PROPERTIES

DESIGN TEMPERATURE DESIGN PRESSURE DESIGN STRESS DENSITY THERMAL EXPANSION PRESSURE EXPANSION MODULUS OF ELASTICITY THERMAL CONDUCTIVITY

HAND LAY-UP OPERATION Resin is mixed with a catalyst or hardener if working with epoxy, otherwise it

will not cure (harden) for days/weeks. Next, the mold is wetted out with the mixture.

The sheets of fiberglass are placed over the mold and rolled down into the mold using steel rollers. The material must be securely attached to the mold, air must not be trapped in between the fiberglass and the mold.

Additional resin is applied and possibly additional sheets of fiberglass. Rollers are used to make sure the resin is between all the layers, the glass is wetted throughout the entire thickness of the laminate, and any air pockets are removed.

The work must be done quickly enough to complete the job before the resin starts to cure. Various curing times can be achieved by altering the amount of catalyst employed. It is important to use the correct ratio of catalyst to resin to ensure the correct curing time.

1% catalyst is a slow cure, 2% is the recommended ratio, and 3% will give a fast cure. Adding more than 4% may result in the resin failing to cure at all.To finish the process, a weight is applied from the top to press out any excess resin and trapped air. Stops (like coins) are used to maintain the thickness which the weight could otherwise compress beyond the desired limit.

SPRAY LAY-UP OPERATION

The fiberglass spray lay-up process is similar to the hand lay-up process but the difference comes from the application of the fiber and resin material to the mold.

Spray-up is an open-molding composites fabrication process where resin and reinforcements are sprayed onto a mold.

The resin and glass may be applied separately or simultaneously "chopped" in a combined stream from a chopper gun.

Workers roll out the spray-up to compact the laminate. Wood, foam or other core material may then be added, and a secondary spray-up layer imbeds the core between the laminates.

The part is then cured, cooled and removed from the reusable mold.

PULTRUSION OPERATION

Pultrusion is a manufacturing method used to make strong light weight composite materials, in this case fiberglass.

Fibers (the glass material) are pulled from spools through a device that coats them with a resin.

They are then typically heat treated and cut to length. Pultrusions can be made in a variety of shapes or cross-sections such as a W or S cross-section.

The word pultrusion describes the method of moving the fibers through the machinery. It is pulled through using either a hand over hand method or a continuous roller method.

This is opposed to an extrusion, which would push the material through dies.

PULTRUSION OPERATION

CHOPPED STRAND MAT

Chopped strand mat or CSM is a form of reinforcement used in fiberglass. It consists of glass-fibers laid randomly across each other and held together by a binder.

It is typically processed using the hand lay-up technique, where sheets of material are placed in a mold and brushed with resin. Because the binder dissolves in resin, the material easily conforms to different shapes when wetted out. After the resin cures, the hardened product can be taken from the mold and finished.

FILAMENT WINDING

Filament-wound fiberglass pipe and fittings are machine-made products made on a rotating male mold.

The mold forms the inside diameter of the part. Filament wound parts are made with or without resin-rich interior corrosion barriers.

Corrosion barriers are made the same as with the hand layup process but may be applied by hand or by the machine.

The reinforced wall for filament-wound pipe and fittings made by drawing glass roving through a resin bath or with a resin-impregnated tape.

The resin-saturated roving or tape is placed on the outside of the corrosion barrier by a fiber placement head.

travels in relation to the rotating mold to properly position the reinforcement on the part.

The roving or tape-on filament-wound pipe is usually placed on the part at a helical angle.

This angle is normally optimized for maximum internal pressure ratings but may be changed for improved pipe stiffness, axial strength, or unsupported span spacing.

The number of layers of reinforcement used on filament wound parts is determined by the strength requirements for the part.

A barrier can be added to the exterior of filament-wound products for corrosion or abrasion protection.

FILAMENT WINDIND

ADVANTAGE

Low weight of pipes lengths that allows for the use of light laying and transport means.

Possibility of nesting of different diameters of pipe thus allowing additional saving in transport operations.

Easy installation procedures due to the kind of mechanical bell and spigot joint.

Corrosion resistance, both of the external wall in contact with the conveyed fluid. No protections such as coating, painting or cathodic are then necessary.

 Smoothness of the internal wall that minimizes the head losses and avoids the formation of deposits.

High mechanical resistance due to the glass reinforcement.

Absolute impermeability of pipes and joints both from external to internal and vice-versa.

Very long life of the material virtually infinite, which does not need maintaining.

higher resistance surge pressure with high stiffness offering very less chance of bursting of pipe

have excellent thermal insulating properties and there is no need for the pipes to be insulated externally to maintain the temperature inside the pipe

DISADVANTAGE

Performance and durability of GRP pipes may be sensitive to damage incurred by poor handling and installation practices.

External impact can induce star cracking of the barrier layer on the pipe bore with no apparent damage to the surface of the pipe.

They are not suitable under major urban carriageways or where there is high risk of third party interference after installation.

Though GRP pipes have excellent corrosion resistant properties, they can suffer strain corrosion in acidic environments.

Anchor blocks must be designed to withstand the bursting stress generated when the GRP pipeline is under pressure.

Even though, pipe cost is higher than HDPE, the total installation cost would compare with any other pipe material and the time saved in construction is significant

APPLICATION

JOINTS

Fiberglass piping is available with a wide range of joining systems to fit the particular application.

IMPORTANT FACTORS WHEN SELECTING THE JOINTING METHOD

A) CRITICALITYB) RELIABILITYC) EASE OF JOINT ASSEMBLYD) EASE OF REPAIR,AND FUTURE MODIFICATION

AND TIE-IN

TYPES OF JOINTS

UNRESTRAINED JOINT (withstand hoop pressure only.)

1) COUPLING OR SOCKET AND SPIGOT GASKET

RESTRAINED JOINT (which can resists longitudinal force and hoop pressure)

1) BUTT AND STRAP JOINT 2) FIXED FLANGED JOINT 3) STUB END WITH STEEL LOOSE FLANGE

METHOD OF JOINTS

ADHESIVE –BONDED JOINTS LAMINATED JOINTS ELASTOMERIC BELL AND SPIGOT SEALED

JOINTS FLANGED JOINTS THREADED JOINTS METALLIC/GRP INTERFACES OTHER METALLIC JOINTS

BUTT AND STRAP The butt and strap joining method (also known as the butt

and wrap, the butt weld, and the reinforcedoverlay joint; and sometimes referred to as an adhesive) is the oldest and most reliable joining method inthe industry today. The butt and strap is made as it is described - two pieces of pipe are butted togetherand layers of chopped strand mat and woven roving are wrapped around the pipe in a resin matrix. Theweld is applied to the exterior of the pipe and, if accessible, the interior as well (usually on pipe largerthan 18" nominal I.D.). Refer to Figure 1 for a typical butt weld joint. By using the same materials as thepipe, the butt weld joint can be designed with axial and bending strength properties equal to or superiorthan the

ADHESIVE BOND

A second type of joint was developed to act as a "joint of convenience" in the industry. This is the adhesive bonded joint. There are three common types of adhesive bonded joints:

1) taper by taper, 2)straight by taper 3) straight by straight.

taper by taper,

The taper by taper joint uses a fitting with a tapered I.D. and a pipe with a tapered O.D., matched and joined by a thin glue line. This joint is slower to make than the other joints, but it is the strongest of the adhesive-bonded joints.

STRAIGHT BY TAPER

A compromise to the taper by taper is the straight by taper joint which replacesthe pipe's tapered O.D. with a plain end uniform O.D. Less installation time is involved, but a thin glueline is not always ensured, thus compromising strength.

ADVANTAGE OF ADHESIVE BONDED JOINING SYSTEM

Can have a lower first time cost Less labor intensive Good under simple tensile and pressure

testing Under extremely adverse installation

conditions, may be preferred over the butt &strap

DISADVANTAGE OF ADHESIVE BONDED JOINING SYSTEM

Less reliable joining method NDT, outside of field hydrotesting and

some X-ray, unavailable Very weak under bending loads Installation time can equal the butt & strap Experienced knowledge of joining method

required to obtain a reliable joint Special tooling may be required Normally requires passive fire protection

when exposed to fire conditions

ADVANTAGE OF BUTT AND STRAP JOINING METHOD

Most reliable joining method Excellent mechanical properties By utilizing the same materials in the pipe,

the butt & strap has axial and bending strengths equal to or greater than the pipe No special tooling required When exposed to certain fire conditions, a fire

retardant version of the joint may not require additional passive fire protection

DISADVANTAGE OF BUTT AND STRAP JOINING METHOD

Can have a higher first time cost Labor intensive Some installation experience required NDT limited to visual inspection, cure

testing, and hydrotesting

CODES AND STANDERED

The following codes are generally followed for GRP piping stress analysis.

  BS 7159 ANSI B31.3, chapter VII, part 5. UKOOA ISO 14692

It is recommended to follow BS 7159 unless otherwise the client specifically requires any other codes

 

FLEXIBILITY ANALYSIS

INPUTA) OERTATING AND DESIGN PRESSURE,TEMPERATURE OF THE PIPEB) MASS PER UNIT LENGHT OF PIPE AND CONTAINC) AXIAL AND HOOP EXPANSTION COEFFICIENT OF PIPE MATERIALD) AXIAL AND HOOP MODULUS OF ELASTICITY OF PIPE MATERTIALE) POISSONS RATIO (LONGITUDINAL AND CIRCUMFERNCIAL)F) PIPE DIAMETER AND WALL THICKNESS FOR PIPEG) ROUTING DIMENTION AND MASSES OF ALL VALVE AND OTHER IN

LINE ITEMSH) VALVE TYPES AND CLOSURE TIMESI) ENVIRONMENTAL LOADINGSJ) STRESS INTENSITY FACTORK) FLEXIBILTTY FACTORL) THE ALLOWABLE STRESS FOR THE MATERIAL

STRESS OCCUR IN PIPE

pressure induced stresses Bending stress due to pipe weight and its

contents(fluid, insulation and rigid) Bending stress due to thermal expansion or

contraction. Bending stress due to Occasional load (wind,

seismic, etc)

The specific requirement of BS 7159 is the maximum combined stresses of four of above calculated stresses should not exceed the allowable design stress.

FAILURE ENVELOPE

THE GENERAL REQUIREMENT IS THAT THE SUM OF ALL AXIAL STRESSES AND ALL HOOP STRESSES IN ANY COMPONENT IN PIPING SYSTEM DUE TO PRESSURE,MASS AND OTHER SUSTAINED LOADING AND OF THE STRESSES PRODUCED BY OCCASIONAL LOADS SUCH AS WIND,BLAST OR EARTHQUAKE SHALL NOT EXCEEDS VALUES DEFINED BY THE FACTORED LONG TERM DESIGN ENVELOPE.

DEVELOPMENT OF ENVELOPE

FORMULAE)A s-qs = f1 * LTHS (For A1=A2=A3=1))B s-a = r * s-qs /2

C) r = 2 * s-sa / s-sh

s-qs - Qualified stress s-a- Extrapolated long term axial strength, MPa r – Biaxial stress ratio. s-sa – Short term axial strength from D2105 s-sh – Short term hoop strength from D15994 f2 = load factor depending on design case. f2 = 0.67 for sustained loads f2 = 0.83 for operating plus sustained loads f3 = 0.89 for occasional loads (water hammer, wind,

earthquakes)