Plastic pipework

Plastic pipework standards for the conveyance of drinking water,waste water, chemicals, heating and cooling fluids, foodstuffs, ultra-pure liquids, slurries, gases, compressed air and vacuum system applications. Plastic Pressure Pipe Systems have many advantages to offer to the designer, installer and end user of pipe systems; they are light weight, easier to install than metal piping systems, faster to install as well as being more cost effective than metal piping systems. They are used for both above and below ground applications. A well installed and well maintained Plastic Pressure Pipe System could have a life cycle of up to 50 years. This is dependent upon the medium, temperature, chemical consistency, pressure and type of plastic pressure pipe system selected. Plastic Pressure Pipe Systems have been in use since the 1950s.

The most common Plastic Pressure Pipe Systems are:

* ABS Pipe Systems
* PVC Pipe Systems uPVC Pipe Systems PVCu Pipe Systems or PVC-U Pipe Systems
* PVC-C Pipe Systems
* PP Pipe Systems
* PE Pipe Systems or MDPE Pipe Systems

Selection of material

In order to select the most suitable material for a pipe system the following factors need to be considered:

* Medium or type of fluid and its chemical composition
* Operating temperature
* Operating pressure

These factors are interlinked and only when all have been addressed can the correct type of Plastic Pressure Pipe System be selected.

Materials used

* ABS (Acrylonitrile butadiene styrene)
* PVC-U (Polyvinyl chloride, unplasticized) also known as PVCu or uPVC
* PVC-C (Polyvinyl chloride, post chlorinated) also known as PVCc or cPVC
* PP (Polypropylene)
* PE (Polyethylene) also known as LDPE, MDPE and HDPE (see note)
* PVDF (Polyvinylidene fluoride)

Note: LDPE, MDPE and HDPE = low, medium, and high density Polyethylene.

Material characteristics

ABS (Acrylonitrile Butadiene Styrene)

ABS is suitable for the conveyance of potable water, slurries and chemicals. Being non toxic ABS complies with the toxicological requirements of the British Plastics Federation and the British Industrial Biological Research Association (BIBRA) code of practice for food usage. ABS Pipe Systems are very suitable for chilled water applications, due to its low temperature properties. ABS is also suitable for use in compressed airline systems.

* Good chemical resistance
* Good abrasion resistance
* Good material strength and high impact resistance
* Operating temperature range -40°C to +80°C
* Solvent welding

PVC-U (Polyvinyl Chloride, Unplasticized)

PVC-U has excellent chemical resistance across its operating temperature range, with a broad band of operating pressures. Due to its long term strength characteristics, high stiffness and cost effectiveness, PVC-U systems account for a large proportion of plastic piping installations. PVC-U is resistant to most solutions of acids, alkalis, salts and organic compounds miscible with water. It is not resistant to solvents, aromatics and some chlorinated hydrocarbons. PVC-U is not at all suitable for compressed air systems.

* Environmental resistance to aggressive caustic and acidic fluids
* Good abrasion resistance
* Operating temperature range 0°C to +60°C
* Bell-and-Spigot gasket-sealed joint
* Solvent cement joint
* fusion welding

PVC-C (Polyvinyl Chloride, Post Chlorinated)

PVC-C has excellent chemical resistance across its operating temperature range, with abroad band of operating pressures. Due to its long-term strength characteristics, high stiffness and cost effectiveness, PVC-C systems are suitable for a wide diversity of plastic piping installations. PVC-C is resistant to many acids, bases, salts, paraffinic hydrocarbons, halogens and alcohols. It is not resistant to solvents, aromatics and some chlorinated hydrocarbons.

* Environmental resistance to aggressive caustic and acidic fluids
* Good abrasion resistance
* Operating temperature range 0°C to +90°C
* Solvent welding

PP (Polypropylene)

Polypropylene is suitable for use with foodstuffs, potable and ultra pure waters, as well as within the pharmaceutical and chemical industries. Polypropylene is adversely affected by UV radiation and requires insulation or a protective coating if installed outside.

* Environmental resistance to most organic and inorganic chemicals
* Good material strength and fatigue resistance
* Operating temperature range -10°C to +110°C
* Fusion Welding

PE (Polyethylene)

When compared to other plastics, PE shows excellent diffusion resistance, and because of this property, polyethylene has been successfully used for the safe conveyance ofgases for many years. Polyethylene has good resistance to acids and caustic substances. Resistant to organic and inorganic solvents at a wide range of temperatures. It is not resistant to strong oxidising acids.

* Resistance to acids, caustic substances, organic and inorganic solvents
* Good material strength and fatigue resistance
* Operating temperature range -40°C to +65°C
* Mechanical compression joint up to 125mm or Fusion Welded

PVDF (Polyvinylidene Fluoride)

PVDF has excellent chemical resistance which means that it is widely used in the chemical industry as a piping system for aggressive liquids. PVDF is a homopolymer without additives such as stabilisers and processing agents. It also displays excellent flame retardant properties. PVDF is listed with many worldwide agencies as suitable for use withfoodstuffs, dairy products, in semi-conductor and pharmaceutical manufacturing, and for other applications in the food and drug sector. PVDF is resistant to most acids, alkalis, salts, halogens, alcohols and chlorinated hydro-carbons. Strong polarized solvents, such as ketones and esters, can cause the material to swell.

* Resistant to most acids, alkalis, salts, halogens, alcohols and chlorinated hydro-carbons
* High mechanical strength,
* Operating temperature range -20°C to 140°C
* IR Welding

Components of Plastic Pressure Pipe Systems

There are four key components that make up a plastic pressure pipe system:

* Pipes
* Fittings
* Valves
* Accessories

The range of pipe diameters for each pipe system does vary. However, the size ranges from 12mm to 400mm and 3/8" to 16".

Pipes

Pipes are extruded and are generally available in:
* 3m straight lengths
* 5m straight lengths
* 6m straight lengths
* 25m, 50m,100m, and 200m coils are used for LDPE and MDPE (See note below)

Note: Coils are only used up to 90mm in LDPE and MDPE byond this 6m straight lengths are the norm.

Pipe fittings

Pipe fittings are moulded and the finished product is available as:
* Tee 90° equal
* Tee 90° reducing
* Tee 45°
* Cross equal
* Elbow 90°
* Elbow 45°
* Short Radius Bend 90°
* Socket/coupler
* Socket/coupler reducing
* Union
* End Caps
* Reducing Bush
* Stub Flange
* Full Face Flange
* Blanking Flange
* Composite Union (Brass BSP Thread one side, plain plastic socket the other)

Valves

Valves are moulded and the finished product is available as:

* Ball Valve
* Multi Port Ball Valve
* Butterfly valve
* Spring Check Non Return Valve
* Ball Check Non Return Valve
* Swing Check Non Return Valve
* Diaphragm valve
* Knife Gate Valve
* Globe Valves
* Pressure Relief Valves
* Pressure Reducing Valves

Accessories

Accessories are available as:

* Solvent Cement Glue
* Cleaner
* Brushes
* PTFE Tape
* Pipe Clips and Fixings
* Mild Steel Backing Ring
* Plastic Backing Ring
* Gaskets (EPDM and FPM)

Note: EPDM = ethylene propylene diene monomer rubber FPM = Fluoropolymer

Connection

Connection of a Plastic Pressure Pipe System can be achieved by the following methods:

* Solvent Cement Glue
* Fusion Welding
* Mechanical Joint, Flange, Compression, BSP or NPT Thread
* IR Welding

Solvent Cement Glue

* Supplied in 125ml, 500ml and 1L tins

Pipe support and hanging

When supporting or hanging plastic pipe systems there are a few factors that have to be considered, so that the correct pipe supports can be selected.

* Material and type of plastic pipe system
* Outside diameter of the plastic pipe
* Temperature of fluid or medium

These factors are interlinked and only when all have been addressed can the correct type of pipe supports be selected. The above information is also critical for determining the distance between each pipe support, this is referred to in the industry as pipe centers or pipe centres depending on your country of origin.

Safety Factors

Each component within a Plastic Pressure Pipe System is given a pressure marking relating to the amount of pressure it can sustain. However, each manufacturer tests the product beyond its individual rating so that a safety factor can be quoted. With all pressurised systems there can be spikes hence the need for safety factors. In general, each manufacturer tests their product to the following safety factors:

* Pipes = X 1.5 the product pressure rating
* Pipe fittings = X 3 the product pressure rating
* Valves = X 3 the product pressure rating

Note: This information is provided for the purpose of explaining why a safety factor exists. Each manufacturer has their own safety factors to which you must refer.

Standards and Approvals

WRAS

Water Regulations Advisory Scheme tested by: WRc (Water Research Centre)

Required standard for any plastic pressure pipe system that connects to a drinking water / potable water source.

BSI

British Standards Institute (BSI Group)

* BS 3505:1986 Specification for PVC-U pressure pipes for cold potable water.Replaced By BS EN 1452-1 to 5 :2000 but remains current.

* BS 4346-3:1982 Specification for PVC-U joints and fittings for use with PVC-U pressure pipes and specification for solvent cement.Partially replaced by parts 1 to 5 of BS EN 1452

* BS 5391-Part 1:1976 Specification for ABS pressure pipes for industrial use

* BS 5392-Part 1:1976 Specification for ABS solvent cement fittings for industrial use

DIN

German Standard

References

*cite book
author=NCCER
title=Plastic Pipe and Fittings: Trainee Guide
publisher=Prentice Hall
isbn=0131600427

*cite book
author=David Willoughby
title=Plastic Piping Handbook
publisher=McGraw-Hill Professional
isbn=0071359567

*cite book
author=Thomas Sixsmith & R. Hanselka
title=Handbook of Thermoplastic Piping System Design
publisher=Marcel Dekker Ltd
isbn=0824798465

*cite book
author=David A. Chasis
title=Plastic Piping Systems
publisher=Industrial Press|isbn=083111181X

*cite book
author=Pipestock Limited
title=Installing Plastic Pressure Pipe Systems
publisher=Pipestock

*cite book
author=Mike Greig
publisher=Effast Pipe Systems
title=Plastic Piping Systems, Guide to Design and Installation
isbn=1904133339

*cite book
author=Dr Tarik Al-shemmeri BSc MSc PhD CEng MIMechE of Staffordshire University
title=The Red Book, A Guide to the Design and Installation of Plastic Pipeline Systems |isbn=1897898819

External links

* [http://www.pipestock.com Pipestock] - A commercial site offering tables, specifications and showing pictures of product