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EF WELDING: HOW PIPE OVALITY PREVENTS GOOD WELDS

The non-brittle and flexible characteristics of polyethylene make it ideal for many pressure and non-pressure applications. Those useful characteristics also mean PE pipe can alter shape. Ovality generally known as ‘out of roundness’ is one of the most common issues found in PE pipe. One of the best tips to ensure a quality electrofusion weld is to ensure that polyethylene pipe is not out-of-round before attempting the electrofusion process.

To determine if out-of-round conditions exists measure the pipe diameter in numerous directions across the pipe end with a tape measure. If the measurements exceed the maximum tolerance, a re-rounding clamp or device must be used to bring the pipe back to a round condition.

HOW DOES POLYETHYLENE PIPE BECOME OUT-OF-ROUND?

MANUFACTURING
Installers need to confirm that polyethylene pipe matches all dimensional requirements for the job and the fitting being installed and that the pipe does not exceed the allowed ovality. If ovality is greater than allowed you must take steps to re-round the pipe.

STORAGE
Polyethylene pipe that is warehoused for a period of time or stacked on top of each other can experience ovality issues (more pronounced with large diameter pipe).

TIME
Large Diameter Polyethylene pipe will tend to relax a little during storage due to a combination of its weight and its natural flexibility.

INSTALLATION
Mechanical forces experienced during some trenchless installation techniques such as Pipe Bursting or Directional Drilling can temporarily leave the polyethylene pipe elongated and out-of-round.

PREVIOUS INSTALLATION
Polyethylene pipe that has been underground for awhile is subjected to earth loads. These earth loads can cause the pipe to sag and/or become out-of-round.

WHY IT IS KEY TO ADDRESS PIPE OVALITY FOR ELECTROFUSION INSTALLATIONS

One of the most critical functions of the electrofusion process is to seal the gap between the pipe and the fitting and to build up interfacial pressures for the fusion process to take place. If this gap is not sealed and interfacial pressures cannot build up, there is no way for the electrofusion joint to effectively achieve the high quality fusion it was designed for.

If a pipe is out-of-round the initial concern is that the surface area of the pipe may not adequately come in contact with the fusion zone of the electrofusion fitting. This could result in the electrofusion fittings cold zones, which are designed to contain the material generated in the melt pool, allowing the molten material to escape out of the fusion area without producing any melt penetration. This is a key concern when installing tapping and branch saddles since they do not fully encircle the pipe like an electrofusion coupling.

HOW TO CORRECT OUT-OF-ROUND PIPE

First, determine if out-of-round conditions exists. This can be done visually for extreme cases or by measuring the pipe diameter in numerous directions across the pipe end with a tape measure. If the measurements exceed the maximum tolerance, a re-rounding clamp or device must be used to bring the pipe back to a round condition.

The following table shows the approved dimensions for PE100 pipe:

The PLASSON range includes high quality tools to prepare pipe correctly for electrofusion, inlcuding re-rounding clamps.

Click here to see PLASSON’s tooling range….

ENGINEERING AN  “O” SO RELIABLE FITTING


How PLASSON compression fittings work is a bit of a yarn that starts way back in 1896. Unless you are a trivia junkie, it will probably come as news that one of the most critical precision mechanical components ever developed was patented on May 12, 1896. That was when a Swedish patent for the O-ring was awarded to J.O. Lundberg.  Niels A. Christensen was granted a US patent for his O-ring design in 1937.


Like all good ideas, it came to the attention of some pretty big players.  The O-ring quickly became the standard seal for hydraulics in the military.  The top brass set out the standard sizes and basic design guidelines that remain in use today.


The humble O-ring delivers a reliable seal through compression and that is why PE pipe joiners that seal via O-rings are described as compression fittings.

PLASSON seals due to a simple solution


PLASSON took the original O-ring from 1896 and did something simple but clever with it.  By placing the O-ring into a special groove machined into the inside of each fitting, the PLASSON O-ring is always in the optimum position for sealing.


This innovative design means the fitting seals water-tight as soon as the pipe passes through the O-ring.  With PLASSON compression fittings, you only tighten the nut to prevent the pipe and fitting from moving apart, or blowing out, under pressure. The design also means the O-Ring can’t fall out and be damaged, contaminated or lost during installation.


The O-ring is a donut-shaped ring (technically, a toroid) with a circular cross section made from different elastomers.

PLASSON compression fittings can have Nitrile NBR O-rings or EPDM O-rings, which has a better chemical resistance than NBR, or Vitron seals, which offer better chemical resistance than EPDM.


The name Viton is a trademark and refers to fluorocarbon O-rings, or FKM/FPM for short. This material has an excellent tolerance for high temperatures, resistance to oils, fuels and hydraulic fluids as well as aromatics and solvents.


O-rings seal by mechanical deformation (caused by compression) which creates a barrier to a fluid’s potential leak path between two closely mated surfaces.


Applying fluid pressure pushes the O-ring against the groove wall on the low-pressure side, increasing the sealing force. At higher pressures, the O-ring deforms to a “D” shape, increasing the contact area further.

PLASSON METRIC COMPRESSION TEES FOR POLY PIPE


The range of PLASSON compression fittings includes small 16mm and popular residential plumbing fittings at 20mm, 25mm and 32mm right up to large 63mm couplers for civil water and waste water pipelines.


PLASSON compression fittings are easy to install – just take a look at our install video:

WHAT IS AN HDPE PIPE FITTING?


HDPE pipe fittings help connect HDPE pipe together. PLASSON fittings can join HDPE pipe in different ways: electrofusion fittings join pipe permanently through fusion; metric compression fittings seal through an internal O-ring being compressed to form a seal between the fitting and the pipe; and BSP threaded fittings join pipe through threaded connections.

There is a surprisingly vast range of poly pipe compression fittings. Even the most familiar options, like couplers, tees and elbows, have a range of reducing and connection options that can take some time to understand.


While pipe fittings or connectors attach one pipe to another in order to lengthen the run or change the flow direction in a plumbing system, there are also lots of clever fittings that do so much more to make plumbing life easier. They can combine, divert or reduce the flow of the water supply. They can monitor flow or stop it, reduce pressure and provide outlets for sampling. 


PLASSON compression fittings have a number of unique features that help deliver leak-free connections and reliable, long-life PE pipelines.

Compression fittings come in a range of standard sizes. PLASSON compression fittings start small for domestic plumbing at 16mm, 20mm, 25mm and 32mm and continue up to civil and industrial sizes like 40mm, 50mm, 63mm and right up there to above 1000mm.


All PLASSON compression fittings seal the instant they go on the pipe due to an innovative O-ring design.  The O-ring is held captive in the body of the fitting in a specially designed groove. This simple piece of engineering means the O-Ring can’t fall out, get contaminated or become easily damaged like other compression fittings.


While most have openings of the same size on each end, some fittings are designed with different-sized openings and serve as the transition from one size pipe to another. The following briefly explains some of the different PLASSON fittings, where and how they are used.


To see the full range of PLASSON metric compression poly pipe fittings click here…

PLASSON METRIC COMPRESSION TEES FOR POLY PIPE

Tee Fittings & Wye Fittings
Tees and wyes are used to connect three pieces of pipe. Tees can have one inlet and two outlets at 90-degree angles in the shape of a “T” and are used to split a supply line, or they can combine two lines into one outlet. You often see tee fittings connected to potable water supply lines. A wye is shaped like a “Y” with the two inlets coming together at roughly 45-degrees into a single outlet in drain applications.


Elbow Fittings
Elbows change the direction of flow between two pipes. Common elbows have 90-, 60-, 45- and 22 ½-degree bends and are used to make a turn. They can be joined together to move around obstructions in a pipe run.

Coupling & Adapter Fittings
Pipe couplers slip over the outside of two pipes to connect them. A coupling can be a reducer, or reducing coupling, meaning they reduce flow by joining a larger pipe to a smaller size. Adapters are used when connecting two pipes of different types. For example, an adapter could be fitted on the end of a plain pipe to allow a threaded connection at the other side of the adapter, or to connect poly pipe with another pipe material, like copper.

PLASSON OFFERS A RANGE OF METRIC COUPLING FITTINGS FOR PLUMBING

Bushing Fittings
Bushings, sometimes called reducer bushings, are used for connecting two pipes of different sizes. The larger diameter of the bushing fits inside of the larger pipe. The smaller pipe is then inserted into the smaller end of the bushing.

Flange Fittings
A flange is a flat, round fitting that creates a tight seal with bolts or clamps. They are used when pipes pass through walls, ceilings and floors. They are also used in electrofusion installations to connect valves to main lines.

Plasson Australia BSP threaded fittings range


Cap Fittings
A cap fits over the end of a pipe to stop the flow of water or gas. These fittings can be used for the permanent termination point of a pipe or used temporarily to cut off supply during a plumbing or pipeline project. 

Plug Fittings
Plugs used at the end of a pipe to seal the opening, similar to a cap. The difference is that a plug fits into the threaded pipe opening to make the seal while caps fit over the opening. They are commonly found at cleanout locations for sewer systems.

PLASSON METRIC COMPRESSION ADAPTORS FOR CONNECTING PE PIPE
https://merchant.plasson.com.au/metric-compression-fittings/


Nipple Fittings
Nipples are short sections of pipe that are male-threaded at each end and used for connecting two female-threaded pipe ends or fittings.


Ag Pipe Fittings
Agricultural pipe is widely used for stock watering, water mains, irrigation systems and bore water reticulation. PLASSON rural couplings and clamp saddles are specially designed to connect imperial-size polyethylene pipes from ¾” to 2″. The range is compatible with PELD, PEHD, PE40, PE80 and PE100 pipes complying with AS/NZS 4130. PLASSON’s special red barbed inserts fit a range of pipe dimensions so that ag pipe can be easily connected without the need for any tools.

Rural Ag pipe couplings from Plasson Australia

The PLASSON range includes solutions for most plumbing situations. You can take a look at the catalogue for the full range here….

TOP SOLUTIONS: POLY PIPE REDUCING FITTINGS

PLASSON reducing adaptor sets can be inserted into will existing PLASSON poly pipe fittings to reduce the size of the outlet whilst maintaining pressure ratings and eliminating leak risk.

THE POLY PIPE ABC’S: PN TO SDR

Here’s a quick look at pipe colours and codes for those new to the game or keen to brush up:

Polyethylene pipes, or PE pipes, have been produced in Australia since the mid 1950’s.  The industry started small with diameters like 20mm, 32mm and 63mm for industrial and agricultural applications but PE pipe and fittings are now available in diameters up to 2000mm.

PE pipe has grown rapidly in popularity and polyethylene pipe connected by compression or electrofusion fittings is now largely made from PE100.  This is the third generation of PE and it delivers high performance, long-life PE pipes that will provide reliable service for 100 years or more.

PE100 pipe is used to convey all types of liquids and gases for above and below ground applications including:

  • Urban water and gas supply
  • Mine dewatering
  • Irrigation supply
  • Slurry pipelines
  • Vacuum, pressure and gravity sewer systems
  • Submarine pipelines and ocean outfalls
  • Trenchless pipeline installation and rehabilitation
  • Industrial process pipe work
  • Compressed air services
  • Electrical and telecommunication cable conduits
  • Upstream coal seam gas and water pipelines

Polyethylene pipe has a coloured stripe extruded into the pipe wall as a permanent reminder of what it is inside. These are the main colour codes you are likely to come across when joining PE pipe with compression or electrofusion fittings:

BLUE = potable water

RED = fire mains

LILAC = recycled/grey water

YELLOW = gas

GREEN = rain water/raw water

CREAM = sewer

Polyethylene, or PE, pipe has been successfully used throughout the world for more than 50 years. The main benefits of PE pipes and fittings are corrosion resistance, high strength, toughness and flexibility, so it’s no wonder it is a popular choice worldwide.

Aside from the colour indicating what is being carried by the pipe, there is valuable detail printed on the pipe too.

What is PN?

PN is printed on the pipe. For blue stripe potable water pipe this is usually PN16. The acronym PN stands for Pressure Nominal. When a pipe has a rating of PN16, it is designed to handle 16 Bar internal pressure.

Poly pipe comes in a range of pressure ratings:

PN10 which has a maximum pressure rating of 1000kpa
PN12.5 which is for a maximum of 1250kpa
PN16 for a maximum of 1600kpa

What is OD?

The OD is also printed on the pipe. This is the Outside Diameter, or OD, of the pipe measured in ‘mm’.

Then there is also the acronym SDR, which stands for Standard Dimension Ratio.

When the outside diameter of the pipe is divided by the wall thickness, it gives the SDR of the pipe.

These are important measurements to know and understand when installing pipes that will carry anything under pressure.

SDr calculations for poly pipe PE100

Why choose PE100 pipe?

PE100 is the third generation of pipe grade PE and is a high performance plastic engineered for to deliver.

It has an optimum balance of three key properties: Minimum Required Strength (MRS) – this provides long-term strength and creep resistance. Stress crack resistance (sometimes referred to as slow crack growth resistance). Rapid crack propagation resistance.

Pipe that carries potable water in Australia is made from PE100 which is a type of plastic resin that has been proven to have a minimum required strength (MSR) of 10 MPa at 50 years and 20 degrees celcius.  The operational service life of PE pipelines is dependent upon a number of factors that include: raw material quality, processing conditions, installation, the aggressiveness of the fluid transported, operating pressure and temperature.

‍Click to watch how OD, SDR and PN work together

what abreviations on poly pipe mean

LEAK-FREE POLY PIPE JOINS

Poly pipe joiners are easy to use, they are long lasting and corrosion-resistant.  As with all pipe lines, joins mean there is a potential for leaks. But, by paying attention to key steps in the installation process, it is possible to achieve leak-free joins.

Incorrect installation
When pushing the plumbing fittings onto the pipe, ensure the pipe is fully inserted. If the fitting is only partially inserted onto the pipe it will not create a watertight seal. When the pipe is traveling through the fitting you will feel some resistance. This can mean you think the pipe has been pushed all the way into the fitting.   Making a witness mark will help show how far the pipe needs to be inserted in order to reach half way into the fitting.

Pipe issues

In order to seal tightly inside the fitting, pipe ends need a clean, straight cut. If the end is jagged or uneven, it will not create a watertight seal

If the tubing is cut on an angle, it is unlikely to seal and could also nick the O-ring

One way to avoid these issues is to cut pipe with a pipe cutter rather than a blade or saw

Read more

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