Doug Sable and his team at Statewide Poly Service Pty Ltd used Plasson Sensor Saddles to connect instrumentation, drain valves, take off’s and pH sensors to a wide range of large bore PE pipe sizes.

The project called for the installation of more than eighty Plasson Electrofusion Sensor Adaptors. The Plasson Sensor Adaptor alleviated the challenge of installing sensors in a limited space environment and negated the requirement for large bore PE saddles and tee pieces.

Plasson Sensor Adaptors are welded to the pipe using electrofusion technology. They are a safe, fast and reliable alternative to connecting instrumentation by means of attaching take-offs with extrusion welded fittings.


    More than eighty sensor points were to be joined to pipes ranging in size from 225mm to 630mm. Due to the compact nature, several sensors were often designed to be installed circumferentially around the pipe.


Initial Situation
In December 2017 SA Water announced the construction of a water recycling plant and associated infrastructure at the Bolivar Waste Water Treatment Plant in Adelaide (SA) to increase the production of recycled water.

The design by Guidera O’Connor called for more than eighty sensor points to be connected to pipes ranging in size from 225mm to 630mm. Due to the compact nature of the installation, several sensors were designed to be installed circumferentially around the pipe. Statewide Poly Service Pty Ltd, were contracted to construct polyethylene pipework infrastructure.

Task & Challenges
Traditionally, products like the Plasson large bore electrofusion transition saddle with a 2” offtake would be used with the outlet and then bushed down to the required outlet size, typically 1/2” or 3/4”.

In this application, the footprint of a large bore saddle would create spacial issues, and the bushing down of the outlet would add unnecessary threaded connections and potential leak points in the system. Other methods such as extrusion welding were not deemed suitable because they would derate the pressure rating of the entire system.

The Plasson Electrofusion Sensor Adaptor overcame these challenges due to its compact footprint and smaller thread allowing direct connection of the sensor.

Installation
The Plasson Sensor Adaptor is held securely in place by a plate during the electrofusion welding process. The plate has two installation methods: Strap method and Bolting method.

1. Strap Method – for live systems
The strap method involves fastening the sensor adaptor to the pipe via a strap which is placed around the circumference of the pipe. The strap includes a Tension Force Indicator (TFI) which visually shows where the correct force has been applied. The strap method can be used on both live and non-live systems.

2. Bolting Method – for dry installations
The bolting method involves drilling a hole into the pipe and securing the plate with a bolt.
This system can only be used for systems which are not live.

As with any electrofusion fittings, preparation of the pipe surface is as per the requirements of the industry guideline PIPA POP001, Electrofusion Jointing of PE Pipes and Fittings for Pressure Applications. Surface preparation and cleaning is critical for successful electrofusion welding.

Surface peeling was conducted using the Plasson electrical saddle peeler. It’s calibrated depth ensures that sufficient oxide layer is removed from the pipe surface prior to welding. This is almost impossible with hand scraping which is not allowed under the POP001 guideline.

Using an electrically-powered tool combined with the ability only to peel the required area of the pipe, saved time and effort compared to using other peeling methods such as a chain peeler.

Outcome & Solution
The Plasson Sensor Adaptor is designed to deal with the challenges of connecting to large PE pipes by obtaining full contact along the welding area. These challenges may be caused by ovality, deformation resulting from ageing, handling and storage.

The use of the Plasson Sensor Adaptor also alleviated the challenges of space and potential for leaks associated with large threaded reductions. Using an electrofusion process certified to an Australian Standard provided a fully rated system where other methods would derate the system or be impractical to install.