Plastics provide lightweight pressure reduction

Edited by the Engineeringtalk editorial team Mar 18, 2003

Ecoplus has selected Zytel HTN for the housing of a cost-effective new pressure reduction tank that is designed to cut domestic central heating bills and CO2 emissions by 25%.

Ecoplus of Tralee, County Kerry (Ireland) has selected DuPont Zytel HTN for the housing of a cost-effective new pressure reduction tank (PRT) that is designed to cut domestic central heating bills and CO2 emissions by 25%.

Zytel HTN was selected because of the high performance polyamide's long-term resistance to hot water, its excellent pressure resistance and its outstanding mechanical strength.

Ecoplus Technical Director, Carl Steinborn, said: "We had heard that Zytel HTN had been used for the manufacture of components in domestic heating systems, so we knew it must have excellent high temperature, hot water and pressure resistance.

Together with Dew Analysis of Winchester (UK), we analysed the design of the PRT, using data from DuPont, to a safety factor of three.

RAPRA Technology of Shrewsbury (UK) has run a series of stress analysis and fatigue analysis tests, where the material was tested under typical boiler cycle conditions, and is currently being tested to its ultimate limits".

The technology behind the Ecoplus PRT has been around for a number of years but commercially available products have appeared only in the past two years.

Until now, PRTs were made of metal, were commonly painted red for identification as a pressure vessel, and weighed almost 30kg.

In contrast, the Ecoplus PRT, made of Zytel HTN, weighs just 4.9kg and is colour-coded by use of an appropriate masterbatch.

The unit has a seven-year warranty.

It has the CE mark and EnergyStar, the North American eco-friendly certification standard.

The Ecoplus PRT is moulded by Ashford Mouldings of Ashford, Kent (UK).

Ashford Technical Director, Tom Clark, said: "We had not worked with Zytel HTN before but we were very impressed with the material's high stiffness, good dimensional stability, incredible toughness and overall structural strength.

During stress analyses, we found Zytel HTN to be about three times as strong as standard 6/6 nylon.

Yet since it is a nylon, it remains flexible when confronted with sharp changes in hot and cold water".

Because Zytel HTN can be moulded using relatively low tool temperatures (80-120C), Ashford was able to use standard equipment.

This may not have been the case with competing high temperature crystalline thermoplastics, which usually require very hot, oil-heated tooling.

When connected to new or existing central heating systems, the Ecoplus PRT uses fluid dynamic principles to clear oxygen and other gases forming air pockets from the water in the system.

Air pockets lead to a variety of central heating inefficiencies such as uneven heat distribution, poor flow rate, noise and corrosion.

According to Ecoplus, most households that install its PRT should experience the removal of air pockets from their central heating systems within a few hours.

Each subsequent circuit of the system removes more gases until only a negligible percentage remains, at which stage the water flows up to 30% faster through the system.

Already available in hardware, DIY and builders' supply stores in Ireland, the Ecoplus PRT is scheduled to also become available from distributors in the UK and Europe in 2003.

The unit retails for Eur 495 including VAT.

It is compatible with most European hot water heating systems including standard radiators, under-floor heating, solid fuel systems and geothermal heat pumps.