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Third-party tests conducted at the University of Michigan have proved that the Vent‑O‑Mat air release valve, a South African product, is indisputably the most effective of any kind available anywhere in the world today for the protection of pipelines against damage caused by vacuum.

The tests were commissioned by Aveng Manufacturing DFC, the Benoni-based developers of the Vent-O-Mat range, to determine valve efficiencies under vacuum.

Air valves from other leading manufacturers were tested at Michigan University at the same time.

Vacuum curves for all valves were plotted, and comparisons carried out.

The results verified that Vent-O-Mat outperforms all other valves for which similar capabilities and characteristics are claimed.

This result is important to all engineers involved in pipeline design and construction, because although most of the air valves classified as air release and vacuum valves, can release air and ensure that trapped air is released under line pressure, the majority have not been designed to manage the potentially catastrophic effect of vacuum.

Many manufacturers ignore completely this aspect of pipeline operation during the design phase of product development, but it is significant because the air that is inevitably present in all pipelines can cause damage as much through vacuum as through air build‑up caused by water surge compressing the air in the pipe.

Vent-O-Mat was designed from its inception in 1982 to cater for pipeline vacuum which, if too large, can cause the sucking in of joint seals and gaskets, the drawing in of debris behind the seals with consequent leakage, the loosening of pipeline joints and, ultimately, pipeline collapse.

Vacuum is caused by pipe rupture, pump failure or routine draining.

To minimise this negative pressure, air needs to be drawn into the pipeline at the rate at which the pipeline is drained, a capability which is arguably the most important and defining function of an air release and vacuum valve.

Vent-O-Mat can do this, but until now not a single air valve from any manufacturer has ever been third party vacuum tested, mainly because of the lack of a facility capable of conducting true tests.

This year, however, such a facility became available at the University of Michigan in the United States of America, and DFC hired it to execute third-party testing on all four Vent-O-Mat valve ranges in all sizes up to DN8”.

Valves from Vent-O-Mat’s main competitors were also tested.

Originally built to vacuum-test thrusters during the era of NASA’s Apollo space missions, the Michigan facility has a 275m3 chamber capable of developing an internal negative pressure of minus nine metres.

For the air valve vacuum tests, each valve was attached in turn to the chamber and the rate of air flow through it recorded as the pressure was dropped to –9m.

The outcome was the creation of the world’s first true vacuum curves for the air valves, delivering empirical data that will allow accurate valve sizing according to application, without any doubt as to the validity of that sizing.

Valves across the Vent-O-Mat range were proven to be more efficient than predicted by manufacturers DFC.

They also significantly outperformed every competitor’s valve to which they were compared.

Vent-O-Mat is the most tested air valve in the world, able to site and verify testing at the CSIR 1989, 1994, 2005 and 2006 and most recently in 2013, when Vent-O-Mat became the first ever air valve to conduct true and full vacuum tests across its four valve ranges, in sizes from DN1” to DN8”.

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