Product category:
Flowmeters and Flow Sensors
News Release from: Ion Science | Subject: VLDs
Edited by the Engineeringtalk Editorial
Team on 02 July 2003
Virtual leak diameters set flow
standards
ISL has developed a unique method to produce VLDs having a single sharp and circular hole and able to withstand a pressure differential of 60bar.
The growing global acceptance of ISO9000 quality standards has led to an increase in commercial requirements for predictable and traceable measurement Leak/flow standards are increasingly specified as maximum VLDs which are calculated from gas laws and physics using Poisseuilles equation as a base
This article was originally published on Engineeringtalk on 28 May 2003 at 8.00am (UK)
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Current flow standards include needle valves and compressed sinters.
In practice these have considerable technical concerns, not least being flow change caused by blockage.
To meet this requirement and overcome current concerns, ISL has developed a unique method to produce VLDs having a single sharp and circular hole and able to withstand a pressure differential of 60bar.
VLDs are 6mm OD and 1mm thick and are available from 4 to 250um diameter.
Depending on the applied pressure this covers a vast flow range.
A VLD has a single circular hole.
We can accurately predict the flow through this hole based on the hole size.
As this leak is virtual, we can define other parameters.
In addition as the walls of the virtual leak are smooth and parallel, perfect Poiseuilles flow occurs.
ISL will advise the VLD from information supplied for any application.
When used as gas, air and liquid flow standards, a single VLD can set a precise flow from an applied pressure.
The VLD may be mounted in the outlet of a pressure regulator providing precise flows.
There is no need to use needle valves etc.
When used as gas, air and vacuum calibration standards, the mounted VLD is plugged into the test circuit, introducing a precise flow (or leak).
Other applications include: safety restrictors used in pneumatic/hydraulic systems; dilution where flows are mixed to provide precise concentrations; and for atomising liquids, such as in ink jet printing.
A VLD may be fitted into a component, or ready mounted in a "quick-fit" stainless-steel body.
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