Evolution and History

Since the Industrial Revolution, measuring process variables such as Level, Flow, Pressure, Density and others has been critical to the efficient operation of a process plant.

If you cannot measure accurately, you cannot run efficiently.

If a Process Tapping Point continually blocks up, confidence in measurement values from field instruments is lost. A field instrument relies on clear unimpeded access to the process to measure the variable the instrument is required to measure.

What have process plants done since the 19th century to measure process variables accurately?

Enlarge the Process Tapping Point Nozzle to “buy time” before the Tapping Point becomes partially or totally plugged.
Increase Purge flow rates through your preferred, reliable, accurate and robust Differential Pressure Transmitter.
Change out to expensive, fragile, complex and “new” non-contact devices.
Run Blind.
Use unsafe, Personnel Intensive, manual rodding or drilling out of Tapping Points.
Shut the unit down.

Why?

Because, until now, there has not been a solution to keeping Process Tapping Points clear! All of the above treat the symptoms – NONE solve the problem.

Now we are in the 21st Century and huge sums of money have been spent and still are being spent on the symptoms of plugged or blocked Process Tapping Points.

What is the use of large, sophisticated and expensive Distributed Control Systems (D.C.S.) computers and software….if you cannot rely on the process measurement at the unit in the field?

Why install instruments with 0.04% accuracy of span, if the tapping point gets plugged? Why do so many industries spend millions of dollars building purge fluid extraction plants as part of their process train? Why use skilled tradesmen to perform the unsafe and risky procedure of manually drilling out a Blocked Tapping Point? How many specialised and skilled maintenance and safety personnel are needed to cover all of the different non-contact devices that have to be used because Tapping Points get plugged? How many unplanned unit outages or plant shutdowns occur because of plugged Process Tapping Points?

Now in the 21st century, there is a solution to the problem.

Confidence in accurate process variable measurement is back.
Sophisticated instruments and expensive D.C.S. hardware and software can now be used to their full capacity.
Purge fluid extraction can now be reduced or totally eliminated.
Plants can now reduce inventories of non-contact devices.
Man hours from not having to drill out Tapping Points can now be better utilized.
Purge fluid extraction facilities can be smaller.
Total plant efficiencies can improve.

How can this be done?

Two years ago prototype mechanical tapping point clearing devices were manufactured and placed into field service in a mineral refinery.

Today Clearguard^® has developed into a simple, reliable and proven solution to keep process tapping points from becoming partially or totally blocked. Clearguard^® is the solution. Clearguard^® keeps the tapping point clear, as often as a plant operator or maintenance person dictates.

Why is Clearguard^® the solution?

A custom built “scraper” is routinely stroked through the tapping point.
Since the “scraper” keeps the hole clean, purge fluid can be reduced to an almost static purge, even replaced with an inert gas purge!
The stroking action does not affect process variable measurement – the field instrument is always on line.
A simple proven pneumatic cylinder provides the motive force for the “scraper”
Can be fitted to most existing tapping points.
Allows the re-introduction and replacement of non-contact devices with the trusted Differential Pressure Transmitter.
Eliminates the Risky manual Rodding out procedure.
Never at any time blocks the Process Tapping Point.
Includes manual “scraper” retraction features in the event of loss of motive power.
Available in process compatible materials.
Requires no special training nor tools.

Following extensive field trials to confirm all of the above parameters, Clearguard^® was launched in March 2002.