Orifice Rangeabilty; Bubblers for Difficult Service

Our Readers Ask and We Answer. How to Choose Suitable Flowmeters? Who Is Interested in the Loop Slooth? How to FIx My Bubbler Application Plugging Problems?

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Always remember that despite flow sheets and declarations by process people, at some time every vessel and every pipe will be exposed to pressures up to the relief valve pressure or failure pressure, and correlatively, every closed system will eventually be exposed to a high vacuum.

The purge-flow supply rate must be more than enough to overcome the maximum rate of pressure rise in the purge system. Note that this involves knowing the gas volume of the purge system, since the pressure of the entire purge system must be raised.

In extreme cases where no level measurement device except a purged dip tube was reliable and the dip tube always eventually would plug, a number of schemes were used to either permit quick dip-tube replacement or to facilitate drilling out the plug. These schemes usually involved systems of ball valves, packed slip joints and other clever mechanical devices.

Moore Products made several purged remote chemical diaphragm seals. These were used where plugging problems were insurmountable or where purge gas flow into the process was not allowed. They used a simple pressure balance scheme where the purge gas pressure on the dry side of the diaphragm rose to match the pressure on the wet side. Excess supply gas was vented outside the vessel through a vent connection as the purge gas rose above the process pressure.

These have limited pressure and temperature ratings. Installation requires a nozzle large enough to pass the assembly. Some small pressure differences will exist across the diaphragm, and errors may result from these.

Cullen Langford, PE

A: If the installation is in an existing plant, the bubbler pipe itself is usually made and installed by the user. If it is a new plant, the engineering firm designing the plant provides it as a piping item. A few suppliers also exist, such as Campbell Scientific, CR10, Omega Engineering, Kele Assoc., Texmate Inc., Introtek International.

The various aspects of bubbler-based level measurement are discussed in Chapter 3.2 of the 4th edition of Volume 1 of the Instrument Engineers’ Handbook.

Béla Lipták

Q: I have a device called the Loop Slooth for rapid troubleshooting of ground loops. Information about it is at  www.loopslooth.com. It gives a brief pictorial overview of how the Loop Slooth works and has links to the instruction manual and to a paper in the Review of Scientific Instruments. I’m interested in finding companies that might be interested in this product.

Paul Bellan
Circuit Insights LLC

A: The best possibility would be with the companies who have related products. Usually their R&D or product development groups are the ones that review concepts from third-party sources and determine their market viability. But certain companies have a policy of developing only those ideas which are created internally.
The Loop Slooth might be of interest to companies like Fluke, AEMC, Elcontrol, BMI/Dranetz, . . .


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