Making non-intrusive pipeline measurements

A Hawco product story

Edited by the Engineeringtalk editorial team Nov 13, 2000

A typical example of a pressure-type pipe separator is the Haenni 1620 Series, an all stainless steel, all-welded, clamp-connected design incorporating a star configuration moulded diaphragm.

It is often the case, that when taking pressure or temperature measurements from within process lines, the application of conventional measurement techniques is not permissible.

In these situations sensors would be exposed to the flowing medium, creating problems of contamination, flow resistance, dead space and deposit build up.

One answer is to be found in the patented design of non-intrusive pipe separators and assemblies that isolate the sensor from the flowing medium.

They allow either the pressure to be transmitted by means of an in-line sealed diaphragm and transmission fluid to an appropriate measurement device, or, in the case of temperature measurement, by a straight-through, circular assembly that senses only the product temperature, not that of the pipework.

Notably, these applications occur within the highly sterile environments demanded by the pharmaceutical, biotechnology and food processing industries but these are by no means the only instances whereby the process fluid must be isolated from the measurement device.

It also applies when the medium is corrosive, toxic or environmentally dangerous and if its nature is viscous, contains solid matter or is likely to crystallise or polymerise.

There may also be a similar need if the measurement device is subjected to extreme pulsations created by the material flow.

A typical example of the pressure-type pipe separator is the Haenni 1620 Series, an all stainless steel, all-welded, clamp-connected design incorporating a star configuration moulded diaphragm.

This one-piece unit, designed to operate at pressures up to 60bar, is 3A certificated for use within the food manufacturing industry.

Similarly, the company's TAR aseptic pipe temperature sensor, with either threaded or clamp-on connection, is designed for operating temperatures up to 200 C.

It is SIP/CIP capable and is available in a variety of formats.

These comprise PT100 (Class A or B), thermocouple, duplex sensor, and with flying lead or a choice of basic, low-cost transmitter or HART.

Typical users of these aseptic measurement methods are companies of the stature of Glaxo Wellcome and Delta Biotechnology.

Maintaining an uninterrupted product flow is not the only temperature measurement problem encountered on the process line.

Whatever type of sensor is employed, the simple fact remains that in the course of time sensor devices will exhibit drift.

If these variances from desired measurement accuracy go undetected, the likely consequence is process line downtime, reduced productivity and unacceptable effects on end product quality.

It follows that quick and efficient instrument calibration with the minimum of interruption is essential to productivity.

A temperature sensor, for instance, needs stable heat to ensure calibration accuracy.

In the case of the aseptic TAR temperature assembly, the sensor is bonded to the inside wall and insulated from the outer casing of the unit.

In this instance, liquid bath calibration procedures need to be adopted using heating media appropriate to the process application.

For conventional intrusive sensor probe and pocket assemblies, the probe is withdrawn from the pocket and inserted into the heater well of a dry block calibrator such as the Jofra ATC series which combines laboratory accuracy with the speed and portability of an on-site calibrator.

In calibrating pressure pipe separators, units are removed from the pipework system, one end is blanked off and the other connected to a pressure source, either a nitrogen bottle or a filtered compressed air supply.

The unit is then linked to a pressure calibration system such as the Ametek PPCE which provides an accuracy level comparable to that of a deadweight tester.

It is important to bear in mind that although there are many and varied methods available for introducing measurement sensors into aseptic process line environments, the best solutions are those where consistent accuracy can be maintained through applying compatible calibration methods and equipment specifically designed for the purpose.