Faster, easier, cost efficient and more reliable
A revolution in maintenance of pH measuring systems –and substantial savings!
They have all tested it – in their own
environments and based on theirown needs – and now they talk about
it here: how their day-to-day tasks
have been transformed for good by
the advent of digital electrodes and atruly innovative maintenance concept
launched by Endress+Hauser.

In the field electrodes are only replaced“Don’t forget the bottles of buffer solution (and are they still ok to use, by theway?), distilled water for rinsing, and a rag for wiping … When you’re out inthe field, it’s essential to have everything at hand: there’s no question of wastingtime going back to get something.” Didier Roussel, Head of Maintenance ata wastewater treatment plant*, is no longer concerned by worries such asthese – which are otherwise too familiar to specialists tasked with measuring
pH values.
* Wastewater treatment plant operated by the Association Syndicale Libreof the Upper Touyre Valley (France)

All he needs to do to calibrate the various
pH measuring points around the plant isdisconnect the electrode to be calibrated
and replace it with another one – precalibrated, of course. The most important
maintenance task is then carried out inthe comfort of the plant laboratory, witheverything at hand.

What is his secret? “Two years ago wechanged over to Orbisint CPS 11D digitalsensors with Memosens transmitters.”
With Memosens technology, the analog/
digital conversion takes place inside thesensor itself, so the sensor is the only item
requiring regular checking and calibration;
the cable and transmitter impact far less on
the measurement process than in an analogsystem, which is sensitive to moisture andelectromagnetic interference, among otherthings. “I check the measurement with a
pH meter every week, and every sensor
is calibrated once a month”, adds Didier
Roussel. Calibration, which is carried out
also provides an opportunity to clean theprobe with a hydrochloric acid solution, anoperation which cannot be easily performedon site. Better maintenance obviouslymeans the probes deliver more reliable
readings and have a longer service life.

Extending sensor service life
Manfred Walter at the Merck production
facility in Gernsheim (Germany) notes
the same thing: “We have increased theservice life of our electrodes by 30%.
Certain sensors have been in operation
for six months – a period never previouslyachieved with analog sensors.” This is in
spite of particularly harsh conditions –temperatures in the region of 176°F (80°C)
and a very acidic pH which can, however,climb to 10 at certain moments –necessitating regular maintenance of thepH measuring systems.
With Memosens technology, it is the toughsensor which is exposed to field conditions,
not the operator, for whom discomfort
is kept to a strict minimum in that he isonly required to extract the electrodeand replace it with one that has been
pre-calibrated. Back in the ‘measurement
and control’ lab, the technicians can thenperform truly predictive maintenance,
including an evaluation of the conditionof the sensor, cleaning – plus regeneration
if necessary – and, finally, calibration andadjustment.
One of the key innovations of Memosens
technology is that the electrode headstores numerous pieces of maintenancerelevant data in digital form. Viewed by thetechnicians when the electrode arrives atthe lab, this data provides a good idea of theelectrode’s operating condition.

Life cycle of Memosens sensors

Data is automatically recovered andstored by Memobase, the comprehensive
management solution for measuring points
based on Memosens technology. Installed
on your PC, Memobase allows you to
document calibration procedures andmaintenance work, an option which isattractive to many companies, particularlyin the chemicals, food and life sciencesindustries. Memobase can display a historyof stored data for the purpose of monitoring
the development of the slope or the zeropoint of each electrode.

On calibration, the entire Memosens data set is transferredand saved in the database. Process and measuring pointrelevant data are documented in addition to the quality
relevant data required for calibration.

Reducing on-site maintenance timeby over 50%
At Lanxess in Leverkusen (Germany), all
the data for a particular measuring point –whether relating to operational phases orcalibration/adjustment – are recorded andanalyzed when the sensor is calibrated. This
gives measurement and control specialists
an easy means of monitoring and analyzing
the entire sensor lifecycle – from themoment it is taken onto stock right throughto disposal. This data also helps ensure theongoing improvement of measuring systems
and maintenance work. Associated withimproved asset management, preventive
maintenance thus becomes an integral partof a new maintenance strategy.

Calibration of Memosens sensors in the laboratory

A central laboratory has been set up andequipped with a computer-aided pH
calibration bench in order to manage
the extensive base of pH measuring
equipment. The tasks are clearly defined:
the operators recover and replace the on-site
sensors – certain installations are difficult
to access – and the measuring specialists
take care of the laboratory maintenance andcalibration work. This reduces time spent on
on-site maintenance by over 50%.
Reproducible laboratory conditions enableprecise calibrations and therefore moreaccurate process management. Here, too, it
has been noted that periodic cleaning andregeneration prolong the service life of thepH sensors, which obviously increases theavailability of the measuring points.

The Memosens technology
Endress+Hauser’s Memosens digitalpH sensor is designed for reliable
and verifiable pH measurement. The
device allows important process data
to be saved directly in the sensor,
guaranteeing interference-freemeasuring signals while also simplifying
process measuring technology. Teamedwith all common fieldbuses, Memosens
systems are open for all process control
and asset management systems. They
are already industry proven even in thechemical and life sciences industries,
food, water and wastewater, pulp andpaper and energy.

For Didier Roussel, calibration is carried out in thecomfort of the plant laboratory, with everything at hand.

Easy qualification of measuring points
Faced with the need to meet many strictlegal requirements, the life sciencesindustry also has much to gain by thisrevolution in pH measuring systems.
Memosens technology allows the user toconsider the digital sensor (comprising themeasurement chain) distinct from the cable+ transmitter duo which takes care of datatransfer to a Process Control System (PCS).
Since the sensor can be calibrated in alaboratory environment, only the cable andtransmitter need be qualified on-site.

work. Another key argument for regulatedindustries: controlled by Memobase, thesensors are managed on the basis of eachone being assigned to one measuring point(TAG), or possibly to a group of similar

measuring points (TAG group). This linkcannot be altered, and guarantees thecoherence and traceability of the measuring
points.
Memosens technology currently covers
measurement of pH, conductivity, oxygenand chlorine… and will also include
turbidity in the near future: enough tosatisfy most users of physico-chemical
analytical tools.
The financial benefits of migration
have been demonstrated in numerous
cases – but let us leave the last word toMr. Werske, a measurement and control
specialist with Merck in Gernsheim: “Interms of quality and cost-savings, there
are so many advantages to having an easymeans of replacing on-site sensors and of
performing maintenance work in a central
laboratory, in ideal conditions, that theexpense of changing over to this system ismore than justified.”

And to simplify this step, Endress+Hauser
can propose its dedicated qualification tool,
Memocheck Plus. This tool will allow theQuality Manager to perform the IQ and OQ
phases with ease (Installation Qualificationand Operational Qualification). An
additional second tool, Memocheck, makes
it easy for maintenance teams to performa fast, easy check of a measurement loop
when carrying out commissioning or repair

Back in the lab, Manfred Walter can perform truly
predictive maintenance, including an evaluation of thecondition of the sensor.

Dedicatedcalibration tools

Memocal T is a calibration
instrument for pH measurement
using digital sensors Wet or numeric calibration(9.8 ft/3 m of cable).

The Memocheck service tool
enables a quick and easy checkof the measuring loop bysimulating fixed sensor status.

Memocheck Plus
enables qualificationof the measuring loop
in the life sciencesindustries.

04.07/MC

Instruments International
Endress+Hauser
Instruments International AG
Kaegenstrasse 2
CH-4153 Reinach
Switzerland
Tel. +41 61 715 81 00
Fax +41 61 715 25 00
http://www.endress.com
info@ii.endress.com

SD145C/07/en/10.09
INDD CS2