Safe and Sound in Hazardous Areas.
Intrinsically Safe (IS) approved field calibrators
reduce breakdown and maintenance costs,
improve process efficiency and safety.
In many process industry sectors, the safe and efficient handling and
production of potentially hazardous liquids and gases is an everyday
challenge. Examples range from sewage treatment to petrochemical
fuel distillation, wet gas separation to hydrogen cooled power generators
amongst many others. Working in such hazardous areas requires
extreme care and the law places great responsibility upon individuals,
because the potential for disaster is high.
Effective process maintenance schedules are essential and need to
be carefully planned, implemented and documented to keep plant
systems running efficiently, whilst safely achieving maximum levels
of productivity. Production costs are extremely high so inevitably a
fast response to any system fault, breakdown or failure is also vital
to keep losses to an absolute minimum. Just a few minutes of plant
downtime can cost tens of thousands of pounds.
Above all, safety is of paramount importance. To improve working
safety, legislation classifies hazardous areas into zones 0, 1 or 2,
according to the continuous, intermittent or abnormal presence of
explosive gases or air mixtures. These gases or air mixtures are
also classified by gas group and temperature. Dependant upon
factors such as gas sensitivity and surface temperatures, just a
few millijoules of electrical spark energy can cause ignition.
The use of electrical equipment such as field calibrators is therefore
restricted within the zoned areas unless it has been approved as
"IntrinsicallySafe" (IS). Non-IS equipment reduces the ability for
plant technicians and other personnel to quickly implement
maintenance schedules, or even worse, their ability to respond
quickly to failures or breakdown. Typically, they must first report
to the plant manager, obtain authorisation documents, locate
suitable gas detectors and then sign a permit to work.
The user is then accepting a burden of responsibility for continually
monitoring the hazardous environment whilst carrying out
maintenance or troubleshooting duties within the often remote or
difficult site conditions. This burden is made worse in the knowledge
that considerable process losses are incurred purely due to the
delay in even entering the affected area.
Intrinsically Safe Calibrators
Dependent on the choice of field calibrator for a particular task,
delays and errors in implementing and documenting test activities
may be avoided or introduced.
Often a calibrator is required to directly measure and/or simulate
parameters such as pressure, temperature, electrical and frequency
in order to find a fault with instruments or associated control loops
under emergency shutdown conditions. Examples include sensors,
switches, gauges, transmitters, thermocouples and RID's, etc.
Calibrators are also used for minimal routine preventative checks
and monitoring instrument or system performance.
As part of a quality assured and often computerised operational
management system, e.g. ISO 9000, they also perform periodic yet
comprehensive in-situ calibration of field instrumentation in
accordance with very specific test procedures and work schedules.
Despite the evolution of non-IS field calibrators, relatively few IS
approved products exist. However, intelligent and fully self-contained
IS field calibrators are available. They are accurate, simple to use
and a choice of specifications can be supplied according to specific
user requirements. Developments in functionality and communications
reduce the demands on operator skill/training and so increase
productivity and peace of mind. Intrinsically safe versions are supplied
fully certified and approved for immediate and direct use in hazardous
areas, avoiding the need for bulky gas detectors and associated
safety documentation, which in turn reduces delays in operator
response and minimises downtime.
The precise choice of IS calibrator will ensure that the most cost effective
and convenient solution is applied for addressing a task or range of tasks
within specific user applications.
This may be a Smart 4 - 20 mA loop tester, a combined pressure/electrical
calibrator and troubleshooter or even a powerful multi-function
documenting process calibrator with PC based management software.
Specialist manufacturers include Druck who have supplied IS calibrators for
almost 20 years and offer a complete product range, enabling the critically
important choice of equipment to be made without compromise.
The user benefits from a "customised" approach which may include just
one calibrator or several different types. Performance capabilities will be
very closely matched to ensure optimum results for the tasks involved.
Product Developments
Today's leading field calibrators embrace a wealth of developments
in measuring, interfacing and packaging technologies which directly
benefit the user in terms of overall test efficiency, speed and quality.
For example, high accuracy measurements can be readily made with
precision low-doped and resonant silicon pressure elements,
auto-detection of 2, 3 or 4 wire RTD's, internal point-of-contact
thermocouple cold junction compensation. This advanced measurement
technology is then complemented by task oriented dual parameter
graphic displays which can be configured for simplified routine calibration
and maintenance or advanced troubleshooting at the touch of a button.
The result is fast set-up and implementation for both process maintenance
and calibration tasks.
Multi-function hand pumps can now precisely and very rapidly source up to
60 bar pneumatic or 700 bar hydraulic test pressures and 95% vacuum.
Compact, rugged and ergonomically designed packaging eases practical
use of the calibrator and prolongs its useful life in harsh field environments.
Complete test routines can be pre-loaded into the calibrator and recalled
for automated field implementation. At the end of a workshift the results
can be simply uploaded direct into a PC.
Using electronic data storage, by means of either RS 232 communications
protocol or PCMCIA card, reduces the possibility for errors because the
recording of data and its transfer to a centralised test and calibration
management system is both automated and paperless.
To further enhance this "low risk" documentation process and to simplify
the necessary compliance with quality standards such as ISO 9000,
approved calibration software can also be supplied. For users who do
not have their own established system, proprietary software packages
are available, often provided by the calibrator manufacturers themselves,
which satisfy the full range of test, calibration and documentation
management requirements.
This includes, for example, the creation of multiple databases to organise
data storage, a powerful search engine for simplified data retrieval and
a multi-level security password system to prevent unauthorised system
entry. Moreover, test procedures and individual specific work orders
can be generated for down loading to the portable calibrator. At the end
of the daily work shift, resulting data collected in the field is simply
uploaded back at the office PC for creating records and further
analysis/processing. Detailed and quality compliant calibration certificates
can then be automatically generated, making the whoIe process far
easier and more reliable than the traditional manual paperwork approach.
These and many other continual developments recognise the importance
of the field calibrator's role in improving hazardous process safety, efficiency,
quality and reliability.
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November 2000
