Dewpoint measurement of medical gases - an update
This summer saw the release of Health Technical Memorandum (HTM) 02, one in a series of ten providing guidance on healthcare specific standards, policies and up to date established best practice.
This summer saw the release of Health Technical Memorandum (HTM) 02. This document is one in a series of ten published by National Health Service Executive (NHSE) each providing guidance on healthcare specific standards, policies and up to date established best practice. HTM 02 covers the subject of Medical Gas Systems, and is divided in two parts: part A deals with design, installation and validation, while part B deals with operational management.
The overall aim is to provide a safe, convenient and cost effective system for the provision of medical gases to the clinical and nursing staff at the point of use.
For the first time HTM regulations give specific information on the specification and measurement of dewpoint or moisture content of the gases.
The relevant section (15.146) states: ‘The plant test point and a representative sample of terminal units distributed throughout the pipeline systems should be tested for total water content.
The water content must not exceed 67 vpm (equivalent to an atmospheric pressure dew-point of approximately -46 C).
The typical water content of medical gas cylinders is normally below 5 vpm.
Water vapour content may be measured using the appropriate test device described in Appendix E (see also paragraph 15.117)’.
Paragraph 15.117 tells us: ‘An electronic dew-point meter should be used in preference to water content measurements’.
More details are given in paragraph 7.41: ‘The dryer control system should ensure that regeneration is operated in proportion to the compressed air usage.
The effectiveness of the control system will become apparent when the efficiency of the compressor system is tested at 10% and 0% of the system design flow.
Evidence of the reliability and performance of a dryer system should be sought from manufacturers, since these items are critical to the overall performance of the compressor system.
The dryer control system should include a dew-point hygrometer and display with a minimum accuracy of +/-3 C in a range from -20 C to -60 C atmospheric dew-point, with an alarm set point of -46 C.
(Note that this supersedes the HTM 2022 requirement for an alarm trigger point of 40 C) It should be arranged that in the event of open circuit, a ‘plant emergency’ alarm be initiated’.
Michell Instruments have in the past been extremely active in supplying portable equipment such as the Cermax Portable dewpointmeter.
More than 40 instruments have been supplied within the UK, many with sampling systems to allow quick and easy connection to medical gas supplies within hospitals and pharmacies.
Michell Instruments have been quick off the mark regarding continuous measurement, and have already received orders from several customers for this application.
Where continuous measurement of dewpoint is required Michell Instruments have the ideal instrument, Easidew On-Line.
The Easidew On-Line utilises the Michell Instruments ceramic sensor to provide stable and accurate measurement of dewpoint in the range of -100 to + 20 C.
The Easidew On-Line monitor provides a large red LED display of the dewpoint.
A 4-20mA analogue output is available for interfacing to data-loggers or a distributed control system, and two alarm relays can be set by the user to provide indication that the gas is approaching, or is outside, the required specification.
To provide a ‘one-stop’ service to the customer Michell Instruments can, if required, provide the Easidew On-Line already mounted within a wall-mounted enclosure, and with a sampling system.
This sampling system includes a filter, to protect the sensor, and a valve and flowmeter so that the appropriate sample flowrate can be set.
This all in one approach requires only that the customer provide a flow of gas and the necessary pipework.
This solution is particularly useful for fitting to existing medical gas dryers.
Easidew On-Line is the perfect solution for new medical gas systems or for those users with older systems wishing to ensure that they meet the new HTM 02 standards.
Capacitive hygro and hygrothermal transducers
The highly successful hygro and hygrothermal transducers from Jumo Instrument are used for the measurement of relative humidity and temperature in HVAC applications.
The highly successful hygro and hygrothermal transducers from Jumo Instrument are used for the measurement of relative humidity and temperature. Their main area of application is in the HVAC sector. The new version of these instruments is now provided with a robust Form J aluminium terminal head and rugged screw clamp terminals.
The grey-painted aluminium shaft has a maximum fitting length of 120mm and a diameter of 20mm.
The fast response of the capacitive humidity sensor ensures that the instrument delivers reliable measurement of relative humidity over the range from 5% to 95% with an accuracy of +/-2%rH or +/-3%rH respectively.
All the sensors that are used have a gauze filter fitted as standard, and can be installed in unpressurised systems, non-corrosive gases and air.
For open-air applications or extreme conditions, plastic grille filters with a stainless steel mesh and stainless steel sinter filters are available as options.
The new instrument version offers a temperature measurement range from -30 to +70C.
The temperature measuring device is a PT100 sensor, Class B, implemented in accordance with DIN 60751.
The minimum air flow required for correct measurement is 1metre/sec.
The instrument also provides active outputs in the form of the usual industry-standard 4 - 20mA, 0 - 1V or 0 - 10V signals.
Instruments can also be supplied with a passive Pt100 output.
This means that these very compact humidity and temperature sensors can be used in a wide range of applications.
The sensor itself has IP30 enclosure protection, and the electronics has IP65.
The operating voltage can be anywhere in the range from 12 to 30VDC.
The instruments can be easily and correctly mounted to suit the site and application.
Just as versatile are the compact rod versions with a connecting cable.
Automated KF moisture analysis systems
Automated KF moisture analysis systems are essential for New Drug Application (NDA) work and also ideal for routine moisture analysis.
Automated KF moisture analysis systems are essential for New Drug Application (NDA) work and also ideal for routine moisture analysis. NDA work requires 36 month stability programmes with intensive testing at regular time intervals and differing temperatures and humidities, and moisture testing is one of the parameters to be monitored. With several NDA running at the same time this can lead to a lot of work and laboratory time.
The Metrohm 774 / 831 moisture analysis system can solve this time consuming test easily.
36 samples can be loaded onto the sample changer with check standards placed between samples.
All samples are hermetically sealed so even toxic products can be analysed safely.
Tablet samples do not have to be ground in a mortar and pestle as whole tablets can be analysed.
The system is operated with CFR 21-11 compliant software.
Alternatively the system can be used as a stand alone instrument.
The system is capable of temperature ramps which allows different types of samples to be tested on the same run.
It is possible to test the surface water as well as the bound moisture, all you have to do is use a different temperature profile.
Samples with large moisture contents can also be analysed using a volumetric KF titrator instead of the coulometer.
If you already use freeze dried samples the heating block can be modified to suit your sample vials.
Reagent exchange is automatic so the possibility of incorrect results due to exhausted solvents is avoided.
Moisture analyser in a transmitter package
Both a moisture analyser and a transmitter, the intrinsically safe multitasking HygroPro combines performance and practicality, features commonly only found in top-of-the-line moisture analysers.
Both a moisture analyser and a transmitter, the multitasking HygroPro from GE-Sensing combines both performance and practicality, features commonly found only in top-of-the-line moisture analysers. The HygroPro offers all of this in a compact, intrinsically safe, loop-powered device - for applications in the process, industrial, and pharmaceutical markets. By integrating moisture, temperature, and pressure sensors on a single probe, the HygroPro reduces the overall installation cost by minimising the number of sensors, and significantly reducing installation points and cabling needs.
‘We have brought the best experiences of the Panametrics and General Eastern product lines together to provide a more comprehensive solution to moisture monitoring in the HygroPro product,’ said John Kerney, product line manager for GE-Sensing.
‘This device gives our customers capabilities that they found previously in our high-end moisture analysers, but in a compact, simple, easy-to-use transmitter package for both gas and liquid applications.
With the intrinsically safe certification, they can use the HygroPro in hazardous areas without the need for cumbersome and expensive explosion-proof enclosures’.
The HygroPro Bafeesa and FM (pending) certified intrinsically safe design (FM pending) in an IP67/Type 4X housing, is ideal for measuring the moisture content in pipeline natural gas, petrochemical applications, power generation, such as transformer oil or sulfur hexafluoride (SF6), and other industrial gas or non-aqueous liquid applications.
The HygroPro features an integral backlit display and six-button keypad to allow viewing of up to three parameters simultaneously, with easy navigation of the software.
Using the GE-Sensing industry-proven aluminium oxide moisture sensor in conjunction with a built-in temperature thermistor and pressure transducer, the HygroPro provides real-time measurement of dew point and calculated parameters such as ppmv in gases, ppmw in liquids, or pounds per million standard cubic feet in natural gas.
Since the display can be oriented in four possible configurations, viewing of the information is simple, whether the transmitter is mounted in the top, bottom, or beside a process pipe.
The HygroPro combines the technologically advanced aluminium oxide moisture sensor with state-of-the-art software and electronics in a package designed specifically for installations where space is at a premium.
Precise humidity measurement for coating processes
Coating processes are widely used in the pharmaceutical and confectionary industries for tablets, pills and sweets: Michell provides the essential humidity measurements needed during coating.
Coating processes are widely used in the pharmaceutical and confectionary industries for tablets, pills and sweets. The Michell Instruments Cooled Mirror range of instruments utilises a fundamental humidity measurement technique, making their products the ideal solution for the accurate measurement of humidity in process control applications. Most tablets consist of a product core and a coated cover.
The coating can be a variety of proprietary compounds or various forms of sugar.
Coating of the product core is used for several reasons including, preventing discoloration of the core, to counteract an unpleasant or bitter taste and to prevent the core from degrading when exposed to the ambient atmosphere.
There are two aspects to tablet coating.
The generation of inlet air of a known humidity and the monitoring of the drying process itself.
In order to ensure a high quality product is maintained it is important that the humidity of the air fed to the drier is validated.
The fundamental Cooled Mirror principle, in products like the Michell Optidew, provide the control signal for the generation of an inlet air with known humidity.
This is passed over the product during the spray coating process to guarantee that the tablets, or sweets have a consistent, smooth, high finish outer coating.
The monitoring of the drying process avoids excessive or under drying of the product.
Excessive drying will incur additional costs and time in manufacturing, as well as possibly causing negative effects to the product itself.
Equally under-drying will result in product spoiling and poor aesthetic qualities.
Therefore, determining the ‘ideal’ drying cycle is the key to this application.
Cooled Mirror dew point sensors are used in the coating process to measure the dew point or absolute humidity of the inlet and exhaust of the drier.
This type of humidity sensor, such as the one used in the Optidew, is typically used because of the fundamental nature of the measurement and its drift free characteristics.
The high performance optical dew point transmitter works on the proven dew point measurement principle offering the user unmatched performance, ease of maintenance and zero drift.
This has led to a number of world leaders in the manufacturing of pharmaceutical and confectionary products moving over to this technology.
The Optidew offers a wide measurement range from the equivalent of <0.5 to 100% RH at ambient temperatures and from -40 to +90C.
The Cooled Mirror instrument also provides two linear 4-20 mA outputs in addition to serial communications, allowing set-up and monitoring by a suitable computer or PLC system via specific Optidew logging software.
An adjustable volt-free contact alarm means Optidew can be used for direct process control.
An optional high definition alphanumeric display provides local indication of the measured humidity.
Determining water content in gases to ISO10101-3
Many of our customers would like to determine the moisture content of their gases: Metrohm has now developed a clever method based on the ISO standard 10101.
Many of our customers would like to determine the moisture content of their gases. Metrohm has now developed a clever method based on the ISO standard 10101: ‘Natural gas: Determination of water by the Karl Fischer method’. The reproducible determination of water content is tricky as many gases usually only contain a few ug/L water.
The problem is not the coulometric measurement itself, but the sample introduction.
An optimal measuring set-up and the exact determination of the gas volume are the be-all and end-all of water determination in the lower ppm range.
In order to ensure a reproducible gas introduction time, the control of the valves should be automated.
The tiamo titration software is also extremely suitable for this purpose: by using a relay box, the valves can be opened and closed according to the conditioning or determination status of the coulometer.
In addition, the duration of the gas introduction is documented and can be used for calculating the gas volume.
The gas to be analysed is passed through the Karl Fischer titration cell in which the water is absorbed by the KF reagent and then determined using the Metrohm 831 KF Coulometer.
In addition to natural gas, the Metrohm method can also be used for other gases (e.g nitrogen) that do not react with the Karl Fischer reagent.
Tank vent dryer prevents damage from condensation
Brownell manufacture a wide range of tank vent dryers and adsorbents which prevent valuable fluids from being contaminated by harmful moisture condensation.
Brownell manufacture a wide range of tank vent dryers and adsorbents which prevent valuable fluids from being contaminated by harmful moisture condensation. They also prevent release of toxic vapours from the tank into the atmosphere. Installation of the units is quick and simple, with a direct connection being made to an existing breather or vent pipe.
Optional electronic detectors enable users to constantly monitor the efficiency and capacity of the dryer.
Saturated adsorbents can be identified by an alarm, taking away the need for routine manual monitoring.
Free software with every moisture analyser!
New moisture analyser software from Mettler Toledo provides efficient and reliable data collection and visualisation, and is free with all new analysers bought.
New moisture analyser software from Mettler Toledo provides efficient and reliable data collection and visualisation. Before the end of January 2007, if you purchase any Mettler Toledo moisture analyser, receive this new moisture analyser software free!. LabX direct moisture transfers your measurement results together with instrument, sample and method information easily onto your PC.
Simply open Excel, start the moisture analysis and the information is automatically transferred into the spreadsheet.
The drying curve is visualised on-line as the data is generated.
You can also.
* Capture sample IDs with a barcode reader and add IDs to results for full documentation.
* Customise reports easily from a selection of layout templates.
* Save time thanks to sophisticated tools for determining optimal drying method parameters (HR83 and HG63 analysers only).
Up-grade to Easidew 2-wire transmitter
Michell Instruments have up-graded their Easidew transmitter into a 2-wire low cost, rugged impedance dew-point transmitter for continuous measurement in compressed air or process gas.
The new Easidew 2-wire transmitter improves the already highly successful range of Easidew instruments that includes portable and on-line hygrometers, as well as dew point transmitters. The Easidew 2-wire is a low cost, rugged impedance dew-point transmitter for continuous measurement in compressed air or process gas. The Easidew 2-wire transmitter offers the customer many more new and improved features.
The modified transmitter can now be connected in a 2-wire loop configuration whilst maintaining complete backwards compatibility with all existing 3-wire installations.
This simplifies the introduction of the new design and the on-going service requirements.
Another new feature of the transmitter is that output is configurable in ppm moisture content.
The improved Easidew has powerful processing capability allowing for the first time the on-board calculation of other moisture units (ranges 0-100, 0-1000ppm and 0-3000ppm).
The 2-wire can also be sold with a new HDPE filter designed to show contamination for service ease which is <10um porosity and impermeable to liquids.
The 2-wire transmitter also provides improved calibration data integrity, with a new design that includes improved software and firmware to protect calibration, even in the most extreme EMC/EMI fields.
Application software also allows the user to configure output parameters, ranges and scaling.
The Easidew 2-wire transmitter is designed for ease of use, incorporating all the features the user could want to make installation and operation as simple as possible.
For the first time, dew point measurement is made as accessible as temperature and pressure with this fully configured, calibrated transmitter that can be instantly incorporated into your air or gas management and control system.
The key to the Easidew transmitter performance is its sensor technology.
The Michell Advanced Ceramic Moisture Sensor is coupled with advanced microprocessor based measurement circuitry to produce a fully calibrated and interchangeable sensor transmitter.
All calibration data is stored within the transmitter flash memory and so calibration exchange, or service, can be effected in seconds, even by untrained personnel.
The Easidew transmitter is simply disconnected, removed from its sampling block and replaced by a new fully calibrated unit.
Aside from all of the new features the Easidew 2-wire tranmitter offers, it is also economical to purchase, install and operate.
Installation costs are minimal because of the transmitters ruggedness and simplicity.
On-going operating costs are low because of the transmitters stability and reliability.
Only periodic re-certification is required to maintain traceability.
Precision hygro-thermometer with digital display
Extech Instruments, a major supplier of test and measurement equipment for the industrial marketplace, announces its new precision hygro-thermometer with direct digital display of RH.
Extech Instruments, a major supplier of test and measurement equipment for the industrial marketplace, announces its new precision hygro-thermometer with direct digital display of humidity, or grains per pound, the model RH490. Ideal for structural drying and water damage restoration, HVAC/R installation and repair, mould inspection and remediation, and plant maintenance, the Extech RH490 features 2% RH accuracy and a RH response time of less than 30 seconds to help tackle the most challenging humidity and moisture problems. The dual backlit display of the RH490 enables the simultaneous viewing of humidity or grains per pound, along with air temperature, dew point or wet bulb.
It incorporates a slim design with rubberised sides for better grip and one-hand operation.
The RH490 features a data hold and auto power off with disable and low battery indicator, and comes complete with carrying case and 9V battery.