http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/RSS.ashxRA PagesWed, 12 Sep 2007 07:46:11 +0200http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=1http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=1Gas detection in refrigeration systems Application guide REFRIGERATION AIR CONDITIONING DIVISION MAKING MODERN LIVING POSSIBLE2007-09-12T07:46:11+02:00http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=2http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=22007-09-12T07:46:11+02:00http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=3http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=3Application guide Gas detection in refrigeration systems Danfoss AS RA Marketing MWA, 08 2007 DKRCI. PA. 000. B2. 02 520H1724 3 Contents Page Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Sensor technology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 EC Electrochemical sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 SC Semiconductor sensor solid state. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 CT Catalytic sensors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 IR Infrared . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Which sensor is suitable to a given refrigerant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Relative cost comparison. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 The need for gas detection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Legislation and standards. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Requirements for gas detection according to EN 3782000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 FGas legislation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Requirements for gas detection according to pr EN 3782006 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 USA Requirements for gas detection according to ASHRAE 152004. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Installation guideline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Location of gas detectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Number of gas detectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 in a facility. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Calibration test. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Calibration test methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Method I Calibration test by means of replacing Sensor PCB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Method II Calibration of gas detectors by using a calibration gas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Bump test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Alarm sensitivity range . . . . . . . . . . . . . . .2007-09-12T07:46:11+02:00http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=4http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=4Application guide Gas detection in refrigeration systems 4 DKRCI. PA. 000. B2. 02 520H1724 Danfoss AS RA Marketing MWA, 08 2007 Introduction Gas detection and leak detection are two distinct activities that covers the same topic, but the methods are very dierent. Gas detection covers the analysis of air samples to determine whether they contain refrigerant gas. Leak detection is a systematic inspection of a refrigeration system to determine whether it is leaking. The terms gas detection and leak detection are not interchangeable, and must not be mixed. Leak detection equipment is normally hand held equipment carried by people, and used for detection of leaks in refrigeration systems. There are several types of leak detectors available, covering from simple techniques like soapy water to sophisticated electrical instruments. Gas detection equipment is usually used in a xed installation with a number of sensors located in areas where refrigerant might be expected to accumulate in the event of a plant leak. These locations depend upon the layout of the machinery room and adjacent spaces, on the conguration of the plant and also on the refrigerant in question. Before selecting the appropiate gas detection equipment, a number of questions have to be answered Which gases has to be measured and in what quantities Which sensor principle is the most suitable How many sensors are needed, where and how shall should they be positioned and calibrated Which alarm limits are appropriate, how many are required, and how is the alarm information processed This application guide will try to answer these questions. Sensor technology Danfoss has, depending on the refrigerant and the actual ppm range required, selected the most appropriate sensor for the target refrigerant gas. EC Electrochemical sensor Danfoss oers the following sensor technologies Electrochemical cells are used mainly for toxic gases and are suitable for ammonia. These generally consist of two electrodes immersed in an electrolyte medium. Time Tolerance range Sensitivity max. min. Max operating time before calibration High gas concentration Low gas concentration An oxidation reduction reaction generates an electric current that is proportional to gas concentration. They are very accurate 0. 02 ppm and tend to be used principally for toxic gases which cannot be otherwise detected or where high levels of accuracy are needed g. 1. They were relatively expensive with a limited lifetime, however Danfoss now oers specic EC sensors for ammonia in the range of 05. 000 ppm with a lifetime of approx. 3 years. Exposure to large ammonia leaks or constant background ammonia will shorten the sensor life g. 2. They are subject only to rare cross interference. They may react to sudden large humidity changes but quickly settle. Fig. 12007-09-12T07:46:11+02:00http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=5http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=5Application guide Gas detection in refrigeration systems Danfoss AS RA Marketing MWA, 08 2007 DKRCI. PA. 000. B2. 02 520H1724 5 EC Electrochemical sensor continued Time Tolerance range Sensitivity max. min. Max operating time before calibration Substantial gas leak Important New sensor has to be installed Gas 1 Gas 2 Gas 3 Target Gas Gas 4 Gas 5 Gas specication Sensitivity Broad sensitivity spectrum Semiconductor Catalytic Narrow sensitivity spectrum Electrochemical Infrared SC Semiconductor sensor solid state The semiconductor functions by measuring the resistance change proportional to the concentration, as gas is absorbed on to the surface of a semiconductor, which is normally made from metal oxides. These can be used for a wide range of gases including combustible, toxic and refrigerant gases. It is claimed that they perform better than the catalytic type in the detection of combustible gases at low concentrations, up to 1. 000 ppm. So they are becoming more popular in this application in refrigeration, given that the hydrocarbon refrigerants should be detected at low levels to avoid potential problems and costs. These are lowcost, long life, sensitive, stable, resistant to poisoning and can be used to detect a large range of gases including all the CFC, HCFC, HFC refrigerants, ammonia and hydrocarbons. However, they are not selective and are not suitable for detecting a single gas in a mixture or for use where high concentrations of interfering gases are likely to be present g. 3. Interference from short term sources e. g. exhaust gas from a truck creating false alarms can be overcomed by enabling a delay of the alarm. Semiconductors for halocarbons can be used to detect simultaneously more than one gas or a mixture. This is particularly useful in monitoring a plant room with a number of dierent refrigerants. Fig. 2 Fig. 32007-09-12T07:46:11+02:00http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=6http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=6Application guide Gas detection in refrigeration systems 6 DKRCI. PA. 000. B2. 02 520H1724 Danfoss AS RA Marketing MWA, 08 2007 CT Catalytic sensors Catalytic sensors sometimes called a bead or pellistor type have mainly been used for combustible gases including ammonia and are the most popular sensors for this application at high detection levels. The sensor functions by burning the gas at the surface of the bead and measuring the resultant resistance change in the bead which is proportional to concentration. These are relatively lowcost, well established and understood, and they have a good life span, up to 5 years. The response time is about 2030 seconds. They can be subject to poisoning in certain applications but not generally in refrigeration and are more eective at gas levels of 1. 000 ppm up to 100 LEL. They are used mainly with combustible gases and are therefore suited for ammonia and the hydrocarbon refrigerants at high concentrations. They do sense all combustible gases but they respond at dierent rates to each and so they can be calibrated for particular gases. There are ammonia specic versions. IR Infrared Infrared technology utilises the fact that most gases have a characteristic absorption band in the infrared region of the spectrum and this can be used to detect them. Comparison with a reference beam allows the concentration to be determined. Infrared sensors when rst introduced were specic to a single gas and therefore not suitable for applications involving monitoring more than one gas. They were very selective and accurate reading down to one part per million. Infrared was typically used where a high level of accuracy and specicity was required. This very precision in performance ensures that they are expensive. However the specicity became a disadvantage in machinery rooms, as phase out resulted in mixed gas installations needing a dierent model for each gas, which was a very expensive solution. New models were developed based on broad infrared wavelength monitoring that could detect a mixture of gases. This, however, reduced the specicity and accuracy. If preferred, refrigerant specic units may be used if a possibility of cross interference exists. Semiconducter Electrochemical Catalytic Infrared Ammonia low concentration 100 ppm4 Ammonia medium concentration 1000 ppm 1444 Ammonia high concentration 10000 ppm444 Ammonia very high concentration 10000 ppm44 Carbon Dioxide CO4 HC Hydrocarbons444 HCFC HFC Halocarbons44 Best solution Suitable but less attractive Not suitable Which sensor is suitable to a given refrigerant Fig. 4 1 Measuring range 01000 ppm. Can be adjusted in the whole range. 2007-09-12T07:46:11+02:00http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=7http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=7Application guide Gas detection in refrigeration systems Danfoss AS RA Marketing MWA, 08 2007 DKRCI. PA. 000. B2. 02 520H1724 7 Relativ sensor cost SCSemiconductor EC Electro chemical CT Catalytic IRInfrared Relative cost comparison The need for gas detection There are dierent reasons why gas detection is needed. It is obvious, that regulation is a very strong argument, but also Reduced service cost cost of replacement gas and the service call. Reduced energy consumption cost due to lack of refrigerant. Risk for damaging stock products due to a substantial leak. Possible reduced Insurance cost. Taxes on non environmentally friendly refrigerants Dierent refrigeration applications requires gas detection for dierent reasons. Ammonia is classied as a toxic substance with a very unique smell, as such it is self alarming. Still gas detectors are very useful to have in a machinery room, as often people are not present to take necessary actions. Further more, ammonia is the only common refrigerant lighter than air. Hydrocarbons are classied as ammable. It is therefore very important to verify that the concentration around the refrigeration system does not exceed the ammability limit. Fluorinated refrigerants all have a certain impact on the environment. It is therefore very important to avoid any leaks from these. CO2 Carbon Dioxide is directly involved in the respiration process, and has to be treated accordingly. Approx. 0. 04 CO2 is present in the air. With higher concentration, some adverse reactions are reported starting with increase in breath rate 100 at 3 CO2 concentration and leading to loss of consciousness and death at CO2 concentrations above 10. Oxygen Oxygen deprivation sensors can be used in some applications, but they are not oered by Danfoss, and will not be described further in this guide. Note Oxygen sensors must never be used in CO2 installations. Legislation and standards The requirements for gas detection are dierent in many countries worldwide. An overview of the most common rules and regulation can be found below. Europe The present safety standard for refrigeration systems in Europe is EN 3782000. During the last few years this standard has been undergoing a very extensive update. This work has been completed pr EN 3782006, but the standard has not been nally approved yet. It is recommended to read this version of the standard, because this version is much more stringent, and with dierent requirements. Note The requirement for gas detection is not identically in EN 3782000 and pr EN 378 2006. Requirements for gas detection equipment in Europe are covered by national legislation in the dierent countries, and can therefore dier from the requirements specied in EN 378. Requirements for gas detection according to EN 3782000 and pr EN 3782006 are limited to machinery rooms. It has to be noted that machinery rooms according to these standards, are restricted arears. The specied alarm levels do not reect long term eects personal safety. Fig. 52007-09-12T07:46:11+02:00http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=8http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=8Application guide Gas detection in refrigeration systems 8 DKRCI. PA. 000. B2. 02 520H1724 Danfoss AS RA Marketing MWA, 08 2007 Requirements for gas detection according to EN 3782000 Gas detection is required by EN 3782000 for all installations where the concentration in the machinery room may exceed the practical limit for that space. In the case of ammable and toxic refrigerants this means virtually all commercial and industrial systems, but in the case of A1 refrigerants it is possible to have small systems, which do not require gas detection. However, in the majority of larger plants it is likely that the practical limit will be exceeded in the event of a major leak, and therefore gas detection is required. Guidance can be found in EN 3782000 part 3 paragraph 7. 2, which states that the refrigerant concentration in each special machinery room shall be monitored at one or more points. This covers all refrigerant groups including A1. However, in paragraph 7. 4. 1 the standard states If a refrigerating system is equipped with refrigerant detectors. raising the question of whether detection is required or not. It can he concluded that, if it can be shown by calculation that the concentration of refrigerant N N Y Y Y N EN 37832000Start Ammonia Clause 6. 2. 5. 1 Clause 7. 5 Norequirements Charge 10 kg Gas detectionrequiredhighlow level Charge practicallimit Gas detectionrequired Norequirements in the special machinery room can never reach the practical limit then there is no need for xed gas detection. However, if the concentration can reach the practical limit, even for A1 refrigerants, then xed detection must he installed. The practical limits for various refrigerants are given in Annex II and III, which are extracted from EN 3782000 part 1 and pr EN 3782006. In these tables the practical limit of ammonia is based upon its toxicity, and the practical limits of the hydrocarbons are based upon their ammability and are set at 20 of their lower ammable limit. The practical limits for all the A1 refrigerants are set at their Acute Toxicity Exposure Limit ATEL. If the total refrigerant charge in a room, divided by the net room volume, is greater than the practical limit see annex II and III, then it is reasonable to conclude that xed gas detection system should be installed. EN 3782000 only requires xed gas detection to be installed in machinery rooms. Fig. 6 FGas legislation The FGas Regulation EC No 8422006. The objective of the Regulation is to contain, prevent and thereby reduce emissions of uorinated greenhouse gases covered by the Kyoto Protocol. The Fgas directive is mandatory in all EU and EFTA member States. The Regulation covers the use of HFCs, PFCs and SF6 GWP 150 in all their applications, except Mobile Air Conditioning, covered by the Directive and Domestic Refrigerators. The Regulation entered into force on 4 July 2006 and a number of the measures will apply from 4 July 2007. Leakage checking requirements, which will be the basis for operators to use all measures which are technically feasible and do not entail disproportionate cost to prevent leakage repair any detected leakage. A periodical leakage check by certied personnel is required, with the following frequency, depending on the quantity used 3 kg or more at least once every 12 months except for hermetically sealed systems containing less than 6 kg 30 kg or more at least once every 6 months 12 months with an appropriate leakage detection system 300 kg or more at least once every 3 months 6 months with an appropriate leakage detection system which is anyway mandatory. Leakage detection systems shall be checked at least once every 12 months. 2007-09-12T07:46:11+02:00http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=9http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=9Application guide Gas detection in refrigeration systems Danfoss AS RA Marketing MWA, 08 2007 DKRCI. PA. 000. B2. 02 520H1724 9 N Y Y N Start Charge 3 kg Machineryroom Clause 7. 2. a Charge limit No requirements Additionalrequirements Gas detectionrequired N YNo requirements Gas detectionrequired Clause 8. 11. 2. 1 Clause 7. 2, table 1 Clause 7. 2. 2 Requirements for gas detection according to pr EN 3782006 pr EN 3782006 is an update of EN3782000. The standard has not been nally approved yet, but it contains important information regarding gas detection. N Y N N Y Y Y N pr EN 37832006Start Ammonia Charge practicallimit Clause 8. 1 Clause 8. 7 Clause 8. 1 Charge 100 ATELODL Gas detectionrequiredhighlow level Charge 25 kg No requirements Charge 50 kg Y N Clause 8. 1 Gas detection required No requirements Gas detection required USA Requirements for gas detection according to ASHRAE 152004 Requirements for gas detection acc. to ASHRAE 152004 state requirements for rooms with refrigerating equipment including machinery rooms. The Low Level alarm values are less or equal to TLVTWA levels. see also Occupational Exposure Limits, page 14 Fig. 7 Fig. 8 Note The charge limit, stated in ASHRAE 152004, can also, for selected refrigerants, be found in Annex IV Practical limit2007-09-12T07:46:11+02:00http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=10http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=10Application guide Gas detection in refrigeration systems 10 DKRCI. PA. 000. B2. 02 520H1724 Danfoss AS RA Marketing MWA, 08 2007 Installation guideline There are two approaches, perimeter protection or point detection. With perimeter detection you place sensors all around the perimeter of the space in question to make sure you monitor the whole space. With point detection you locate a sensor at a particular position where you are concerned about a leak e. g. at the compressor. For gases heavier than air, sensors should be located close to the groundlowest point. For gases lighter than air, sensors should be mounted high up on the walls, ceiling or near exhaust, but convenient for maintenance. If equal density, mount at face level. In some countries it can be mandatory to have an UPS Uninterruptible Power Supply connected to the Gas detectors, to ensure safely operation during a power failure. Relativ densityair refrigerant 25C 1 bar 0 1 2 3 4 R717 R744 R22 R134a R404A R407C R410A R507 R290 R600 R600a R1270 Location of gas detectors Gas detectors must be powered as specied in the instruction manual and located within the specied cable length from the central control unit monitor. In general Do not mount to a structure that is subject to vibration and shock, such as piping and piping supports. Do not locate near excessive heat or in wet or damp locations. Do not mount where it will be exposed to direct solar heating. Do not install in areas where condensation may form. The two methods of locating sensors Point Detection, where sensors are located as near as possible to the most likely sources of leakage. Perimeter Detection, where sensors completely surround the hazardous area. The most appropriate method is selected depending on the size and nature of the site. Detectors shall be located high low according to the density of the actual refrigerant. If mechanical ventilation exists in a machinery room, air will move towards the fan. In problematic locations a smoke tube can indicate air movements in a space and assist in the location of sensors. In a cold store, sensors should if possible be placed on the wall in the return airow below head height. Important Do not place immediately in front of a coil due to temp and humidity uctuations. These can occur especially during defrost or loading of a cold store. Make sure that pits, stairwells and trenches are monitored since they may ll with stagnant pockets of gas. Monitoring such areas is generally required by standards. Fig. 92007-09-12T07:46:11+02:00http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=11http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=11Application guide Gas detection in refrigeration systems Danfoss AS RA Marketing MWA, 08 2007 DKRCI. PA. 000. B2. 02 520H1724 11 Location of gas detectors continued The arrangement of the equipment in the room can also have an impact on the most eective place to sample. As general guideline If there is one compressor chiller in the room sample at the perimeter of the unit. For two chillers, sample between them, with three or more chillers, sample between and on each side. Ensure that the area being sampled is suciently monitored. Dont skimp on sensors. Place the sensor in the locations most likely to develop a gas leak including mechanical joints, seals, and where there are regular changes in the systems temperature and pressure or excessive vibration such as compressors and evaporator control valves. Locations requiring most protection in a machinery or plant room would be around gas boilers, compressors, pressurised storage tanks, gas cylinders or storage rooms or pipelines. Most vulnerable are valves, gauges, anges, Tjoints, lling or draining connections etc. Sensors should be positioned a little way back from any highpressure parts to allow gas clouds to form. Otherwise any leakage of gas is likely to pass by in a highspeed jet and will not be detected by the sensor. Accessibility to enable calibration and service in the future must be considered. You should not mount to a structure that is subject to vibration and shock, such as piping and piping supports. Avoid areas of excessive heat, wet, damp or where condensation may form. Consideration should also be given to areas where it is anticipated that leaks may occur for example in the vicinity of valves, pipe anges, compressors etc, and also the possibility of pockets of gas collecting in the event of a leak. Number of gas detectors in a facility The requirements for the number of gas detectors in a facility are not specically stated in standards. As general guideline A detector can normally cover an area of about 50100 m2 depending on the actual condition of the space to be covered. In spaces with several obstructions, and lack of ventilation the coverage is approx. 50 m2, provided it is mounted near ceiling level or near oor level depending on the refrigerant density. In nonobstructed spaces with good mechanical ventilation, the coverage can be increased up to approx. 100 m2. Machinery rooms It is recommended that detectors are sited above or at both sides of compressors or other nonstatic parts of the system or down wind of such equipment in the direction of continuously operating ventilation extractors. Where there are deep beams and lighter than air refrigerants it is recommended that the detectors are mounted between pairs of beams and also on the underside of the beams. If there is a continuous airow in the room a sensorsensing point should be located downstream from the last potential leak source. Calibration test Calibration test of gas detectors is an extremely important issue. Dierent factors have to be taken into consideration. Generally three issues are of particular importance Requirements of national legislation. Gas detectors like electrochemical sensors are consuming products, which have to be renewed periodically, depending on actual type and refrigeration concentration. Generally lifetime of the sensors. Estimated life time year Min. recomended calibration interval year Recomended test interval year SCSemiconductor521 ECElectrochemical2321 CTCatalytic521 IRInfrared521 The sensor has to be renewed if it has been exposed to high ammonia concentrations Should be a bump test From a technically and safety point of view, the sensors oered by Danfoss have to be calibrated tested according to the stated intervals in the table g. 10. IMPORTANT If national legislation requires calibration test with intervals less than stated in table g. 10, these intervals have to be followed. Note EN 378 requires testing on an annual basis. Fig. 102007-09-12T07:46:11+02:00http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=12http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=12Application guide Gas detection in refrigeration systems 12 DKRCI. PA. 000. B2. 02 520H1724 Danfoss AS RA Marketing MWA, 08 2007 Calibration on site with gasrequires specialcompetence Gas calibration Test procedure Gas sensor tested Two dierent methods are available for performing calibration test procedures. By replacing the Sensor PCB Print Circuit Board By using a Calibration Gas In addition to these methods, a bump test can be used. Calibration test methods Certiicate XXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXX Certiicate Gas calibration levels etc. Traceability Exchange of PCB sensor board Electricaltest of alarm Gas sensor tested Method I Calibration test by means of replacing Sensor PCB This method requires that the supplier oers factory calibrated PCB sensor boards with calibration certicate and traceability codes. Additionally an electrically simulation is required to verify the output signals and alarm settings. This method can by compared with the method used for safety valves. The manufacturer produces, tests and certies the product, which can then be mounted in the system. Danfoss oers the above mentioned solution. The PCB sensor board, which is the essential measuring element of the gas detector, is produced, calibrated, tested and certied by Danfoss. After the main PCB of the gas detector has been tested with the GD tester, the new calibrated Sensor PCB can be installed. Danfoss recommends that the calibration test procedure is done by means of replacing the Sensor PCB, because This method ensures that the customer basically has a new Gas Detector after replacing the Sensor PCB, because the sensor is the component whose lifetime is reduced over time. This method, when oered by Danfoss, is very price competitive, compared to the calibra tion test carried out on site Method II Calibration of gas detectors by using a calibration gas The calibration of gas detectors by means of calibration gas is relatively complicated, time consuming and expensive. The method requires special test equipment and competence in calibration. Calibration equipment calibration kit consists at least of Valve ow regulator Gas cylinder with the correct calibration gas for each refrigerant and concentration ppm Calibration instruction for the specic sensortype EC, SC, CT or IR sensor. Some calibration gas cylinders are treated as dangerous substances, and therefore specic requirements have to be fullled to ship them. Fig. 11 Fig. 12 Test and calibration of GD Main Board by the use of GD tester2007-09-12T07:46:11+02:00http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=13http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=13Application guide Gas detection in refrigeration systems Danfoss AS RA Marketing MWA, 08 2007 DKRCI. PA. 000. B2. 02 520H1724 13 Bump test A bump test can not supersede any tests involving calibration it is only a function test. signal or no signal Bump test of gas sensors this test is a function test it is not a calibration Method Refrigerant SCECCTIR Semiconductor Electro chemical Catalytic Infrared Ampoules Ammonia4 Ampoules or Lighter gas HCFC, HCF44 Lighter gas HC Hydro Carbon44 Ampoules or Breath on sensor CO24 The dierent types of refrigerants can be grouped in dierent families. In the HFC group many dierent types of refrigerants exist. A specic Gas detector calibrated for a specic gas may also be used with a good result on other refrigerant within the same group, but in this case the sensitivity is slightly dierent see g. 14. Sensitivity of sensors with gases dierent than calibration gas Calibration gas Actual Refrigerant Relative Sensitivity Ammonia R717R717100 Carbon Dioxide CO2R744R744100 Halocarbon HCFCR22R22100 Halocarbon HFCR404AR404A R507 100 95 Hydrocarbon HCR290 R290 R600 R600a R1270 100 104 101 94 0 1000 ppm 100 Calibration gas Actual gas Example Relative sensitivity 0 950 ppm 95 Fig. 13 Fig. 14 Danfoss can upon request calibrate for all most common used refrigerants. Please contact your local Danfoss sales oce. 2007-09-12T07:46:11+02:00http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=14http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=14Application guide Gas detection in refrigeration systems 14 DKRCI. PA. 000. B2. 02 520H1724 Danfoss AS RA Marketing MWA, 08 2007 Alarm sensitivity range gas detectors All commonly used gas detectors have a proportional output signal 420 m A, 010 V, or 05 V, and some preset alarm settings. When selecting the actual measuring range and sensor type, several factors have to be considered In general, alarm levels should be as low as practically possible, depending on the actual refrigerant, and the purpose of the alarm. There are often requests for more alarm levels, but experience shows that two alarm limits are sucient for gas detection. The prealarm provokes a reaction, either automatically andor in the form of alarm instructions if not, the main alarm may be triggered. This entails a whole series of consequences, including switching o machines. A main alarm should rarely and preferably never be necessary Alarms can be chosen to warn against gas concentrations less than levels acceptable for personal safety on short term or long term. Alarm levels can also be chosen to specic levels due to ammability exclusivity risk. The following recommendations are based on the present experience with suitable limits, taking into account the above mentioned conditions, but also requirements in EN 3782000, pr EN3782006 and ASRAE 152004. The GD gas detector oers two preset alarms and a proportional output signal. With this conguration, is it possible to full all requirements for alarm levels needed, within the specic operation range of the sensor. DANFOSS recommendations for alarm levels EN 3782000 pr EN 3782006 National requirements Comply EN 378 pr EN 378 Sensor type LEVEL I Personal safety occupational TWAvalues Sensor type LEVEL II prealarm Sensor type LEVEL III mainalarm ppmppmppm Ammonia R717 Machinery rooms EC500CT10000 Machinery rooms EC25EC150 Safety valves vent line SC1000 Carbon Dioxide R744 CO2IR5000IR10000 Halocarbon HCFCR22SC5001SC1000 Halocarbon HFC R134a, R404A, R407C, R410A, R507 SC5001SC1000 Hydrocarbon HC R290, R600, R600a, R1270 Concentration 20 of LFL CT800CT2500 1 50 of TWAvalue Note All proposed levels are the max. values in EN 3782000 pr EN 3782006 Danfoss recommendations for alarm levels DANFOSS recommendations for alarm levels ASRAE 152004 Comply ASRAE 152004 Sensor type LEVEL I Personal safety occupational TWAvalues Sensor type LEVEL II prealarm ppmppm Ammonia R717 Machinery rooms EC25EC500 Safety valves vent line SC1000 Carbon Dioxide R744 CO2IR5000IR10000 Halocarbon HCFCR22SC5001SC1000 Halocarbon HFC R134a, R404A, R407C, R410A, R507 SC5001SC1000 Hydrocarbon HC R290, R600, R600a, R1270 Concentration 25 of LFLCT800CT2500 1 50 of TWAvalue Note All proposed levels are the max. values in ASRAE 152004 Fig. 15 Fig. 162007-09-12T07:46:11+02:00http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=15http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=15Application guide Gas detection in refrigeration systems Danfoss AS RA Marketing MWA, 08 2007 DKRCI. PA. 000. B2. 02 520H1724 15 Occupational Exposure Limits The Occupational Exposure Limits are dierent in EUUSA and worldwide. Below, a short description from selected countries is shown. It is strongly recommended that you check the relevant national legislation. Further information can be found on the following homepage httpagency. osha. eu. intgoodpracticerisks dangeroussubstancesoelmembers. stm documentview Germany In Germany, there are two kinds of OELs for air in the workplace TRKs Technische Richtkonzentrationen, which are technical guidance concentrations, and MAKs Maximale Arbeitsplatzkonzentrationen, which give the maximum concentration of a chemical substance in the workplace. The Netherlands In the Netherlands, there are two types of OELs Legally binding OELs, and administrative OELs. They both have a dierent basis and a dierent status. Occupational Exposure Limits OELs are called MACvalues Maximaal Aanvaarde Concentraties. Europe Italy The Italian exposure limits are identical with the TLVs established by the ACGIH USA France In France, the Occupational Air Exposure Limits OELs are called Valeurs limites dexposition professionnelle aux agents chimiques en France VL. Denmark In the Danish OSH system, the Grænseværdier for stoer og materialer limit values for substances and materials, are administrative instructions that are enforced under the Working Environment Act. The Ministry of Labour sets up the regulation on these limit values and the Arbejdstilsynet Labour Inspectorate publishes the OEL list and supervises their execution. The Occupational Safety Systems in the United States vary from state to state. Here, information is given on major providers of the Occupational Exposure Limits in the USA ACGIH, OSHA, and NIOSH. ACGIH The American Conference of Governmental Industrial Hygienists ACGIH TLVTWA Threshold Limit Value Time Weighted Average, the timeweighted average concentration for a conventional 8hour workday and a 40hour workweek, to which it is believed that nearly all workers may be repeatedly exposed, day after day, without adverse eect. TLVSTEL Threshold Limit Value Short Term Exposure Limit, the concentration to which it is believed that workers can be exposed continuously for a short period of time without suering from it. ACGIHTLVs do not have a legal force in the USA, they are only recommendations. OSHA The Occupational Safety and Health Administration OSHA of the U. S. Department of Labour USDOL publishes PEL Permissible Exposure Limits PELs are regulatory limits on the amount or concentration of a substance in the air, and they are enforceable. OSHA uses in a similar way as the ACGIH the following types of OELs TWAs, Action Levels, Ceiling Limits, STELs, Excursion Limits and in some cases BEIs. NIOSH The National Institute for Occupational Safety and Health NIOSH has the statutory responsibility for recommending exposure levels that are protective to workers. NIOSH has identied Recommended Exposure Levels RELs for around 700 hazardous substances. These limits have no legal force. REL Recommended Exposure Levels. USA References EN 3782000 Refrigerating systems and heat pumps Safety and environmental requirements. pr EN 3782006 Refrigerating systems and heat pumps Safety and environmental requirementsdraft. ASRAE 152004 Safety Standard for Refrigeration Systems. Io R Safety code for Refrigeration systems Utilising Carbon Dioxide 2003. Io R Guidance Note 13, Refrigeration Detection httpagency. osha. eu. intgoodpracticerisks dangeroussubstancesoelmembers. stm documentview Danfoss Literature GD sensor Literature No. RD7HA. FGas Regulation EC No 84220062007-09-12T07:46:11+02:00http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=16http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=16Application guide Gas detection in refrigeration systems 16 DKRCI. PA. 000. B2. 02 520H1724 Danfoss AS RA Marketing MWA, 08 2007 Annex I Common refrigeration data Refrigerant type Refrigerant Name Formula Safety group Vapour density 25C 1 bar Relativ density 25C 1 bar ODP Ozone Pepletion Portential GWP 100 Global Warming Portential kgm 3 R717Ammonia NH 3 B20. 7040. 600 R744Carbon Dioxide CO 2 A11. 8081. 501 HCFCR22Chlorodiuoromethane CHCIF 2 A13. 5873. 10. 0551700 HFCR134a1, 1, 1, 2tetraouroroethane CH 2 FCF 3 A14. 2583. 601300 HFCR404AR125143a134a 44524A14. 0573. 503260 HFCR407CR32125134a 232552A13. 5823. 101520 HFCR410AR32125 5050A13. 0072. 601900 HFCR507R125143a 5050A24. 1083. 503800 HCR290Propane CH 3 CH 2 CH 3 A31. 8321. 603 HCR600Butane CH 3 CH 2 CH 2 CH 3 A32. 4402. 103 HCR600a Isobutane2CHCH 3 3A32. 4402. 103 HCR1270Propylene CH 3 CHCH 2 A31. 7451. 53 Safety groups Increased toxicity Increased ammability A1B1 Increased ammability A2B2 A3B32007-09-12T07:46:11+02:00http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=17http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=17Application guide Gas detection in refrigeration systems Danfoss AS RA Marketing MWA, 08 2007 DKRCI. PA. 000. B2. 02 520H1724 17 Annex II EN 3782000 Refrigerant type Refrigerant Name Safety group L group Practical Limit Practical Limit Flammabillity LFL Flammabillity LFL 20 Prealarm level MAX refrigeration concentration 20 LFL or Practical limit R717500ppm Mainalarm MAX refrigeration concentration pr EN 3782006 TWA NIOSH 40 hours work week without eect kgm 3 ppmkgm 3 ppmppmppmppm R717Ammonia B2L20. 000354970. 104295455003000025 R744Carbon Dioxide A1L10. 155310550005000 HCFCR22Chlorodiuoromethane A1L10. 383635840001000 HFCR134a1, 1, 1, 2tetraouroroethane A1L10. 255871359000 HFCR404AR125143a134a 44524A1L10. 48118314120000 HFCR407CR32125134a 232552A1L10. 318654487000 HFCR410AR32125 5050A1L10. 44146325145000 HFCR507R125143a 5050A2L20. 49119279120000 HCR290Propane A3L30. 0080. 038414842001000 HCR600Butane A3L30. 0080. 03629513000800 HCR600a Isobutane A3L30. 0080. 04335253500800 HCR1270Propylene A3L30. 0080. 04349285000 Safety groups Safety groups L groups Increased toxicity Increased toxicity Increased ammability A1B1 Increased ammability A1 L1B1 L2 A2B2A2 L2B2 L2 A3B3A3 L3B3 L32007-09-12T07:46:11+02:00http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=18http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=18Application guide Gas detection in refrigeration systems 18 DKRCI. PA. 000. B2. 02 520H1724 Danfoss AS RA Marketing MWA, 08 2007 Annex III pr EN 3782006 Refrigerant type Refrigerant Name Safety group Practical Limit ATEL ODLATEL ODL 50 Flammabillity LFL Flammabillity LFL 20 Prealarm level MAX refrigeration concentration 20 LFL or Practical limit R717500ppm Mainalarm MAX refrigeration concentration pr EN 3782006 TWA NIOSH 40 hours work week without eect kgm 3 kgm3ppmkgm 3 ppmppmppmppm R717Ammonia B20. 000350. 000352490. 104295455003000025 R744Carbon Dioxide A10. 070. 0719358195005000 HCFCR22Chlorodiuoromethane A10. 30. 341818420001000 HFCR134a1, 1, 1, 2tetraouroroethane A10. 250. 252935729400 HFCR404AR125143a134a 44524A10. 480. 485915759200 HFCR407CR32125134a 232552A10. 310. 314327243300 HFCR410AR32125 5050A10. 440. 447316373200 HFCR507AR125143a 5050A20. 49 HCR290Propane A30. 0080. 09245630. 038414842001000 HCR600Butane A30. 00860. 19389340. 04335253000800 HCR600a Isobutane A30. 00860. 06122950. 04335253500800 HCR1270Propylene A30. 0080. 0128650. 04045855000 Safety groups Increased toxicity Increased ammability A1B1 A2B2 A3B32007-09-12T07:46:11+02:00http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=19http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=19Application guide Gas detection in refrigeration systems Danfoss AS RA Marketing MWA, 08 2007 DKRCI. PA. 000. B2. 02 520H1724 19 Annex IV ASHRAE 152004 Refrigerant type Refrigerant Name Safety group L group Practical Limit Practical Limit TWA NIOSH 40 hours work week without eect gm 3 ppmppm R717Ammonia B2L20. 3550025 R744Carbon Dioxide A1L191500005000 HCFCR22Chlorodiuoromethane A1L1150420001000 HFCR134a1, 1, 1, 2tetraouroroethane A1L125060000 HFCR404AR125143a134a 44524A1L1 HFCR407CR32125134a 232552A1L1 HFCR410AR32125 5050A1L1 HFCR507R125143a 5050A2L2 HCR290Propane A3L3844001000 HCR600Butane A3L38. 23400800 HCR600a Isobutane A3L38. 23400800 HCR1270Propylene A3L35. 934002007-09-12T07:46:11+02:00http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=20http://danfoss.ipapercms.dk/refrigerationandairconditioning/RA/DanfossIndustrialRefrigeration/GasDetection/?Page=20DKRCI. PA. 000. B2. 02 520H1724Produced by Danfoss RA Marketing, MWA. 072007 The Danfoss product range for the refrigeration and air conditioning industry Danfoss Refrigeration Air Conditioning is a worldwide manufacturer with a leading position in industrial, commercial and supermarket refrigeration as well as air conditioning and climate solutions. We focus on our core business of making quality products, components and systems that enhance performance and reduce total life cycle costs the key to major savings. Controls for Commercial Refrigeration Controls for Industrial Refrigeration Industrial Automation Household Compressors Commercial Compressors Thermostats Sub Assemblies Electronic Controls Sensors We are oering a single source for one of the widest ranges of innovative refrigeration and air conditioning components and systems in the world. And, we back technical solutions with business solution to help your company reduce costs, streamline processes and achieve your business goals. Danfoss AS www. danfoss. com2007-09-12T07:46:11+02:00