【 Weak current College 】 breathing smoke detector application in cold storage

Author Peter gas sensing technology co., Ltd. United Kingdom · Fox (PeterFox) provide us with some application in cold storage in air-breathing smoke detector to obtain the most effective and reliable smoke effects of specific information.

In the early 1980s, air-breathing smoke detector began to be accepted in order to protect the telephone Office, computer rooms and other places of a universal fire method. The reliable detection of large air flow in the range of extremely low concentration of smoke, means that the detector will rapidly be these environment accepted as a standard fire detectors. Indeed, such a detector be actual fire prevention, not just to detect fire, this is the first time. Just recently, such as identification algorithm used dust high sensitivity of aspirating systems can remove dust Stratos-HSSD, and other non-fire-suspension air particles signal, which means that it can be widely used in flour mills and other areas. In the United Kingdom, air-breathing smoke detector was first used in cold storage, in 1985, however, because at that time some unforeseen defects, also cannot be said that the previous installation is an extremely successful example. Fortunately, since then, we have this kind of detector for installation and use, have made a lot of experience. Gas sensing technology co., Ltd. on breathing smoke detector in this special field of application, has the rich experience. This article will be based on the company's system design manual on air-breathing smoke detector for practical application.

As a result of anomalies in the refrigerator, air-breathing smoke detector applications require special technology is a general fire regulations and standards do not provide. In particular, in order to ensure detection of gas sample collection, cold storage of health and safety of personnel, on gas sampling pipe installation location, special attention should be given.

Gas sampling tube and its location

Aspirating detection system gas sampling tube should be installed in the main parts of cold storage, and not located in the ceiling or auxiliary spaces. Gas sampling tube should be used in acrylonitrile-butadiene-styrene copolymers or thin stainless steel material. Because PVC-u in low temperature embrittlement will, therefore, is not suitable. In addition, it should be borne in mind that, as the installation of metal gas sampling system must be earthed.

Gas sampling tube system installed, should, as far as possible away from the building structure, because it can come into contact with or proximity to the above there are a lot of condensation water and ice in the inner surface of the building structure. Despite the cold storage temperature range tend to below 0 ° c, however, thermal radiation, convection and conduction discernible difference in temperature. Gas sampling system must not directly located in the cooling system of forced airflow paths. Cooling temperature intermittent blowing most-35 to-40 degrees centigrade of working temperature is much lower than cold air, this cooling system is stopped, the gas sampling tube will use some time to reach the cold ambient temperature, ease of icing. In General, the gas sampling hole should gas sampling tube side drill, as here, the possibility of condensation and freezing are very small (depending on the temperature of cold storage).

Should return to the cooling airflow monitor be taken into account. Monitoring return air flow with the use of air to breathe the smoke gas sampling system advantages (also referred to as "initial" probe). However, do not forget that this flow is not contiguous, you should not rely on the flue gas transportation.

Of aspirating controller hosts usually must be installed on the outside, because the cold store at temperature below zero degrees Celsius, the detector will not be able to work continuously. If the probe installed in the exterior wall or ceiling cold storage, you should apply insulation Board shall make separate detectors and mounting surface (e.g. 50 × 50 mm Cork), because in some cases, the outer surface of the formation of condensate on the Council. If the probe installed in the Stratos, the outside should be installed in suitable all-weather coat. If the detector to shell exhaust, the shell not to seal, it is desirable that there should be the emission, Shell returns to protected areas of the facility.

The gas sampling tubes from cold storage point, air heating device should be installed so as to not making the cooling gas sampling tube exposed to cold outside air temperature is high. Is cooling piping works such as exposure to the air temperature is higher, its surface has the potential to produce large amounts of condensation water, especially in humid circumstances, ice-thawing cycles, if not properly managed, this will give the cold storage of health and safety risk. Heater can improve the acquisition of air and pipeline project of temperature to prevent condensation of water. Experience shows that sometimes the recommended basic trajectory of heating, temperature in Celsius sub-zero cold storage, it is not applicable. Leads to the heater unit of gas sampling pipeline project should always horizontal or inclined to lay, to prevent condensation of water to gas sampling tube and preventing icing, pipe plug.

Installation problems

If there is no secondary space around cold room, heater cartridges should be installed in all-weather enclosure, and the size of Stratos detectors should be installed on the roof of the auxiliary spaces. Heaters should not be installed on the roof of the cold store, because it can cause problems (this article will detail the issues behind). If you do not have a secondary cold storage space heater and gas emission detectors can be back to the protected area. This will prevent the cold and the surrounding area of pressure differential on the air through the detector.

Air heaters have a power supply, and to the work of the heater to be continuously monitored. To this end, to probe the intake Department set up a factory Assembly of precision presetting of the thermal power switch. You can use this switch output values generated fault alarm. You must install the temperature change during the gas sampling tube of given consideration. For a new installation, you may put gas sampling pipe system on for example the temperature 20 ° c, and cold storage will work in the low temperature 40 ° c to 50 ° c. So, should the gas sampling tube linear coefficient of expansion and contraction will be ready to consider, and during installation on the installation of pipe length of final changes to the appropriate supplement. Sometimes surprising to discover that the use of cold storage in General gas sampling tube length at high temperature and low temperature difference of dozens of cm. It is not difficult to imagine that this kind of situation as in the later stages of the project, which was corrected.

InLow temperature applications

Stratos-HSSP detector with all other suction system, are not suitable for installation in temperature below minus 10 ° c in the region. In the protected zone of the air temperature remains below the temperature, the most basic requirement is that the detector is installed on the outside of the protected area. You can use the heater unit, by automatically adjusting temperature heating elements have just left the reserve of cold air inhaled in the environment, to increase its temperature. This approach, you can significantly reduce the protected areas outside of the gas sample collection piping condensation problems. Heating air gas sample also guaranteed Stratos-HSSD components work in prescriptive temperature tolerance, and in fact the Elimination of the possibility of condensation on the surface.

In order to monitor a air heater elements, also provides precision air thermal power switch tools. This tool can monitor the gas sample collection in the left inlet temperature of the blower Assembly. If the heater element fails, you can put this energy power switch contact, producing a common fault signal. In connection to a Stratos-HSSD analogue addressable fire alarm system, can be used to monitor interface gives a specific fault alarm.

The installer can avoid the problem of

The proposal seemed to installer provides only a limited number of options, these recommendations are considered, since the establishment of gas sampling system used in many trivial technology will bring to its application.

Experience has shown that there is a "normal" installation technology can not be used anyway, this is the gas sampling pipe laying from the freezer to the refrigerator within vertical insulation wall outside a relatively high temperature area. This is the General consequences will be water pipe, block. The tube is how water plug depends on entering any air cold storage relative humidity and the resulting air concentration of ice particles, as well as cold and temperature difference between the surrounding area.

In can guarantee that the air inside the cold store without ice particle, that won't happen with this phenomenon. However, this is not possible, because the cold storage of work means that each time access will bring cold air flows and temperature.

Extension of the gas sampling points (also called capillary) are particularly vulnerable to the pipe plug, as its diameter is relatively small, therefore, does not advocate this approach.

Gas sampling tube through the cold wall vertical laying, also in the cold store outside of the pipe outer surface to produce large amounts of condensation water. This is very difficult to control, if unchecked, the cold storage of health and safety risk, also damaged cold storage structure.

Cold storage

Freezer temperatures generally remain at 0 ° c to + 5 ° c, the temperature of the similar refrigerators. In order to maintain the temperature of the freezer will have type similar freezer cooler cooling machine, this cooling function passes the cooler air cooling to 0 degrees centigrade. As a result, the direct blowing-in of air stream of any substance is cooled to a temperature below 0 degrees centigrade.

Cooling machine is not possible to continue working, it can only be under constant temperature control needs to be protected.

The cold storage of cooling machine structure is different, therefore, should be considered in the investigation phase to determine how to install the cooler and the flow of cooling air.

Enter the cold storage of warm air is expected to rise and reached the dew point, temperature, water vapour which is condensed. This condensing steam flow in the heating will rise, and in cooler air stream does not alter the flow direction, condensing steam will cross the cooler cooling of the surface. If these surface at 0 ° c, condensing steam is above freezing. Because of this phenomenon, in particular gas sampling pipe installation should stay away from the cooler forced air flow. Gas sampling tubes are also exposed to the air temperature is extremely high, then, in the cooler for defrosting cycle, condensing steam will cause unnecessary alarm. To solve this problem, Stratos-HSSD detector is equipped with a special "remote isolation facilities.