Fire and gas detector

Generally, electrical control systems are designed Fail-Safe. If power is temporarily lost, unnecessary shutdown of the process may occur. Thus, most safety systems such as fire and gas detectors, Nav-Aids, communications, and emergency lighting require standby D.C. power. 

How much operational experience we need to rely on operational experience alone, is not easy to know. Where a large number of similar components are installed at the same installation, like fire and gas detectors, there may be a significant amount of experience data available already after a year of operation. With few components of the same type, it may be necessary to wait several years before sufficient operational experience has been obtained. 

Certain components are not given unique tag numbers in the maintenance system, like for example programmable electronic controllers (PLCs) and fire centrals. Failures are instead recorded against other connected components, for example transmitters and fire and gas detectors. In addition, software related failures, which are highly relevant for PLCs and fire centrals, are often not recorded in the maintenance system at all, but in separate systems. This means that the performance of the PLCs is not fully known. 

SIL Information How Can lEC 61508 Approval Aid Users in the Selection and Application of SIL Suitable Fire and Gas Detectors General Monitors http //www. gmsystemsgroup.com/sil/sil info 105.html. 

The fire and gas detectors should be installed in locations accessible for calibration and maintenance but not in frequently used accessways. 

Alarms should be displayed on a conventional dedicated window annuciator panel or if control room based on a dedicated CRT display for fire and gas detection systems. Each detector location should be highlighted with indications for trouble, alarm low, and alarm high. Where annuciator panel window alarms the alarm indication lights should be provided with specific labels indicating the exact alarm locations. 

Flame detectors designed for burner protection are quite different than flame detectors designed for fire and gas systems. Burner flame detectors monitor the flame inside a combustion chamber and look for lack of flame. The dangerous condition is loss of flame. 

Conversely, in detectors designed for fire and gas mitigation systems presence of flame is the dangerous condition. Since the dangerous situation is reversed for these two applications, the overall design of the sensor is different especially the fail-safe characteristics. 

The present paper considers the safety of different systems or components. A safety instrumented system (SIS) is a system which consists of sensors, logic solvers and actuating items. The sensors may for instance be gas detectors, the logic solver could be a computer and the actuating items may be shut down valves. A fire and gas detection system with an alarm or a sprinkler system is an example of a SIS. A SIS is constructed to take the process into a safe state if a dangerous event occurs. 

The objective of the verification and validation activity is to ensure that the installed FGS system is in compliance with standards, and with the FGS specification having various performance parameters. There are two distinct phases. The first phase shall be a verification of installed equipment against the FGS requirements of specifications. During this phase, aU detectors will be viewed at the facility in order to verify that they are the correct type, and installed in the proper orientation and location as per specification. The second phase of this task will involve validation testing. The validation testing shall be accomplished by physically activating each detector by either simulating a fire with a fire simulator, and gas detectors with calibrated gas of tbe supplier. In each case, the audio-visual alarm, etc. is to be verified also. 

It is important that the tests are realistic and that they cover all subsystems to check the availability of the system as a whole. The fire and gas detection system, for example, is tested all the way from the detector, which is activated by gas, light or smoke, to the display in the central control room. 

We put a lot of effort into improving safety by adding protective equipment onto our plants, new and old gas detectors, emergency isolation valves, interlocks, steam curtains, fire insulation, catchment pits for LPG storage tanks, and so on. We also introduced new procedures, such as hazard and operability studies and modification control, or persuaded people to follow old ones, such as permits-to-work and audits. 

The hazard tree also helps identify protection devices to include in equipment design that may minimize the possibility that a source will develop into a condition. Examples would be flame arrestors and stack arrestors on fire tubes to prevent flash back and exhaust sparks, gas detectors to sense the presence of a fuel in a confined space, and fire... 

Combustible gas detection systems are frequently used in areas of poor ventilation. By the early detection of combustible gas releases before ignitible concentration levels occur, corrective procedures such as shutting down equipment, deactivating electrical circuits and activating ventilation fans can be implemented prior to fire or explosion. Combustible gas detectors are also used to substantiate adequate ventilation. Most combustible gas detection systems, although responsive to a wide range of combustible gases and vapors, are normally calibrated specifically to indicate concentrations of methane since most natural gas is comprised primarily of methane. 

After the fire, the pump (and others) was relocated in the open air, under a canopy, so that small leaks would be dispersed by natural ventilation. It was surrounded by a steam curtain to disperse larger leaks. This would not have been necessary if the pump could have been located more than 150 m from sources of ignition. Gas detectors were installed to give early warning of any leaks. Emergency isolation valves (Section 7.2.1) were provided so that the pumps could be isolated safely from a distance [9]. What happened when another leak occurred is described in Section 7.2.1 (d). 

The leak could have been stopped as soon as it was detected if an emergency isolation valve (Section 7.2.1) had been fitted in the pump suction line. On the rebuilt plant such valves were fitted on the pump suction lines, more combustible gas detectors and more extensive insulation were installed, plastic pump bodies were replaced by metal ones, and spillages were directed to collection pits. The plant was built in 1972, when these features were not common practice many improvements had been made since then, but they did not go far enough. Most of those made after the fire could have been made beforehand. 

CR Yellow Alert Gas leak in MSM Audible alarm, yellow flashing light on fire gas panel Uncertain could be real 1. Accept alarm 2. Cz area technician 3. Make PA announcement 4. Determine which gas detector is in alarm (its location) Suspend current operation. Scan panels for flashing yellow or red light. Turn around to MSM Fire Gas panel. Press "accept" button CCR Layout MSM Fire Gas panel Visual and audible Whatever op is doing when alarm occurs Initially disorientating because MSM does not have its own sound source. Alarm could be missed if second simultaneous alarm occurs on main bank of Fire Gas panels... 

Security and safety Intruder alarm Security systems Fire detection systems, with sensors for - temperature - toxic gases like CO, C02, exhaust gases, smoke, etc. - combustible gases like CH4, C2H6 flame detection, fire detectors, caravans with gas detectors, etc. 

The process area has combustible gas detectors, fireproofing, and a water deluge system. Cable trays are protected with deluge, and portable dry chemical extinguishers are in the process area. Diesel-powered fire water pumps can provide a maximum fire water demand for 4 hr. 

Loss control features include combustible gas detectors installed around the containment area and transfer system. A diesel-driven fire pump is capable of handling the emergency demand for 4 hr. A water deluge system has been installed around the storage tank and transfer pump. 

To assist in the location of combustible gas detectors and fire detection equipment. 

The use of two separate electrical or mechanical zones of detectors, both of which must be actuated before the confirmation of a fire or gas detection. For example, the detectors in one zone could all be placed on the north side of a protected area, and positioned to view the protected area looking south, while the detectors in the second zone would be located on the south side and positioned to view the northern area. Requiring both zones to be actuated reduces the probability of a false alarm activated by a false alarm source such as welding operations, from either the north or the south outside the protected area. However this method is not effective if the zone facing away from the source, sees the radiation. Another method of cross zoning is to have one set of detectors cover the area to be protected and another set located to face away from the protected area to intercept external sources of nuisance UV. If welding or lighting should occur outside the protected area, activation of the alarm for the protected area would be inhibited by second... 

Because of the dead air space that might be missed by turbulent hot air above a fire, smoke detectors should be installed either on the ceiling at least four inches from the nearest wall, or high on a wall at least four, but no further than 12 inches from the ceiling. Detectors should not be mounted near windows, exterior doors, or other places where drafts might direct the smoke away from the unit. Nor should they be placed in kitchens and garages, where cooking and gas fumes are likely to set off false alarms. 

Coal Mines, Determination of Firedamp and of Coal Dust In Atmospheres of. Although many instruments have been designed to detect the presence of firedamp (or rather methane) in mine atmospheres, the principles of the flame safety lamp (Davy-type lamp) still form the basis of many detectors. The Davy lamp invented in 1815 is briefly described under COAL MINE EXPLOSIONS AND FIRES and it is stated that each US mine should have at least two Davy-type lamps to serve as detectors of firedamp or of lack of oxygen. If firedamp is present in small quantity, the flame of Davy lamp elongates and if the gas is present in considerable quantity, the lamp becomes filled with blue flame. For more definite detection of gas, the flame of the lamp is lowered until the yel part is at a minimum. Then the gas will be discernible as a small blue cap over the flame. This method is described in Refs 1, 9, 12 25. Some investigators consider that the safety lamp method of detection of firedamp is not very reliable (Ref 7)... 

Various methods and instruments are available for measuring gas concentrations in fire effluents, e.g., gas detector tubes, ion-selective electrodes, GC/MS (gas chromatography/mass spectrometry), and Fourier Transform Infrared (FTIR) spectroscopy. An extensive review of the methods is provided in ASTM E 800 and ISO 19701. 

Water, gas, electrical and drain lines are contained in chases which run vertically between floors on either side of the hall. Outside each laboratory there is a locked access panel in the chase, the key to which is kept in the laboratory. In an emergency any utilities to a single laboratory may be shut off from this chase. Of course, the building is equipped with the usual array of smoke and heat detectors and fire alarms. 

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