Flammable detector

Detailed information to do with toxic gas terminology and the effects of these gases on the human body are provided in Process Risk and Reliability Management Much of the guidance to do with flammable detectors can be applied to toxic gas detection also. However, the following additional issues should be considered ... 

Waste facihties should be designed to prevent explosions in sewer systems and typically are comprised of suitable traps, vents, clean-outs, collecting chambers, etc. Flammable gas detectors are installed in sewers to warn of ha2ardous concentrations, and inert gas blanketing of closed process sumps generally is advisable. 

Flammable Vapor Detectors These should be installed to warn of leaks, although such devices do not effectively control UVCEs with sudden, massive releases. 

Flevated or Remote Air Intakes Elevated or remote air intakes for control rooms will help in reducing ingress of dense, flammable vapors into those rooms. Ordinarily, elevating the tip of the air intake duct 9 m (30 ft) above the ground is sufficient. Installing flammable vapor detectors in the air intake ducts provides additional protection. Controls that automatically stop air to control rooms if vapor concentrations reach 25 percent of their LFL should also be considered. 

With flammable gases, eliminate all ignition sources (refer to Chapter 6). Possibly provide additional high/low level ventilation background gas detectors to alarm, e.g. at 40% of the LEL. With toxic gases, possibly provide additional local ventilation monitors connected to alarms appropriate air-fed respirators. (The flammable/toxic gas detectors may be linked to automatic shutdown instrumentation.)... 

Industrial use of flammable gas detectors Storage of highly flammable liquids... 

FIRE SIMULATOR predicts the effects of fire growth in a 1-room, 2-vent compartment with sprinkler and detector. It predicts temperature and smoke properties (Oj/CO/COj concentrations and optical densities), heat transfer through room walls and ceilings, sprinkler/heat and smoke detector activation time, heating history of sprinkler/heat detector links, smoke detector response, sprinkler activation, ceiling jet temperature and velocity history (at specified radius from the flre i, sprinkler suppression rate of fire, time to flashover, post-flashover burning rates and duration, doors and windows which open and close, forced ventilation, post-flashover ventilation-limited combustion, lower flammability limit, smoke emissivity, and generation rates of CO/CO, pro iri i post-flashover. 

It is usual to test for the presence of flammable gas or vapor with a combustible gas detector before maintenance, especially welding or other hot work, is allowed to start. The following incidents show what can happen if these tests are not carried out or not earned out thoroughly. Large pieces of equipment or those of complex shape should be tested in several places, using detector heads at the ends of long leads if necessary (see Section 5.4.2 d). 

No one realized, when a site for the furnace was decided, that flammable vapors could come out of the cooling tower. Direct contact condensers are not common, but flammable vapors can appear in many cooling towers if there are leaks on water-cooled heat exchangers. After the incident, a combustible gas detector was mounted permanently between the furnace and the tower (Figure 2-8). 

It is possible to measure the extent of a leak of flammable gas or vapor with a combustible gas detector. If the leak is small, a person may be allowed (but not expected) to put his hands, suitably protected, inside the flammable cloud. But only in the most exceptional circumstances should a person be allowed to put more of his body into the cloud. 

On many occasions combustible gas detectors have detected a leak soon after it started, and action to control it has been taken promptly. Installation of these detectors is strongly recommended whenever liquefied flammable gases or other flashing liquids are handled or when experience shows there is a significant chance of a leak [3]. Detectors are also... 

The main rises of a sintered metal flame arrester are in the sensing heads of flammable gas detectors and in flame arresters for gas welding (oxyacetylene) equipment. 

Other properties of solvents which need to be considered are boiling point, viscosity (lower viscosity generally gives greater chromatographic efficiency), detector compatibility, flammability, and toxicity. Many of the common solvents used in HPLC are flammable and some are toxic and it is therefore advisable for HPLC instrumentation to be used in a well-ventilated laboratory, if possible under an extraction duct or hood. 

If a flammable gas or vapour is present, a pre-fire condition may be identified by a flammable-gas detector. Fire detection may be by ... 

If a flammable gas or vapour is present, a pre-fire condition may be identified by a flammable-gas detector. This will actuate an alarm at a fraction of the LFL. Banks of detectors may be installed at high or low level depending, in part, upon the gas density. Fire detection may be by ... 

Multi-sensor fire detectors provide faster detection with fewer false alarms. These sensors are capable of monitoring the environment for multiple purposes, e.g. carbon monoxide concentration, concentration of flammable gases and indoor air quality, too. 

This accident emphasizes the importance of adding gas detectors that measure flammable gases at low concentrations so that alarms and block valves can be actuated before large quantities of gas are released. 

Methane leaks from a tank in a 50 m3 sealed room. Its concentration is found to be 30 % by volume, as recorded by a combustible gas detector. The watchman runs to open the door of the room. The lighter mixture of the room gases flows out to the door at a steady rate of 50 g/s. The flammable limits are 5 and 15 % by volume for the methane in air. Assume a constant temperature at 25 °C and well-mixed conditions in the room. The mixture of the room gases can be approximated at a constant molecular weight and density of 25 g/mol and 1.05 kg/m3 respectively. After the door is opened, when will the mixture in the room become flammable ... 

Sprinklers and fire protection systems are required by NFPA Codes, but are often dependent on the overall size of the facility and quantity of stored flammable/combustible material. The wisest course of action is to provide heat and smoke detectors in each laboratory and provide a sprinkler system at least in the hallways. Each laboratory should have at least one ABC portable fire extinguisher. Computers have become more important to laboratories than ever. Halon fire extinguishing systems are available which are nondestructive to both electronic equipment and human life. These should be employed for fire protection. 

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