Safety purging

The startup speed and temperature acceleration curves as shown in Figure 19-2 are one such safety measure. If the temperature or speed are not reached in a certain time span from ignition, the turbine will be shutdown. In the early days when these acceleration and temperature curves were not used, the fuel, which was not ignited, was carried from the combustor and then deposited at the first or second turbine nozzle, where the fuel combusted which resulted in the burnout of the turbine nozzles. After an aborted start the turbine must be fully purged of any fuel before the next start is attempted. To achieve the purge of any fuel residual from the turbine, there must be about seven times the turbine volume of air that must be exhausted before combustion is once again attempted. 

In the case of heavier-than-air purge gas, there is no buoyancy mechanism causing air entry into the stack, and there is thus no incentive to include a dry seal. Unlike a water seal, a dry seal cannot prevent a flashback from traveling upstream if a combustible mixture has been formed by the entry of air into the safety valve or flare headers. It only protects against internal burning flashback... 

Safety requires that only the most reliable experimentally determined flammable limit data be considered in purging calculations. This is included in Table 3. 

Increased maintenance cost for process equipment due to safety requirements (for example, safety permits, cleaning and purging equipment, personal protective equipment, training, and restricted access to process areas). 

On the boiler that exploded the manual individual burner valves were not closed when the boiler shut down. After the purge period, fuel gas was admitted to the header from remote manual controls in the control room and into the firebox. Low fuel gas pressure tripped the master safety valve after each attempt to pressure the fuel header. Three attempts were made to purge the boiler and on each of these occasions fuel gas was dumped into the furnace through the open manual burner gas valves. On the third attempt a severe explosion occurred. 

Used to summarize and detail the interrelationship of utilities such as air, water (various types), steam (various types), heat transfer mediums such as Dowtherm, process vents and purges, safety relief blow-down, etc., to the basic process. The amount of detail is often too great to combine on other sheets, so separate sheets are prepared. 

The amount of process plant that can be defined accurately as automatic is relatively small, and manual intervention is often involved at some stage. The relevant design criteria are therefore often IM/12 or IM/18. In practice, fully automatic burner controllers tested and certified by British Gas are available that comply with the requirements of BS 5885. Although these have features which may not be applicable to non-automatic plant, it may be more appropriate to use such a controller, particularly as its safety is well proven. It may also be less expensive than buying and installing separate timers, relays, etc. For some processes (for example, those that do not need and cannot tolerate a long purge) such controllers may not be appropriate. 

After testing for soundness it will be necessary to safely introduce gas into the pipework displacing the air or inert gas that is in it. Similarly, if pipework is decommissioned for any reason fuel gas must be displaced by air or inert gas. This is a requirement of the Gas Safety (Installation and Use) Regulations, Regulation 21. Guidance on recommended procedures is given in the British Gas publication Purging Procedures for Non-Domestic Gas Installations (IM/2). 

After soundness testing and purging, a competent person must commission the item of plant. It is a requirement of the Gas Safety (Installation and Use) Regulations, Regulation 33, that an appliance is fully commissioned at the time that gas is made available to it or that it is isolated in such a manner that it cannot be used. 

Code of Practice No. 14, Hoses for the transfer of LPG in bulk. Installation, inspection, testing and maintenance. Code of Practice No. 15, Valve for LPG cylinders. Part 1. Safety valves for LPG cylinders. Part 2. Outlet valves for butane cylinders - quick coupling types Code of Practice No. 17, Purging LPG vessels and systems... 

Control the carriage of dangerous substances in all road tankers and in tank containers with a capacity of 3 m or more. They apply to all substances which exhibit any of the dangerous properties detailed in Schedule 1 to the regulations, from the commencement of loading until the tank has been emptied and cleaned or purged, so that any residual substance or its vapour is not sufficient to create a risk to health and safety. 

Many commercial hplc instruments optionally provide a forced air oven which will control temperature with a stability of typically 0.1 °C from ambient temperature to 100 °C. Because of the use of flammable solvents, safety considerations are important, so the ovens are usually provided with a facility for nitrogen purging and are designed to prevent the build up of solvent vapour in the event of a leak. If temperature control is used, it is important that the sam-... 

Hazards attendant on use of ethylene oxide in steriliser chambers arise from difficulties in its subsequent removal by evacuation procedures, owing to its ready absorption or adsorption by the treated material. Even after 2 evacuation cycles the oxide may still be present. Safety is ensured by using the oxide diluted with up to 90% of Freon or carbon dioxide. If high concentrations of oxide are used, an inert gas purge between cycles is essential [7], The main factors in safe handling... 

To determine PCT cnrve by volnmetric method at first we have to know mass of analyzed powder (hydride or pnre metal). The typical mass of powder used in volumetric method is in a range 50-500 mg and depends on (reactor volume with volume of connecting pipes, valves, and transdncer). After the mass measurement, the powder is loaded into specimen holder and then it is placed in the Sieverts apparatus reactor. To prevent any oxidation and for safety reason the system must be purged a few times by argon and then evacnated. However, one must be careful how much powder is appropriate for the absorption/desorption volume of a Sieverts-type apparatus. 

---