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exhaust cycle. In such instances use of acoalescing exhaust silencer should be considered. The action of this device is exactly as those for oil removal filters which cause the small oil droplets to mergetogether into large droplets which fall into acontainer for removal. (See figure 34.) In the course of this process the porous material employed also reduces the noise level of the exhaust air.Since these devices are on theexhaust side of the pneumatic system they are exposed to sudden shock loading, whichmeans their oil removal capabilities are not as good as those employed in coalescingfilters. A good exhaust coalescing silencer will however give figures of typically 2 ppm under average usage conditions.

Clean Compressed Air Brochure - 14694 PROTECTION DEVICESELECTION OTHER PRODUCTS FOR SAFESYSTEMS

(i) Decide which parts of the system cannotwithstand the maximum pressure which can be developed in the distribution system (or compressor).Determine which type of relief valveis required to control this air pressure mosteffectively with consideration of failure flow through that part of the system. Consider using a restrictor (orifice) without producing excessive pressure losses in the normal operation of that part of the system.For very large flows consider a pilotoperated regulator as a dump valve.For machines consider an in-linedevice to build-up one complete integral modular preparation assembly for ease of piping, location and servicing.(ii) Decide upon which parts of thesystem can suffer from problems on initial start up, or resetting where excessive initial speeds can lead to wear problems or entrap- ment, or where an emergency stop/dump function is required.Employ one soft start/dump valve foreach section of the system operated in this way. The larger the system the longer the dump or emergency stop function will take to fully empty the system.Locate soft start/dump valves in theFRL assembly at the downstream end to prevent high back flows through the lubri- cator.(iii) Where large volumes of air areto be exhausted consider fitting a silencer ifthe air cannot be piped away to a convenientposition.Where rapid cycling of exhaust ispresent fit a heavy duty silencer.Where the exhaust air can be heavilyladen with lubricant, usually from equipment requiring high levels of lubrication fit a coalescing exhaust silencer. Other air line products that can help createsafe pneumatic systems -Preset pressure regulators - whereunauthorised adjustment of the set pressure can be injurious to personnel.Guidance Document: HS (G) 39Lockable shut-off valves - ensurethat a ‘safe to work’ procedure can be adopted without jeopardy from the unautho- rised re-application of pressure.Legislation: BS EN 983 5.1.6 Guidance Document HS (G) 39 Tamper resistant kits - can be fittedto pressure regulators, filter/regulators, relief valves and lubricators to ensure that flow,pressure and other settings are secured against unauthorised adjustment.Legislation Reference:BSEN9835.1.9
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