Issue link: https://onenorgren.uberflip.com/i/736668
Solutions Q&A 07 In general, air service equipment should be maintained annually. Use, quality of air and condition at examination may indicate adjustment of the maintenance interval. The following guidelines can be given: General purpose Replace/maintain annually. The element can filter: lose 15% efficiency each time it is cleaned. Elements are low cost, so it is advisable to replace them. Coalescing: Evaluate after 12 months of servicing. If the pressure drop across the element exceeds 0.7bar then the element requires changing. Activated carbon Should be changed every 1,000 hours usage or when odor packs: is detected. The life depends significantly on ambient temperature. 2.3 Plastic bowls IMI Norgren transparent plastic bowls are made from polycarbonate. Transparent plastics will degrade when subjected to excessive heat, solvents and some chemicals, which can lead to crazing and finally bowl failure. Over the last few years metal bowls and guarded plastic bowls have become increasingly popular driven by the emergence of guidelines recommending the use of guards. Never use polycarbonate bowls at conditions which exceed the maximum rated pressure and temperature of 150 psig (10 bar) and 125°F (50°C). Certain chemicals, common in some oils and solvents, can attack polycarbonate and cause the bowl to burst. If the compressor intake is located in an area containing incompatible vapors, these contaminants can be drawn into the compressor and conveyed to the bowl in the compressed air. This can result in bowl failure. Synthetic compressor oils may be drawn infrom the compressor and can also result in bowl failure. If doubt exists as to the compatibility of certain fluids with polycarbonate, please contact IMI Norgren. Metal bowls should be used where temperatures exceed 125°F (50°C) and/ or pressures exceed 150 psig (10 bar), or when materials are present which are incompatible with polycarbonate. Maximum rated operating conditions for metal bowls depend on the range; check the catalog sheets. 2.4 Drains 2.4.1 Semi automatic: A semi-auto drain is one which operates when the airline is depressurized eg at the end of a shift. It is a normally open two-way valve which is held closed by 7-10 psig (0.7-0.8 bar). When the filter is pressurized, the drain may be operated manually by pushing the tube, which protrudes outside the bowl, upwards. 2.4.2 Automatic: An automatic drain is a two-way valve, which will close when the system is pressurized. The drain opens when the float rises due to accumulated liquid and on depressurization. ? 2.4.3 Where should an automatic drain be Used? Automatic drains should be used where the filter location may make servicing difficult, where filters may be hidden from view and consequently be overlooked or where equipment is in continual use. Areas where large quantities of liquid may accumulate over a short period of time should also be equipped with auto-drain filters. High labor costs for draining a large number of filters manually will generally justify the use of autodrains. Machines which have been shut down for a long period of time, such as over a weekend, can draw slugs of water during start-up which can overload a filter unless drained immediately. (This situation can normally be handled by a drip leg drain, see 2.5.7.) IMI Norgren float type automatic drains are 'normally open' type drains. During periods when the air line pressure is shut off, the automatic drain will open allowing liquids to drain rather than flood the air line piping system. When re-pressurizing the air line, the automatic drain valve will close when pressure reaches approximately 0.7bar (10psig). This results in a flow through the drain to atmosphere of about (0.84dm3/s) until the valve automatically closes. (See 2.4.4 below.) 2.4.4 -07 Series Automatic (spitter) drain: When a rapid increase in flow occurs through the filter it results in the pressure above the drain's diaphragm being less than that below it. This differential pressure causes the drain to momentarily lift and 'spit' out the condensate collected underneath the drain. ? 2.4.5 Where should a drip leg drain be Used? The drip leg drain is a system protection device. Most compressed air distribution systems have varying flows and/or are shut down at the end of a working day. As the system cools, water in the compressed air condenses and collects in the distribution pipe work. This water will run along the pipe work and settle at the low point(s). On start up of the plant this water can be pushed under pressure into the nearest device or process and cause malfunction or damage. By running a vertical pipe down from these low points water will flow into the drip leg drain where the automatic drain will expel it. A filter screen within the drip leg drain prevents particles interfering with the auto-drain operation. A ball valve should be included above the drip leg drain to allow for maintenance when the system is running.