SECTION 4.0 4.1 COMPRESSED AIR FILTRATION THE PROBLEM Most pneumatic air supply stations, for controls, have a coalescing filter. They are excellent filters; however, the indication to change the filter element is based on a pressure drop through the filter at a specific flow rate. (Often a 10 PSIG pressure drop at a 10 SCFM flow rate.) It is extremely rare to find a control air supply at exactly 10 SCFM; therefore, the pressure drop is not relevant in most cases. (A 7.5 HP compressor, running 33% of the time, should produce approximately 10 SCFM.) Most operators do not have a reliable means to determine when the element requires changing. We often witness elements saturated to the point of allowing oil into the control system. In one case, the element was laying in the bottom of the filter bowl. The operators did not have an indicator to trigger correction of the dangerous situation. THE SOLUTION Install a Deltech filter after your existing filter station to act as an "INDICATOR/SAFETY NET". (See the photograph on page 9.174.) As an "INDICATOR", the element of the Deltech filter turns a deep red as it absorbs oil from the control air passing through.. The red starts at the bottom of the element and gradually advances to the top. (See photograph on page 9-175.) The red colour will not start its advance until the upstream coalescing filter starts to fail and pass oil. When the red advances about one-half of an inch, change the coalescing filter element. Follow this procedure with each new coalescing element, until the Deltech filter is red about two thirds of the element's height. At this time, change both the coalescing and Deltech filter elements. As a "SAFETYNET", the Deltech filter captures oil that passes the coalescing filter, as well as filtering particles down to about one micron in size. CLEAN, DRY CONTROL AIR IS THE MOST IMPORTANT REQUIREMENT OF A RELIABLE PNEUMATIC CONTROL SYSTEM. YOU MUST GIVE THIS THE ATTENTION IT DESERVES TO AVOID SEVERE PROBLEMS AND ASSOCIATED COSTS. FIGURE "E" ON PAGE 9-176 ILLUSTRATES A SUGGESTED FILTER ARRANGEMENT. 9-173
RkJQdWJsaXNoZXIy ODY1ODQy