Compressed Air Best Practices-August 2008

| 08/08 Focus Industry COMPRESSED AIR AUDITS | COMPRESSED AIR AUDIT OF THE MONTH A Vacuum System Audit It is important that testing be completed on a completely modified table (table, mechanical arm and drop leg) to determine the maximum flow rate, the allowable pressure differential and threshold vacuum level for the smallest part manufactured. Automatic Shut-Off Valves Automatic shut-off valves to the central vacuum system are installed on most of the production machines and should be installed on all remaining units so that when production machinery is off or in standby mode, the vacuum supply is also off. The addition of positive closure valves will keep non-productive vacuum use to a minimum by ensuring supply closure during machine downtime. The shut-off valves in place should be checked for proper functioning. Mechanical Vacuum Supply Arm The mechanical vacuum supply arm was tested on both the modified table and on the standard table and was found to be a significant source of pressure differential. Pressure differential was found to be any where from 3" HgV to 5" HgV for the mechanical arm. When cutting starts, there is not the maximum amount of air flow through the arm and therefore low pressure differential. As cutting progresses, air flow and pressure differential increase. These types of mechanical vacuum supply arms are historically significant sources of pressure differential, but they are needed due to the motion of the table on two axis. One potential solution is to attach a flexible hose to the mechanical arm and supply vacuum in parallel to the arm itself. To do this effectively, a new table inlet fixture must be installed. The table inlet must have an extra port to connect the vacuum supply tube with the existing inlet/mechanical arm arrangement. Flow Rate from a Table A flow test was conducted to determine the flow rate from a standard routing table and a modified routing table. The test was set up so that only one 100 hp vacuum pump was operating during a lunch break. All other vacuum pumps were shut down and all production machines were closed off from the vacuum system with the exception of the machine being tested. Modified table #ZTR-2 was tested first and was found to flow 451 scfm initially and as cutting continued reached a maximum of 558 scfm. Standard (unmodified) table #ZTR-4 was tested using the same cutting program and was found to flow 344 scfm when cutting started and 439 scfm at peak flow conditions. The differences in flow rate can be attributed to the lower differential pressure on the modified table. This indicates that when changes are made to system components that exhibit high differential pressure, airflow will increase into the vacuum system. This will lower the vacuum level further if capacity is not available to remove the additional air. 14 www.airbestpractices.com Specify 12" HgV All new production equipment scheduled for this facility should have specifications for normal operation with supply vacuum at 12" HgV or below. This will ensure that all new production equipment will be able to work within the new system parameters. D. Vacuum Supply Issues The central vacuum system of eight existing rotary screw vacuum pumps supply site requirements for vacuum. There is 675 nameplate horsepower in vacuum pumps of which 790 actual brake horsepower is being used during normal production. These pumps deliver a total of 11,020 acfm at an average header vacuum level of 16" HgV. Vacuum pump amp draw and vacuum level at the vacuum pumps varied significantly during the audit indicating a fluctuating demand load from production equipment. The only significant change in vacuum level occurs during shift change and breaks when vacuum levels increase to approximately 28.6" HgV. Note that data-logger graphs read vacuum in PSIA. Readings are converted on each graph to “HgV to illustrate significant points. If further conversions are necessary, the formula to convert PSIA to HgV is: HgV = 29.92 - (PSIA x 2.04). http://www.airbestpractices.com

Table of Contents Feed for the Digital Edition of Compressed Air Best Practices-August 2008

Compressed Air Best Practices- August 2008 Contents From the Editor Utility-Air News The August Audit of the Month: A Vacuum System Audit Energized for Savings at Seattle City Light and Tacoma Power Know Your System CASE: Compressed Air Supply Efficiency Ecos Air: Managing Incentive Programs Kaeser Compressors: Loyalty, Energy and Growth Building Relationships at Cummins-Wagner McIntire is Moving Forward The 2008 A.I.C.D. Conference & Exhibition Tuthill Vacuum and Blower Systems Resources for Energy Engineers: Training Calendar & Product Picks Wall Street Watch Advertiser Index Job Market

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.