tailieunhanh - FLAME SAFEGUARn CONTRULS phần 9

e dẫn có bậc để xác định các đặc điểm liO'N vaive; cung cấp mối quan hệ dự đoán giữa thân trayel khí llow, dValye Seal Overtravel Interlock. Van 2 seais và thiết bị truyền động có dấu hiệu chuyển đổi một van đóng. | sQf-larfle. ữụýãị ị ưi tu I y ĩ Ọ tr CAPACITY CFH SP GR GAS FIG. 7 PRESSURE DROP vs. CAPACITY CHART SHOWING SIZING PROCEDURE OF A DOUBLE ssov PIPED IN SERIES. c. Lt point X tails only a very short distance to the right of the diagonal line increasing the pressure drop might allow use of the next smaller valve size. Remember that we estimated only 45 percent of the available ssov pressure drop for each valve. A margin of safety of 5 percent per valve remains to allow slight oversizing. Therefore we can increase the pressure drop 5 percent of or inch wc without exceeding the estimated total pressure drop over both SSOVs. 5 of in. wc To determine the extra pressure drop move upward from X to the next diagonal line z. Then move horizontally to the Pressure Drop Scale to find the pressure drop needed for a 2 inch valve. In this case the actual pressure drop is inches wc which is 1 inch wc greater than the estimated individual pressure drop of inches wc. - in. wc Since our excess pressure drop Is greater than the 0-6 inch wc allowed we should use the 2-1 2 inch valve. Using a 2 inch valve may still be possible. The actual total ssov pressure drop would be 2 X or inches wc. The difference between the estimated and actual pressure drop must be taken from another part of the manifold to keep the required burner inlet pressure. We cannot reduce the Firing Rate Control pressure drop past our minimum estimated figure of 30 percent of the manifold pressure drop. Therefore we must increase the pres- 293 71-97558-1 FIG. 8-PRESSURE DROP vs. CAPACITY FOR A TYPICAL BUTTERFLY VALVE. MAXIMUM OPENING ANGLES SHOWN ARE USEO as trial settings when adjusting VALVES FOR HIGH FIRE. sure regulator outlet pressure by in. wc to allow tor the additional pressure drop across the 2 inch SSOVs. This requires estimating a new pressure drop tor the pressure regulator. SSOVs and Firing Rafe Control plus repeating the sizing procedure. SIZING