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Purge Curves A - 3
HYDROBLOC LS SERIES
PURGE CURVES
Calculation of Purge Pressure Setting
6. Locate the Purge Adjusting Valve. Slowly rotate
dryer’s Purge Adjusting Valve until the Purge Pres-
sure Indicator indicates the calculated purge pressure
setting. (See following Note).
Note: The purge pressure can only be read and ad-
justed when an off-line desiccant chamber has de-
pressurized for regeneration. (When the off-line cham-
ber is pressurized, the Purge Pressure Indicator will
read “system pressure”.)
1. Determine air pressure (psig) at the dryer inlet.
2. Refer to Table A-1. Determine the inlet airflow for your
model and inlet air pressure.
3. To calculate purge flow consumption on the critical
orifice curve:
Inlet Flow (SCFM) × 14.7 PSIG
× 1.15 = Purge (SCFM)
Inlet Pressure (PSIG) + 14.7 PSIG
4. Locate the Critical Orifice Calibration Curve that has
been sized for your specific dryer model.
5. Cross the Purge Flow requirement calculated above
to the same number on the Critical Orifice Calibration
Curve. Follow this line vertically and then horizontally
once intersection is made with the curve line to find
the actual purge pressure setting.
Table A - 1 Inlet Airflow at Various Inlet Air Pressures¹
Inlet Air Pressure (psig)
Model 60 70 80 90 100 110 120 130 140 150
Average Inlet Airflow (scfm)²
LS60 39 44 50 55 60 65 70 76 81 86
LS110 72 81 91 100 110 120 129 139 148 158
LS130 85 96 107 119 130 141 153 164 175 187
LS185 120 137 153 169 185 201 217 233 250 266
LS240 156 177 198 219 240 261 282 303 324 345
LS270 176 199 223 246 270 294 317 341 364 388
LS360 234 266 297 329 360 391 423 454 486 517
LS505 329 373 417 461 505 549 593 637 681 725
LS630 410 465 520 575 630 685 740 795 850 905
LS760 495 561 627 694 760 826 893 959 1025 1091
LS1000 651 738 826 913 1000 1087 1174 1262 1349 1436
LS1250 814 923 1032 1141 1250 1359 1468 1577 1686 1795
LS1500 977 1108 1238 1369 1500 1631 1762 1892 2023 2154
LS2070 1348 1529 1709 1890 2070 2250 2431 2611 2792 2972
LS2580 1680 1905 2130 2355 2580 2805 3030 3255 3480 3705
¹ Maximum inlet air pressure, 150 psig.
² Based on 100°F inlet air temperature and -40°F pressure dew point. Maximum recommended inlet temperature, 120°F. For capacity at inlet
temperature higher than 100°F, consult your local distributor.