Industrial Water Softener Application & Sizing Guide – Resin Exchange Zone
Much of an industrial water softener’s performance is based on resin performance and design criteria. Water with high TDS (total dissolved solids, sodium or hardness) will result in a deeper exchange zone than low-TDS water. The deeper active exchange zone will reduce capacity. See the industrial water softener resin performance figure below. You will also find the Industrial Water Softener Sizing & Application – Hardness Leakage resource to be helpful as well as the Industrial Water Solutions high performance water softener systems.
Water softener flow rate has a large impact on resin performance and hardness leakage. As the rate of flow increases through the resin, hardness ions will be driven deeper into the bed before they are removed. This causes an increase in the depth of the active exchange zone and a decrease in capacity. See the resin exchange table below.
| Per cubic foot per minute exhaustion flow | Equals Grains per cubic foot exchange capacity as CACO3 |
| 1 GPM per cubic foot per minute exhaustion flow | 30,000-Grains per cubic foot exchange capacity as CACO3 |
| 2 GPM per cubic foot per minute exhaustion flow | 29,500-Grains per cubic foot exchange capacity as CACO3 |
| 4 GPM per cubic foot per minute exhaustion flow | 28,800-Grains per cubic foot exchange capacity as CACO3 |
| 6 GPM per cubic foot per minute exhaustion flow | 28,300-Grains per cubic foot exchange capacity as CACO3 |
| 8 GPM per cubic foot per minute exhaustion flow | 28,100-Grains per cubic foot exchange capacity as CACO3 |
| 10 GPM per cubic foot per minute exhaustion flow | 28,000-Grains per cubic foot exchange capacity as CACO3 |
| 12 GPM per cubic foot per minute exhaustion flow | 28,000-Grains per cubic foot exchange capacity as CACO3 |
The flow-rate effect on capacity is small up to 4 gpm per cubic foot. At higher flows, the capacity is more severely affected. Extremely low flows of less than 0.5 gpm per cubic foot will cause channeling that will result in loss of capacity. Typically, industrial water softener resin functions best from 4 gpm per square foot to 10 gpm per square foot of tank diameter. In some non critical applications where hardness leakage is not critical, water softeners can be sized to handle 20 gpm per square foot. See our helpful online water softener sizing guides for additional information, as well as our total hardness calculator.
Industrial Water Softener Resin depth also has an influence on capacity. In shallow softener resin beds, most of the depth is used by the active exchange zone (e.g., a 20″ bed with a 5″ active exchange zone has 25% of the bed used up in the process of exchanging hardness). Increasing the bed depth to 50″ with the same 5″ active zone would cause only 10% of the bed to be used by the active zone. Deeper beds have a greater overall capacity because a greater percentage of the resin is available for softening. See water softener comparison below.
Industrial Water Softener resins have a very rapid rate of exchange. Temperature increases do not have a large effect on exchange rate, and do not reduce the depth of the active exchange zone by much. Roughly 1,000 grains per cubic foot additional capacity could be realized at temperatures over 180° F. An example of a hot water softener use like this would be a condensate polisher system.
Industrial Water Softener Sizing Calculators & Guides – Steel
You may also find our industrial water technical articles helpful.
