XL pumps series (hydraulic diaphragm positive return) since they were launched on the market achieved a great deal of success thanks to the incredible price/quality ratio. They were further developed and improved with the XLB and XLC pumps. These pumps, with cast iron casing, designed and manufactured in full conformity with API 675 STD and ATEX 94/9/CE, zone of danger 1/21 e 2/22, are suitable for 24/7 demanding industrial applications. As all OBL hydraulic diaphragm, these pumps come with built-in relief valve, air purge valve and mechanically actuated re-plenishing (smart diaphragm). This valve guarantees at all times a constant hydraulic balance that overcomes all suction problems (suction valve closing, decreasing of NPSH available). In case of worsening of the NPSH available, though volumetric efficiency would decrease, pump would still deliver chemical. In case of complete closing of suction isolating valve, pump would not over-replenish oil and diaphragm would not be over-stretched. Once operating condition are restored, pump automatically starts delivering with no damage whatsoever.