D40 Hydra-Cell pumps are a sealless
triplex positive displacement pumps for tough, continuous duty
applications and for fluids and slurries containing particles up
to 1/8" in diameter. Until the turn of the century this
was the Hydra-Cell pump option for flow rates >20 GPM, however
the pentaplex design
D35 Hydra-Cell pump achieves almost the
same flow rate and pressure (up to 36 GPM and 1200 PSI) so most
customers go with the smoother flowing D35 Hydra-Cell pump
unless they really need those extra 4 gallons per minute OR if
their fluid contains larger particles which the D35 Hydra-Cell
pump would not handle.
The D35 pentaplex design is based upon the H25 triplex design and both use the same inlet and outlet check valves. Same goes for the D40 and D66, the D40 Hydra-Cell pump is a triplex design and the D66 is the same pump with 5 pump chambers (pentaplex design). The D40 and D66 Hydra-Cell pumps use the same check valves.
The maximum free passage for the H25 and D35 Hydra-Cell Pumps is 1/16" diameter and for the D40 and D66 Hydra-Cell pumps it is 1/8" diameter. While these are the "maximum free passage sizes" in operational reality the free passage will be slightly less because the maximum free passage values are based on a specific RPM that may or may not be how you are operating the pump. Pump inlet filtration should fall withing 25%-50% of the maximum free passage depending upon the particle characteristics.
In addition to handling larger size particles, the D40 check valves are larger than the D35 check valves, so if you are pumping an abrasive slurry, the wearlife for D40 check valves might be longer than D35's due to their larger valve size and the lower pump speed for a given flow rate (reduces the velocity across the check valve and its seat).
Whle Wanner Engineering does not list the D40 Hydra-Cell pump in its literature or website, it is still available and lead times are typically 2-3 weeks just like most of the other Hydra-Cell pump models.