How To Connect a Hydraulic Oil Cooler For Single or Double Pass

cooler2When locating an air blast oil cooler on a machine, it should be situated so that it is at least half the fan diameter clear of any obstructions on both sides of the core. I recommend connecting the cooler so that oil flows from bottom to top, or if the tanks are on the sides, from lower connection (inlet) to upper connection (outlet). The reason for this is to purge all air from the unit quickly, and fill it completely, for maximum efficiency.

The other connection issue for air-blast oil coolers, which requires attention during initial installation, relates to whether it is single or double pass. These days, many oil cooler cores are designed so that during manufacture, they can be configured as either single or double pass. This means they have at least 3 ports – two ports in one tank and one port in the other (see diagram inset above). A single pass oil cooler is converted to double pass by the insertion of a fully welded baffle in the middle of one of the tanks at the factory This makes the oil flow down one half of its core, and then back up the other half.

Considering the above diagram, if the oil cooler is single pass (no baffle in the top tank), I would connect it so that port 1 is the inlet and either port 2 or port 3 (but preferably port 3) is the outlet. BUT, if the oil cooler is double pass, the correct connection is: port 2 inlet, port 3 outlet (or vice versa).

Note that if the unit is double pass and the technician doing the initial installation is not on the ball, he’ll likely connect the unit in such a way that port 1 is used. Doing so means that only half the oil cooler’s core is effective. That is, if connection is made using ports 1 and 2, only the right-hand side of the cooler is effective. If connection is made using ports 1 and 3, only the left-hand half of the cooler is effective. Believe it or not, I’ve seen this mistake made more than once. And to discover six other costly mistakes you want to be sure to avoid with your hydraulic equipment, get “Six Costly Mistakes Most Hydraulics Users Make… And How You Can Avoid Them!” available for FREE download here.

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