Internal Gear pumps can be easily converted from one direction of rotation and flow to the other; or even be made to run in two directions of rotation and in two directions of flow. The capacity of the pump remains constant in either direction, making this a beneficial and unique feature of the Internal Gear pumping principle.

There are 4 key points to check before changing the rotation of an Internal Gear Pump:

1. Can the Pump Be Reversed?

The first “red flag” would be a rotation arrow on the casting or nameplate of the pump. Common examples for Viking Pump include Mag Drive pumps from the 895 Series™ , or the 4 inch and larger Motor Speed pumps from the 4195 Series™. In either case, these pumps have design features that make them rotational, so running them in reverse rotation is not advised.

The second “red flag” would be differences in port sizes. Internal Gear pumps typically feature identical port sizes so that the inlet and outlet can be swapped. However, some pumps are designed to have a designated inlet and outlet port. In these cases, the inlet is always larger than the outlet for the same reason that this is done in centrifugal pumps: to better feed liquid into the pump and to remove any confusion as to which port is “in” and which port is “out”.

2. Does the Pump Have a Relief Valve?

Viking pump-mounted relief valves, whether internal or return-to-tank, are directional. They only provide over-pressure protection in one direction of rotation and flow. Most are reversible though. By removing the valve from the pump, changing the valve orientation by 180°, and reinstalling it, the direction of overpressure protection for the pump reversed. Modifying the valve orientation is the most common required modification for changing the direction of flow of an Internal Gear pump.

There are two important things to note:

First, there are a few Viking models where the relief valve is not a separate component, but rather built into the body of the pump itself. One common example of this is the smallest 432 Series™ sizes where the valve is built into the casing. For these models the direction of overpressure protection cannot be reversed.

Second, if a pump is to be run in both directions this could mean that an overpressure, upset condition could occur on either side of the pump. If running the pump in both directions, both sides of the pump need over-pressure protection. A Viking internal relief valve, which only functions in one direction of flow, could not be used as the only means of over-pressure protection.

3. Does the Pump Have a Seal Circulation Plan?

Many pumps feature either an internal or external seal circulation plan. These include internal holes or external tubing which route pumped fluid through the seal chamber to help lubricate, and ultimately extend the life of, the seal and pump parts. Common examples include an API Plan 11 or an API Plan 13. For these seal circulation plans a line is connected between the seal to the discharge port or suction port, respectively.

Reversing the rotation of the pump and direction of flow will reverse the flow through the seal plan, turning a Plan 11 into a Plan 13. For some applications either API plan may be acceptable, or no modifications would be needed. For others the appropriate seal circulation plan should be used; the line would need to be removed and replaced accordingly.

4. Does the Pump Have Any Internal Lubrication Paths?

Some Internal Gear Pump models and sizes feature additional paths for internal lubrication of bushings, or to improve flow behind the rotor. A common feature is the pressure lubricated idler pin, which has a hole that allows liquid to be fed in from the discharge side of the pump and exit underneath the bushing. This helps to ensure the bushing and pin always have plenty of lubrication, and the life of these parts is extended. When reversing the rotation of the pump, this internal lubrication path reverses. While still providing lubrication, its effectiveness is somewhat diminished. It’s preferable to have the discharge side hole open to pressure-feed the idler pin. Often this can be done by simply changing the location of a pipe plug, though some models and sizes feature check valves which require no modification to change direction.

For more information watch here: Running Internal Gear Pumps in Reverse