Perspective on Commissioning – Connecting the DOP’s

DOP pump and power pack, ready for commissioning

A DOP pump1 and it’s drive go together like a horse and carriage, you can’t have one without the other. Basically one product, but two units. Whether hydraulic or electric driven. OK, in some cases, you could use the extra power take off from the excavator or crane, but you still have to hook them up, before they can do any useful work.

And connecting the DOP to its drive is an elementary job, that can cause some headaches, when not done carefully. The modern electric drives require some more certified wizardry, that is beyond the scope of this post. Hydraulic power packs have their own peculiar quirks, that are worth mentioning here.

Usually, the hydraulic hoses come supplied with Snap-tite® connections2. These are quick and prevent most oil spills in the environment. They come with a disadvantage in price and resistance. Ultimately, the DOP should be connected to the power pack like this:

Hydraulic diagram DOP pump and power pack

So, even with such a simple diagram, still things can go horribly wrong. Off course, don’t switch the ‘Pump’ and ‘Return’ line, you will blow some seals on the motor. Most common is a failed connection of the Snap-tite®. When it is not completely tight, the internal valve is not completely open and you have a lot of resistance. So a lot of power on the power pack gets converted to heat on the connection and no performance on the DOP pump. Another common problem is the resistance in the leak line. This can cause terrible things on the hydraulic motor.

One client followed all the instructions in the manual and all advise from the service department, but still could not coach his new DOP to work. Lots of flow at the power pack, but almost no pressure. And the impeller could still be turned by hand. (Warning: never put your hand in an impeller when there is power on the drive!) One of our engineers went over to have a look on board. Well, here is an impression of the situation on deck.

Situation on board during commissioning

He quickly began cleaning up the mess on deck and uncovered how the hydraulic hoses were actually connected.

How the DOP pump was connected (not), actually

Well, that makes sense! Now it was easy to see, why the DOP was not working. Solution, connect the lines correctly and dredge away. Oh, and educate the crew about a tidy workplace.

Ship shape and ready to rumble

Well, after this first basic lesson in connecting the DOP, you are ready to connect your own DOP project. It’s easy as child’s play.

Connect the dots to set up a DOP project yourself (pdf version)


  1. Hydraulically driven submersible dredge pump DOP, Damen
  2. Quick Disconnect and Valve Division, Parker Snap-tite

See also