Ensure good workmanship around your ship’s pump systems

“Ninety-nine percent of pump breakdowns onboard ships are not due to faulty pumps. They are instead due to lack of knowledge or skills”, DESMI’s experienced sales engineer, John Nielsen says. Here is John’s list of recommendations.

“Ninety-nine percent of pump breakdowns onboard ships are not due to faulty pumps. They are instead due to lack of knowledge or skills”, DESMI’s experienced sales engineer, John Nielsen says. Here is John’s list of recommendations.

DESMI’s Sales and Application Manager in China, John Nielsen has a message for ship owners all over the world: “Be aware of how your pump systems are installed. Ensure good workmanship!”, he says. “That’s the bottom line. There are too many outfitting crews lacking practical experience.”

“Ship owners must thus make sure their site teams follow key guidelines for proper pump installation. Because most of the time, a pump breakdown is not due to a faulty pump”, John says.

“Ninety-nine percent of the time, a breakdown is linked to a lack of installation knowledge during installation. Or missing parts. Or incorrect operation – like starting the pump without liquid inside – that’s a killer. It is linked to a lot of things”, he says.

With several years at DESMI and more than 20 years as a shipbuilder, John Nielsen knows what he is talking about. He offers a list of “do’s and don’ts” in pump installation for ship owners, superintendents, site teams and shipyards. “You need to be aware of these things”, he says. “A pump is just a component that will do exactly what it is designed to do. But if it’s not installed properly, then you can destroy it. It’s a bit like Murphy’s Law: If something can go wrong, it will. And in the end, the ship owners will have to bear the costs.”

A solid foundation

Solid pump foundations are at the top of John’s list. “It is extremely important that these are done correctly. The foundation has to be supported so there’s no chance of wobbling.” In other words, do not install the pump on a soft plate – a steel plate with no or missing support below. “There’s an old shipyard saying: You need the same amount of steel below the plate as you have on top of it.”

If the outfitting team wants to use weighted or spring-loaded supports, they must first check the design with DESMI or the steel engineer. “It is not up to the individual outfitting team to decide”, John says. “Most pumps today are vertical. And two-thirds of a pump’s weight is actually the electrical motor. Some pumps are four and a half tons meaning the electrical motor is three tons. This all calls for very good foundations to avoid vibration, etc.”

Pipes and valves

There are standard ISO rules for pipe routing, but these can be tricky to follow onboard a ship due to limited space. “So that means you have to think a bit alternatively,” John says. On a ship, make sure that the pipe design allows the liquid flowing to the pump on the suction side at a maximum velocity of 1 meter per second (m/s). This is a rule of thumb so that you avoid creating water vortex or cavitation that will eventually destroy the pump.

And then there are valve choices. On ships, a big number of valves are butterfly valves, mainly because this is an inexpensive valve type. But a butterfly valve only works in the pumping direction. This is why there are always a non-return valve in series with the butterfly on pumps pressure side. Otherwise, if pumps are working in parallel and one pump is dormant without installed non-return valve, the active pump will pump liquid to the other pump instead – no matter butterfly valve open or closed.

Furthermore, it is important that the valves are full bore (full port). This means that when the valve is open, it has the same diameter as the pipe. Don't use valves that are slightly smaller in diameter than the pipe. This will create small vortexes inside the pipe and will eventually destroy the pipe and the valve.

Read the complete article here: https://www.desmi.com/news/ensure-good-workmanship-around-your-ship-s-pump-systems/