The needle valve that makes all the difference in desalination systems for boats

Twenty years ago, HP Watermakers launched the first automatic watermakers, a significant innovation in the industry that has optimized and simplified water production and interfaced watermakers to on-board plotters. This advancement is crucial for desalination for boats, ensuring a reliable fresh water supply at sea.

A needle valve is the basis of the technology found in HP Watermakers’ automatic watermakers. Since its introduction, RP Tronic, a high-precision motorized and automatic micrometer valve, has enabled the creation of the two major families present today: automatic and manual watermakers, making it a vital component in any desalination system for boats.

At the Düsseldorf boat show last January, the company celebrated twenty years by presenting a restyling of the RP Tronic valve.

“We decided to color RP Tronic blue, our institutional color,” explains co-founder Gianni Zucco, “so that it would be more easily identifiable on the machine while also highlighting its name and our brand. In recent years, we may not have promoted enough the enormous competitive advantage this solution provides, so now is the time to let the whole boating world know what a revolution it constitutes!“.

Target 60 BAR

“RP Tronic makes it possible to automate the regulation of seawater pressure on osmotic membranes,” Zucco explains. “Basically, the high-pressure pump sends seawater to the membranes; the RP Tronic valve, downstream of them, ensures that the pressure is kept constant at 60 bar because when this does not happen freshwater production suffers. It is a very ordinary needle valve, but the innovation of RP Tronic, a system patented by HP Watermakers, is in its automatic adjustment; with manual ones, on the contrary, you have to go down to the engine room to do it on-site whenever the salinity and temperature of the seawater change. And as we navigate, these parameters are constantly changing.“

Continuous pressure regulation on the reverse osmosis membranes to 60 bar is the optimal condition under which to operate the watermakers, a key feature for any effective desalination system for boats. The entire system developed by the company revolves around this.

During the startup phase, RP TRONIC gradually closes and adjusts the pressure to 60 bar in a 2-minute up cycle, checking all parameters and optimizing the startup cycle before operating at full capacity.

Once at full capacity, it keeps the pressure on the membranes constant even when salinity and water temperature vary: these are two closely related elements that are crucial to the operation of the system. In the case of high salinity, if the system is not adjusted accordingly, pressure increases (so that the system may shut down) and water production is reduced; in the case of rising water temperatures, pressure is reduced, and so is production.

Automatic Washing

An additional advantage related to the presence of the RP Tronic valve is the automatic flushing system found on all HP Watermakers products.

RP Tronic, like all pressure regulating valves, is located at the end of the circuit as if it were a closed faucet; when the system is turned off, the valve opens fully and drains all salt water from the system and especially the membranes, after which the system proceeds to flush with fresh water.

“If you don’t flush properly, the salt deposited on the membranes will crystallize in the long run, requiring chemical flushing to restore full efficiency: an eventuality that is the norm with a manual valve. In addition, since our plant is perfectly rinsed with fresh water, all metal parts in contact with seawater are protected from corrosion and rust.”

To counteract the proliferation of bacteria and mucilage on the membranes, during each shutdown and flushing cycle the Automatic Membrane Conservic System (AMCS) injects a few drops of sodium metabisulfite, an inert acid that is harmless to the membranes but essential for preventing bacterial proliferation, which is always possible considering the absence of chlorine. “With all these systems,” Gianni Zucco points out, “the lifetime of the membranes can reach up to 10 years.”

Part-net for the interface on on-board plotters

In addition to convenience and ease of use and maintenance, since 2019 the RP Tronic valve has made it possible to interface the watermakers created by the company with all plotters and multifunction displays on the market, enhancing the efficiency of desalination for boats.

HP Watermakers has developed the Part-Net user interface, which takes advantage of the protocols HTML5 and uses them in the intranet environment. “This, too, is exclusive to us and allows full control of its operations from the bridge. The interface is also available with the Sea0Spot system, the device that combines the functions of a watermaker with MWT (Marina Water Treatment) for softening the water supplied by the marina: an increasingly felt need, especially during summer periods when water supplied by marinas is often brackish.”

An exclusive project aboard the al waab

Complex water treatment systems such as those found on large yachts are the result of ad hoc study and design. Each boat does its own thing because the needs of owners and crews are different, as are the available spaces.

On board the yacht Al Waab, HP Watermakers installed a complete water treatment system, ranging from watermaker to potable water at the delivery point. Al Waab, built in Turkey, is 54.85 m long and still under 500 GT thanks to careful management of space, weight, and volume. The compact technical space freed up more interior volume for the accommodation of the 18 guests and 10 crew members.

“The set-up of HP Watermakers for Al Waab is the result of an exclusive project based on a redundant, but precisely because of this, emergency-proof system: double watermaker, double sterilization system and remineralization of the produced water,” Zucco says. “In addition, the marina water softening system ensures water that is always free of limestone.”

Two watermakers, one debacterializer and one remineralizer

The core of the system is the SC DOUBLE 880 watermaker, which, as its name suggests, has two SC series watermakers installed within its chassis. The device can produce large quantities of water: with a consumption of only 6 kW (2×3 kW) up to 880 L/h of fresh water.

The operation of the two products is independent; they can work individually or in tandem for maximum flexibility. The watermaker is fully automatic, it can be operated like a normal start&stop appliance.

For water sterilization, downstream from the double watermaker, a system that doses silver ions prevents bacterial colonies from forming inside the tanks; at the outlet of the tanks a UV debacterializer further sterilizes the water. This is important in case the ion dosing is not in operation due to maintenance or possible inactivity of the watermaker to which its operation is connected.

Completing the system is a remineralizer that stabilizes pH levels in the produced and sterilized water so that it is suitable for human consumption.

Softeners

On board there is also the HP DEMIDOUBLE system that softens the water embarked from the dock, which is often hard due to high calcium content.

“DEMI DOUBLE,” explains Gianni Zucco, “uses special high ion exchange resins and is capable of reaching flow rates of 1,500 liters/hour; conventional softeners, on the other hand, reach flow rates of only 300 liters/hour. DEMI DOUBLE softeners, while having higher flow rates than conventional softeners five times larger, use 50 to 70 percent less water and salt during regeneration. For example, a crew of 4-6 people with a consumption of 200 m3/year of water at 30° F hardness will have an annual consumption of only 100 kg of salt per year. The system works without electricity and is fully automatic.“

API files 

“In the nautical world, a bit like what has happened with the supercar world, there is a growing trend of fitting out increasingly customized dashboards, with panels defined by the shipyard in shape, graphics, and controls,” says the company’s co-founder.

One example is the Dutch shipyard Wajer Yachts, which has chosen to outfit the next five Wajer 77s with HP Watermakers RP Tronic SC140. In addition, the shipyard asked to adapt the management software to a custom panel that did not include all of the ancillary features of the standard, but only those covered in their design; in addition, it wanted the ability to interface it with the rest of the on-board services and equipment.

“From this request, the idea was sparked to develop API (Application Programming Interface) files dedicated to our watermakers that would allow shipyards, but also individual shipowners in the yacht building phase, to customize their own interface protocols between our machines and the rest of the onboard equipment,” explains Gianni Zucco. “We could have simply responded to the Wajer Yachts shipyard’s single request, but we took the opportunity to develop a solution that would allow this sort of customization to be handled more easily and quickly in the future because we are convinced that it will be a trend that will be increasingly in demand in the future.”

In practice, each site will be able to easily and quickly customize its watermaker management systems, to interface with the rest of the plant and related management software. “For Wajer Yachts, the API protocol has been developed in-house by our technicians, and it will soon be possible to release it to any shipyard that requests it, with its technicians directly managing the customization through a simple and intuitive path“.