George B. Bellwoar

In our past newsletters, we discussed diurnal emissions and what the USA has done to reduce them. In addition, we described the basic ways these systems work. This month we’ll talk about different fuel system design goals and costs.

Boat builders often have different fuel system requirements. Perhaps safety is primary. Or, maybe installed cost is the focus. It could be that customer satisfaction from the ease of refueling is the goal. Maybe system simplicity or commonality of design across many models fits a builder with a continually changing workforce. Another builder may want to reduce long-term maintenance costs. And for some, achieving the maximum range possible is paramount. The list is endless.

Some of these goals are complementary. Others are mutually exclusive. Numerous factors make these goals easier or harder to achieve. The supplier matters. So does the shape of the tank and the size of the boat. Regardless, deciding on the performance requirements for a fuel system should be the first step of the design process.

So, what goals are common? And, what are the characteristics of those systems?

Safety – Generally, the safest systems operate at atmospheric pressure and may use more control valves. The lack of daily pressure swings puts less strain on seals, hoses, and clamps. Adding additional valves and more complex plumbing reduces the likelihood of venting problems. But that also adds to the installed cost.

Range – Adding more control valves or using two small tanks versus one large tank can increase the fuel a boat can carry. However, both will increase the installed cost.

System component cost – A pressurized system will cost less than an atmospheric system on smaller boats with one engine and one tank. That will be reversed for larger boats with a couple of tanks and two or more engines. The reason is that every additional engine and tank each requires its own fuel demand valve to prevent engine feedline pressurization. That isn’t the case with canisters. Many tanks and engines can share the same large canister. At 30 Euros or more per fuel demand valve, more engines and more tanks quickly add additional cost to pressurized systems.

Low Maintenance – There are systems available that use only one valve or have almost no moving parts to fail. They use air-fuel separators and stanchion tubes instead of tank-mounted valves. These systems are also among the least expensive options to purchase.

Ease of refueling – Adding an additional vent to handle only refueling vapors can significantly improve the ease and speed of refueling, but it will add slightly to the cost of the system.

Installed cost – Connecting valves in series can reduce hose length and the number of connections involved, lowering installed cost. But safety can be compromised in long-term storage at angles much beyond static rest.

So, what might one of these systems cost? The components (valves and canisters or FDVs) for a common 1-tank, 1-engine system would run around 110 Euros for a boat with one engine and one tank. Getting fancy might up that to nearly 135 Euros, and getting creative could drop it down to as little as 60 Euros. Installation and higher costing tanks could add another 100 to 150 Euros. So, systems for small boats probably cost between 175 and 275 Euros more than today’s systems.

For that, you get increased safety, easier refueling, cleaner air, and cleaner water. And over time, you will save on fuel. But, unless you understand these systems, it is easy to fall short of your goals in the design process. American fuel system component manufacturers and consultants developed a high level of expertise by working with these systems for a decade. Any of them can help European boatbuilders determine approaches that best fit their goals.

That is a significant advantage that American builders lacked. The EU will likely implement similar regulations on boats sold throughout Europe in the next three years. Then, no one builder will have a “green advantage” over any other. A proactive approach to move in this direction before competitors offers European builders two advantages. First, numerous people have the time and expertise to help builders design the best system for their needs. That will not be the case when this is regulated. The number of builders needing help will stretch the few groups with that knowledge too thin – just like they did in the USA 10 years ago. Not every builder will get the type of help to make a cost and performance difference. And second, there is no green advantage to promote when all your competitors are doing the same thing.

It won’t be long before all European builders install these systems. Now is the time to determine whether the best strategy for your company is to be proactive or reactive. Two years from now, that strategic option will likely be gone.

George B. Bellwoar, GMBA United States
Email: george.bellwoar@gmba.blue
Tel:: +1 954 646 5920

Disclaimer: Global Marine Business Advisors is a registered legal entity and is a network of independent marine industry advisors. In all articles the opinions expressed are those of the author and does not necessarily reflect those of GMBA.

As mentioned in our last newsletter, there are numerous benefits to adding a diurnal emissions control fuel system to gasoline-powered boats. But how do these systems work?

Today’s two most popular diurnal emissions control systems are pressurized systems and canister (often called atmospheric) systems. Pressurized systems prevent outward venting until internal system pressure exceeds roughly 1.25 psi. This usually happens only with significant temperature swings.

Canister systems operate at atmospheric pressure. Certified carbon canisters in the vent line capture hydrocarbons from venting vapors during the day and expel them back into the tank at night when cool air causes the system to breathe in. Most automobiles use a complex version of the marine canister system.

Both systems need airspace (or ullage) at the top of the tank to ensure that a gas (air or vapor) will be vented, not liquid fuel. Both systems can (and usually do) use the same approach to creating that ullage. Typically, they use three different mechanical control valves.

• Fill Limit Valves (FLVV) – These valves control the ullage volume. A large 5/8″ (16mm) vent allows a high volume of vapor to pass through during refueling.
• Tank Vent Valves (TVV) – These are also called Rollover Valves (ROV) or Grade Valves (GRV), depending on the manufacturer. They have a much smaller 5/16″ (8mm) vent size and control venting anytime the FLVV is closed. Diurnal venting often passes through TVVs.
• Inlet Check Valves (ICV) – ICVs are usually mounted in the fill hose and prevent fuel from coming out of the fuel fill if the tank “burps” immediately after the FLVV closes. ICVs prevent wellback.

Systems typically have one FLVV, one or two TVVs, and one ICV. Variations exist depending on the size and shape of the tank and the overall system design. During refueling, incoming fuel hits the ICV and opens it. An FLVV vents the high volume of refueling vapor until the fuel level in the tank reaches and closes it. Tank pressure then spikes as fuel comes in, but no air leaves. This closes the ICV, fuel backs up the fill hose, and shuts off the pump. Then, the TVVs slowly vent the tank pressure. As it drops, the ICV opens, and the fuel in the fill hose drains into the tank. When someone rounds off the cost by clicking the pump several times, they repeatedly refill and empty the fill hose into the tank. If someone does this long enough, they will reduce the airspace and eventually defeat the system. Hence the warning on cars and pumps not to overfill.

The fuel cap is another critical component in these systems. It seals when closed and “clicks” like your car’s. Caps used in pressurized systems have built-in pressure and vacuum relief valves, usually the only system vents. Caps used in canister systems often have the same built-in pressure and vacuum relief valves. But these are used as a system failsafe or for additional makeup air when high horsepower engines run flat out. Actual venting in canister systems is often via a conventional vent on the side of the hull.

In simple terms, that is how these systems work.

While these are the two most common approaches, other unique ways to control diurnal emissions are available. Enviro-Fil systems use a venturi effect rather than a pressure spike to shut off the pump. And Perko also offers a system to control emissions without any tank-mounted valves. There are options to fit every application. System integrators like Perko and Attwood help fuel tank manufacturers and boat builders to determine and then design the system that best fits the need of every boat model.

Look for our next newsletter, where we’ll talk about matching system design with system goals like safety, installed cost, range, and ease of refueling. We’ll also discuss the cost of these systems and the advantages and disadvantages of the most common approaches.

George B. Bellwoar, GMBA United States
Email: george.bellwoar@gmba.blue
Tel:: +1 954 646 5920

Disclaimer: Global Marine Business Advisors is a registered legal entity and is a network of independent marine industry advisors. In all articles the opinions expressed are those of the author and does not necessarily reflect those of GMBA.

When considering emissions control in the marine industry, many look at engines and manufacturing processes as the culprits. For sure, both contribute. But they are not the only sources of emissions. For example, spilled gasoline and diesel fuel both pollute our water. And evaporating gasoline adds to air pollution. And there is another source of pollution from boats that many don’t even realize exists – diurnal emissions.

The diurnal cycle describes the daily temperature swing from nighttime to daytime. As the earth rotates, the sun warms the parts it faces during the day. Then those parts cool at night. Materials expand when heated and contract when cooled. Gasoline is no different. It expands quite a bit with temperature changes. It can grow nearly 1% for every 15⁰ F (or 1% for every 8⁰ C.). So, a tank with 200 liters at 6⁰C. could have 210 liters at 46⁰C., a reachable temperature in a boat stored in blue shrink wrap.

Unlike water, a molecule, gasoline is a complex liquid solution of many different (mostly hydrocarbon) molecules. Several of these molecules evaporate around room temperature. It is one of the reasons that gasoline gets “stale” over time. So, the top of a half-filled tank contains hydrocarbon vapor, not the air you’d want to breathe.

We have diurnal emissions when the evaporation of hydrocarbons combines with the diurnal cycle that expands and contracts fuel and pushes vapors out of the tank daily. Gasoline-powered boats stored outside emit hydrocarbons from their tank through the vent and into the atmosphere daily.

Since 2010, the United States has controlled diurnal emissions from boats by law. It has been the only country to do so. There is “talk” in Europe and Australia, but regulations are probably 3 to 5 years away.

Therein lies an opportunity for boat builders. Many talk the green talk. However, when it comes to diurnal emissions, only a few European builders walk the green walk.

Automobile manufacturers worldwide added diurnal emission control nearly 50 years ago. Boats sold in America have had similar features for over a decade. This technology is proven. It even offers benefits beyond diurnal emission control, some of which apply to diesel-powered boats. For example, boats using these systems force automatic pump shutoff – just like in cars. So gone are the days of watching for a squirt of fuel to know when your boat is full. Also gone are the days of fuel leaking out of your vent on a hot day. These systems make filling boats easy and eliminate premature shutoffs. Ensuring ullage (airspace) in the tank allows room for fuel expansion. The release of harmful vapors into the atmosphere gets controlled while the evaporation of expensive gasoline is limited.

Diesel systems differ from gasoline systems because, unlike gasoline, diesel fuel doesn’t readily evaporate once spilled. So, spillage is the problem, not diurnal or evaporative emissions. When spilled, diesel fuel floats around until it eventually sticks to something. Therefore, avoiding diesel spills is especially important. And doing so is surprisingly inexpensive. Since we’re not worried about evaporative emissions, diesel systems only need to create airspace and shut off fuel pumps to prevent spills, which can often be done for less than 100 Euros on smaller diesel boats under about 20 meters.

In most cases, even complex systems are affordable. In all cases, the benefits are great. And boat builders, system integrators, and designers can customize these systems based on varying goals, such as tighter emission control, ease of installation, price, safety, space utilization, and even range.

In our next article on diurnal emissions, we’ll explain how US builders do this, describe the different types of systems available, and then discuss the pros and cons of each approach.

George B. Bellwoar, GMBA United States
Email: george.bellwoar@gmba.blue
Tel:: +1 954 646 5920

Disclaimer: Global Marine Business Advisors is a registered legal entity and is a network of independent marine industry advisors. In all articles the opinions expressed are those of the author and does not necessarily reflect those of GMBA.