Fuel Blowback

Wanderlust leaves Caversham on the way to her first fuel fill.

Wanderlust leaves Caversham on the way to her first fuel fill.

At the end of the 2015 we documented Wanderlust’s fuel blowback problem using the pump at the fuel depot in St. Mammes on the Seine. Carefully timing the gauge on the fuel pump with a stopwatch we observed a steady filling rate of 23L/min. As usual we shut off the pump at the first sound coming up from the fill pipe. Seconds later, also as usual, a foaming mass of diesel emerged from the filling port.

This blowback has happened every time we’ve added diesel no matter how slow we keep the flow. Indeed, the 23L/min we measured, though not a rapid pumping rate, is faster than we usually fill. Normally we add fuel more slowly triggering the pump at the slowest possible rate. But it doesn’t matter. The fuel always blows out of the fill point. It makes a mess. We have found no way to avoid it.

Foaming fuel backing out of Wanderlust's filling port.

Foaming fuel backing out of Wanderlust’s filling port in St. Mammes.

Make no mistake; this is not an overfilled fuel tank. Blowback is occurring when the red diesel tank gauge indicates around 75% full. And 75% on the gauge does not even mean that the tank is actually 75% full. At launch the fuel tank level indicators were set to show “full” after 1000L of fuel had been added at the plant into the empty tank. The build contract and Wanderlust’s Owner’s Manual states that both the red and white diesel tanks each hold 1200 L. Thus “full” on the gauge means that the tank is only at 83% of its labeled capacity (1000 L/1200 L). From the mathematics, three-quarters full on the gauge should mean that the tank is at 63% of its stated capacity (83% x 75%). When blowback happens, the Wanderlust’s tank is around two-thirds full. This is not an overfilled tank.

Blowback creates problems. The functional size of Wanderlust’s fuel tanks is reduced considerably. Her “1200 L” tanks effectively have a net useable volume of less than 750 L. And cleaning up the mess of a couple of liters of fuel blowback after every fill is a serious annoyance.

Wanderlust's tank level indicators

Wanderlust’s tank level indicators: The white diesel tank indicator on the right failed in 2015 apparently due to a wiring problem.

The pencil indicates the position of the drain slot adjacent to the red diesel fill port. In natural like it looks like a weld.

The pencil indicates the position of the drain slot adjacent to the red diesel fill port. In natural light it looks like a weld.

But there’s an even more serious problem. What we hadn’t realized until St. Mammes is that there is a drain slot in our fuel locker is two inches from the red diesel filling point. From the top in the sunlight the slot around the drainpipe looks like a weld. Before St. Mammes we had figured the fuel locker was sealed. The locker’s purpose was to contain any fuel spills. It seemed like a good idea if blowback was possible each time we filled.

But the gap is not a weld. It is the top of a wider pipe that leads to a hole in the side of the boat. The space was left open to allow spilled fuel to drain away from the boat; it is an environmentally unfriendly requirement in the build standards. For Wanderlust this means that the foaming mass of fuel that comes out of the fill pipe two inches away goes down the drain and directly into the water. Putting fuel into the water is a serious no-no anywhere that Wanderlust goes; it puts us at risk of serious environmental penalties and fines.

The dark area on the hull is where the fuel has come out of drain from the gap in the locker.

The dark area on the hull is where the fuel has come out of drain from the gap in the locker on its way to the water.

The St. Mammes fuel spill was not a one-time event. Each time we’d filled Wanderlust’s tanks with fuel we’d noticed fuel in the water. The diesel in the water, we figured, was coming from leaky old boats nearby. Somebody should do something about those old boats, we thought.

But it wasn’t old boats that were putting diesel into the water. The fuel in the water was coming from our almost new barge. Every time we filled the fuel tanks we damaged the water environment.

So why does the blowback occur in the first place? There’s a clue; when blowback happens fuel also comes out of the tank vents. The tanks have vents to allow the air inside the chamber to escape as the fuel level changes. Only air is supposed to come out of the vent. If fuel is coming out of the tank vents, it is an indication that there is a problem: The vent pipes have filled with fuel, become blocked, and are rendered ineffective. On the surface it seems to be a clear design flaw.

Wanderlust at St. Mammes in 2014: The fuel depot is across the river.

Wanderlust at St. Mammes in 2014: The fuel depot is across the river.

Shallow sloped fuel fill and vent lines seem to be the cause of Wanderlust's fuel system problems.

Shallow sloped fuel fill and vent lines (back left) seem to be the cause of Wanderlust’s fuel system problems.

Investigating further, we looked back at the pictures taken during the build. These pictures were taken before the flooring covered the fuel fill and vent pipes. With analysis we could see that the pipes, if perfectly positioned, can raise a maximum of 75 mm over about 3600 mm, a slope of 2%. At the same time, Wanderlust, as she sits in the water, is trimmed to the stern. Indeed, we can measure the slope of the floor greater than 2% in the galley, depending on the how much freshwater is in the tank at the bow. Even in the best-case scenario, the red tank’s fill and vent plumbing is extremely close to level. Any deviation from a perfect upward slope in the fuel lines would allow them to collect fuel and become ineffective.

A close of view of the red diesel tank fill and vent arrangements

A close of view of the red diesel tank fill and vent arrangements:  The 90-degree bend at the tank may cause the fuel to foam.

Subsequently we’ve shown the build pictures of the tanks, fill lines, and vent arrangements taken during construction to several marine professionals (surveyors, marine engineers, and boatyard owners). The response has been consistent; Wanderlust’s fuel tank venting arrangement had no chance of working properly. We were told that a proper vent should be attached to the top of the tank and run as vertically as possible to its outlet; Wanderlust’s tank vent connections are on the top of the tank’s sides. For the red tank, the vent is routed with three 90-degree bends over about 16 feet until it reaches the flame arrester on the side of the fuel locker. The route between the tank and the outlet is neither vertical nor direct. For the white diesel tank, the situation is slightly better. The number of bends is the same, but the overall distance is shorter. We do observe blowback from the white diesel fuel fill point also, but the problem is less severe.

The first two times blowback occurred we notified the builder. There was never a response. At the time we knew nothing about the regulations pertaining to the fuel system configuration and blowback. But the builder had to know. These details are covered in the regulatory standards that governed Wanderlust build. In the Declaration of Conformity included with the boat, the builder certifies that Wanderlust “complies all with all of the essential requirements in the manner specified”.  When we reported blowback, the builder had to be concerned that Wanderlust, and all boats he had constructed similarly, was non-compliant to the rules that govern her construction.

From the build: Wanderlust's fuel tank vent and fill pipes emerge from the engine compartment bulkhead and turn 90-degrees to follow the shpae of the hull on the way to the hull fittings.

From the build: Wanderlust’s fuel tank vent and fill pipes emerge on the lower right from the engine compartment bulkhead and turn 90-degrees to follow the shape of the hull on the way to the hull fittings.

The fill and vent pipes connect to the deck fittings via a rubber hose.

The fill and vent pipes connect to the deck fittings via a rubber hose.

So what are the build standards relevant to blowback? According to Wanderlust’s Owner’s Manual, the fuel system standards she was built to are included in EN ISO 10088:2001 and EN ISO 21487:2006. (The cited standards appear to be out of date but typically only small changes were made as the standards evolved.) On Wanderlust’s official Declaration of Conformity these boxes are the checked and signed off by the company’s Director of Marketing, a person only casually acquainted at best with the technical details of Wanderlust’s build.

It takes work to find the official copies of the ISO standards online. For some reason copies of the trading regulations generated by a public agency are only available at a steep price. But with considerable effort we did find information on the Internet.

Wanderlust's small red diesel tank clean out port and fuel sensor: Tank venting could be improved by opening the inspection port during a fill but this would create an unacceptable risk of a spill.

Wanderlust’s small red diesel tank clean out port and fuel sensor: Tank venting could be improved by opening the inspection port during a fill but this would create an unacceptable risk of a spill into the boat, particularly with an uncertain volume of fuel in the tank after the initial fill.

Once we located the standards we found several areas of concern. All told we could find at least nine elements of Wanderlust’s fuel system that that quite possibly deviate from the standards. (It was the tip of the iceberg; later an RCD-specialist UK marine surveyor identified over 40 places where Wanderlust’s build did not comply with the standards.) Particularly relevant to Wanderlust blowback issue were these three:

EN ISO 10088:2009 4.1.7: “Fuel filling systems shall be designed to avoid blowback of fuel through the fill fitting.”

EN ISO 10088:2001 C.2.3: “Vent-line connections shall be at the top of the tank.” (“Top of the tank” is differentiated from “”highest point on the sides or ends of the tank” in the text.)

ISO 10088:2001 6.1.5; ISO 10088:2009 5.1.4: “Fuel filling lines shall run as directly as practicable, preferably in a direct line from the deck plate or equivalent filling point to the spud of the tank.”

In these cases Wanderlust appears to be demonstrably non-compliant to the standards.

At the end of the 2015 season, after we again raised the blowback issue. The builder responded telling us that Wanderlust was filled at 50L/min in the plant without issue. We don’t doubt this; we were there at the time though not allow on the boat due to what we were told were safety concerns. The fill was from a tanker. It is not unreasonable that the actual 1000L fill took only 20 minutes per tank. Nevertheless, being able to achieve this rate of fill without blowback is quite curious to us, as we have always seen blowback no matter how slow we fill the tank. And trust me, we have tried to creep the fuel into the tanks as slowly as possible, well less than 23L/min we measured at St. Mammes.

Wanderlust takes on fuel while under construction.

Wanderlust takes on fuel while under construction.

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Per the invoice, 1000L of red and white diesel were added to Wanderlust’s tanks.

Why could have the fuel been added at the plant without blowback? Was the trim of the boat that much different when she was on the hard in the plant? Or was there something done to improve the tank’s ventilation?

It didn’t seem like Wanderlust was tilting forward when we were in the shop. But without a level is difficult to tell with certainty. Nevertheless, if she was tilting forward unusually steeply to the bow in the plant, filling at 50L/min would not have proved anything about the effectiveness of the fuel tanks fill and vent pipe arrangements. A filling test should have been done under the static trim conditions. This would require that the test fueling be done when Wanderlust was in the water.

For those keeping score, “static trim” is defined by the standards as the “attitude in which the craft floats in calm water, with each fuel tank filled to its rated capacity, but with no person or portable equipment on board, with tanks such as water and holding tanks being empty and permanently installed equipment supplied by the craftbuilder in place.”

Wanderlust in the plant: From this perspective her trim seems normal.

Wanderlust in the plant: From this perspective her trim seems normal.

Wanderlust after launch with her water tank at the bow near full.

Wanderlust after launch with her water tank at the bow near full.  Pictures can be deceiving, but if anything she looks to be more optimally trimmed to avoid blowback.

For Wanderlust, static trim is the worst-case scenario for the fuel tank venting; it maximizes the tilt to the stern and reduces the slope of both the fill and vent lines. In reality, all of the Wanderlust fuel fills have occurred in near optimal trim conditions with the 1800+-liter water tank at the bow close to full. This is the best case for the fuel tank vent and fill lines as the tilt to the stern is minimized. Nevertheless, we have always experienced blowback.

As we learn more about the proper configuration of the fuel system on barges and decipher the details of how Wanderlust was constructed our concerns have only increased. Before the build it was most important to us that any builder we chose did things right. The last thing we wanted was hidden, difficult to rectify nightmares. We didn’t want a builder that took chances by engineering the systems on the limit. An experienced builder with a seemingly good track record would do things the right way, or so we thought. The last thing we expected was fundamental, difficult to resolve engineering problems on our barge. But it appears that that is exactly what we got.

Adding fuel in St. Jean de Losne

Adding fuel in St. Jean de Losne

 

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One thought on “Fuel Blowback

  1. Pingback: Wanderlust Wanders: Auxerre to Migennes | Wanderlust

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