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Living with alternative fuels

TMC panel discussion explored practicalities of working with natural gas, including required shop modifications.


NASHVILLE, Tenn. — The two natural gas proponents at the Technology & Maintenance Council (of the American Trucking Associations) spring meeting focused on the practicalities of living with natural gas alternative-fuelled vehicles rather than the technologies and vehicle modifications that are usually the topic at these meetings.

Scott Barraclough, project manager, product segmentation at Mack Trucks talked about the vocational fit for natural gas in different operations. Analloyd Thomason, co-founder of the Natural Gas Vehicle Institute (NGVi) addressed the upgrading of shop practices and facilities to accommodate the maintenance of the vehicles.

Barraclough’s presentation started out with the comment that natural gas’ competitive advantage over clean diesel has been eroded by recent moves in the petroleum market. Now its advantage has shrunk to 15-20% from the 20-30% advantage at the height of diesel prices.

However, this likely will not slow by much the interest in natural gas as a preferred alternative. Important in the business decisions for those making the switch are gas pricing stability and the fact that it is domestically available. And as more filling stations for both liquid and compressed natural gas are coming on-line, the day-to-day availability is also improving.

CNG infrastructure outpacing LNG

In fact, said Barraclough, across the US more than 1,500 compressed natural gas (CNG) stations are open, two-thirds of which can accommodate heavy vehicles.

By contrast, there are a scant 100 liquefied natural gas (LNG) public fuelling facilities, he said.

Even with better public availability of natural gas, the vehicles today still only account for 3% of the truck market. But, said Barraclough, it is a segment that garners a wide and growing attention.

Obvious vocations for natural gas are those where trucks return to an operations centre on a daily basis, and that includes dump trucks, transit, mixers, local distribution trucks and of course refuse trucks where CNG is powering the lion’s share of trucks sold today.

Subsequent to the session Mack announced that natural gas-powered versions of its Pinnacle models are available with the Eaton UltraShift Plus transmission and Bendix Wingman Advanced collision mitigation technology.

“Our customers told us they wanted the option of an automated transmission, as well as the benefits of Wingman Advanced safety technology in the natural gas Pinnacle model,” said Stephen Roy, president of Mack Trucks North America in a news release.

Equipped with the Cummins Westport ISX12 G natural gas engine, Mack Pinnacle models can run on either CNG or LNG, making them eminently suitable for regional-haul and distribution. The maintenance-free aftertreatment system, combined with low-cost natural gas, reduces vehicle life-cycle costs and thereby improves customers’ return on investment, said the company in its news release.

Training and maintaining

Back at the TMC meeting, Thomason introduced the NGVi, an organization that offers training and consulting in all areas of natural gas for gas vehicle owners and users.

In particular and in a breathlessly fast overview, she touched on the mandatory requirements for storage tanks, gas quality and building modifications to accommodate the gas-fuelled vehicles’ maintenance.

It’s important, she said, to realize that it is a National Highway Traffic Safety Administration (NHTSA) requirement that vehicle tanks for CNG be inspected every three years or 36,000 miles.

This regulation is obviously intended for passenger vehicles and she used a client, Frito-Lay, as an example of a commercial operation that has to check and re-certify tanks every 13 weeks or four times a year. Following industry best practices, this check should be accompanied by an inspection of the whole natural gas system on the vehicle, she said.

Technician training and certification is highly desirable, said Thomason, from a safety perspective but also because techs need to understand how natural gas differs from conventional fuels.

One of the main considerations is the highly variable quality of the natural gas, which does not have the same rigorous standards of composition as do other petroleum fuels.

In particular, natural gas can come laden with water and suffer widely varying BTU content depending on the gas utility supplying it.

Also, during compression of the gas, oil can leak into the gas, which is why coalescing filters are included in the fuel system on the vehicle.

However, for them to work satisfactorily they must be properly maintained.

Technicians should also understand that oil or water in the fuel will cause hard starting and ragged performance and that such symptoms indicate a fuel problem and not a mechanical issue within the engine.

If they see fouled spark plugs or even poisoned expensive catalytic converters (they can cost as much as $23,000) then steps have to be taken to address the quality of the fuel rather than turning to conventional diagnostic tools and fault-tree service procedures.

The implication was made that such unforeseen events can severely impact the cost of running natural gas vehicles as well as their uptime availability.

And, should a gas-powered vehicle be in for repair, technicians must be aware of procedures to de-fuel the vehicle, whether it be to a storage tank, another vehicle or, in special circumstance, to the atmosphere.

Because natural gas is lighter than air, there are building constraints to be aware of that could result in a combustible mixture pooling in the roof or rafters of a building. To guard against this not only should the building have no areas where gas can collect, but a ventilation system must be provided as well. Since the requirement is for 0.75 to 1.0 cubic foot for every square foot of floor area, providing full-time ventilation 24/7 could prove very expensive.

A better alternative would be a combination ventilation system interlocked with methane detection. And methane detection is one of the industry best practices that should be considered.

Given the variable quality of the gas, the question of owning the fuelling facility often arises.

According to Thomason having on-site fuelling assures the user of quality control and gas consistency.

Also there’s a financial advantage of directly receiving rebates and tax credits for using the gaseous fuel.

The disadvantages include the significant up-front investment and the training to operate the facility safely, along with associated maintenance costs.


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