A Powerful Cost-saving Combination

Weight and space are precious commodities on almost any vocational truck. You can always use more payload capacity and storage space. For those of you who need a welder, generator and compressor on your truck, a multipurpose unit can offer several advantages that address these concerns.

“Combination units have grown and continue to grow in popularity,” says Dean Strathman, national sales manager, Vanair Air N Arc All-in-One Power Systems. Emissions regulations have increased chassis costs. “To combat the rising costs, fleet managers are reducing individual chassis size by going to a lower GVW vehicle. By utilizing combination units, the fleet manager can reduce the weight and give the operator additional payload capacity to carry the necessary tools.”

“Naturally, the most basic advantage is that you have all of that functionality in one centralized place, but there are other operational benefits, as well,” says John Leisner, product manager with Miller Electric’s Power Products Group. “We’ve seen instances where people have been able to move to a smaller truck because of the reduction in weight. Ultimately, that helps lower fuel costs and reduces wear and tear on the truck. It also helps ensure that your truck is under weight restrictions, and opens up more space on the back for hauling tools and other materials.”

In the past, many fleets purchased a separate welder, generator and air compressor. “Combining the compressor, welder and generator into one unit reduces vehicle weight and provides savings on service costs,” says Tim Worman, product manager for commercial vehicles, IMT.

For example, the IMT CAS35WG consists of a hydraulically driven 35-cfm reciprocating air compressor, 250-amp welder and 5,000-watt generator. It takes up no more space than a separate compressed air system, and offers less combined weight and is more compact than an engine-driven welder/generator and compressor. “The space savings allow operators more payload capacity on their mechanics trucks, which helps increase overall productivity,” Worman points out.

Combination units enable fleet managers to maximize use of the vehicle, as well. “More fleets are reducing overall fleet numbers and equipping the vehicles with more capability,” notes Strathman. Most combination units are designed to fit either in the load space of the body, or on top of the side pack. “This allows the fleet manager to be able to purchase a more standard body vs. having a custom body made to accommodate a welder cut-out, or reducing the cabinet space by adding a welding deck.”

In addition, many units have added functionality. All of the Vanair systems from 150 to 300 amps have four functions: air compressor, generator, welder and battery booster. Miller Electric also offers a 12- and 24-volt battery booster.

Consider the application

“Combination machines are ideal for anyone who will use multiple functions on a regular basis,” says Leisner. “The most obvious is on service trucks. People who work in the field and service equipment will regularly use all three.”

They’ve also seen popularity in structural steel applications. “Those contractors are regularly using all three functions for the joining of frames, decking and every other piece of steel on the site,” says Leisner. “In general, MRO (maintenance, repair and overhaul) and structural steel are the biggest, but most general construction applications will often find good use for all three components. It makes the most sense in any application where the machine(s) will stay truck mounted.”

Some combination units can supply better quality electrical power. “An advantage to our unit over a welder/generator unit is the ability to multifunction the welder and 120/140-volt AC output without worry of voltage spikes or varying voltage,” says Strathman. “Many welder/generator units of today produce the weld current and the AC output within the same generator casting. This type of generator is limited in its ability to provide the clean power needed by today’s power tools.”

A few other combination units, such as the Miller Electric Trailblazer, also incorporate independent weld/generator elements to provide clean power.

Fuel savings rank near the top of the list of requirements for many applications, and a combination welder/generator/compressor package may help. “For light-duty applications, it is a simple solution. For light or intermittent use, there can be a fuel savings, which of course saves you money and is better for the planet,” says Tod Gilbert, M.Sc, P.Eng, VMAC business transformation manager.

Maintenance and Reliability

Consider utilization of the various standalone components. “Fuel right now is as low quality as it has ever been,” says Leisner. “If it sits too long and separates, it can be harmful to your engine.” A combination unit will run the engine more consistently. It will therefore use up fuel faster than some individual units.

“In that same vein, you’re maintaining only one engine instead of two or three,” says Leisner. “In terms of scheduled maintenance and general upkeep, maintenance and repair is simplified because you’re only maintaining one machine. And you’re only dealing with depreciation on one machine.”

Reliability is also a consideration. “Most combination machines come standard with screw compressors, which produce 100% deliverable air all of the time, whereas you often have to stop and wait for reciprocating compressors to build up and kick in,” says Leisner. “Miller’s combination units are rated at 104° F, whereas many standalone units are only rated at 68° F. This higher rating means that you’re going to have greater performance and reliability regardless of your working conditions.”

Customers often have a misperception that combination units are more likely to overheat. “They actually cool more efficiently than standalone machines because there is an additional fan to pull air through the radiator for the compressor,” says Leisner. “It assists airflow through the machine rather than fighting it. Therefore, these machines tend to run slightly cooler.”

Vanair also dismisses concerns about excessive heat. “Some of our units are not enclosed in sheet metal and resemble more of a compressor design,” says Strathman. “This wide open design eliminates any concern of overheating. The enclosed combination units were designed with many features to prevent overheating. By utilizing remote engine oil coolers and 12-volt cooling fans, the units are rated for operation in ambient conditions up to 110° F.”

Realize potential limitations

There are limitations to combination units. This is especially true with the coming emissions regulations.

“Engines above a certain size are going to require a more advanced emission system, which is going to drive up cost,” says Gilbert. “If you are limited to engine size and splitting the power between multiple requirements, each one is going to be more limited. If you only really need one option, it is better to buy an individual product where all of the power available is dedicated to that feature.”

“The only real concern is the reduced horsepower,” agrees Strathman. “Combination units typically are sized to multifunction, but not at 100% capacity of all functions. Therefore, if you need to utilize the unit at 100% of multiple functions, you would be better off to stay with separate units.”

Building multiple functions into one machine also adds complexity to the design. “If there are more systems involved, there is potential for more to go wrong. The more complex units involve a greater understanding of all the systems for repair,” notes Gilbert. “Most systems are nicely designed with service and repair in mind. But again, if you don’t need an option, then there is no point in maintaining it.”

It is important to stick with the recommended preventive maintenance schedules. On the other hand, service is simplified. “Having the compressor, welder and generator in one self-contained unit actually makes repairs easier because there is only one service point for all three components,” says Worman.

Lack of flexibility can be another drawback of combination units. “If you are working on an expansive jobsite and you have a guy on one end who needs a welder and another guy 300 ft. away who needs a compressor, you are suddenly limited and find yourself in a situation where one guy is waiting on the other,” says Leisner.

“The combination machines are also typically larger than the standalone units, so moving around a jobsite, if not truck mounted, can be slightly more difficult,” Leisner acknowledges. “We’ve found ways to engineer these machines so that they are not much bigger than a welder/generator.” This ensures performance is not compromised due to size limitations of the “box.”

“Having said that, most workers on different ends of a jobsite will still require the functionality of multiple pieces of equipment,” he notes. “Having all functionality in one compact unit that is relatively easy to move may provide an advantage. In this case, it may also make sense to have multiple combination units.”

Assess Output requirements

“When IMT developed the CAS35WG, the welding, generator and air pressure capabilities were all based on customer input,” says Worman. “Customers told us that a 250-amp welder, 5,000-watt generator and 35-cfm compressor would be ideal to meet their wide variety of application needs.”

Even so, such systems may not offer all of the capabilities you require. “If you have serious requirements for air or welding... individual units are better options,” says Gilbert. “If you regularly use a lot of compressed air, for example, an underhood compressor is going to give you more air and it is one less engine to maintain.

“Having right-sized equipment can save a lot of waiting time and avoid frustration,” he adds. “It has to be realized that these units are typically large and heavy, so you are giving up payload and space to carry around all of these options, whether you use them or not. If you are never or rarely going to use some of the functions, you are going to be spending money to drive those items whether they are used or not.”

In this case, it can make more sense to go with an individual unit. “If you are going to be using a lot of air tools, it is better to buy a system specifically designed to be a high-output air compressor,” says Gilbert.

If multiple functions are regularly required, however, a combination unit should be seriously considered. “If your equipment is truck mounted and you will use all three functions (or four functions in the case of the Trailblazer 302 Air Pak with battery charger/jump starter), it’s a no-brainer — go with the combination machine,” says Leisner. “You will save on weight, space and fuel. Especially if you work in MRO, you can’t lose. There are also industries such as structural steel erection where all three functions are used consistently. Two or three separate machines in these applications are not efficient.

“If you find yourself in a job where you only need air a small percentage of the time, then a standard welder, generator or combo welder/generator will work for you,” says Leisner. “Also, if you will have workers needing different functions on opposite sides of a jobsite, separate units (or multiple combo units, depending upon the work) may make more sense.”

“When weighing whether to purchase a separate welder, generator and compressor or a combination unit, consider the benefits realized when you avoid adding an engine-driven welder/generator to the floor of the mechanics truck body,” Worman advises. “A combination unit can be mounted to the top of a side pack, freeing up the load bed and increasing payload while eliminating maintenance costs associated with a separate drive engine.”