July 2007

 

The Time Has Come For Pto Pumps

By Paul C. Darley

(Editor’s note: Paul C. Darley is president of W.S. Darley & Co., which is headquartered in Melrose Park, Ill.)

There was a time when power take off (pto) driven fire pumps were only thought of as small pumps for applications such as tankers and mini-pumpers. Times have changed, and I firmly believe that fire pumps driven via a transmission-mounted or rear-engine pto clearly make the most sense for today’s fire service and will be the most common form of pump on the market within 10 years.

The introduction of the Allison World Transmission in 1992 really rewrote the rules for pto-driven pumps in the United States. The reason is that the Allison World Transmission (marketed as the EVS transmission for Emergency Vehicle Service) offered multiple pto openings, allowing more engine horsepower to be transmitted through a pto than previously available on automatic transmissions. The EVS transmission is now available on virtually every commercial and custom chassis offered to the fire service.

In 1993, Darley and Spartan teamed up to test a 1,500 gpm PSP pump on a Spartan chassis to prove the concept of running a large volume pump off of a Chelsea pto mounted to this transmission. The vehicle was run through a rigorous testing program at Allison’s factory, using a Chelsea 855 pto and the Allison HD4060P transmission.

All of the components passed this test with flying colors. Since that time, Darley has manufactured literally thousands of large pto-driven pumps without one pto, pump or transmission failure.

These 10-bolt ptos, manufactured by Chelsea and Muncie, give fire pump manufacturers the ability to rate their pto pumps up to 1,500 gpm. Both pto manufacturers publish torque limits. Some applications are limited to 1,000 or 1,250 gpm, so be sure to check all pump and truck manufacturers for available options.

The fact is, for most of the fire services around the world, pto pumps have been the standard for many years – from smaller vehicles to large city pumpers.

Today, major cities around the world from Beijing, China, to Melbourne, Australia, run large volume pto pumps – and there is no turning back now. These departments are sold on the benefits, and have been for years.

Oddly enough, the concept has not been embraced by the U.S. fire service as quickly as it has been in other parts of the world. However, some U.S. fire apparatus manufacturers, like Rosenbauer America, have been successfully marketing this concept for years.

The introduction of the Pierce PUC equipped with a pump driven by a rear-engine pto (REPTO) will have departments taking a new look at this application. The REPTO has been the standard drive for a multitude of heavy-duty applications for the construction, mining, refuse and other industries.

Over the years, Pierce has invested significantly into new product development – cab safety systems, frontal crash, side roll, electronic stability control, independent suspension – and now the PUC.

Slow To Embrace

So why hasn’t the U.S. fire service embraced pto-driven pumps?

First, pto pumps have not been heavily marketed to the fire service. Pierce and Rosenbauer have been the only two fire apparatus manufacturers to truly embrace the concept so far. They are both industry leaders in new technology innovation, and it makes sense that they are the ones to introduce new technology.

Second, we all know that America’s fire service is deeply rooted in tradition and historically slow to adopt new technology. There is a school of thought that says, “Fire pumps should be midship mounted and driven from the truck driveline via a split-shaft pump transmission.”

Third, our experience shows a general lack of understanding by some departments as to how pumps are driven and the different drive methods available. Some customers seem to think that the pto units on the market are not ratable pumps because they are not driven by the truck driveline.

Finally, it has been suggested that the pump manufacturers are not pushing the concept because we would now sell a pump for roughly 50 percent of the price of a traditional midship pump.

Our company conducts a lot of market research, and there are a number of industry trends that make pto pumps particularly marketable and an excellent solution for many of today’s large city, municipal and rural fire departments.

Published statistics show that fire apparatus today are being built for multipurpose applications. Statistics also show that with more stringent National Fire Protection Association (NFPA) building standards, sprinkler systems, fewer smokers and flame resistant materials in everything from carpet to furniture, there are far fewer fires than there were only 15 years ago.

Traditional pumpers with a 60-inch pump panel and a 500- to 1000-gallon water tank may soon be things of the past, as they leave little room for all the equipment and tools needed to respond to today’s emergency needs.

Pumpers Ill-equipped

These large pumpers are ill-equipped to meet today’s emergency response needs because they are geared toward firefighting, when in fact, the pump is only engaged about 5 to 10 percent of the time on emergency response calls. Ironically, 80 percent of the vehicle space and weight is committed to the firefighting function.

Alan Brunacini, recently retired chief of the Phoenix Fire Department, has been preaching this for years. He used a famous metaphor that today’s pumpers responding to most emergency calls are similar to “delivering pizza in a cement mixer.” Another of his favorite sayings was that if you are building a pumper today without compressed air foam (CAFS), it’s already obsolete.

Incorporating CAFS

Most of the pto-driven pumps on the market can incorporate a CAFS, where the compressor is integrated into the pump transmission or powered by a second pto. CAFS usually uses much lower flow rates, but with pto pumps, departments still have the ability to provide the “big water” fire protection when it is needed.

Large volume pto pumps offer a number of advantages. First, they are more economical – pto pumps are very simple and, as a result, very economical.

We, as pump manufacturers, need to sell two or three pto pumps to realize the same sales dollar volume as the cost of one fully manifolded mid-ship pump.

Most of today’s manufacturers fabricate the suction and discharge manifolds themselves and the gear box is simply a two-gear transmission as opposed to a traditional three-gear transmission with sliding clutch gear, tail shaft bearings, and all the rest.

Fire apparatus manufacturers are not only paying less money for the pump, but the manifolding on these large pto pumps is quite simple and custom designed. They are able to pre-fabricate custom suction and discharge manifolds that specifically meet their plumbing designs.

All of this adds up to a more economical fire apparatus for the end user.

The second major advantage is space savings. The pto pumps can be literally tucked underneath the cab or located immediately behind the cab, using space that would most often be wasted.

With the movement toward multipurpose vehicles, any savings in weight and space dedicated solely to the pump and manifolding can be a huge advantage for fire departments. This is especially true when considering the needs for a pumper and a rescue truck – one vehicle for all emergency needs. Combining vehicle uses is becoming even more critical with reduced staffing in both volunteer and career departments.

None of this is rocket science. Pto-driven pumps make for compact pump modules, and there may not be a need for a pump module at all, freeing up compartment space in the vehicle. Pump panels can be as narrow as 18 inches in these applications.

It should also be noted a compact pump design allows for a shorter wheelbase on the trucks, which translates into smaller turning radius and shorter overall length, while not compromising on storage space or pump performance.

Further, it should be noted that, in the United States, many of the compressors being used for CAFS applications are being driven off a separate pto.

Another big advantage is easier operations. Rather than an engagement process for a traditional split-shaft, mid-ship pump, there are fewer steps involved for a pto-operation.

With a traditional, split-shaft, mid-ship pump, the operator must first put the truck in neutral, set the parking brake, engage the pump and put the truck back into drive.

With a pto pump, engagement is much simpler – especially for pump and roll operations. The operator simply engages the pto by pushing a button in the cab, regardless of whether the truck is in drive, neutral or park. Moving from site to site with a split-shaft pump is cumbersome, at best, compared to a pto-driven model. For stationary pumping, the first three steps remain the same with a pto pump.

Interlocks, on a pto-driven pump set up, will prevent the pump throttle from being active at the pump panel unless the parking brake is set. Wheel chocks must be positioned for both split-shaft and pto operations.

Pto-driven pumps offer safer operations. The traditional split-shaft pump, when engaged, cuts off power to the rear differential when the pump is engaged in order to drive the pump. The pto engagement mechanism reduces the chances of operator error and the possibility of the vehicle “running away” due to incomplete shifting of a split-shaft pump.

Pto pumps permit pump-and-roll capabilities. While performance curves for larger pto pumps may not accurately define pump-and-roll performance, I can speak from experience that walking alongside an apparatus with an 1.75-inch line at 100 gpm at 80 psi provides sufficient pumping capability in most types of applications such as brush fires, highway fires, and other applications that call for a pump-and- roll operation.

Easier Maintenance

Although many firefighters may not think they need pump-and-roll capabilities, it is certainly nice to have it in the arsenal in the event the need arises. And, that advantage comes with no additional charge compared to the cost of adding an auxiliary pump to handle this type of application.

Maintenance is easier and less costly because of a pretty simple rule – fewer parts means less maintenance and headaches in terms of both repair and regular preventative maintenance of a pump. This has become a significant issue, particularly for departments which don’t have a full-time service department to service their vehicles.

Our market research has also shown that members of today’s fire departments are not as mechanically orientated as they were in the past. This is particularly true with the younger fire department personnel. The newer recruits entering both career and volunteer departments today don’t have that mechanical knowledge, as everything is electrical.

Today, when I open the hood of my car, I’m not even sure how to check the oil, much less how to adjust the fuel injectors or other electronics. As a result, today’s chiefs are looking for a simpler and safer pump. However, they know they still need pumps capable of providing high water volume for those large fires that still do happen occasionally.

In my 25 years in the fire service, I have seen a lot of new products come and go. Granted, a lot of them don’t pass the “firefighter-proof” test and get tossed in the heap as just another gimmick.

In this case, however, I’m willing to stake my career on the fact that pto pumps are here to stay.

W.S. Darley & Co. has developed a pto pump, called the PSP, capable of producing 1,500 gpm running off a transmission-mounted Chelsea pto.

Short wheelbases can be maintained with pto-driven pumps as the pump module is greatly reduced and apparatus cabinet space can also be preserved.

Pto pumps offer a major space saving advantage in they can be literally tucked under the cab or located immediately behind the cab using space that would most often be wasted.    (Darley Photo)