|Some tankers, like the one in service with the Williamstown (Vt.) Fire Department, built by VTEC are really pumpers with tanker capacity. It has a 2,000-gallon tank and a 1,750 gpm Qmax pump. (Fire Apparatus Photo by Earl Everhart)|
|West Forks, Maine, has a VTEC tanker with a bigger Hale Qpak 1,000 gpm pump with a pump enclosure which can serve as a supply apparatus or an attack pumper as needed. (Fire Apparatus Photo by James Pinard)|
|New Portland (Maine) Fire Department’s 3,000-gallon tanker was also built by VTEC in Williamstown, Vt., and has a 1,000 gpm Hale Qpak pto pump, a very compact designed midship unit. (Fire Apparatus Photo by Earl Everhart)|
Is there a new tanker or tender in your future? Have you thought about putting a pump on it?
Believe it or not, 98 percent of all tanker/tender have some kind of water pump whether it’s a portable or floating pump or a full National Fire Protection Association (NFPA) midship pump or something in between.
No other type of fire apparatus has as many pump options to choose from. This makes selecting the pump and its related components one of the biggest challenges when specifying a tanker/tender.
In preparing to make that decision, it’s important to ask the right questions. The biggest question to ask, and eventually answer is what purpose will the pump have. Without realistic answers to this question, the resulting apparatus could windup being inefficient, too big, more costly and not effective or any combination of these situations. It boils down to an apparatus that won’t do what you want it to do – sort of defeating the reason for buying one in the first place.
Things to consider when deciding what kind of pump to equip your tanker with include: whether the unit will be drafting from a portable tank or other static source; how will the water supply in the apparatus be delivered; will it be used for wildland firefighting; will it need some means of self protection; will it ever be a fire attack apparatus (tanker/pumper); will it’s mission be assigned to be a full pumper; and how will it affect your state insurance/ISO rating.
Once you’ve got solid answers to those questions, and it’s OK if the apparatus has more than one or two missions, it’s time to take a look at the options available for each of the eight common pumping requirements.
Looking at tank filling, the kind of performance needed depend on the tank size and the required tanker shuttle cycle time. If 300 to 400 gpm is sufficient, a float pump may be the best option. There is a proviso, however, as discharge elevation change can be a big factor in whether the float pump will do the job. As the required pressure goes up to feed the tank, the flow will go down. An additional 10 psi can cost 50 gpm of deliverable water.
A mounted portable pump can also achieve this 300 to 400 gpm, but the limiting factor will not be the discharge elevation change, rather the drafting height.
As lift increases, flow will go down. To maximize the drafting performance, buy a pump specifically designed for fire fighting water supply or transfer.
Most fire service pumps are designed for drafting and are equipped with high-lift, fast-acting priming systems. Trash pumps and general industrial dewatering pumps will not perform as well, if at all, at high lift, and priming can be slow.
For higher performance, consider a pto or split drive line driven pump. Whether full NFPA pump ratings are needed or not, buy an NFPA 1901 primer system and a pump which will provide the suction inlet performance required in NFPA 1901.
Why you ask? The hydraulic design of a fire pump is special, so is the priming system, to operate from draft under a wide range of conditions. Getting a pump or primer that’s not NFPA compliant might reduce the drafting performance.
By the way, a prime can be achieved by back filling from the tank to the suction hose, but the operator must be very good and there must be water in the tank to start. Do not count on being able to do this every time.
To improve this method of priming, use a foot valve strainer on the end of the suction hose, this will prevent losing the water out the end of the hose. Note, the foot valve strainer is very restrictive and will negatively affect pump capacity. Hence, this is not always a reliable priming method, and is best left as a back up emergency procedure.
To save money, some departments will buy an NFPA pump, but not all the controls and instruments. If the pump is used for tank filling, water supply or usage with no more than one hand line at a time, this is an acceptable approach.
With any tank refill system, the tank will need to be designed to allow the desired refill rate. Over pressurizing or filling too fast could damage or destroy the tank and someone could be injured or killed.
When considering water supply from the apparatus’ tank, priming is not important. Neither is the pump’s performance from draft. The required pump performance will depend on what is needed at the end of the supply hose, in gpm and psi plus any hose loses and elevation change.
Fire pumps are rated based on specific drafting conditions. Pumping from a flooded suction will normally provide higher flows than the pump’s basic rating. Sometimes this could be as much as 50 percent more than its rating, if the tank to pump line is big enough and the tank baffles, vents and sump are designed for the flow.
The piping, valve and tank design can be a major limiting factor, even if the pump is the size needed to do the job. Again, the tank venting system and baffle design can also limit tank to pump performance. Always specify the required tank to pump performance when buying a tanker/tender.
The following provides some general performances which can be expected from a midship or rear-mounted fire pump, assuming good tank design and full flow direct piping: A pump with an NFPA rating of 250 to 500 gpm and a tank to pump line size of 3 inches will deliver 400 to 500 gpm at 150 psi. A pump with a 500 gpm rating and a 4-inch tank to pump line will deliver 650 to 700 gpm at 150 psi and pumps rated at 750 gpm or more with a 3-inch line will provide 500 to 700 gpm. Increasing the tank to pump line of that same set up by one inch, to 4 inches, will increase the output up to 800 to 1,000 gpm.
It is possible to use non-NFPA compliant pumps for water supply from tank operation, but if they’re used, make sure the pump will withstand the operating speed and power needed to provide the required performance.
Non-Fire Service Pumps
Incompatible pump materials can also lead to corrosion problems and seal failures. Many oil, fuel, milk delivery pumps were never designed to produce the pressures we commonly operate at in the fire service. Many can’t survive the water and corrosive environments encountered in fire suppression. The lower price of non-compliant pumps may be attractive, but the performance and life may be limited.
Moving on to water supply from draft, the basics are the same as water supply from the tank other than the pumps performance will be limited by its rating and by the drafting conditions.
Here again an NFPA 1901 fire pump and its primer were designed for drafting. NFPA rates the pumps at very specific suction conditions, but in actual field conditions the pump’s performance may be better or worse depending on the situation.
A few basic rules may help to understand the principals of drafting. When the lift is reduced, the performance improves. When the lift is increased, the performance is reduced. So, keep the lift as low as practical but, it makes no sense to unnecessarily damage the apparatus trying to get it as close to the pond as possible just to reduce the lift.
Also, keep in mind that when the altitude is below 2,000 feet, pump performance is improved and conversely, when altitude is more than 2,000 feet, the pump performance will drop.
Use Big Suction Hose
Another good tip to keep in mind is that as suction hose increases in diameter, pump performance increases. Use the biggest hose practical. It’s OK to use 6-inch suction hose on a 500 to 750 gpm pump as its performance will be enhanced significantly. And, most apparatus use 6-inch suction hose anyway, so why not standardize it on all apparatus including the tanker/tender. It will make it better for interoperability.
Don’t worry about the weight as the current plastic flex suction hose, even the 6-inch diameter products, are light and easy to handle. It will also be easier to buy the 6-inch suction hose because it has a higher sales volume than 4-, 4.5-, and 5-inch hose.
As far as the NFPA ratings go, the pump manufacturer must certify the pump for the 4-, 4.5-, 5- or 6-inch suction hose size listed in 1901, so the pump, by design and test, is correct. The total system pump test done at the end of the truck build, sometimes called the third-party test, allows for variations in suction conditions anyway to allow for different site and equipment conditions, so why not use the hose that makes the most sense for the department and have the higher volume.
The rule is the same for wildland fire fighting pumps – buy NFPA 1906 or 1901 conforming products. Wildland pumps start off with small gasoline portables and go on up, way up, to midship mounted units.
When determining pump needs and performance, it’s a good idea to look at the number of hand lines that will be used simultaneously, add the hose and elevation losses and factor in the gpm and psi needed at the nozzles. Those numbers will help determine the size of the pump required to meet the needs as well as the NFPA rating.
When considering the needs for self protection, a single line flowing 50 to 100 gpm at 110 to 150 psi, while pumping from the tank, will do the trick. That’s an amount a small gasoline portable pump will handle well.
Tankers/tenders can also be designed to be fire attack capable. Adding a pump of sufficient size for attack purposes creates what is often called a tanker pumper.
An NFPA 1901 500 gpm pto pump system is the starting point for this application. This is a pump system which more than just a pump with minimal controls. Pressure controls, line gauges, two 2-inch preconnect lines and the correct 2.5-inch, or larger, valve count are all required. In this scenario, the total system, not just the pump, should meet NFPA 1901 standards. This makes for a tanker/tender that is very flexible while still being affordable. Apparatus with this configuration can serve as a back up to a pumper, if properly equipped with hose, tools, ladders, nozzles and the like.
Some tankers can be configured to be fully pumper capable. These units are called pumper tankers and usually have all the NFPA 1901 pumper equipment, nozzles, hoses, SCBAs and other equipment found on pumpers.
When making decisions about tankers with pumps, keep in mind that each state sets fire department ISO ratings or minimum standards. In some states, ISO rating of 9 or 8 are the base line which drives the pump size on a fire apparatus including tankers/tenders.
An ISO 9 rating only requires a 50 gpm at 150 psi from draft pump, which is a small portable pump.
An ISO 8 is a 250 gpm at 150 psi pump from draft. This pump takes a 45 hp engine to do the job – an option that will make for a more expensive pump/engine package. A pto pump makes more sense with its added performance flexibility while using less space and gross vehicle weight capacity than a larger, engine-driven pump package.
Some departments might need a 750 gpm, or higher, pump, to meet the desired insurance rating. In most states, 750 gpm is the starting point for full fire pump credit.
Obviously, each of the options costs different amounts with the least expensive, that being a floating pump, cost in the average range of $2,400 to $3,000 list.
A basic 11 hp gasoline-driven portable pump system cost in the $4,500 to $6,500 list range, while a basis 18 hp gas pump system sells for $7,500 to $9,000 range.
Non NFPA compliant pto pump systems list for $9,000 to $19,000 while NFPA compliant systems of 500 to 750 gpm, with crosslays, are in the $25,000 to $32,000 price range.
At the top of the NFPA complaint package, the 1,250 gpm mid-ship pump, sells for $35,000 to $42,000.
The do-it-yourself route is fraught with problems and here is some of the issues people face.
For instance, some departments find that the oil delivery pump they decided to use for a fire pump doesn’t deliver sufficient pressure. To remedy the problem, they’ll try changing the pto for a faster one. That gives more pressure, but it blows the gear box in the pump. So, what went wrong? It’s pretty simple actually.
Say ‘No’ To Oil Pumps
Home heating oil pumps are designed for 200 to 400 gpm at low pressures. For that kind of pump, 80 psi is very high and not intended for full gpm capacity. To save money, oil pumps gears and bearings were designed for low speeds – about 1,000 rpm input speed – delivered by a 50 percent pto on the truck and low power loads. That’s fine for oil delivery. However, changing the pto to 125 percent speed, the pump not only doubles in output pressure, but also the power usage. The combination of added speed and power now exceeds the pump gear box and bearing design leading to failure of the pump’s gear box.
Along those same lines, some departments look to hydraulic wet line systems, like those found on dump trucks as a method of boosting pump performance. The price is right and it looks like a good solution to get more power out of the truck’s pto, but that notion is far from reality. The reality is hydraulic systems take power to operate, they don’t create power. The water pump capacity will actually be smaller for a given pto power capacity. Add to that the fact the hydraulic components cost more than a driveshaft and it equals a very poor solution that flat out doesn’t work.
Some departments buy their own cabs and chassis, new or used, to save money on the apparatus. Many times, it works out fine, but sometimes it doesn’t. Departments will order engines and transmission configurations that won’t do the job they expect.
Always check the pump requirements before you buy chassis. All pump manufacturers will help you with the selection process. It’s as simple as an email or making a telephone call.
When you do contact the pump manufacture they will be looking for information, make sure you are prepared to answer the questions. You’ll have to know the exact make and model of the engine along with its horsepower and torque rating as well as the maximum full load rpm.
You’ll also need to know the exact make and model of the transmission. That information will be stamped on a machined surface on the main transmission body, or on a metal tag attached to it. The numbers cast into the body are not sufficient.
You’ll be asked about the department’s preferences for pump rating and capacity too. And, of course, you’ll need the easy-to-find information like the make year and model of the cab and chassis itself.
So, when you start thinking about putting a pump on a tanker/tender, and most of them do have some means of moving water, keep in mind all the options, get all the answers to all the questions and, when in doubt ask for help from the experts. They’re all more than willing to offer advice to make sure you get the pump performance your department requires.