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Making the Right Decision - Choosing the Right Pump Comes with the Territory
by Tim Schanno, Regional Sales Manager - Asia

Just as cultures, architecture and language differ in each part of the world, so do fire fighting pumps. Bucket brigades, the universal and long entrenched standard for transferring water from the source to the fire, eventually gave way to modern innovations that better served the needs of each world region.

Today, there are but a handful of mobile fire pump manufacturers worldwide. Although there is a vast
differentiation in technology between these manufacturers, the centrifugal fire pumps they produce generally work on the same principles. And, depending on what region of the world the fire brigade is based in will typically determine whether a single-stage or multi-stage vehicle mounted fire pump will be used.

Rear-Mounted High/Low Pumps:
Europe & Asia/Pacific Most European and Asian communities use rear-mounted, simultaneous (multi-stage) pumps, referred to as High/Low or HL pumps. A popular choice due to the smaller chassis design that is common among apparatus manufactured in these regions.

HL pumps are specifically designed for this type of application and are mounted on the rear of the apparatus, with the intake and discharges also facing the rear. This allows the remainder of the vehicle to be used for lockers that can house additional rescue and firefighting gear. The rear access design also keeps the sides of the apparatus clear, which makes pump operations in close quarters much more efficient. This is one of the key features that make the HL pump a popular choice for these regions.

Though compact, the HL loses nothing in performance due to its size. In fact, for this type of application the pump’ operation allows for both low pressure (10 bar) with high water volume and high pressure (40 bar) with low water volume operating simultaneously. The basic range of the HL pumps is anywhere from 2000 l/m to 3000 l/m.

Typical HL pumps are designed as a two-stage pump featuring one common impeller shaft with two impellers. The first stage is the larger, highvolume stage. The second stage is the high-pressure side. Ideally, HL pumps use a two-impeller design, but some manufacturers choose to use multiple stages in order to develop the high pressures.

HL pumps are typically driven via the chassis power take off (PTO). The kW requirements vary by manufacturer and also depend on what water flow and pressures are required. When specifying an HL pump, check to make sure that the chassis /transmission /PTO will allow the required amount of torque and kW needed to perform your firefighting operations efficiently.

HL pumps should also be equipped with an overheat protection device, since these pumps run at high pressures for extended periods of time with little or no water flow. The water inside the pump will rapidly heat up and when an operator discharges the water he/she can get injured from the scalding water. With an overheat protection device, the system will alert the pump operator to this condition, while also discharging a small amount of water to keep the pump cool and in safe operating condition. In addition to an overheat protection device a discharge relief system is also critical to safe operations. HL pump priming systems are automatic and must be capable of deep draughing. Due to the high operating pressures that may be achieved by this type of pump, a discharge relief system should be incorporated into the pump design. These are internal, require no adjustment and provide a margin of safety for the firefighter when operating the hose line.

Mid-Ship Multi-Stage Fire Pumps: Asia/Pacific & North America
Another popular pump design that is used both in the Pacific Rim and North America is a mid-ship style pump. Mounted in the middle of the chassis or just behind the passenger compartment, the midship pump features intake and discharges on both the near and far side of the vehicle. This type of pump is generally capable of 8,000– l/m at 10 bar and additionally features a second stage capable of pressures in excess of 40 bar in series operation. Some manufacturers will also carry a pump with a third stage that can boost pressures in excess of 55 bar with flows of 16-l/m. These mid-ship, multi-stage pumps use a transfer valve during operation. When the transfer valve is in the VOLUME (parallel) position, the water enters each impeller eye from a common intake and leaves through a common pump discharge. When the transfer valve is in the PRESSURE (series) position, the first stage discharges its full volume and pressure directly to the second stage intake, instead of discharging its full volume and pressure directly to the second stage intake, instead of discharging out to a hose line. The second stage then moves this same volume of water, but at the pressure of the first stage discharge.

This type of design is very efficient, since it does not require a mechanical reduction of water pressure. In fact, very little water pressure is lost using this method. Mid-ship pumps are driven via a split shift PTO, manufactured by the pump supplier. Split-shaft PTO’s allow 100% of the available kW and torque provided by the chassis engine. Most models will feature a switch in the driver’s compartment that will allow the operator to switch the pump to ROAD when driving, and when operating on the fire ground the switch will be in the PUMP position. This in effect disengages the drive wheels of the chassis and supplies full power to drive the pump.

Two types of drive mechanisms are used for this PTO. One style is driven by a large 64-mm chain, which can handle more than 23,000 Nm of torque. The other style of drive is a gear drive, and depending on the manufacturer, it will have either a two or three gear set. Chain drives have a distinct over the gear drives from the standpoint of noise. The chain drive is hardly audible to the ear when the pump is engaged whereas a gear drive will have a distinct gear whine that is quite loud when in operation. This can be critical if you have hearing protection regulations.

Mid-ship pumps offer the same advantages of the HL pumps and a few additional ones. They allow larger water flow volumes at the same or higher pressure ranges. They can also be equipped with pressure relief systems that are adjustable to suit fire ground operations. For instance if you have several hose lines and an un-manned monitor flowing, and for some reason the monitor was shut down, the hand lines may still operate at their same pressure. The pressure relief valve will compensate when the monitors water flow is stopped, the valve opens and allows the monitors water to flow back into the intake side of the pump and not cause the hand lines to increase their water flow and pressure. The pump operator typically operates priming systems on the mid-ship pumps manually. This is achieved using a rotary vane primer motor and a manual priming valve.

On both the mid-ship and HL pumps manufacturers like Waterous use a process called “flame-platting” on the wear surfaces of the impellers. This process helps prevent normal wear and tear due to fine sand and grit in the water systems or when drafting. Flame-platting is a process by which the impeller is plated at a very high temperature with liquid tungsten. Once hardened this makes the wear surfaces of the impeller nearly indestructible. When specifying a pump make sure you specify one with a flame-plated impeller, it will reduce downtime and save you from maintenance headaches.

Self-Contained Pumping Unit (SCPU):Asia/Pacific Region
The SCPU pumps are very much like a portable style pump…but on steroids. The SCPU has its own petrol engine to drive the pump and easily carried by two or more firefighters. These pumps are used as a primary pump or as a back-up pump in most cases. They are capable of large flows and high pressure depending on the model and manufacturer your specify.

Advantages to this style of pump are many. They are small, compact and extremely powerful. Typical SCPU’s weigh less than 160 kg, while at the same time able to deliver in excess of 1600 1/m and 20 bar. They feature automatic priming very similar to the priming systems found on HL pumps. With a small chassis they may be used as a first attack vehicle in rural or smaller communities or as a backup unit in the city.

Although small in size you shouldn’t underestimate the capabilities of these little guys. They will fully support two 64 mm discharge lines in excess of 300 meters, with good flows and pressures. Depending on the manufacturer they may be liquid-cooled for extended run period in the tropical areas.

Making Smart Decisions
Take a look around at all the pump manufacturers and you will find that there are differences in innovation in each one. And even though a centrifugal pump is still just that, the efficiencies and operation have changed significantly. That makes choosing the right tool for the job all the more important. Don’t buy a pump just because it is less expensive, it may cost you more in the long run. Remember fire pumps save lives and when it comes to saving lives you want the most dependable pump backing you up.

Serving in the fire service industry for over 18 years, I saw my fair share of misused applications of fire pumps in expensive vehicles because they didn’t do their research. Make sure your vehicle committee doesn’t make the same mistakes, do your research or talk to a professional who can walk you through the specification process. You and your department will be glad that you did.

About Waterous
Revolutionizing firefighting since 1886, Waterous has been manufacturing the most reliable, performance-enhancing pumps, power take-offs, valves and hydrants the fire service industry has to offer. Based out of South Saint Paul, Minnesota Waterous manufactures its complete product line in the USA.

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