Fixed & portable pumps
Published: 01 January, 2006
After the disaster in New Orleans the emergency services -with the co-operation of the military- had to pump 250 billion gallons out of the city. Clearly, a disaster like this only serves to underscore the importance of having the right pump for the right job, argues Pete Perkins.
Only last month, personnel working for the city finished draining New Orleans of floodwater left after the city was devastated by Hurricane Katrina.
When Hurricane Katrina barrelled in to New Orleans with winds of almost Category Five speeds no-one was surprised to see the levee system fail. Major breaches on the London Avenue Canal, the wide, navigable Industrial Canal and on 17th Street Canal, left 80% of the city flooded.
In three weeks the pumping efforts had succeeded in drying out 90% of the city, but then Hurricane Rita arrived, bringing further heavy rain. Knowing the patched up levees were already weak, the Corps’ engineers sealed up the mouths of the 17th Street and London Avenue canals with metal sheets, but the areas flooded anyway.
In the end, engineers mostly relied on mobile pumps to shift the bulk of the water at around 64,000 litres (2,250 cubic feet) per second. Many of the city’s own powerful pumping stations were initially out of commission due to flood water or power failure. Gradually these 16 Drainage Pumping Stations and scores of other pumps have been brought back into service to pump out what remained of the 95 billion litres (3.6bn cubic feet).
The previous month had been a different story: as of 7th September, about 60% of New Orleans remained ‘underwater’ and the city’s pumping capacity was only about 10% of the norm, the US Army Corps of Engineers (USACE) said.
Engineers said they had to take special care to watch for human remains swept into the grates of pumping stations. “A tremendous amount of debris was accumulating there,” said one of the rescue contingent.
Colonel Joe Spraggins is the head of emergency operations in Harrison County, which includes Gulfport and Biloxi. Speaking to FIRE & RESCUE he was phlegmatic about the pumping operations of the emergency services:
“For so many years,” he said, “we’ve had everything so easy, so perfect. When God gives us a disaster, we have to find out why. It might be to bring us back to reality.”
Why did it flood?
Right at the mouth of the Mississippi River, the USA’s mightiest river system, lies New Orleans. For aeons the river has been depositing silt in the Mississippi Delta, creating a buffer zone between the city and the Gulf of Mexico.
Business and industry have controlled the shape and extent of the Mississippi for the convenience of business and industry, severely reducing the size of the delta. So when Katrina hit, New Orleans had little protection from one of the greatest storm surges America has ever seen.
Experts are pleading with government and business to think seriously before New Orleans embarks on its next major engineering project - completely rebuilding itself.
Portable Protection:
Portable pumps can include anything from high capacity trailer pumps to small units that can be carried by hand. The usefulness of trailer pumps has increased in recent years due to the advent of large diameter hoses which can move water from remote sources to the fire scene without unacceptable pressure losses while the development of hose layers has made the deployment time required more acceptable.
In fighting minor fires, for tank cooling and for flooding incidents portable pumps have always found a niche. There is now a greater choice in capacities and whereas most portables used to be designed around their 7-bar performance for branch pipe or monitor use some units now have more emphasis on their maximum flow.
Their flexibility in unforeseeable situations will always make them a necessary part of the firefighting armoury but all portable systems have the disadvantage of slower deployment when time is critical.
Ultimately, the needs of firefighters who will seldom leave an urban environment are vastly different to those of rural users. The urban requirement may be for equipment that will be pumping from hydrant, river or sea and can approach these sources without resorting to manhandling. The rural user may need equipment that can use remote sources such as lakes and rivers, which cannot always be accessed by road.
On large industrial sites such as refineries and chemical complexes it is possible to provide mobile pumping equipment which can deliver up to 4000+ litres/min from predetermined supplies independent of fire tenders ring mains or power supplies.
Specification is always a matter of judgement, but as a general rule I would say that the tendency to overspecify, with increased use and maintenance complexity is at least as dangerous a tendency as its reverse!
Pumping out basements: Floating fire pumps are generally powered by twostroke air cooled single cylinder units (for low centre of gravity) driving a pump with its inlet mounted directly into the water source through a plastic float. Their main application is rural or pumping out basements in town areas.
Advantages: weighing in at around 25kg or less they can be carried for long distances to a water source. Pressures of around 10bar are available where fog devices are envisaged with low flows or other models give flows of 400 litres plus for flooding incidents They are simple in construction, have hand start and speed governing in water protected electronics. Hand start is the normal option.
The usual 2-stroke disadvantage of oiling at low speed does not apply as they are always run at full throttle and they require no gauges. They can use very shallow water sources.
Disadvantages: these pumps are relatively low output devices suitable for a single outlet. Their output can only be controlled at the branch-pipe. In fast flowing water they require a mooring arrangement to prevent them swinging into the bank, and even in still water the tendency to drift must be controlled. Weeds or floating debris can cause fouling, and 2 stroke engines can be difficult to start after a long interval between use.
Rural applications & forestry Forestry and rural application pumps will be driven by either a 2 or 4 stroke engine of 1 or 2 cylinders. It will be capable of being carried for reasonable distances over rough ground by 2 men.
It will be driven by either a 2 stroke or 4 stroke air cooled engine of 1 or 2 cylinders, have a priming device, 1 or 2 outlets, a suction hose, and suction and pressure gauges. Again, hand start is the norm for simplicity and the smaller units are sometimes hand primed.
Advantages: these pumps use volume production light weight engines such as Briggs and Stratton or Honda which have world wide spares networks. Local overhaul and repair is thus simplified. 2 strokes can give enhanced performance for a given weight, while 4 strokes have increased reliability and simple primers.
They are suitable for wild terrain. Disadvantages: no obvious ones for this type of use though it should always be remembered that fuel supplies and hoses have to be transported separately. Of course, their ease of deployment puts a ceiling on output.
Pumps for fire departments There is no clear dividing line between this and the previous category, but generally fire departments look for water delivery of 1,000 litres+ at pressures of 7 bar or more since they have to deliver into multi-floor buildings or relay at some distance to a fire tender.
Where the pump is to be carried on a fire appliance locker width is a constraint - and since the pump competes with an increasing range of other equipment volume occupied is becoming more critical. Health and Safety rules also require that the weight carried by each member of a pump team does not exceed a defined limit. In some countries where portables are treated as a separate emergency resource and held in depots width and volume limits can be relaxed.
It would be totally uneconomic to produce the multi-cylinder engines needed for these outputs for individual pump designs - so most manufacturers rely on industrial versions of existing automotive engines. Water cooling is universal on automotive engines but this is no handicap to the pump designer as the pumped water itself provides a compact cooling method via a heat exchanger. Stainless steel is widely used in auxiliary components due to its corrosion resistant properties. Since alternative starting devices have been a longstanding requirement in some countries, battery and hand starting are often specified with consequent weight/ performance penalty.
Advantages: clearly these pumps will deliver quantities and pressures of water that provide credible backup or assistance to main appliances.
