Raw Sewage Pumping:

How to Select the Right Sewage Pump

Pumping raw sewage is not an easy job for a sewage pump, and working in the sewage pumping environment is not easy or safe for the operators involved. Selecting the best sewage pump needs careful consideration.

For pumps, the presence of all manner of foreign materials such as cans, bottles, rags wet wipes, hair and other stringy materials provide a difficult challenge. For operators, there are many dangers. Working at heights, working over water, working with heavy swinging weights, and working with cranes just to name a few.

Different styles of pumps are applied to the pumping of raw sewage, with the most common being the submersible pump. There are numerous brands and several good quality manufacturers, but all have basically the same set-up. They are suspended [lowered and raised] by rated lifting chains, and are set on guide rails to enable them to engage with a permanently installed discharge bend inside the wet well.

The submersible style of sewage pump (shown below) has been the industry standard for several decades. As the cost of implementing safety systems and controls increase, considerations for more sustainable long term solutions that offer not only more reliable pumping capabilities with longer lasting parts, but additionally much safer to trouble shoot and maintain.

SEWAGE PUMP STATIONS AND THE HIERARCHY OF CONTROLS

There are numerous risks that operators face in maintaining sewage pump station assets. In a survey conducted by Hydro Innovations, the following risks were highlighted by water industry operators:

– Working over water

– Working at heights

– Working with heavy swinging weights

– Working with cranes

– Slips and falls in damp valve vaults

– Working in confined spaces

When a Water Authority elects to go with self-priming centrifugal sewage pumps for their wastewater pump stations, many, if not all, of these risks are eliminated.

By eliminating these risks, the effectiveness and sustainability of the asset is increased. This in turn, reduces participation and supervision, which in turn naturally has an impact on maintenance costs.

Whenever chokes need to be removed, pump maintenance needs to be done or guide rails or discharge bends need attention in the  “conventional” system, the risks require the increased participation and supervision depicted in the above diagram. Those choosing self-priming pumps have eliminated these risks.

 

What are some of the hidden costs associated with maintaining a conventional sewage pump station?

While there is increased costs associated with more operators and supervision required when using submersible pumps, there are also  some “hidden” costs associated with operating “conventional” systems.

– Power consumption is one. A sewage pump is losing efficiency from day one, and the only way to get “factory settings” back to worn wear rings is to replace them or adjust clearances. Until then, pumps are not delivering their published efficiency. Getting back to published efficiency requires the sewage pump to be removed from the wet well [with a small crew and a crane]. Until this is done, costs are “leaking” from the system. This is not usually picked up by Net Present Value [NPV] calculations.

– Again on power consumption, all submersible pumps rely on the sealing between the pump and the discharge bend. This may be all fine on “Day 1”, but at some point in time, that metal to metal “seal” will wear, and begin leaking. After leaks start, they get larger as more material passes through that point. Also, as pumps get lowered back onto discharge bends, they may not always seat properly [because of foreign matter], again causing leaks. Again, this is never factored into NPV calculations.

– All lifting chains for these submersible pumps need to be rated/certified. They need to be inspected or replaced every single year. This may appear in a general tools ledger or civil maintenance costs, but again, would probably not get factored into an NPV analysis.

– Some Councils or Water Authorities require a permanent personnel anchor point to be installed adjacent to sewage pump station wet wells. These are part and parcel of ownership of the conventional pump station, but costs associated with these, along with harnesses, winches etc are not often [if ever] factored into calculations when comparing alternative pump technologies [like comparing them to self priming pumps that don’t require anywhere near the same level of access to the wet well].

– Ownership of vehicles fitted with lifting apparatus is also part of the ownership cost of operating submersible pump stations. Again, when comparing other technologies, this cost burden is almost always overlooked.

– The number of personnel to provide maintenance services on sewage pump stations is also a factor often overlooked.

– The cost of carrying support stock is also a large burden for submersible pump station asset owners. These pumps have narrow performance envelopes [when compared to self priming pumps], and can require 5-10 times more stock holdings to support them.

hierarchy of control
hidden cost of submersible pumps
there are many WHS issues when servicing a submersible pump
submersible pump needs to be lifted out of pit

SELECTING THE RIGHT SELF-PRIMING SEWAGE PUMP

Self priming sewage pumps are mounted on the surface at ground level, with only the suction lines entering the wet well. Wet well lids remain closed for all routine maintenance events [such as oil changes, clearance adjustments, valve greasing], and even major overhauls are all done with the wet well lids sealed. All mechanical and electrical equipment is mounted at ground level. This does make them substantially safer to operate than conventional systems.

If the decision has been made to install self priming pumps because of safety or maintenance cost savings, selecting the right one is important.

Gorman-Rupp grey water super u series

SAFETY FEATURES

If you have selected a self priming pump for safety reasons, make sure your self priming pump offers its operators the right level of protection. The better self priming pumps will have some or all of the following safety features:

– A priming fill port retained by a clamp bar with a finely threaded screw, and the cover plate sealed with a Teflon gasket. This is important because if operators attempt to open the port while the pump is pressurised, pressure is released horizontally, not vertically.

– The better self priming pumps will have a shielded fill port cover.

– A good quality pressure relief valve to vent excessive pressure from the casing if the pump is accidentally operated against a closed head [and your pump supplier should know the pressure these valves will start to “vent”]

– A non-return suction flap valve with a safety burst disc centre to vent excessive pressure in case of a water hammer spike.

– The pump should have external adjustment of the internal impeller/wear plate clearances, and for convenience and safety, operators should be able to do this from the non-drive side of the pump.

Safety features of Gorman-Rupp pumps

MAINTENANCE FEATURES

It is very easy to think that all self priming pumps will have the same features, because they look the same, have the same shape, and are marketed as “equivalent”. But appearances can be very deceiving. A good quality self priming sewage pump will have some or all of the following maintenance features:

– Good self-priming pumps will have shim-less adjustable clearances. The better ones will have their adjustment systems on the suction side of the pump [away from the drive end, to make it easier and safer for operators]]. The best ones will have their clearance settings easy to index and lockable so that they remain in place during other maintenance events.

– Good self priming pumps will have at least 3mm of wear built into the impeller/ wear plate clearance system. The best ones will have up to 6mm of wear built into their clearance adjustment system.

-A good self priming sewage pump will have a replaceable suction flap valve that can be accessed for cleaning and/or replacing without the need for disconnecting suction piping. The best ones will enable access to the flap valve without the need to open the pump.

– Good quality self priming pumps will be able to pass solids [in sizes as advertised on curves and data sheets] through all internal passages inside the pump. Not only the impeller, but advertised solids size spheres should be able to pass through the recirculation port, discharge nozzle and all other passages. Quality manufacturers can guarantee this and even have certified drawings to support this claim.

– The better self priming pumps will have pusher-bolt capability on both the cover-plate and rotating assembly to make it easier for operators to remove these items for service even if they’ve been operating for “years” without being removed.

– Non-clogging/blocking ability is a very important feature if operator intervention is to be kept to a minimum. Besides having through-let sizes big enough to pass published sphere sizes, pumps need to be able to handle stringy materials such as rags. Pumps with standard wear plates will not measure up in this area. Only select pumps with “self-cleaning” wear plates or with specialist rag handling systems like Gorman-Rupp’s “Eradicator Solids Management System™”.

Having the right safety and maintenance features is extremely important, but pumps need to be able to deliver the required service and have the required after market support.

gorman-rupp-pusher-bolts-pump-maintenance
Cross section of Gorman-Rupp pump

DELIVERING ON PERFORMANCE

Safety and maintenance features are very important, but so is delivering the right flow and pressure for a given application. The pump also needs to have a Net Positive Suction Head Required [NPSHr] that is lower than the NPSH available. These are all aspects of the pump selection that need to be considered by the pump supplier. The chosen sewage pump manufacturer’s literature in this area therefore needs to be trusted. The market leaders in self priming pump technology have years of R&D put into the development of pump curves and NPSHr curves, so can be trusted to provide pumps that will deliver published performance. Getting references from other Water Authorities or Councils is a good approach in determining those brands that can be trusted to deliver on performance.

A long service life is also an important factor in determining the right pump. Pumps that are safe and easy to work on are an excellent start. Pumps that have features that protect the pump as it operates year in-year out will deliver the desired asset longevity. Features like a double lip seal and atmospheric vent protecting the bearings and shaft will add years to the replacement intervals for these parts. Anti-rotation ribs in the seal area will also add to mechanical seal life by slowing velocities down within the seal area.

“After Market” performance is also a measure of a good supplier. Parts and replacement pumps should be readily available for ex-stock delivery.  An unsupported sewage pump is a poor investment.

Here at Hydro Innovations, we hold  a very large inventory of pumps and spare parts allows us to deliver industry leading service. With over 80 years combined experience in applying, selecting and troubleshooting pumps, we are experts at designing the most successful and cost-effective fluid transfer systems to meet your requirements. Call us now on (02) 9898 1800, email here or use the form below to find out more information about your pumping needs.

Gorman-Rupp above ground self-priming pump station

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Pump Maintenance Videos:

Watch instructional videos here showing how simple the maintenance activities are for Gorman-Rupp surface mounted self-priming pumps:

INTRODUCTION AND SAFETY

BACK COVER AND WEAR PLATE REMOVAL

SUCTION CHECK VALVE REMOVAL

ROTATING ASSEMBLY REMOVAL

CARTRIDGE SEAL REMOVAL

SHAFT AND BEARING REMOVAL

CARTRIDGE SEAL INSTALLATION

IMPELLER INSTALLATION AND ADJUSTMENT

ROTATING ASSEMBLY INSTALLATION

BACK COVER INSTALLATION

PRESSURE RELIEF VALVE MAINTENANCE

SETTING PACE CLEARANCE

Our expert team is standing by for any questions you have about how best to configure your pump system.

Self Priming Raw Sewage Pumps:

Download the Brochure | Ask Our Team

The Gorman-Rupp Super T Series self-priming centrifugal wastewater/sewage pump has been the world benchmark for this technology since 1963 (>50 years). They have been designed for economical, trouble-free operation, with superior solids handling capability and a large inspection cover to access pump internals for service or blockage removal.

Advantages include:

  • Self-Priming pump has the ability to mount high and dry above the wet well (not in it)
  • Low cost of ownership
  • Greatly reduced OH&S issues – no more working over water/heights/cranes/heavy swinging weights
  • Surface-mounted pumps with easy access for monitoring or service
  • Advanced safety features including pressure relief valve to protect operators
  • Improved maintenance features to greatly reduce maintenance time and costs, with removable rotating assembly
  • A variety of materials of construction to handle abrasive and/or corrosive fluids

The Gorman-Rupp Super T Series sewage and wastewater pumps with Eradicator™ Solids Management System are a series of self-priming centrifugal pumps designed specifically for handling municipal and industrial wastewater containing stringy, difficult to pump, solids in suspension (such as wet wipes, rags and feathers).

They have been designed for economical, trouble-free operation, with design features that deliver superior solids handling capability and a large inspection cover to access pump internals for service or blockage removal. Gorman-Rupp Super T Series wastewater and sewage pumps have been used for pumping of WAS and RAS and for digester recirculation with great success in wastewater treatment plants around the country, as well as food process plants, paper mills and other heavy industries. The Eradicator™ system advances the solids handling capabilities of this range.

Advantages include:

  • Ability to mount high and dry above the wet well [not in it]
  • Low cost of ownership
  • Greatly reduced OH&S issues
  • Easy access for monitoring or service
  • Advanced safety features to protect operators
  • Improved maintenance features to greatly reduce maintenance time and costs, with removable rotating assembly
  • A variety of materials of construction to handle abrasive and/or corrosive fluids

The Gorman-Rupp Ultra V Series solids handling sewage and wastewater pumps with Eradicator™ Solids Management System are a series of self-priming centrifugal pumps designed specifically for handling municipal and industrial wastewater containing stringy, difficult to pump, solids in suspension (such as “wet wipes” , rags and feathers).

They have been designed for economical, trouble-free operation, with design features that deliver superior solids handling capability and a large inspection cover to access pump internals for service or blockage removal. Gorman-Rupp Ultra V Series wastewater and sewage pumps have been used for pumping of WAS and RAS and for digester recirculation with great success in wastewater treatment plants around the country, as well as food process plants, paper mills and other heavy industries. The Eradicator™ system advances the solids handling capabilities of this range.

Advantages include:

  • Ability to mount high and dry above the wet well [not in it]
  • Low cost of ownership
  • Greatly reduced OH&S issues
  • Easy access for monitoring or service
  • Advanced safety features to protect operators
  • Improved maintenance features to greatly reduce maintenance time and costs, with removable rotating assembly
  • A variety of materials of construction to handle abrasive and/or corrosive fluids

Ask Our Team

The EDUR LBU multiphase pump is a multi-stage centrifugal pump with the unique capability of being able to pump a liquid/gas mixture. The centrifugal pump is constructed of either C.I./ Bz/ SS, Nodular Cast Iron, All-Bronze, Stainless Steel, or Super-Duplex Stainless Steel construction, so may be used to handle a variety of liquids.

Air, Oxygen, Carbon Dioxide and Ozone gases can be introduced into the suction line and transported and used to mix or disperse the gases. This makes the pump ideal for DAF plants, where the multiphase pumps provide the task of air saturation without the use of compressed air (no compressor, air saturation tank or associated controls).

Advantages include:

  • Liquid flows to 16 l/s
  • Gas content up to 20%
  • Cast iron/Bronze/Stainless steel, Nodular cast Iron, All-Bronze, Stainless Steel, or Super-Duplex Stainless Steel construction
  • Completely replace the “old” DAF system with a single pump

Download the Brochure | Ask Our Team

Trailer mounted multi-purpose machines designed to speed up and simplify the deployment of emergency response equipment for municipalities, emergency services and contractors.

Advantages include:

  • Enables deployment of multiple pieces of equipment, using only one vehicle.
  • Diesel-driven power generator complete with variable frequency drive [VFD] powers a lighting tower and a rugged and reliable Gorman-Rupp pump.
  • The cleverly designed unit can light up a work area while operators set up the self-priming pump or operate numerous electric tools from the power generator.
  • The VFD allows for soft starting electrical equipment, including the pump, and can vary the speeds of these machines to suit the duty at hand. While all this is happening, the compressor can be driving air nibblers, air-operated nail guns, wrenches or tyre inflators.
  • The Lampo units also come standard with an air compressor, discharge hose reel, suction hoses and a robust mounted toolbox.

The central components of the Lampo – the generator, VFD and lighting system are manufactured by quality equipment manufacturer, Euromacchine in Italy. They are housed in an acoustically rated enclosure constructed from powder-coated galvanised steel plates.

The Lampo multipurpose units are then mounted on an Australian heavy-duty built hot-dip galvanised double axle trailer and fitted with a self-priming Gorman-Rupp trash pump.

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Hydro’s experts are standing by to help you get the best pump, aerators and genuine spare parts for your specific project.

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Over 88 years

Of Team Experience in Abattoir Pumping.

We bring you the technical knowledge & experience

We are leaders in Self Priming Centrifugal Wastewater Pump Technology. Hydro Innovations is the exclusive distributor of Gorman-Rupp pumps for all the municipal and industrial markets in Australia. Gorman-Rupp is one of the world’s leading manufacturers of self-priming sewage pumps and wastewater pumping equipment and has been for more than 75 years.

Holding a very large inventory of pumps and spare parts allows us to deliver industry-leading service. With over 88 years combined experience in applying, selecting and troubleshooting pumps, we are also in a good position to help design the best and most cost-effective fluid transfer systems for our customers.

Aricles and Projects Self Priming Raw sewage pumps

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