Self Priming Pumps:

Where to use them, why to use them, and the misconceptions

gorman-rupp self-priming pump training

Self priming centrifugal pumps are often overlooked because they are not as commonly used as either standard centrifugal pumps or submersible pumps, and not understood by many who specify pumps. They can be misapplied  to pumping applications by people not properly trained in their application or who do not fully understand their applications.

WHAT IS A SELF PRIMING PUMP?

self priming pump is like any other centrifugal pump, but it is designed with an external casing that “floods” the inner pump or volute. The casing is filled with liquid [usually the same as the liquid to be pumped] and the pump is ready to go. When the impeller rotates in the casing, a low pressure area is formed at the eye of the impeller. Because the pressure is lower than atmosphere, water is pushed up the suction pipe by atmospheric pressure, forcing all the air in the suction line into the pump. The self priming pump mixes the air with the recirculating water in the casing. The air separates from the liquid and is discharged from the casing. When all the air in the suction line has been displaced, the pump is dynamic and delivers flow like any other centrifugal pump.

Centrifugal-pump-drawing-1

WHERE TO USE THEM?

Self-priming centrifugal pumps can be applied to any application that standard centrifugal pumps are applied, within their hydraulic limitations. Applications from water, fuels, effluent or “grey water”, right through to raw sewage, industrial wastewater and sewage sludge can be effectively handled by self-priming centrifugal pumps. Provided they are within their hydraulic limits, and they are manufactured with the right features for their intended duty, self-priming pumps can deliver the safest and most cost-effective of pump solutions.

Gorman-Rupp grey water super u series

WHY USE A SELF PRIMING PUMP?

Self priming pumps are mounted above the liquid source [generally at “ground level”], so less infrastructure is required to set them up. And because they are located at ground level, they are easier to access and much easier to maintain and repair. As there is no mechanical equipment in the wet well, there is no need to open wet well lids, and there is no need for hoists or cranes [as in the case of submersible pumps], making them a much safer option for operators.

why use a self priming pump?

HOW TO APPLY SELF PRIMING PUMPS

Firstly, the right type of pump needs to be selected for the duty [fuel pumps for fuel applications, solids handling pumps for wastewater applications etc].

The right size pump for head and flow then needs to be selected.

Then, an NPSH calculation needs to be done to ensure there is enough atmospheric pressure to support the intended flow, and the speed of the pump needs to be fast enough to prime the pump.

Selection of the suction line size is also important. It needs to be large enough to support the desired flow, and small enough to keep priming times to a minimum. It is best to avoid long suction lines, but if there is no choice, keeping part of it full during priming cycles will help [talk to Hydro Innovations about the “P Trap” design].

edur self priming pump performance

WHAT ARE THE LIMITATIONS OF SELF PRIMING PUMPS?

Self-priming centrifugal pumps are limited in their suction lift [usually a maximum of 7.6m]. Some claims by some that 8.0 or even 8.5 metre suction lifts are possible are misleading. Although some pumps in Australia may be able to generate a vacuum in excess of these figures [as can Gorman Rupp pumps], they cannot physically pump on these lifts because of limitations in NPSH of the pump, the temperature of the liquid, and friction losses in the suction line.

A single pump is also limited to a flow rate of about 300 litres per second. And heads above 90 metres are also difficult to achieve for true self-priming pumps.

Gorman-Rupp above ground self-priming pump station

MISCONCEPTIONS ABOUT THE USE OF A SELF-PRIMING PUMP

Some of the misconceptions about the self-priming pump are as follows:

1. Self-priming pumps need to be re-primed with water after a pumping cycle. This is not the case with “guaranteed re-primers”, like Gorman-Rupp’s Super T, Super U, and Ultra V. These pumps only need to be charged with liquid once, and they retain enough liquid in their casings to guarantee re-priming each and every time they are called upon to pump.

2. Self-priming pumps are inefficient. In most cases, the hydraulic efficiency of a self-priming pump will not be as high as that of a standard centrifugal pump or submersible pump. If engineers looked no further than this, self-priming pumps would never be used, and asset owners would pay a lot more for infrastructure costs and/or the maintenance of these pumps for the life of the asset. But as many engineers and asset owners have found, the cost savings in infrastructure and maintenance can far outweigh the savings one may achieve in selecting a slightly more hydraulically efficient pump.

3. Self-priming pumps are too expensive. It is true that self-priming pumps are more expensive than standard centrifugal pumps. This is because there is a lot more material [because of the need for an outer casing], more components and more machining. This should be weighed up against the capital cost savings [no dry well], the ease of access and the ease of maintenance offered by a self-priming pump. Also, some self-priming pumps are more expensive than others. Again the facts need to be weighed up. A pump purchased that has been engineered and produced by a company that has been manufacturing pumps for over 80 years [like Gorman-Rupp] can be considered as an investment in reliability. Pumps manufactured by companies attempting to copy market leaders will invariably not be able to meet efficiency, quality, repeatability and reliability standards of the market leaders, and purchasers can rightly consider these as costs.

Ready to build the perfect pump system for your project? We’re standing by to help.

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Gorman-Rupp 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

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

TROUBLESHOOTING SELF PRIMING CENTRIFUGAL PUMPS

The self-priming pump is one of the easiest pumps to troubleshoot if you have all the right tools. You will need a good set of gauges and the manufacturer’s performance curve for the particular pump you are analysing.

Issues with the pump are often problems with the system. A good set of gauges will lead you to the problem:-

– A high discharge gauge reading points to a blockage in the discharge line

– A high suction reading points to blockage in the suction line.

– A low or no suction gauge reading points to a suction leak

– A fluctuating suction gauge points to vortexing or some other form of air entrainment.

– A low reading on both suction and discharge gauges points to a problem with the pump.

Some common troubleshooting issues include:-

– Noisy operation.

– Pump won’t prime or is slow to prime.

– Pump stops or fails to deliver rated flow.

– Pump clogs frequently.

Centrifugal-pump-drawing-1

Noisy operation

The first thing to establish when confronted with a noisy pump is whether the noise is mechanical or hydraulic. To determine this, drain the liquid from the pump casing and run the pump for a short period of time. If the noise is still apparent, the problem is mechanical. Check for loose hardware and bearing noise [both pump and motor].

If the noise has gone, the problem with be hydraulic. It can be cavitation, vortexing or air entrainment.

Cavitation is the most damaging. A dictionary defines cavitation as “the formation of partial vacuums in a flowing liquid as a result of the separation of its parts. When these collapse, pitting or other damage is caused on metal surfaces in contact”. In pumping systems, negative pressure can and will be created in certain areas. If this negative pressure exceeds the vapor pressure of the liquid being pumped, vacuum bubbles form and remain until they migrate through the system and find enough local pressure to cause their collapse. When these vacuum bubbles collapse, the concentrated force of implosion can exceed 100,000 PSI. If this implosion occurs next to metal, it is likely to cause a tiny chip to flake off the surface.

Torubleshooting Pumps Cavitation

Cavitation will sound like the pump has rocks or marbles going through it. The most accurate way to detect cavitation is to take gauge readings [both suction and discharge], obtain an accurate speed [rpm] of the pump shaft, then look at the pump performance curve to determine where the pump is operating. If the suction gauge reading is higher than it should be, the problem will be suction cavitation. The cause could be: blockage in suction line [clear blockage]; Suction line too small [increase size of line]; suction lift too high [raise the off level or get the pump closer to the water].

If the discharge gauge reading is too high, the pump will be suffering discharge or “tip” cavitation. The discharge line could be blocked [remove blockage], or the discharge line could be too small, or the static head could be too high. These conditions can often be overcome by increasing pump speed, but check gauge readings against manufacturer’s performance curve to determine the correct course of action.

An-impeller-showing-signs-of-“tip”-cavitation

If the suction gauge is fluctuating and the pump is making a growling noise, the problem will be vortexing. This means that the pump is pulling air from the surface of the liquid. Often a whirlpool will form on the surface, but not always. This can be solved by lowering the suction line, increasing the diameter of the suction line inlet [suction “bell”], or lowering the off level.

If the pump won’t prime or is slow to prime, there could be a suction leak. Check this by wrapping cling wrap around each joint. Repair the joint where the cling wrap is “sucked in”. If there is no leak, the suction line may be too long or its diameter too large. These things could possibly be solved by speeding the pump up, reducing the pipe diameter or construction a “P Trap”. Talk to Hydro innovations about this.

If the pump stops or fails to deliver the desired flow, check the gauges. A high suction reading will indicate a blocked or partially blocked suction line. A high discharge gauge reading will indicate a blocked or partially blocked discharge line. If both gauges are low, the pump may need a clearances adjustment or the pump may have a blocked or partially blocked impeller.

suction line shown with bell mouth

If the pump is blocking frequently, check where the pump is operating on its curve. If it is too far left, it may not have the velocity through the pump to avoid blockages. Speed pump up. If the pump is operating at its BEP [best efficiency point], the pump may not be suited to the application. Hard to fix without changing pumps [unless the pump can be upgraded with a solids handling impeller, cutting mechanism or other form of solids handling system] or fitting a strainer to the suction line [which may only move the problem].

gorman-rupp-removable-coverplate

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

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Self-Priming Centrifugal 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

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The Gorman-Rupp 80 Series range of self priming centrifugal grey water are heavy duty 24/7, quick priming “work horses” for industry. With multi-vane impellers and a “straight-in” suction design, the 80 Series pumps deliver high efficiencies and quick positive self priming.

Advantages include:

  • Ability to mount high and dry above the wet well [not in it]
  • Capital cost savings over wet well/ dry well constructions
  • Low cost of ownership
  • Greatly reduced OH&S issues
  • Easy access for monitoring or service

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The Gorman-Rupp Super U Series self priming dewatering and grey water pumps combines the best features of quality trash pumps in Australia with increased fuel efficiency and higher heads to pump through smaller and/or longer discharge piping systems or overcome the losses in filter systems.

These centrifugal pumps have been designed for economical, heavy duty (24/7) trouble-free operation.

Advantages include:

  • Ability to mount high and dry above the water (not in it)(to 7.6m)
  • 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
  • Any engine brand required by the customer
  • Choice of skid or trailer mounted configuration

Ask Our Team

The Gorman-Rupp 10 Series grey water pump range of self priming centrifugal pumps and effluent pumps have been delivering excellent service to industry since 1946. With large inspection cover to access pump internals for service or blockage removal and a very thick vaned solids handling impeller, 10 Series pumps are the choice for many an abattoir, concrete batch plant or chemical plant.

Advantages include:

  • Ability to mount high and dry above the wet well [not in it]
  • Capital cost savings over wet well/ dry well constructions
  • Low cost of ownership
  • Greatly reduced OH&S issues
  • Easy access for monitoring or service
  • Improved maintenance features to greatly reduce maintenance time and costs
  • A variety of materials of construction to handle abrasive and/or corrosive fluids

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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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.

Articles and Projects Self-Priming Centrifugal Pumps

Wastewater Pump Selected For Safety and Reliability

A NSW fruit juice manufacturer has recently selected Gorman-Rupp self priming pumps for their wastewater pump service. They selected Gorman Rupp pumps because they were the safest option for their operators, and because they considered them the most economical solution, according to Gorman-Rupp distributors, Hydro Innovations. Gorman-Rupp self priming pumps are installed at ground level, […]

Pump Products And Repairs | Preventative Maintenance‎

When things are running smoothly it’s easy to overlook common pump maintenance tasks and not complete regular inspections and check pump parts. But a neglected pump can cause major headaches and even plant shut-downs if it fails. A stitch in time, saves 9.

At Hydro Innovations, we carry plenty of spare parts, and can ship quickly, but prevention is better than cure.

Coliban Water Plant Chooses Gorman-Rupp Pump

Coliban Water choose Gorman Rupp self-priming pumps at their new recycled water C-B polishing plant.

The project Engineer wanted robust  pumps that could handle a wide range of water conditions to supply the new plant.  Gorman Rupp pumps where chosen for this situation.

Ready to build the perfect pump system for your project? We’re standing by to help.

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