Key features
L54 at 14 m³/h through to 76M at 420 m³/h, so one range covers transfer duties a standard-geometry pump cannot reach.
Pressure does not vary with size on the RL. If the duty needs more than 6 bar, it needs a different Roto range.
Roto's extended rotor and stator geometry runs at lower rubbing velocities than conventional geometry, and ties that to less wear on abrasive media.
Rated to 15,000 cSt kinematic viscosity, up to 7% solids, and up to 150°C.
Suction lift to 9.5 metres water column, and the pump will run on snore.
The stuffing box is externally mounted, so gland packing or a mechanical seal is maintained without dismantling the bearing housing.
About the Roto RL series
The RL is the extra-large-capacity end of Roto's progressive cavity range, and it is the only part of that range built on extended rotor and stator geometry. The 18 sizes run L54, 54M, L57, 57M, L59, 59M, 61M, L63, 63M, 65M, L67, 67M, L71, 69M, 71M, L75, 73M and 76M, from 14 to 420 m³/h, in close-coupled or bare shaft configuration. Roto rates the range to 15,000 cSt, up to 7% solids and up to 150°C, and points it at sewage and effluent treatment.
The RL is not a bigger RD, and treating it as one is how the selection goes wrong. The RD and RM are standard geometry and Roto lists them as multi stage, to 48 bar. The RL is extended geometry and Roto lists it as single stage, at 6 bar, and that 6 bar applies to L54 at 14 m³/h exactly as it applies to 76M at 420 m³/h. The RL buys volume by giving up pressure. Size it against the discharge pressure first, because that is the figure that rules it in or out.
The viscosity rating catches people out too. The RL is rated thinner than the small RD, not thicker: 15,000 cSt against the RD's 30,000. Bigger does not mean it handles more. If the medium is heavier than that, or if it will not flow into a standard suction on its own, the wide throat WM is the build to look at rather than a larger RL.
Where the RL earns its place is a low-head duty with something in the medium. Digested sludge, effluent, a shear-sensitive product, anything that needs metering rather than throttling: flow is proportional to shaft speed and largely independent of discharge pressure, so the pump holds its rate as the system changes. If the medium is clean and as water and you simply want 300 m³/h moved against a few metres of head, this is the wrong pump. A centrifugal will cost less to buy, less to run, and will not have a stator in it.
The stator is the real cost of ownership. It is an elastomer wear part, it has to be matched to the medium, and it is the component you will be buying again. Dry running is what kills it: with no liquid to carry the heat away the stator burns out and takes the rotor with it, in minutes rather than hours. Roto's dry running protection device screws a temperature sensor into the stator wall and trips the pump at a preset temperature, and on any duty where the suction can be lost we would fit one. Abrasive media want pumping slowly, for the same reason.
Send us the flow, the discharge pressure, the medium and how thick it gets, the solids content, and how the pump is fed. If the answer is an RL we will size it. If the answer is a centrifugal, we will say that instead.
How the Roto RL series works
The wet end is two parts. A precision-machined single external helix rotor turns inside a double internal helix elastomer stator. The rotor profile holds a sealing line along the axis of the pump, static and dynamic, so cavities form at the suction end and progress along the pump to discharge. Each revolution carries a fixed volume. That is why the flow is metered and near enough non-pulsating, why capacity is proportionate to speed, and why the head the pump develops is not.
What makes the RL an RL is the geometry of that rotor and stator pair. Roto's extended geometry runs at lower rubbing velocities than conventional geometry, which matters most on abrasive media, and Roto credits it with lower starting torque, an effective sealing line and better volumetric efficiency, so less power for the same duty and a longer service life. A progressive cavity pump develops its pressure stage by stage, and the RL is a single-stage pump. That is why the whole range sits at 6 bar while the multi-stage standard-geometry sizes reach 48.
The housing is sloped to cut entry losses and to drain, and the suction port rotates in steps of 90° to suit the pipework. The stator has a tapered entry, which eases fluid in and improves suction capability. The range is self-priming to 9.5 metres water column and will run on snore, so it needs no foot valve. Torque reaches the rotor through double-sealed cardan universal joints. Each joint uses two sets of perpendicular pins, which gives freedom of angular movement and smoother transmission of angular loads, and it is built to take the high axial forces that dominate in a progressive cavity pump. The bearing housing is separate from the wet end, so the medium is not contaminated by it.
The build is what you actually specify. Housings come in cast iron, cast stainless steel, fabricated steel or fabricated stainless steel, with rubber lining or epoxy coating where the medium attacks the casing. Rotors come in tool steel, case-hardened steel, alloy steel or stainless steel, with ceramic, tungsten carbide or hard chrome coatings for abrasive duty. Coupling rods and shafts are alloy steel or stainless steel, and Roto will quote duplex, super duplex, Alloy 20 and Haste Alloy where the chemistry demands it. Stator elastomers run natural rubber, nitrile, high nitrile, EPDM, chloro-sulphonated rubber, fluoroelastomer, Aflas and HNBR. That elastomer is the material decision that matters most: get it wrong for the medium or the temperature and the stator swells, hardens or is attacked, whatever the housing is made of.
Shaft sealing is gland packing or a mechanical seal, chosen from Roto's seal codes. Codes M and L are single-acting elastomer bellow seals rated to 12 bar for sewage duties, which is the duty Roto points the RL at. N and P are wave-spring seals to 25 bar and R and S multiple-spring seals to 25 bar, all for solids-laden or corrosive media. T is a double-acting seal to 25 bar for toxic, food and pharmaceutical media, and V is a metal bellow seal to 12 bar for high temperature and high viscosity work such as bitumen and asphalt. Tell us the medium and the temperature and we will specify the seal with the pump, not after it.
Specifications
| Sizes | L54, 54M, L57, 57M, L59, 59M, 61M, L63, 63M, 65M, L67, 67M, L71, 69M, 71M, L75, 73M, 76M | extra large capacity, extended geometry |
|---|---|---|
| Flow rate | 14–420 m³/h | L54 to 76M |
| Pressure | 6 bar | every size in the range |
| Viscosity | up to 15,000 cSt | |
| Temperature | up to 150°C | |
| Solids handling | up to 7% | |
| Suction lift | up to 9.5 metres water column | |
| Configuration | close-coupled or bare shaft | single stage |
| Housing materials | cast iron, cast stainless steel, fabricated steel, fabricated stainless steel | rubber lining or epoxy coating available |
| Rotor materials | tool steel, case-hardened steel, alloy steel, stainless steel | ceramic, tungsten carbide or hard chrome coatings available |
| Stator elastomers | natural, nitrile, high nitrile, EPDM, chloro-sulphonated rubber, fluoroelastomer, Aflas, HNBR | |
| Shaft sealing | gland packing or mechanical seal | Roto seal codes M, L and V to 12 bar; N, P, R, S and T to 25 bar |
Channel Pumps sizes and supplies the Roto RL series. Send us the flow, the discharge pressure, the medium and its viscosity and temperature, the solids content, and how the pump is fed on the suction side. We will come back with the size, the stator elastomer and the sealing arrangement, and tell you plainly if the duty wants a centrifugal or a wide throat pump instead.
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Frequently asked
What flow and pressure does the Roto RL series cover?
The RL series covers 14–420 m³/h across 18 sizes, from L54 at 14 m³/h to 76M at 420 m³/h. Every size is rated to 6 bar. Unlike the RD and RM, pressure does not fall as capacity rises, because it never rises in the first place.
Why is every Roto RL size rated to 6 bar?
Because the RL is a single-stage pump. A progressive cavity pump develops its pressure stage by stage, so more pressure means more stages. Roto lists the extended-geometry RL under single stage at 6 bar, and the standard-geometry RD and RM under multi stage to 48 bar. If your duty needs more than 6 bar, you need standard geometry, not a larger RL.
What is the difference between the Roto RD and RL series?
Geometry, capacity and pressure. The RD is standard geometry, 0.11–17 m³/h, and reaches 48 bar. The RL is extended geometry, 14–420 m³/h, and every size sits at 6 bar. The RM fills the middle on standard geometry at 4–250 m³/h. The RL is also rated thinner, to 15,000 cSt against the RD's 30,000, so it is not simply a larger version of the same pump.
What sizes are in the Roto RL series?
There are 18. L54, 54M, L57, 57M, L59, 59M, 61M, L63, 63M, 65M, L67, 67M, L71, 69M, 71M, L75, 73M and 76M, in close-coupled or bare shaft configuration.
Can a Roto RL handle sludge and solids?
Yes, and that is what Roto builds it for. The range is rated to 15,000 cSt kinematic viscosity, up to 7% solids and up to 150°C, and Roto points it at sewage and effluent treatment. The stator elastomer has to match the medium, so tell us what you are pumping and how hot it gets.
Is the Roto RL self-priming?
Yes. Roto quotes suction lift of up to 9.5 metres water column, and the pump will run on snore, so no foot valve is needed. Suction conditions still decide whether the pump survives, so give us the tank level and the suction pipework when you enquire.
When should you choose a centrifugal pump instead of a Roto RL?
When the medium is clean and as water and the duty is high flow against modest head. At that duty a centrifugal costs less to buy, less to run, and has no stator to replace. The RL earns its keep when the medium carries solids, is shear-sensitive, or has to be metered.