What drives pump and piping selection for bitumen is not how easily the product flows at normal operating temperature, but how quickly it stops flowing when it cools. Depending on temperature, bitumen behaves like anything from a near-solid to a readily pumpable liquid. A sound transfer system therefore has to do more than move hot product: it must start a cold pump safely, stand idle without plugging its lines, and never push the product past its safe temperature limit.
The general rules for sizing pumps and lines in viscous service, such as suction conditions, pressure loss and line diameter, are covered on the viscous product transfer page. Here those rules are applied to problems specific to bitumen: jacketed positive displacement pumps, cold starts, shaft sealing, pressure relief and line clearing.
Why bitumen is harder to move than other viscous products
· A narrow temperature window with a hard ceiling: The product has to be heated to be pumped, yet Eurobitume recommends maximum handling and storage temperatures of 200 °C for bitumen and air-rectified bitumen and 230 °C for severely oxidized grades, mainly to avoid flammable atmospheres and limit emissions. Heating must eliminate cold spots without breaching that ceiling.
· Shock cooling on cold surfaces: Hot bitumen entering a cold pipe chills against the wall and can narrow the bore. A partial blockage builds back pressure and can produce a fine spray of hot product when a connection is broken.
· Heating that causes its own problems: Tracing that runs too hot or stays on too long can leave carbon deposits that also restrict the bore, so heating has to be both sufficient and controlled.
· Hydrogen sulfide in vapor spaces: H2S is commonly present in the vapor space of tanks and vehicles holding hot bitumen, so pump stations and line connections are laid out to keep operators clear of emission plumes.
Pump type: why positive displacement is the usual choice
On viscous liquids, centrifugal pumps lose efficiency, head and flow, while input power and starting torque rise. Rotary positive displacement (PD) pumps behave the other way: higher viscosity reduces internal slip and improves volumetric efficiency, and they can handle far more viscous liquids than centrifugal designs. Internal gear pumps are widely used on bitumen partly because they can be built with heating jackets, robust gear materials and a range of sealing arrangements.
That does not mean every bitumen line gets the same pump. Flow rate, discharge pressure, product grade (paving, polymer-modified or oxidized), whether the duty is loading or unloading, and the operating pattern of the station all feed into the choice. Because the inlet pressure a PD pump needs also increases with viscosity, the pump is placed low and close to the supply tank or vehicle outlet.
Jacketed pumps and cold starts
The most demanding moment for a bitumen pump is start-up. During a shutdown, product left in the casing, behind the rotor and in the relief valve can cool and solidify. That is why it matters that the heating jacket covers both the casing and the relief valve, and that jacketing behind the rotor removes a well-known cold spot; without it, hard starts and early pump or seal failures are likely. Steam or thermal oil can serve as the heating medium, usually chosen to match the site's existing heating system.
In practice, the motor should not be started until the pump body and the connected pipe spools have reached working temperature. A written start-up procedure defines the preheating time, a temperature permissive and a check that product flows freely. The same procedure should also cap heating time to reduce the risk of coking.
Shaft sealing
Packing is still the most common shaft seal on bitumen pumps, but packing has to leak slightly to run reliably. Where leakage is not acceptable, cartridge lip seals or mechanical seals can be used, ideally with a quench that heats the seal, keeps air out and prevents bitumen from coking near the seal faces. The right choice balances burn hazard from hot product, housekeeping effort and maintenance intervals.
Pressure relief and blockage scenarios
A PD pump that keeps running against a closed valve or a plugged line will raise pressure rapidly, so a relief arrangement is fitted on or directly downstream of the pump. On bitumen that relief valve must be heated too, because product frozen inside a cold relief valve can leave it unable to open. Storage tanks are not pressure vessels either, so inflow has to be matched to the tank's venting capacity. When a ground-based pump unloads a road tanker, its rating must also suit the vehicle's vent capacity; that topic is covered in more detail on the bitumen unloading page.
Line routing, heating and clearing
The most effective defense against blockage is the pipe route itself. Industry guidance calls for short runs, a fall toward the tank so the line drains, and as few bends as possible; long runs, many bends, cold spots and poor venting are recognized causes of blockage and back pressure. All bitumen pipework should be insulated, and trace heating is strongly recommended, particularly for stiffer grades such as polymer-modified and hard bitumen. Partial tracing is not recommended. Jacketed pipe and jacketed loading arm design are covered on a separate page.
Between transfers, lines can be protected in three basic ways: continuous circulation, holding them hot with tracing, or draining them. Which one fits depends on how often product moves, how long the line is and how much energy the site is willing to spend. Where lines are blown clear with gas, the volume of air pushed into the receiving tank should be kept to a minimum to avoid creating a flammable headspace.
Selection criteria
Parameter | Why it matters in design | Effect on selection |
Grade and viscosity–temperature data | Polymer-modified and hard grades flow less readily at the same temperature | Pump type and size, heating intensity, line diameter |
Maximum product temperature | Recommended ceilings are based on flammable-atmosphere and emission risk | Heating medium temperature and control scheme |
Operating pattern | Continuous transfer and intermittent batches carry different idle-time risks | Circulation, hold-hot or drain-down strategy |
Pump location and suction | Required inlet pressure rises with viscosity | Distance and elevation relative to tank or vehicle |
Available heating utilities | Steam, thermal oil or electric tracing may already exist on site | Heating method for pump jacket, valves and lines |
Leakage tolerance | Packing leakage creates housekeeping and burn hazards | Packing, lip seal or mechanical seal with quench |
Pipe route | Length, number of bends and slope govern blockage risk | Layout, drain points and tracing circuits |
How TLY Enerji can support the project
Depending on project scope, TLY Enerji can provide engineering support for a bitumen transfer line: reviewing process data, supplying pumps, valves and instruments, defining temperature and pressure monitoring points, configuring PLC-based permissives and interlocks, and handling site installation, testing and commissioning. Which party supplies the pump jacketing and line heating is agreed through the technical specification for each project.
Data we need to assess your application
· Bitumen grades to be handled and supplier viscosity–temperature curves
· Storage and transfer temperatures, plus the maximum temperature defined for each product
· Required flow rate, line length, elevation changes and number of bends
· Type of transfer: tank to tank, truck loading or truck unloading
· Heating utilities available on site: steam, thermal oil or electric
· Typical idle periods and your preferred way of protecting the line when idle
· Acceptable leakage level and any maintenance access constraints
Related pages
· Viscous product transfer systems: General principles for sizing pumps and lines in viscous service.
· Jacketed piping and loading arm systems: Jacket design, heat continuity and thermal expansion on bitumen lines.
· Bitumen truck unloading systems: Unloading with a ground-based pump and matching vent capacity.
· Bitumen metering skids: Choosing measurement technology for hot, viscous bitumen.
· Heat tracing systems: Comparing electric and steam tracing methods.
Frequently asked questions
Can a centrifugal pump be used for bitumen?
There may be cases where it works, but centrifugal pumps lose efficiency, head and flow as viscosity increases, and they need more power and starting torque. For high-viscosity bitumen, rotary positive displacement pumps are therefore usually the first option considered. The final decision depends on grade, transfer temperature, flow rate and discharge pressure taken together.
How do you start a cold bitumen pump safely?
The casing, the space behind the rotor, the relief valve and the connected pipe spools are heated until the product is fully fluid. The motor should not start until a temperature permissive is satisfied and free flow is confirmed. Preheating time and checks belong in a written procedure, which should also limit unnecessary heating to avoid coking.
Is partial heat tracing enough on a bitumen line?
Industry guidance advises against it. An unheated valve, flange or short spool becomes a cold spot where hot product can solidify on the wall and restrict the bore. The recommended approach is to insulate the whole line and extend tracing over valves and fittings, while avoiding overheating that can lead to carbon deposits.
Should a bitumen line be left full or drained after transfer?
Both approaches are used. On short, frequently used lines, circulation or holding the line hot with tracing is often practical; long lines that see occasional use may be better drained. If gas is used to blow the line clear, the air sent into the tank should be minimized because it can create a flammable atmosphere in the headspace.