Bitumen Overview
Bitumen is an important material used in a wide range of industrial processes such as refining, pipe coating and in road, pavement, and roof construction. Also referred to as asphalt, it is insoluble in water and has glue like properties that allow it to bind with aggregate particles to create strength. Once set it seals the surface and protects against water ingress. These excellent properties combined with its durability, economical cost and huge supply continue to make it a popular solution today.
Bitumen needs to be handled at high temperatures in its liquid form, most commonly around 140 to 170°C, this state allows it to be sprayed, transferred, or unloaded to be used in processes such as mixing with aggregate and laying roads. Even when hot it is viscous, these properties combined with its sticky nature require very careful consideration during the pump selection process.
Tanker Loading of Bitumen
An engineering consultancy group specialising in the energy and industrial sectors secured a €2.1 million project for upgrading a fuel and bitumen processing plant. Chemical Processors, manufacturers and storage terminals are often located at ports to enable the quick and efficient transport of bulk liquids via tanker loading and unloading.
This upgrade involved increasing the number and capacity of tanks for delivering higher volumes to tankers, this therefore included the installation of larger positive displacement pumps to deliver high flow rates in a shorter amount of time, accommodating larger vessels, and reducing vessel waiting time. Having a very limited time frame for supply and requiring pump selection support, they approached North Ridge in the hopes we could support them in an efficient manner, which we did.
Pump Optimisation for Asphalt
This project required 6 units in 3 different sizes, with differing internal design (External and Internal Gear) to produce the varying flow rates and pressure demanded on site.
The 4” and 10” Pumps were handling Bitumen with a possibility of 1mm solids, and so External Gear pumps operating slowly with hardened teeth for minimising wear, were selected as the solution for handling this blend of high viscosity asphalt. Due to the size of pumps selected, their internal tolerances meant they are able to accommodate 1mm suspended solids without issue. We did however recommend that inlet strainers were installed to capture any particles above this size which is something we always recommend with gear pumps.
The smaller flow rate of 5M³H of clean Asphalt without solids meant two 2” Internal Gear Pumps were selected for this duty as they were better suited to handle the clean blend.
Experience has taught us to specify larger gear pumps installed with gearboxes, to reduce the operating speed to as low as 250RPM. This gentler pumping action allows the passing of viscous fluids, with small solids whilst reducing gear wear from the abrasive and tacky nature of the bitumen.
As bitumen can cool quickly and increase viscosity or harden completely, we typically recommend units are fitted with heating jackets to prevent this from occurring, on this occasion the customer had already installed trace heating on the pipework and had a readily available solution for the pumps also.
To further protect the units from damage, we fitted gland packing instead of mechanical seals, as if the bitumen were to harden then gland packing is less susceptible to damage when the pump starts up again.
As the asphalt pumps are used to fill tankers and trucks, it is possible that a discharge valve may be closed during loading operations, therefore we installed each unit with built-in pressure relief valves to protect the units and system components. The valve is normally set to 10% above the operating pressure, it then opens if the system pressure increases too high and recirculates the fluid inside the pump head to avoid damaging the pipework or the pump itself.
Outcome
We delivered two 2” Internal Gear Pumps, two 4” External Gear Pumps and two 10” External Gear pumps, the largest unit delivering 250m³/hr at 9 bar, all fitted with ABB Atex motors suitable for installation in non-safe areas.
The site now has reliable and robust bitumen pumps which will enable increased plant output and productivity, ensure larger bulk carriers can be accommodated, decrease tanker loading time, and reduce the likelihood of vessel demurrage.
The varying sizes of pumps and flow rates allow the plant to remain flexible in loading a range of bulk carriers and vehicles simultaneously, regardless of their location on site.
If you have an application you are unsure of the correct solution, visit www.northridgepumps.com to see how we can help.
