For foundry sand conveying, engineers first define the process duty, operating range and system resistance before selecting a blower. Foundries move large quantities of silica, chromite, zircon and other moulding sands between storage, preparation, moulding and reclamation systems. Pneumatic conveying can provide enclosed transfer with flexible routing, but sand is dense and abrasive. Incorrect system design can produce severe pipeline wear and grain degradation. For this foundry and metal casting duty, selection depends on material or gas behaviour, the feeder or pickup, pipework, separation, filtration, controls and the operating cycle. The process designer defines capacity and product requirements, while the blower supplier confirms performance against the specified operating limits.
Application and Process Requirements
The system may transport: new silica sand, reclaimed silica sand, chromite sand, zircon sand, olivine sand, ceramic foundry media, coated core sand, green-sand return and dry no-bake sand. Each material has different density, grain shape, hardness and flow behaviour. The material should be reviewed at the condition in which it actually enters the system. Storage time, aeration, compaction, temperature and prior handling can change how a powder or granule flows. Those changes affect feeder output and the amount of gas needed to keep transfer stable. A trial with representative material is especially valuable when the product is cohesive, friable, hygroscopic or abrasive, because a generic name does not define its behaviour in the pipeline or receiver. A positive-pressure system normally uses: roots blower, pressure vessel or blow tank, conveying pipeline, diverter valves, receiving silo and vent filter. The blower supplies clean air before the sand enters the pipeline. For dense sand, a pressure vessel may provide more reliable feeding than a rotary airlock. Flow and pressure should be treated as a paired requirement. A blower may deliver an approximately fixed volume per revolution, but the installed system determines the pressure needed to move gas through its restrictions. Use a stated reference basis for any standard or free-air figure, then convert it to the conditions at the inlet or process connection. The pressure budget should include fittings and equipment losses as well as the straight pipe, and should be checked for both normal operation and the expected high-resistance case. The engineering record should state the blower duty point, differential pressure and discharge temperature on one consistent reference basis.
Vacuum systems can collect sand from multiple sources and draw it toward a central receiver. The roots vacuum blower should be installed after receiver, sand separator, main filter and safety filter. Abrasive particles must not reach the blower. For a vacuum system, the design team should define the required absolute pressure, evacuation time and steady leakage load separately. These values can differ substantially between pump-down and holding. Filters, hoses and receivers operate at the lower pressure and therefore see a larger actual gas volume than the equivalent reference flow. The machine should be protected against dust carryover and sudden isolation, and the control sequence should prevent a leak or damaged connection from affecting every user on a common header.
System Design and Blower Selection
High air velocity can cause grain breakage, creation of fines, bend wear, pipeline erosion, receiver damage, higher filter loading and loss of sand quality. The preferred system normally uses the lowest velocity that provides stable transport. The design calculation should distinguish actual inlet volume from standard or reference volume and should use absolute pressure where gas expansion or compression is involved. After establishing the required flow, add the losses from the complete route and compare the resulting differential pressure with the approved machine data. A single nominal point can conceal a high-pressure start-up or a low-flow operating condition, so the control range and credible extremes belong in the same review. The engineering record should state the blower duty point, differential pressure and discharge temperature on one consistent reference basis. Moulding performance depends partly on grain-size distribution and shape. Excessive conveying damage can change: permeability, binder demand, surface finish, compaction behaviour, gas evolution and reclamation efficiency. Conveying should preserve usable grain structure. A material assessment should connect physical properties to the components that handle it. Fines can raise filter loading, moisture can promote adhesion, and hard or sharp particles can accelerate wear at bends and valves. Fragile granules may lose their specified size distribution if velocity or impact is too high. The engineer should confirm these risks against samples from the intended supply stream and specify inspection access where the material can accumulate or damage surfaces.
Bends are common wear locations. Possible protection includes long-radius bends, wear-backed elbows, replaceable sections, ceramic or hardened liners, reduced velocity, gentle direction changes and maintenance access. Wear monitoring can prevent sudden sand leakage. A useful process description connects the production objective to measurable equipment conditions. It identifies the source, destination, intermediate vessels and the events that change flow, such as a batch change, a valve movement or a filter-cleaning cycle. This context helps the design team decide whether a continuous or intermittent duty is involved and whether the blower can serve one circuit or several. It also prevents a nominal capacity figure from being mistaken for a complete system design.
Operation and Reliability
Fill the pressure vessel. Close and seal the inlet. Pressurize the vessel. Open the conveying valve. Transfer sand. Purge the line. Depressurize. Refill. Valve timing affects conveying stability and blower pressure. Wet sand can: bridge in hoppers, block conveying lines, blind filters, adhere to valves, corrode equipment and create inconsistent feeding. Moisture is a separate design consideration. Pneumatic conveying is normally better suited to dry, free-flowing sand. Good system design makes the relationship between the air mover and the process visible. It sets a defined duty point, includes the resistance of connected equipment and identifies which variables operators can change safely. Pipe routing, filter access, valve position and discharge conditions should be resolved before installation. The package can then be commissioned against an agreed operating range rather than tuned by trial and error after production begins. The destination silo must include adequate vent filtration, level control, high-level alarm, pressure monitoring, safe discharge and structural pressure protection. A blocked silo filter can raise pressure throughout the conveying system. The equipment boundary should include the components that directly affect the process, even when they are supplied by different contractors. A feeder, air-distribution header, separator, filter and receiving vessel each influence the pressure seen by the blower. The process designer should record how these components interact during routine operation and foreseeable transitions. That information gives the blower supplier a defined duty point and gives the plant team a practical basis for commissioning and fault diagnosis.
Required information includes sand type, bulk density, grain-size distribution, conveying capacity, pipeline length, vertical lift, number of bends, feeder type, operating pressure and maximum acceptable grain degradation. Blower selection should be coordinated with the blow tank and pipeline rather than based only on tonnes of sand per hour. The blower should be selected from the duty at its inlet rather than from a product name or a single production-rate figure. The enquiry should show how the system behaves at low and high demand, which branches operate together and what losses occur through the feeder, pipe, valves and filter. Material trials may be needed if flow behaviour or degradation is uncertain. Selection remains conditional on the model’s permitted pressure, temperature, speed and power envelope. The engineering record should state the blower duty point, differential pressure and discharge temperature on one consistent reference basis.
For foundry sand conveying, the technical specification should describe how the process changes between normal production, start-up, shutdown and cleaning. State the required flow at its reference conditions, the pressure or vacuum at a defined connection, the expected operating hours and the site ambient range. Include the resistance of the installed route and the condition of filters or separators that affect the air circuit. These details let the equipment supplier check the selected model against its approved speed, differential pressure, absorbed power and temperature limits, while the process designer remains responsible for capacity and product performance.
At commissioning, capture the material rate and conveying-air conditions together. Record blower inlet conditions, line pressure near the pickup, airflow, feeder speed and filter differential pressure while feed is stable. Repeat the readings at expected low and peak rates; a single design-point measurement will not show how the system responds to a recipe change or intermittent feed. Compare a rise in line resistance with material condition, particle-size variation and filter loading before changing blower speed. A baseline built this way helps the team locate a developing restriction in the solids path, filter or air source and gives maintenance a reference after service. For foundry sand, document moisture, grading and the condition of reclaimed material alongside feeder rate. These properties influence how reliably the solids enter the line and how the receiver filter loads, especially when several sand grades share a conveying route.
Specify the conveying duty around the real product and complete route. The enquiry should state bulk density, moisture range, particle-size distribution, required throughput, conveying distance, vertical sections, bends, feeder type and expected operating cycle. Include the pressure loss across the receiver and filter at both clean and terminal conditions, and state who is responsible for the capacity guarantee. The selected operating point must be checked against the blower’s permitted pressure, speed, power and discharge temperature. This makes the stated production rate traceable to the line conditions that create it, rather than to a nominal airflow value on its own. If sand batches vary, define an acceptable material envelope and confirm capacity at its difficult end. The test basis should also reflect the actual pipe route and bends, since a short test line may not represent pressure losses in the installed system.
Glossary
Blind Filters: A severe filtration failure mode where fine foundry dust or moisture completely coats and chokes the receiver vent filter media, spiking system pressure.
Blow Tank (Pressure Vessel): A heavy-duty, sealed vessel utilized in dense-phase pneumatic conveying to batch-feed abrasive foundry sands reliably without the rapid mechanical wear associated with rotary airlocks.
Bridge in Hoppers: A troublesome arching phenomenon where cohesive or damp foundry sand locks together across a hopper outlet, completely halting gravity feed into the conveying line.
Ceramic Foundry Media: Advanced, highly durable spherical artificial particles used in place of natural sand to minimize thermal distortion and pipeline wear in high-precision casting lines.
Chromite Sand / Zircon Sand: High-density, specialized specialty foundry sands used for their high thermal conductivity and refractoriness, requiring carefully tuned conveying pressures and air velocities.
Dry No-Bake Sand: Chemically bonded foundry sand mixtures that cure at room temperature, requiring dedicated pneumatic transport parameters to avoid premature binder activation or moisture absorption.
Evacuation Time: The specific duration required for an industrial vacuum system to draw down the network to its target absolute pressure before mould preparation or sand collection commences.
Grain Degradation: The undesirable physical breakdown and fracturing of sand granules into finer particles caused by excessive velocity or harsh mechanical impacts during pneumatic conveying.
Green-Sand Return: The recycling stream of traditional, clay- and moisture-bonded moulding sand within a foundry, requiring specialized handling to prevent caking and pipeline blockage.
Wear-Backed Elbows: Specially reinforced pipe bends featuring extra wall thickness or sacrificial wear plates designed to withstand the severe abrasive erosion caused by high-velocity sand streams.