Dense Phase Conveying Selection & Design Guide

Dense phase conveying design is an iterative engineering task. The material determines which flow modes are feasible. The required rate and route determine the pressure duty. Product quality, wear, hygiene and safety determine the acceptable operating window and equipment details.

1. Define the process duty

State the source, destination, required mass flow, batch size, operating hours, route, lift and available utilities. Include startup, normal transfer, shutdown, cleaning and restart. Note the pressure condition at the source and destination because the conveyor must operate as part of the complete process.

Separate requirements from assumptions. Required capacity, product quality and containment limits should be explicit. Estimated bulk density or an unverified route should be marked for confirmation.

2. Characterize representative material

Record particle size distribution, bulk density, true density, moisture, cohesion, permeability, air retention, friability, hardness, shape and temperature where relevant. Include variation between suppliers, batches and storage conditions.

Particle size distribution is especially important because it influences whether a material can support plug flow, slug flow, a moving bed or only a leaner suspension regime. Published criteria can guide screening, but representative conveying tests remain the strongest evidence for an unfamiliar material.

3. Establish the feasible flow mode

Dense phase is a family of nonsuspension flow modes, not one universal condition. Fine powders with good air retention can behave differently from coarse, permeable granules. Define the observed flow pattern and its stable operating range.

Monitor pressure fluctuations and restart behavior during tests. A system that reaches capacity while close to blockage is not robust. The selected point needs margin for expected material and production variation.

4. Develop the pressure and gas balance

The calculation should cover feed equipment, straight pipe, vertical lift, bends, valves, receiver and gas separation. It should also consider acceleration and any gas added along the route. Use material specific test data or a validated design method within its proven range.

Do not select the compressor or blower from nominal pressure alone. Define required flow at pressure, gas quality, temperature, control range, energy use, noise and the consequence of a utility interruption.

5. Design feeding and receiving as part of the conveyor

Pressure vessels, rotary devices, screw feeders or other feed arrangements must meter solids into the line consistently. The feed sequence influences plug formation, pressure stability and capacity.

At the destination, size the receiver and filter for the gas and solids duty. Review entry velocity, product impact, filter loading, discharge sequence and pressure equalization. The destination must be ready before material arrives.

6. Protect product and equipment

For fragile materials, define the permitted change in particle size, fines or another quality measure. For abrasive materials, identify wear locations, materials, replaceable sections and inspection intervals. Route layout and bend geometry affect both objectives.

Check segregation, temperature change, moisture pickup and contamination when they matter to the process. A capacity test alone cannot prove product protection.

7. Complete the hazard review

Combustible dust guidance identifies ignition sources, dust containment and connected equipment as system concerns. Review electrostatic charge, grounding, hot surfaces, foreign material, isolation and the consequences of a filter or receiver event. Applicable controls depend on the powder, process and jurisdiction.

Do not assume that enclosed or low velocity transfer is inherently safe. Document the hazard data and the basis for every protective measure.

8. Define controls and recovery

The sequence should cover filling, pressurization, material discharge, gas control, receiver discharge and line clearing where used. Define alarms, permissives and the response to high pressure, low pressure, loss of gas, failed discharge and blockage.

Recovery should avoid an uncontrolled release of stored pressure or a sudden surge of material. Operators need a documented method for diagnosis, isolation and restart.

9. Plan cleaning, inspection and maintenance

List product contact components and access points. Define the cleaning method, inspection interval, wear limit, filter service and the method for opening pressure containing equipment safely.

Place routine maintenance points where they can be reached. Record critical settings and component condition so gradual changes can be identified.

10. Prove the duty with an acceptance test

Use representative material and the intended route where practical. Measure mass transferred, cycle time, pressure profile, gas use, filter behavior, residual material, product condition and restart performance. Run repeated cycles and include expected operating extremes.

The acceptance report should distinguish measured results from predictions. Record the tested configuration and all deviations. This becomes the reference for commissioning and future process changes.

Questions to put in the supplier specification

• Which material samples and properties support the proposed flow mode?
• What operating range has been demonstrated for rate, pressure and gas use?
• How are blockage, product damage and wear controlled?
• Which settings and route details are critical to the guarantee?
• What will be measured during acceptance?
• Which changes require a new engineering review or test?

Convert pilot results into scale-up rules

A pilot trial is useful only when the material condition, test loop, pipe diameter, route, solids rate, gas flow and pressure measurements are documented. Identify which behavior is directly observed and which part of the full-scale design is extrapolated. Scale-up should preserve the flow mechanism and account for longer routes, elevation, bends, feeding and receiver pressure rather than multiplying capacity from one favorable run.

Test repeatability and a credible difficult condition. Record pressure signatures and the location of deposits or plug formation, not just average throughput. If secondary air is used, document each injection point, flow or control basis and its effect on product velocity.

Write recovery requirements into the supplier scope

State whether the line must restart after an interrupted batch, after loss of air or with material settled in a vertical section. Require the offered controls to detect an abnormal pressure rise, stop further feeding and leave the system in a condition that can be isolated and depressurized. Identify access points and the method for confirming zero pressure before opening.

Recovery performance should be demonstrated under an agreed scenario. Repeated purging at maximum gas flow may clear the pipe while destroying fragile material or moving the system into a high-wear regime. The accepted method must protect people, equipment and product.

Define evidence for final acceptance

The site test should cover sustained capacity, cycle repeatability, pressure margin, product quality, receiver and filter duty, valve sequencing and relevant emissions or containment checks. Include startup, normal stop, emergency interruption and restart where the process requires it. Record the exact material batch and condition used.

Handover should contain the validated operating window, alarm and trip responses, inspection points, acceptable wear observations and the changes that trigger a new engineering review. Dense phase reliability depends on preserving the relationship between material, air, feeding and route after commissioning.