How to Select a
Pneumatic Conveying Elbow

1. Identify the Material and Duty

Start with the actual bulk solid: composition, grade, particle size and shape, bulk density, moisture, flow characteristics and sensitivity to damage. Record the design throughput and how the line is used. For a replacement, identify the present elbow and the reason for change: erosion, cracking, leakage, product damage, streamers, blockage, cleaning or maintenance cost.

Useful evidence: samples, safety information where relevant, photographs, wear maps and records of operating hours or conveyed tonnes. A statement such as “the elbow wears rapidly” becomes much more useful when accompanied by measured operating conditions.

2. Confirm Operating Pressure and Conveying Mode

Record normal and maximum pressure or vacuum, air or other conveying gas, flow rate and measurement conditions, temperature and conveying mode. Distinguish actual volumetric flow at operating conditions from standardized flow values. If the conveying regime or solids loading is unknown, mark it as unknown rather than guessing.

A change in airflow can alter both particle velocity and wear at a bend. Where the failure appears suddenly, review upstream valves, blowers, feeding rate, temperature and material condition, not just the elbow itself.

3. Choose Pocket, Sweep or Segmented Geometry

A pocket elbow has a chamber intended to redirect the solids and potentially create a material cushion. Its fit is governed by flange-face offsets and body envelope. A sweep elbow provides a continuous curved route with defined CLR. A segmented elbow has discrete welded joints and must be evaluated for internal transitions and local impacts.

Consider outlet-pipe wear and pressure demand as well as the elbow wall. A shorter body does not inherently mean lower pressure loss; a larger radius does not inherently mean less particle damage.

4. Assess Abrasion and Wear-Protection Options

Determine whether failure results mainly from sliding abrasion, direct particle impact, corrosion or a combination. Basalt liners, ceramic liners and WC hardfacing are candidate construction choices with different impact, temperature and maintenance considerations. If the product is fragile, contamination-sensitive or changes frequently, examine the internal surface and cleanability alongside hardness.

5. Determine Nominal Diameter and Finished Bore

Record DN or NPS, actual pipe outside diameter, wall thickness and clear internal bore. A nominal designation is not itself a dimensioned specification. For lined bends, check whether the published DN describes the connection size or the finished bore after applying the lining.

Reducing the clear bore at one elbow can create a local restriction. Confirm any internal steps between the adjacent pipe, flange transition and liner.

6. Choose Angle and Fixed Radius

Pocket designs are proposed at 45° and 90°; pipe-based designs at 30°, 45° and 90°. For pipe bends, select a preferred fixed CLR per nominal size from the candidate radius schedule, then have Polimak confirm whether that radius can be manufactured in the specified metal and wear construction. Segmented bends require a separate miter geometry drawing. See radius guide.

7. Select DIN/ANSI Flanges or Plain Ends

For pocket elbows, choose an approved flanged connection. For pipe bends, choose plain ends or flanged ends. State the applicable standard, flange facing, bolt hole arrangement, gasket and exact mating pipe dimensions. EN PN and ASME Class naming must not be treated as substitutes for the approved pressure/temperature rating of the entire assembly.

8. Review Pressure Drop, Cleaning and Maintenance

Agree what matters to the installation: power demand, startup stability, product degradation, product hold-up, inspection access, replacement interval, noise, vibration or downtime. Establish the required cleaning method and allowable residue before recommending a pocket or lined design where retained solids or liner joints may matter.

If comparing two elbows, define equivalent test conditions and acceptance measures—throughput, pressure, particle damage, conveyed tonnes to wear limit and cleaning time.

9. Submit an Engineering Enquiry

A complete initial enquiry does not require perfect information. Identify unknown values explicitly, attach a sketch and include the names of the parameters that must be certified or documented for your project. We can help develop the technical specification after reviewing the application. Configure an enquiry.