Sieving and Screening Accessories for Better Testing

Test sieves, sieve shakers, and particle-sizing instruments are frequent topics in this blog, but we don’t often talk about sieving accessories. Particle sizing with test sieves is a hands-on process with many small, repetitive tasks that must be carried out properly. Selecting the right accessories for each job and using them correctly makes the work faster and easier, but it also significantly affects testing efficiency, accuracy, and repeatability.

This article closely examines the tools that optimize test sieving procedures and ensure your sieves meet the requirements of standard test methods.

Sieve Cleaning & Storage

Test sieves are precision measuring instruments, and maximizing their usable life depends as much on proper care and cleaning as on tracking the number of uses. A clean sieve is essential for accurate and efficient particle size determinations. However, overly aggressive cleaning may distort the openings and damage the sieve. A sieve with worn or damaged wire cloth that exceeds the allowable tolerances in ASTM E11 or ISO 3310-1 cannot be repaired or adjusted and must be removed from service. Proper storage between uses protects test sieves and keeps them organized.

Sieve Brushes

Primary cleaning of sieves with mesh openings No. 325 (45µm) and coarser is performed with a sieve brush during particle size testing as sample fractions are recovered for weighing. A sieve brush, matched to the mesh size of the sieve, is used to dislodge particles from the mesh and collect the separated fractions into a weighing scoop. In an alternate method for small, fine-grained samples, each fraction is weighed in the sieve, the tare weight of the sieve is subtracted, and the sieve is brushed out later in a separate operation. The charts below are a guide to selecting brushes for ranges of sieve mesh sizes. 

Some sieve brushes are designed for efficient use in specific applications.

Ultrasonic Sieve Cleaners

Ultrasonic Sieve Cleaners are an effective way to clean any sieve but are the only safe and effective method for test sieves with mesh finer than No. 325 (45µm). The sieves are immersed in a water tank where energy from an ultrasonic generator is directed. The high-frequency sound waves create millions of microscopic bubbles in the liquid that quickly form and implode in a process called cavitation. The agitation caused by the sudden release of energy dislodges particles trapped in the sieve mesh. Ultrasonic cleaning is fast, effective, yet very gentle on even the finest woven-wire or precision electroformed mesh. The cleaners are available in various models for particular applications and sieve frame sizes. A mild cleaning solution concentrate is also available.

Sieve Storage Racks

Storage Racks keep your test sieves organized and accessible, clearing up clutter in your laboratory. More importantly, they protect sensitive sieve cloth from damage. Select from wall-mount, benchtop, and adjustable models to customize your storage space for any size sieve.

• Wall-Mount Sieve Rack is designed for 8in (203mm) test sieves and can store up to 11 full-height sieves.
• Adjustable Wall-Mount Sieve Rack can also be for table-top use and accommodates eight full-height 12in (305mm) test sieves.
• Adjustable Bench Sieve Rack accommodates multiple sieve frame diameters from 3 to 12in (76 to 305mm) and holds up to 40 test sieves.

Sieve Inspection: Taking a Closer Look

Periodic examination of test sieves ensures the sieve cloth is in good condition and securely mounted in the frame. While precision micrometers or optical comparators are often required to determine compliance of sieve cloth apertures and wire diameters, simpler measuring and magnification sieve inspection tools are effective for detecting damage and distortion or identifying standard opening sizes.

• Digital Calipers are a must-have tool for many lab and field applications and are helpful when measuring the aperture sizes of coarse sieves and screen trays.
• Screen Opening Gauge is as simple as it gets for quickly identifying opening sizes. The 22ga stainless steel wedge is dropped into an opening and reads where the mesh contacts the sides. Measures from 1/8 to 1-1/8in on one side and 3mm to 28mm on the other.
• Pocket Magnifier measures approximate opening sizes, assists in the visual detection of minor irregularities in all sizes of sieve mesh and identifies cracked or broken solder joints between the sieve frame and mesh. It folds flat for easy portability.
• 10x Optical Comparator performs many of the same functions as the Pocket Magnifier but with greater precision for examining finer meshes. Sharply focused and illuminated views of glass reticle inserts in inch or metric units. They are packed in a wooden case with nine interchangeable reticles.

Quality Control: Ongoing Confirmation of Test Sieve Compliance

New test sieves from Gilson are always supplied with a certificate of manufacturing compliance. Optionally, Verification Services perform measurements on individual sieves to ensure they meet the upgraded requirements for Inspection Grade or Calibration Grade sieves. That’s fine for a brand-new sieve, but how do you demonstrate that the sieve still meets specified tolerances after extended use?

Standard Reference Materials (SRMs) are carefully measured NIST-certified glass beads or powders used to check the mesh opening sizes of test sieves. As the central component of a sieving quality control program or just a simple performance check, SRMs help decide when sieves should be sent out for reverification or removed from service. Standard Reference Materials are efficient, convenient, and easy to use. A previous Gilson blog article post takes a deep dive into SRMs, their applications, and even how to make your own.

• Whitehouse Sieve Standards are precision-sized beads packaged in single-use vials to determine the effective openings of individual sieve sizes from No. 6 to No. 635 (3.35mm to 20µm).
• NIST Reference Materials are five different selections of sand or glass beads, sorted to test specific ranges of sieve sizes.

Sample Handling for Laborsaving Efficiency

Careful selection of even the simplest tools for selecting, gathering, and moving sample material around the lab can upgrade productivity and reduce the time and effort required to complete particle size determinations.

• Sample Scoops are available in various sizes to suit the volume of material and different types to suit the application.
• Flat bottom scoops ensure full recovery of material from pans and trays. Round-bottom scoops are easier to handle when gathering samples from stockpiled material.
• Plastic scoops are good for lightweight materials or to avoid sparking hazards.
• Aluminum scoops are durable and corrosion free.
• Stainless-Steel Scoops resist corrosion and prevent sample contamination.
• Sample Pans, Bowls, and Trays can be chosen for properties such as size, function, heat tolerance, corrosion resistance, and more. Some are designed for ergonomic handling and easy transfer of granular materials.
• Material Handling Chute takes care of scooping, dispensing, and weighing applications for large samples. The unit has sturdy handles for lifting, and the integral feet make it stable on flat surfaces.
• Steel Handling Pans are heavy-duty welded steel for long life and feature a chute end and swing-down handle.

Sample Preparation: Test the Best Sample

Whether it’s simply splitting to acquire a representative sample or washing away excess fines, every particle sizing sample has to be prepared before testing.

• Sample Splitters are available in all types and sizes to divide bulk material into representative samples for sieve tests. No test accurately characterizes a material unless the specimen is representative of the whole. Gilson has the best selection and the broadest range of sample dividers for materials from cobble-size to fine powders.
• Gilson Universal Sample Splitters are the only sample dividers in the industry offering the versatility of adjustable-width chutes and the accuracy of lever-release hoppers over a range of particle sizes from 4in (100mm) to fine powders. Hopper capacities from 3.5ft³ to 103.7in³ (99.1L to 1.7L) ensure sample volumes are correct in relation to particle sizes.
• Precision Splitters for granular materials from 5mm to fine powders offer the same gate-release hopper design as Universal Splitters but feature precision fixed-width chutes, compact size, and stainless-steel construction.
• Specialty Splitters feature unique designs that pass materials through multiple stages in one pass with the Gilson Laboratory Split-O-Matic Splitters, enclosed splitters control dust or divide bulk samples of hot asphalt.
• Spinning Rifflers in benchtop or floor models offer the highest level of precision for representative samples of dry granular materials. These rotary dividers yield highly accurate multiple fractions in one pass.

• Aggregate Washers prepare soil and aggregate samples with high fines content for easier and more accurate testing with sieves. A continuous stream of water directed into the revolving stainless-steel drum flushes out fines. The discharge is directed over a sieve, usually No. 200 or No. 325 (75µm or 45µm), to ensure oversize particles are not lost.

Accessories for the Sieve Stack

Various accessories can be used when performing particle size tests to optimize accuracy and efficiency.

• Sieve Pans and Covers are more necessities than accessories for some test methods.
• Sieve Pans are positioned at the bottom of a sieve stack, with the test sieves progressively nested on top to collect finer material and prevent sample loss.
• Sieve Covers (lids) prevent sample loss or contamination during manual or mechanical agitation. Many popular Gilson Sieve Shakers have built-in covers.
• Clear Acrylic Spacers are available for 3 or 8in (76 or 203mm) frame diameter test sieves to allow user to easily view sample materials during sieving operations or to maintain required stack height.
• Sieve Seal Gaskets are sieve frame size specific and used to prevent fluid and sample loss.
• Flow Agents is silicon dioxide powder that is used to mix in specimens to help prevent problems from static charges and humidity.
• Wet Sieving Essentials: such as pans with drains, spray fittings, and tubing allow efficient wet-sieving operations while preventing loss of sample.

Finally, there is one type of accessory that Gilson does NOT recommend. Hard rubber sieving balls, “jack rocks,” and other devices are sometimes used in sieves during agitation to force particles through the mesh openings. These items stretch the openings apart and fracture the material to make it pass. The wire mesh is permanently distorted, rendering the sieve useless, and crushed sample particles guarantee inaccurate results. These products may be helpful for the production processing of materials but should never be used for particle size determinations.

We hope this discussion on test sieving accessories and their use has been helpful. To discuss your specific application, please contact the Testing Experts at Gilson.