API shaker screen for solids separation

API shaker screen lead easy selection on certain screen. Since new API guidelines for testing and labeling shaker screens should simplify the screen selection process and provide screens that will efficiently filter cuttings from drilling mud. This text is a practical guide to choose shaker screen compliant with API RP 13C.

New API RP 13C

The new recommended practice covers a variety of subjects, but the discussion in this article is limited predominantly to the test that describes the openings on a shaker screen by comparing it to a known standard (US test sieves calibrated according to ASTM E-11).

API Shaker screen

API RP 13C describes how a section of a shaker screen is properly mounted in a holder which is then put in the middle of a stack of calibrated US test sieves. The sieves and test screen are mounted on a Ro-Tap (orbital shaker with a tapping arm) and a defined master grit sample (aluminum oxide) is sieved. The amount of grit on each screen is calculated and graphed. This process defines the absolute D100 separation of grit in microns (µm). Any particle larger than the microns value will not pass through the screen. This value is then compared to Table 5 in the API RP 13C document

For example, if the separation of the test screen is 114.88μm, the table will show that it compares closest to the US test 140 sieve. Therefore, if it is labeled as API shaker screen would be an API 140 screen panel.

Two things will become apparent when API-compliant shaker screens are used:

1. You will find you were not screening as fine as previously thought.
2. You may not need to screen as fine as previously thought.

For example, if you have been using one manufacturer’s screens labeled Number 210 with good results (i.e., the screen was keeping the drilled solids in the allowable range without excessive dilution and giving reasonable life), then that screen is acceptable for what you are doing.

There is a good possibility, however, it isn’t a 210-mesh screen (according to the current API test); it might actually be an API 140 (which is what the API test indicated for some screens previously called 210 mesh). The screen hasn’t changed, just the way it was tested and labeled.

The definition of “mesh” is the number of openings/inch of the screen. However, mesh never defines the size of the openings on a screen panel, or the size particles the screen would remove. If the diameters of the wires are different, the mesh can stay the same, but the openings will be different

 Comparing API shaker screens

Sales literature may claim that a screen was tested “in actual field conditions” and “our test showed our screen performed better than the API RP13C test,” which may be true, but, these are two entirely different tests and different results should be expected. The API test only describes the openings; it is not a performance test.

API shaker screen easily allow an apple-to-apple comparison. If you want to compare performance of screens from different manufacturers, simply choose screens with the same API number. For example, choose two screens labeled API 170; in most cases the solids removed will be similar. With the solids removal being similar, the issues to be addressed would be the relative capacity of the screen (related to conductance, which will be covered in detail in the conclusion of this series), screen life, and cost.

Using API-compliant screens will eliminate the confusion caused by mislabeled screens. For example, four different screens from four different manufacturers. These are the screens that operators supplied to an independent lab for testing funded by API. You can see that using what was formerly called the “mesh” of the screen (200 mesh, 180 mesh, etc.) could be very misleading. Unless you use a microscope to check all the screens, you might not know that screens with the same mesh number, from different manufacturers, could give substantially different results when it comes to solids removed. It is best to think of the old names of the screens as simply the part number when you need to order more.

Labels on API 13C screen

API RP 13C states that the new designation system will consist of no fewer than the following minimum elements:

• API screen designation or API number (this is to be printed two times larger than other information on the label)
• Equivalent aperture in μm.
• Conductance (kilodarcies/mm).
• Non blanked screen area (sq ft).
• Manufacturer’s designation or part number.

API recommends that the label also include the manufacturer’s name and the country of manufacture or assembly, but these are optional.

The manufacturer can arrange the information any way it wants on a tag. This tag is to be permanently attached to the screen in a visible place.

Choice, conductance of API shaker screen

With API-compliant shaker screens you can make a more informed choice based on the uniform characteristics. You know what you are getting and there should be no surprises. This will make screen comparison and evaluation much easier because it eliminates the confusion caused by misleading labeling.