Here are some frequently asked questions (FAQS) of shaker screens:


What is API RP 13C (ISO 13501)?

  • A new physical testing and labeling procedure for shaker screens. To be API RP 13C compliant, a screen must be tested and labeled in accordance with the new recommended practice.

  • Two tests were devised: cut point and conductance. The tests describe a screen without predicting its performance and can be performed anywhere in the world.

  • After identifying the cut point and conductance, complying with API RP 13C requires application of a permanent tag or label to the screen in a position that will be both visible and legible. Both cut point expressed as an API number and conductance shown in kD/mm are required on the screen label.

  • Internationally, API RP 13C is ISO 13501.

  • The new procedure is a revision of the previous API RP 13E, which was based on optical measurements of the screen opening using a microscope and computer analysis. Under API RP 13E, screen designations were based on individual manufacturer test methods, producing inconsistent labeling.

What is the practical value of RP13C to the end user?

a. RP13C provides an unequivocal procedure and benchmark for comparing different screens.
b. The primary intent of RP13C is to provide a standard measuring system for screens

Should I screen with a finer screen now if what used to be called a ‘200 mesh’ screen is now labeled API 120?

Users are advised to determine the screens that work best in their applications regardless of what the new API Screen Number happens to be.

Should I use the old screen number or the new API Screen Number when ordering replacement screens?

Although some companies are changing their part numbers to reflect their conformance to RP13C, others are not. It is therefore best to specify the RP13C value you want.

Why is there such a large variance between the old and new labeling values?

a. The biggest variation is due to the shift from using D50 to D100.
b. The previous test procedure (RP13E) measured the distribution of the apertures in the screen.RP13C uses a physical and repeatable test using actual solids (dry aluminum oxide) which measures the coarsest particle that can pass through the screen.

Will a screen with a D100 of 172µ remove solids finer than 172µ?

By definition, every particle of the D100 size or coarser will be discarded. b.   In practice some portion of solids finer than 172µ may be removed.

What does the API Screen Number NOT tell us?

The API Screen Number is a single number which defines solids separation potential under specific test conditions. It does NOT define how a screen will operate on a shaker in the field as this will depend upon several other parameters such as fluid type & properties, shaker design, operating parameters, ROP, bit type, etc.

What does the API Screen Number tell us?

The API Screen Number corresponds to the API defined range of sizes into which the D100 value falls.

What is the D100?

a. The D100 cut point of a screen is the particle size at which no particles will pass through the screen.
b. D100 is a single number determined from a prescribed laboratory procedure – the results of the procedure should yield the same value for any given screen.
c. The D100 should not be compared in any way to the D50 value used in RP13E.
d. The method used in RP13C provides only the D100 value with no provision for D16, D50, or D84 values.


Non-Blanked Area

The non-blanked area of a screen describes the net unblocked area in square feet (ft²) or square meters (m²) available to permit the passage of fluid.

Screen Conductance

Conductance, measured in kilodarcies per millimeter (kD/mm), defines a Newtonian fluid’s ability to flow through a unit area of screen in a laminar flow regime under prescribed test conditions. All other factors being equal the screen with the higher conductance number should process more flow.

D100 Cut Point

The D100 cut point of a screen is the particle size at which no particles will pass through the screen.

D50 Cut Point

The D50  cut point of a screen is the particle size at which half of those particles reporting to the screen will pass through the screen and half will be retained.


Mesh, as it relates to a piece of woven wirecloth, is a measure of the number of holes in a linear inch (such as 100 mesh) or in a linear inch in each direction (such as 100 x 60 mesh).

API Screen Number

API Screen Number is determined using a specific test procedure (asset out in API RP 13C).The test a specifically graded sample of Aluminum Oxide which is passed through a stack of sieves including the test sieve  and mounted on a Tyler Ro-Tap®.  The method determines the D100 cut point of the test screen and relates it to the D100  of an ‘equivalent’ standard ASTM test sieve.