Demystifying API RP 13C: Understanding the Global Standard for Shale Shaker Screens
Technical Standard Guide (ISO 13501): D100 Cut Points, Conductance, Non-Blanked Area & Screen Selection
In oil and gas drilling solids control, comparing shaker screens historically caused operational confusion due to arbitrary manufacturer "mesh count" claims.
The adoption of API RP 13C (internationally harmonized as ISO 13501) replaced the obsolete API RP 13E standard. It establishes an unambiguous, repeatable laboratory physical testing and standardized labeling procedure, giving drilling contractors, mud engineers, and rig managers an objective benchmark to evaluate screen separation and fluid throughput.
API RP 13C Standard Cut-Point Range Classification
| API Screen Number | D100 Separation Range (μm) | Primary Deck Application | Target Solids Removal |
|---|---|---|---|
| API 20 to API 35 | > 500.0 to 1000.0 μm | Scalping / Gumbo Removal | Very coarse gravel, large agglomerated cuttings |
| API 40 to API 70 | > 215.0 to 425.0 μm | Top Deck / Fast Surface Drilling | Coarse sand, high ROP formation solids |
| API 80 to API 170 | > 88.0 to 180.0 μm | Primary Shaker Decks | Medium-to-fine formation sands, sandstone cuttings |
| API 200 to API 325 | > 43.5 to 77.5 μm | Fine Screening / Weighted Mud | Fine abrasive silts, barite retention circuits |
| API 400+ | ≤ 38.5 μm | Ultra-Fine Polishing / Mud Cleaners | Microscopic low-gravity solids (LGS) |
API RP 13C Technical Q&A Breakdown
1. What are the two mandatory physical tests required by API RP 13C?
To achieve certified compliance, every screen design undergoes two standardized tests:
- D100 Separation Cut-Point Test: Determines the exact particle size (in micrometers) at which 100% of standard aluminum oxide grit sample of that size and larger is retained by the screen during standardized dry-sieving.
- Fluid Conductance Test: Measures the fluid transmission capability per unit thickness of a static (non-vibrating) screen in kilodarcies per millimeter (kD/mm) under laminar flow conditions.
2. Why is D100 superior to the obsolete D50 (API RP 13E) rating?
The old RP 13E standard utilized D50 (the particle size where 50% of solids are discarded and 50% pass through). However, D50 allowed screens with identical ratings to allow radically different maximum particle sizes into the mud system. D100 provides an absolute upper ceiling: no particle larger than the D100 rating can pass through the mesh openings.
3. Why are the historical terms "Mesh" and "Mesh Count" obsolete?
Historically, "mesh" referred merely to the number of wire openings per linear inch. This metric ignored wire diameter, rectangular aspect ratios (e.g., 70×30 mesh), and multi-layer cloth interference. Two screens labeled "200 mesh" from different suppliers could have completely different separation cut points. The API Screen Number replaces ambiguous mesh counts with a laboratory-proven D100 range.
4. What is Non-Blanked Area, and why does it matter?
The non-blanked area is the net, unblocked open surface area (expressed in ft² or m²) available for fluid passage after accounting for frame ribs, structural bonding strips, and seal perimeters. A screen with a higher non-blanked area maximizes total fluid throughput, lowers fluid surface velocity, and reduces the fluid pool depth on the shaker deck.
5. What does the API Screen Number NOT tell the operator?
While API RP 13C describes the physical properties of a screen in a controlled laboratory, it does not predict real-world field performance. Operational mud throughput and screen run-life also depend on:
- Drilling fluid rheology (viscosity, yield point, OBM/WBM base)
- Solids loading and formation stickiness (gumbo clays vs. brittle shales)
- Shaker motion dynamics (Linear vs. Balanced Elliptical, G-force rating)
- Deck angle and drilling Rate of Penetration (ROP)
API RP 13C Mandatory Tagging & Ordering Best Practices
Under the standard, compliant screens must feature a permanent, legible label attached in a visible position displaying:
- API Screen Number (e.g., API 140)
- D100 Separation Cut Point in micrometers (μm)
- Conductance Rating in kD/mm
- Non-Blanked Area in ft² (or m²)
- Manufacturer Part Number & Lot Traceability
Pro Tip for Purchasing Managers: When ordering replacement screens, specify the required API Screen Number and minimum Conductance (kD/mm) rather than legacy mesh counts or OEM brand references to ensure exact process compatibility.
Frequently Asked Questions (FAQ)
Q: What is the primary difference between API RP 13C and the obsolete API RP 13E?
A: API RP 13C replaces the theoretical D50 separation cut point and traditional mesh count with a laboratory-measured D100 cut point using aluminum oxide dry-sieving, alongside static fluid conductance ratings (kD/mm).
Q: What does the API Screen Number represent?
A: The API Screen Number designates the specific ASTM particle size range into which the screen's laboratory D100 cut point falls, establishing an objective baseline for comparing screens from different manufacturers.
Q: Why is screen conductance (kD/mm) critical for mud processing capacity?
A: Conductance defines fluid permeability per unit thickness under laminar flow. A screen with higher conductance processes greater mud volumes with lower fluid friction, reducing the risk of screen blinding and mud loss.
Source Certified API RP 13C Compliant Shaker Screens
We manufacture high-conductance, API RP 13C verified replacement screens (Flat, Pyramid 3D, and Composite Frame formats) fully compatible with Derrick, NOV Brandt, MI SWACO, and Kemtron equipment.
- 100% Laboratory Tested D100 Cut Points & Conductance Ratings
- Permanent Compliant Tagging & Batch Traceability
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Contact our solids control engineering specialists today to request API RP 13C compliance certificates and sample testing!
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