A shaker can have the correct API-designated screen, no visible flooding, and a normal-looking cuttings discharge while some return flow passes around or through a damaged screen. The right question is not simply whether the shaker runs. It is whether every intended flow path passes through intact, properly seated screen media, and whether the evidence is strong enough to accept the deck after maintenance.
Purpose. This is a documented inspection and handover method after screen change-out, refurbishment or a suspected bypass event. For symptom-by-symptom fault repair, use the existing Shaker Solids Bypass troubleshooting guide and, for torn panels, the screen failure guide. This audit adds defined inspection points, findings, witness checks, acceptance logic and traceable close-out records; it does not duplicate the fault list.
Do not confuse three different faults
| Condition | Actual flow path | Why it matters |
|---|---|---|
| Deck-edge or panel-joint bypass | Flow travels through gaps around the intended screen-media path | Unscreened solids enter the downstream system despite good screen classification |
| Holed or damaged screen | Flow passes through a torn or missing screen-media zone | Coarse solids pass locally although the rest of the panel is intact |
| Deck flooding / solids carryover | Flow runs above the screen toward the discharge end | Useful drilling fluid may be lost with cuttings, especially under overload |
A sample of downstream mud alone cannot identify which fault exists; and a stable downstream LGS trend does not prove a leak-free seal. The first step is tracing the physical flow path, not interpreting one lab number as proof of bypass.
Before the inspection: a safe, repeatable setup
Agree the specific shaker, screen type and OEM installation procedure; record the test duty, fluid system, operational status, maintenance authorization and current LCM program. A visual inspection of the deck, seals, retainers or screen undersides must be done only under the site's approved isolation and safe-access procedure. Never reach into or remove a screen from an energized vibrating shaker. Guards, pneumatic/hydraulic pressure and pinch points must be controlled according to the equipment manual and permit system.
During a live operating observation, use only designated safe viewing points. Do not pour dye, water, tracer chemicals or loose solids into operating equipment as an improvised leak test; any approved tracer or flow-path demonstration requires an engineered procedure and protection against fluid contamination, splashing and uncontrolled discharge.
Eight physical checkpoints for the deck
- Panel identity and fit: correct OEM-approved panel geometry, frame and retention system for this shaker; record part number and installed API designation where applicable.
- Bed and support rails: inspect contact surfaces for damage, deposits, wear, bent components and missing support or rubbers.
- Perimeter gaskets: look for flattened, cut, chemically attacked or missing material; verify correct position and compression to manufacturer requirements.
- Screen-to-screen interfaces: examine interlocking edges, seals and end joints for an uninterrupted contact path.
- Latches, wedges and tension: verify all fasteners/locking devices are present, correctly engaged and within OEM procedure. Do not guess a torque or tension setting.
- Media integrity: inspect tears, unsupported holes, missing repair plugs, delamination, severe abrasion and damaged bonding at frame transitions.
- Flow distribution and bypass routes: confirm weirs, gates, overflow equalizers and any intentional bypass are documented and correctly positioned for the planned test. An approved LCM bypass is a controlled process decision, not proof of a sealing defect.
- Discharge and return-side evidence: check for accumulated coarse material under suspect joints, dried mud tracking, abnormal local leakage and unexpected solids in the screened-mud compartment; record where the evidence was seen.
NOV's Pinnacle screen description identifies perimeter sealing as a means to minimize bypass. SLB's DURAFLO range describes screen-to-screen latching and specific soft-gasket designs. Those examples demonstrate why the exact fitted panel and OEM manual matter; they are not interchangeable installation instructions.
The acceptance test must have a before-and-after record
| Evidence item | Before corrective work | After corrective work |
|---|---|---|
| Unit / deck / screen ID | Record location and affected panel | Confirm replacement and part number |
| Visible tracking / gap | Photo with safe viewing position and scale where feasible | Equivalent photo showing seated joint |
| Gasket / retainer / media defect | Describe mechanism, not only "bad screen" | Document renewed or repaired component per OEM |
| Intentional bypass path | Valve/gate status and reason | Signed status and approved process routing |
| Operating conditions | Flow, mud system, screen type, solids load and fluid properties | Comparable stable duty if the conditions permit |
| Witness and close-out | Inspector, date, required action | Retest outcome, owner and authorization |
Use objective, observable acceptance criteria: correct fit and lock; no visible unapproved gap; intact media; no observed unintended unscreened flow path under the witnessed operating condition; no unresolved defect impacting separation; and written agreement that the OEM and site procedure have been followed. A single pass at low flow must not be presented as acceptance at maximum duty.
Illustrative defect log and decision logic
Example only, not a reported rig incident. A newly installed panel has a visibly displaced side gasket and a retainer that is not completely engaged. The outlet looks visually acceptable at the current low flow. The record should still be marked Fail / Not accepted: the installation criteria are not satisfied. Isolate under site procedure, reseat or replace the affected component to the OEM method, reinspect, then witness the deck at the required approved duty.
| Status | Suggested acceptance meaning | Next action |
|---|---|---|
| Pass | All agreed inspections met, evidence attached, witnessed within specified tested duty | Return to routine monitoring |
| Conditional | Physical correction made but duty, access or sampling limitation prevents full verification | Specify outstanding test, owner and deadline; follow site authorization |
| Fail | Confirmed gap, damaged screen, incorrect lock/fit or unintended bypass path | Do not accept; correct under maintenance controls and retest |
These are suggested audit categories, not API or OEM pass/fail classifications. Local acceptance criteria take precedence; record any inability to inspect explicitly.
What can quantify the consequence?
Where safe and practical, trend downstream sand content, PSD, LGS indicators and centrifuge or cyclone loading before and after correction at comparable mud properties, return flow and drilled-solids generation. Treat these as supporting evidence; none uniquely measures the bypass rate. If a controlled, independently validated bypass-flow measurement is available, document the collection boundary, measurement uncertainty and duration before estimating the fraction of total shaker flow that avoided the media.
Screen certification under API RP 13C describes laboratory screen characteristics and designation; it does not certify that a given field installation is leak-free. Avoid using a screen's API number as an inspection result or a downstream PSD alone as proof of the seal.
Handover: six items that make the result auditable
Record asset and screen identifiers, test date, fluid/flow conditions, inspection-photo references, defect-and-action log, and sign-off against agreed acceptance criteria. Attach a retest record after any repair. If a controlled LCM routing decision deliberately bypasses fine screens, document the operational approval and its impact on solids removal rather than calling it an accidental leak.
This deck-level acceptance audit belongs inside the wider surface-process balance. For the connection between solids generation, screen retention, fluid losses and waste generation, see From Formation to Waste, the free SC DrillTech field engineering report.
Common questions
What is solids bypass on a shale shaker?
Flow that reaches the screened-mud compartment without passing through intact screen media, either through gaps at the deck edge or panel joints, or through a torn screen. It sends coarse solids downstream even when the screen designation is correct.
Can sand content or PSD prove the deck is sealed?
No. Downstream sand content, PSD and LGS trends support a finding, but none of them measures bypass directly. Acceptance comes from physical inspection of fit, seals, locks and media, plus a witnessed run at the required duty.
Does an API RP 13C screen label mean the installation is leak-free?
No. API RP 13C describes the screen as tested in the laboratory, including its API designation and conductance. Seating, gaskets and latching on the rig are a separate check.
Technical basis
NOV, Pinnacle Series Screen (individual perimeter seals); SLB, DURAFLO composite shaker screens (frame locking and gasket sealing); SLB Energy Glossary, bypass (routing flow around equipment). Exact acceptance settings require the installed manufacturer's documentation and the rig's authorized procedure.
