Through Conduit Gate Valve (Slab Gate) — API 6D
API 6D through conduit slab gate valve (TCC) — ASTM A105N body, F6 (13%Cr) trim, PTFE Xylan-coated B7M bolting, Class 300 RF flanged. Full bore piggable pipeline valve. Sizes 2–24 inch. Export to EPCM pipeline projects.
The through conduit (TCC) slab gate valve is a full-bore API 6D pipeline valve designed specifically for piggable pipeline systems. Unlike a conventional wedge gate valve, the TCC design uses a flat slab gate with a conduit bore machined through it, which aligns flush with the pipeline bore when fully open, allowing pipeline inspection gauges (PIGs), cleaning pigs, and caliper tools to pass without obstruction. The slab gate seals by pressing the upstream line pressure against the downstream seat (pressure-energised seat), providing positive isolation in the principal flow direction. The ASTM A105N forged or ASTM A216 WCB cast body with 3mm corrosion allowance, F6 (13%Cr stainless) trim, and PTFE Xylan-coated A193 B7M bolting make this valve suitable for crude oil, condensate, and gas transmission pipelines in both onshore and offshore trench environments.
Technical Specifications
Applications
- Crude oil trunk pipeline block valves where pigging frequency is high
- SPM (Single Point Mooring) hose and pipeline isolation at jetty manifolds
- Gas transmission pipeline block and sectionalising valves
- Condensate and product pipelines requiring regular PIG passage
- Offshore buried trench pipeline valves in piggable loops
- PLEM (Pipeline End Manifold) isolation for offshore fields
Related Products
Also see: API 600 Wedge Gate Valve, Large Bore Pipeline Ball Valve, Motor Operated Ball Valve (MOV).
Frequently Asked Questions
What makes a through conduit gate valve piggable?
In a through conduit (slab gate or TCC) design, the gate has a conduit bore machined through it equal to the pipeline bore. When the valve is fully open, the conduit bore is aligned with the pipeline bore, creating a smooth, uninterrupted passage with no cavities or step changes. This allows pipeline inspection gauges (PIGs) and cleaning pigs to pass through without obstruction, making the valve compliant with API 6D pigging requirements.
What is the difference between a slab gate and a wedge gate valve?
A wedge gate valve uses a tapered solid or split wedge that seats into angled body seats; in the open position the wedge parks in the bonnet cavity, leaving the body bore exposed with possible step changes not suitable for pigging. A through conduit slab gate uses a flat slab with a bore hole that is flush with the body bore when open. TCC valves also have positive downstream seat sealing (upstream line pressure pushes the slab against the downstream seat), making them suitable for isolation in both flow directions.
What corrosion protection is applied to the valve bolting?
Pipeline TCC valves often operate in buried or offshore environments where standard carbon steel bolts are prone to corrosion and galling. PTFE Xylan/Xylar coating (approximately 20–25 microns DFT) is applied to studs and nuts to provide corrosion resistance, reduce make-up torque friction, and prevent hydrogen embrittlement in sour service. Bolting material is ASTM A193 B7M (NACE compliant) with A194 2HM heavy hex nuts.
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