I. Product Overview

The API Standard Wedge Gate Valve is a shut-off valve designed in strict accordance with API 600, API 6D, or ASME B16.34 standards. It controls the flow of media by vertically raising or lowering a wedge-shaped gate along the stem. Key features include:

• Wedge-Type Sealing Structure: The sealing surfaces of the gate and seat are angled (typically 5°–8°). When closed, the gate is forced into the seat by external torque and further sealed by medium pressure, ensuring zero leakage under high temperature, high pressure, and severe wear conditions.

• Metal-to-Metal Hard Sealing: Sealing surfaces are typically made of Stellite alloy, tungsten carbide (WC), or hardened stainless steel overlay, suitable for demanding media such as steam, oil, natural gas, and acid/alkaline solutions.

• Rising Stem Drive System: The stem moves with the gate and is fully exposed (trapezoidal thread drive). The number of handwheel turns intuitively indicates valve opening (fully open → stem at top; fully closed → stem at bottom).

• Bidirectional Pressure Adaptability: No strict flow direction requirement (body arrow is for long-term reference only), suitable for complex pipelines with variable flow directions.

• Flanged / Butt-Welded Connection Design: Commonly uses ANSI B16.5 flanged ends (RF/RTJ sealing faces) or ASME B16.25 butt-welded ends, ideal for petroleum, chemical, and power systems.

II. Model and Coding System

Example: Z41Y-300LB

• Z: Gate valve type   • 4: Connection type (flanged; alternatives: welded – Z61Y, threaded – Z11Y)   • 1: Structure type (single wedge gate with elastic compensation; double gate – Z42Y)   • Y: Sealing surface material (Stellite alloy hard seal; alternatives: H – stainless steel overlay, X – rubber soft seal)   • 300LB: Pressure rating (Class 300, equivalent to 5.0 MPa)   • Body Material: Default is WCB carbon steel if omitted; optional materials include CF8 stainless steel, WC6 chrome-moly steel, LCB low-temperature steel

Other common models:

• Z941Y: Electric actuated type   • Z641Y: Pneumatic actuated type   • Z40Y: Socket weld end (requires matching flange)   • Z41W: Stainless steel body seal (non-alloy sealing surface)

III. Main Technical Parameters

1. Pressure Ratings and Test Standards

• Nominal Pressure (Class):    – Class 150 (PN20)    – Class 300 (PN50)    – Class 600 (PN100)    – Class 900 (PN150)    – Class 1500 (PN250)    – Class 2500 (PN420)

• Strength Test Pressure: 1.5×Rated Pressure (≥15 min pressure holding without deformation or leakage; e.g., Class 300 = 7.5 MPa hydrostatic)

• Sealing Test Pressure: 1.1×Rated Pressure (≥15 min bidirectional pressure holding without leakage; e.g., Class 300 = 5.5 MPa air/water)

• Test Standards: Strictly comply with API 598 (Valve Inspection & Testing), ASME B16.34, or GB/T 13927 to ensure long-term sealing and structural integrity

2. Applicable Operating Conditions

• Operating Temperature:    – Standard stainless steel overlay: -29℃ ~ +425℃    – Stellite alloy sealing surface: -29℃ ~ +550℃ (custom options up to +650℃)

• Applicable Media:    – Water (including particle-laden wastewater)    – Steam (superheated/saturated)    – Crude oil / heavy oil    – Natural gas    – Nitric acid, acetic acid, urea solution    – Sour gas (requires NACE certification)

• Body / Bonnet Materials:    – Carbon steel (WCB)    – Stainless steel (CF8 / CF8M)    – Chrome-moly alloy steel (WC6 / WC9)    – Low-temperature steel (LCB / LCC)

• Gate / Seat Sealing Surface:    – Stellite 6 (HRC45–50)    – Hardened stainless steel (13CrSTL, HRC38–42)

• Stem Material:    – Nitrided stainless steel (2Cr13, quenched and tempered, anti-scuffing and corrosion-resistant)    – Chrome-moly steel (for high-temperature service)

• Packing Seal:    – Braided flexible graphite (for high-temperature steam)    – Reinforced PTFE (high chemical compatibility)

3. Structural Dimensions

• Nominal Diameter: DN25~DN1500 mm (larger sizes customizable)   • Flange dimensions and face-to-face length strictly match ASME B16.10 or EN 558   • Full bore flow path with near-zero flow resistance coefficient

IV. Core Structure and Operating Principle

1. Wedge-Type Sealing Mechanism

• Wedge surface pairing: Gate and seat use materials with differential hardness (seat slightly harder), e.g., Stellite seat + hardened steel gate, reducing scuffing risk

• Bidirectional sealing:

– Self-sealing: High-pressure medium pushes the gate tightly against the downstream seat (optimized outlet sealing)

– Forced sealing: External torque (handwheel / actuator) wedges the gate into the seat, ensuring reliable sealing under low pressure or bidirectional flow

• Elastic compensation:    – Single elastic wedge gate includes a central deformation allowance (~0.1 mm) to adapt to thermal expansion/contraction or installation deviation    – Rigid double gate uses spherical top pin to automatically adjust gate spacing and compensate for long-term wear

2. Rising Stem Drive System

• Visual opening indication: Exposed stem length directly reflects gate position (fully closed → stem retracted; fully open → stem at top)

• Trapezoidal thread drive: Handwheel rotation converted to linear stem motion via nut; efficient and low-torque (worm gear mechanism used for DN ≥300 valves)

• Triple sealing protection: Stem packing chamber includes braided flexible graphite + metal bellows ring, significantly reducing leakage risk under high-temperature steam

3. Opening and Closing Process

• Opening: Counterclockwise rotation of handwheel raises stem, gate lifts off seat, flow path fully opens (flow resistance coefficient ≈0.1)

• Closing: Clockwise rotation lowers gate to seat, wedge surface forced into position + medium pressure self-tightening ensures zero-leakage shut-off

• Thermal expansion compensation: After full opening, reverse 1/4–1/2 turn to prevent stem lock-up due to temperature changes (especially in high-temperature steam service)

V. Technical Standards

1. Compliance Standards

• Design Codes:    – API 600 (Steel Flanged / Butt-Welded Gate Valves)    – API 6D (Pipeline Valves for Petroleum Industry)    – ASME B16.34

• Test Standards:    – API 598    – GB/T 13927    – BS 6755 (Fire-Safe Compliance)

• Connection Standards:    – ANSI B16.5 (Flanged Ends)    – ASME B16.47 (Large Diameter Flanges)    – ASME B16.25 (Butt-Weld Ends)

• Special Certifications:    – NACE MR0175 (Sour Service Resistance)    – ATEX (Explosion Protection)    – CRN (Canadian Pressure Vessel Registration)

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