Needle Type Stop Valve

I. Product Introduction

The stop valve, also known as a gate valve, is a forced sealing type valve. In the closed state, the valve disc must be pressed with force to ensure the sealing surfaces are tightly closed, preventing media leakage. In conventional structure stop valves, media flows in from below the valve disc. During opening/closing operations, the valve stem must overcome packing friction and media pressure thrust. The closing force is greater than the opening force, so the valve stem diameter is larger to prevent stem bending deformation during opening/closing.

With the iterative upgrade of self-sealing valve bodies, the stop valve media flow direction has changed from valve disc side flow to valve chamber flow, reducing media pressure force and opening load. The valve stem diameter can be reduced accordingly, while valve body pressure-bearing sealing performance is improved and media sealing tightness is further enhanced. The domestic valve industry three-standard standard specifies that enclosed stop valves uniformly adopt top-to-bottom media flow direction for installation and use.

II. Connection Methods

Stop valve on-site pipeline connections are available in three types, adaptable to different working condition pipeline installations:

1. Flanged Connection: Convenient disassembly, suitable for high-pressure, high-frequency maintenance pipeline conditions.

2. Clamped Connection: Quick installation, suitable for small to medium diameter, modular pipeline layouts.

3. Welded Connection: Excellent sealing, suitable for buried pipelines and high-pressure sealed long-term pipeline conditions.

III. Open/Close Determination Principle

The stop valve opening degree is controllable. When the valve disc opening height reaches 25%-30% of the valve nominal diameter, the pipeline media flow reaches the rated flow capacity, and the valve is determined to be in the fully open state. The fully open position is determined by the actual valve disc lift stroke as the standard, and cannot be judged solely by handle opening degree.

IV. Structure Classification

1. Conventional Pressure-Bearing Type: Bottom-in top-out media flow, large closing force, thickened valve stem design, strong structural bearing capacity, suitable for conventional high-pressure pipeline shut-off.

2. Self-Sealing Type: Valve chamber flow structure, balanced opening/closing force, smaller valve stem specifications, labor-saving operation, media self-pressure sealing, better anti-leakage effect.

V. Product Features

1. Excellent sealing performance, forced pressure sealing structure, effectively blocking media leakage after closing, isolating pipeline media flow.

2. Low flow resistance, valve disc fully open for direct media flow, small pipeline pressure loss, suitable for large-flow media transfer pipelines.

3. Diverse selection adaptability, three connection types available, conventional and self-sealing types for high/low pressure various pipeline conditions.

4. High open/close recognition, fixed opening degree achieves rated flow, controllable stroke, convenient for on-site full-open operation status control.

5. Compliant standardized design, conforming to domestic valve industry three-standard flow direction standards, suitable for engineering project acceptance and standardized pipeline construction.

VI. Application Fields

Suitable for hydraulic energy storage pipelines, oil and gas transfer pipelines, municipal water supply and drainage, heat pipeline networks, chemical process pipelines, and industrial and mining fluid pipelines. Mainly used for pipeline on/off isolation, not as a flow regulating valve. Can be used with accumulator hydraulic systems for oil circuit isolation protection.

VII. Usage Precautions

1. Strictly follow the top-to-bottom standard media flow direction during installation; do not install in reverse to avoid sealing force failure.

2. Apply pressure evenly when closing the valve; stop when sealing surfaces are engaged to avoid damaging sealing surfaces with excessive force.

3. Do not use for long-term throttling pressure regulation; only suitable for full-open and full-close operations to prevent long-term erosion wear of the valve disc.

4. Select flanged, clamped, or welded connection types based on pipeline pressure and maintenance frequency to improve installation stability.

5. Regularly inspect valve stem and packing seal wear; conventional type valve stems should avoid over-load opening/closing to prevent bending damage.

6. Determine full-open status by valve disc stroke; do not subjectively judge valve opening degree by handle position.