Slit Valve

1. What Is a Slit (Slot) Valve?

A slit valve (also known as a slot valve or sliding gate valve) features a long, narrow opening designed to allow plates, sheets, or continuous materials to pass through while maintaining system isolation.

Seals are typically installed:

• Around the slit perimeter
• On sliding or gate interfaces
• Between dynamic and static sealing surfaces

The main sealing challenge is:
Long sealing length, non-uniform load, sliding motion, and high cycling frequency.

2. Core Functions of Slit Valve Seals

1) Sealing & Isolation

·         Prevents leakage of gases, liquids, or powders

·         Maintains sealing integrity in both open and closed states

2) Allow Sliding Motion

·         The gate or plate slides across the seal surface

·         Requires low friction and high wear resistance

3) Tolerance Compensation

·         Absorbs flatness and alignment deviations of valve components

3. Typical Applications

4. Common Seal Designs

• Rectangular strip seals (most common)
• Lip-type or chamfered profiles to reduce friction
• Composite seals (rubber + PTFE or metal backing)

5. Common Rubber Materials & Selection

For semiconductor vacuum applications, key requirements include:
Low outgassing, low extractables, and minimal particle generation.

6. Key Performance Requirements

7. Common Failure Modes