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Basic Principle of Direct-Type Gas Pressure Regulators

A direct-type gas pressure regulator is a device that achieves automatic adjustment through the self-pressure of the medium (gas), requiring no external energy drive. It primarily uses the principle of pressure balance and mechanical feedback mechanisms to reduce and stabilize pressure. Its core structure includes sensing elements (e.g., diaphragms, springs), regulating elements (e.g., valve cores, valve seats), and feedback mechanisms, with the working principle as follows:

1. Initial State: Pressure Balance

• Inlet Pressure: Gas flows into the regulator from the inlet. At this time, the inlet pressure P1​ acts on the valve core through the lower part of the diaphragm, attempting to push the valve core upward (closing the valve).
• Outlet Pressure: The outlet pressure P2​ forms a reverse balance with the spring force through the upper part of the diaphragm (or spring chamber), attempting to push the valve core downward (opening the valve).
• Balanced State: When the resultant force of P2​ and the spring force equals P1​, the valve core remains stationary, the valve opening stabilizes, and the outlet pressure maintains the set value.
   

2. Adjustment Process During Pressure Fluctuations

Case 1: Outlet Pressure P2​ Decreases (e.g., increased gas consumption)

• Sensing Stage: The outlet pressure drops, reducing the pressure above the diaphragm (or in the spring chamber) and breaking the original balance.
• Action Stage: The diaphragm moves downward under the action of the inlet pressure P1​, driving the valve core downward. The valve opening increases, allowing more gas to flow to the outlet.
• Feedback Stage: As the gas flow increases, the outlet pressure P2​ gradually rises until it rebalances with the spring force. The valve core stops moving, and the outlet pressure returns to the set value.

Case 2: Outlet Pressure P2​ Increases (e.g., decreased gas consumption)

• Sensing Stage: The outlet pressure rises, increasing the pressure above the diaphragm (or in the spring chamber) and exceeding the resultant force of the inlet pressure P1​ and the spring force.
• Action Stage: The diaphragm moves upward, driving the valve core upward. The valve opening decreases, reducing the gas flow.
• Feedback Stage: The outlet pressure P2​ subsequently drops until it rebalances with the spring force. The valve core stops moving, and the outlet pressure stabilizes at the set value.
   

3. Roles of Key Components

4. Characteristics and Application Scenarios

• Advantages:
  • Simple structure, low cost, and easy maintenance;
  • Fast response, suitable for scenarios with frequent flow changes;
  • No external power required, relying on the gas’s own pressure for operation, with high reliability.
• Disadvantages:
  • Adjustment accuracy is significantly affected by inlet pressure fluctuations (when the inlet pressure P1​ changes drastically, the outlet pressure P2​ may deviate from the set value);
  • Limited applicable flow range, typically used in small-to-medium flow scenarios.
• Typical Applications:
  • Single-household pressure regulation for residential users (e.g., regulators behind household gas meters);
  • Small commercial users (e.g., restaurants, small boiler rooms);
  • Regional pressure regulation boxes or building-level pressure regulation devices at the end of the pipeline network.

5. Comparison with Indirect-Type Regulators

Thanks to its simplicity and self-sufficiency, the direct-type pressure regulator has become one of the most commonly used basic pressure regulation devices in gas transmission and distribution systems, particularly in end-user and small-scale systems.

Information Source: http://www.ccgas.net (Gas Technology Knowledge Column)