Large‑size O‑rings are critical sealing components for industrial equipment. Their production and selection directly determine sealing performance and operational stability. Compared with standard O‑rings, large‑size versions require special considerations in material selection, design, and manufacturing due to their dimensions and harsh working conditions.

They are widely used in heavy‑duty, high‑pressure equipment including large machine tools, ships, petroleum machinery, and construction machinery. Seal quality and compatibility directly affect leakage risk and equipment reliability. Mastering proper selection criteria and processing standards is essential to ensure sealing performance and extend service life.

Three core technical details must be strictly controlled to prevent sealing failure and ensure optimal performance:

1. Accurate Calculation of Key Sealing Parameters

Precisely calculate critical parameters:

• Pre‑stretch ratio for piston seals

• Pre‑compression ratio for rod seals

• Cross‑section shrinkage ratio

These parameters determine fit and sealing performance. Incorrect values may cause poor sealing, excessive deformation, premature wear, or early failure.

2. Material Compatibility and Swelling Resistance

Verify compatibility between the O‑ring material and sealed media, and evaluate swelling behavior in service.

Incompatible materials can cause swelling, deformation, strength loss, seal rupture, and leakage. Compatibility testing is mandatory before selection.

3. Thermal Expansion and Dimensional Matching

Large O‑rings expand and contract with temperature changes. Allow sufficient dimensional tolerance based on operating temperature to avoid sealing failure.

Practical dimensional guidelines:

(1) Piston seal:

If groove diameter = 780 mm, O‑ring inner diameter (including tolerance) must be ≤ 780 mm to ensure proper pre‑stretch and tight sealing.

(2) Rod seal:

If groove diameter = 780 mm, O‑ring outer diameter (including tolerance) must be ≥ 780 mm to ensure sufficient pre‑compression and prevent leakage.