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I. Impact on Sealing Performance

1. Grade VI

The medium hardly leaks from the sealing surface. The storage and pressure retention effect is excellent when the pipeline is fully closed; it is suitable for applications requiring strict isolation: tap water, pure water, pharmaceutical solutions, gas. It can maintain pressure without leakage during shutdown.

2. Grade IV

There is a slight leakage. It meets the requirements for industrial conventional isolation. For steam, heat transfer oil, and flue gas conditions, slight leakage is allowed. The pressure retention is achieved through slow pressure release.

3. Grade II and Grade III have relatively larger leakage, which cannot be used for strict isolation. They can only be used for throttling and regulation, and cannot be applied to flammable and explosive, or valuable liquid isolation.

II. Impact on Dielectric Loss and Production Costs

High leakage level (Ⅱ/Ⅲ): Even when the valve is fully closed, there is still continuous leakage of materials. Long-term leakage of oil products, chemical raw materials, and steam leads to waste of raw materials and increased energy consumption;

Level VI low leakage: Shutting down without any leakage, saving dielectric loss, and making the chemical and heating projects more cost-effective in the long run (product selling point).

III. Impact on Working Condition Safety

1. Flammable and explosive media (gas, chemical solvents)

Must be of VI level or high IV level. Excessive leakage will cause flammable media to accumulate, leading to fire and explosion; Valves with low leakage levels must not be used in hazardous chemical pipelines.

2. Toxic and corrosive media

Excessive leakage will corrode pipelines, pollute the environment, and endanger personal safety. V/IV level precision sealing is strictly required.

3. Drinking water and food media

VI-level sealing must have no leakage and no stagnant water accumulation, to prevent bacterial growth and comply with hygiene standards.

IV. Impact on Flow Regulation Performance

1. High Sealing (Grade VI): Completely sealed without leakage, precise opening degree, high regulation accuracy, capable of precisely controlling flow for central air conditioning and water treatment systems;

2. Excessive Leakage (Grade II/III): Even when fully closed, there is a fixed leakage rate. The minimum flow cannot be controlled, making precise regulation impossible. It is only suitable for rough on-off operations.

V. Correlation between Operating Temperature, Pressure and Service Life

1. Grade VI Soft Sealing: Optimal performance at normal temperature and low pressure. After rubber aging at high temperatures, the leakage level decreases and the leakage volume increases;

2. Grade IV-V Triangular Eccentric Hard Sealing: Strong sealing stability at high temperatures and high pressures. The leakage level decays slowly under long-term high-temperature conditions, resulting in a longer service life;

3. Inferior Ordinary Hard Sealing: Sealing wears out after a period of use, with the grade dropping from Grade III to Grade II. The leakage gradually increases and frequent maintenance is required.