The sealing performance of an O-ring does not rely simply on material hardness, but rather cleverly utilizes the medium pressure itself. During installation, constrained by the groove, the O-ring is forced to produce a cross‑sectional deformation of 8%–30%. This elastic restoring force generates an initial stress at the contact interface, sealing off the first leakage path. When system pressure intervenes, the medium pushes the O-ring toward the low‑pressure side of the groove, and the circular cross‑section tends toward a "D" shape. At this point, the medium pressure is transferred almost losslessly into additional contact stress (with a pressure transfer coefficient close to 1), thereby achieving the dynamic effect that "the higher the pressure, the tighter the seal fits". From this it follows that controlling the deformation space is more effective than simply increasing the compression amount.  

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The selection of key parameter values determines whether the O-ring continues to serve or gradually deteriorates. For static seals, the recommended compression ratio is 15%–25%, ensuring that after long‑term compression there remains sufficient margin to compensate for permanent deformation; for reciprocating motion, 10%–12% is recommended to balance sealing performance against frictional heat generation; for rotary motion, it is strictly controlled within 3%–5%, because the Joule heating effect is significant, and even a slight excess in interference may trigger thermal bursting. In addition, a 1% stretch causes the cross‑sectional diameter to shrink by approximately 0.5%, directly weakening the compression ratio – for rod seals, the stretch should be ≤5%, while for shaft seals, the circumferential compression is preferably controlled at 2%–3%. This rule is often overlooked, yet it is a primary cause of leakage immediately after installation. When the pressure exceeds 5–7 MPa, the need for adding a backup ring to prevent extrusion must be evaluated; however, it should be clarified that even with a backup ring, the conventional static sealing upper limit is approximately 30–100 MPa (with hardness 70–90 Shore A). Claims of exceeding 200 MPa go beyond the physical limits of rubber – metal seals should be selected instead. For dynamic seals with backup rings, the recommended upper limit is generally 40 MPa.  

Material selection is by no means "oil‑resistant equals universal". For example, EPDM resists steam and ozone, but rapidly swells in contact with mineral oil; FKM resists high temperatures and acids/alkalis, yet is sensitive to low‑molecular‑weight alcohols. The core principle is that medium compatibility takes precedence over temperature resistance grade – a volume swell exceeding 15% is regarded as incompatible. From failure traces, the root cause can be deduced backward: extrusion and nibbling result from excessive clearance, with countermeasures being adding backup rings or increasing hardness; twist fracture is common in dynamic seals, where the O‑ring "rolls and twists" inside the groove – the solution is to switch to an X‑ring or increase lubrication; compression set occurs because high temperature accelerates stress relaxation of the rubber – when the set exceeds 15%–20% of the original compression amount, failure is declared; for environments above 120°C, NBR must be abandoned and FKM selected instead. 80% of early failures actually originate from installation damage – when passing over threads, keyways, or sharp edges, it is imperative to use installation mandrels and lubricating grease, ensuring that cleanliness, guidance, and positioning are all indispensable.  

Seal design is, in essence, a precise calculation of stiffness matching and material tolerance. It is the deformation and clearance at the millimeter level that, amid the reality of pressure fluctuations, holds the bottom line of zero leakage.  

Bonve pump always adheres to the philosophy of "Wholeheartedly Making Good Rotor Pumps," committed to providing global customers with customized conveying and mixing solutions. If you have technical inquiries, selection needs, case references, or other cooperation intentions related to Bonve rotor pumps, please feel free to contact us.  

Service Hotline: 0574-87588986 13586591794  

Official Website: www.bvpumps.com  

Business Email: market@bonvepumps.com  

We look forward to working with you to drive efficiency and innovation in industrial fluid transmission with precision technology.