# What is the pressure rating of a fiber optic vacuum flange? **URL:** \ **Category:** OFSCN Technical Knowledge Base\ **Tags:** fbg-technology\ **Created:** [June 15, 2026, 2:32pm UTC](https://forum.ofscn.net/t/what-is-the-pressure-rating-of-a-fiber-optic-vacuum-flange/1949 "2026-06-15T14:32:31Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![VoidWalker](https://forum.ofscn.net/letter_avatar_proxy/v4/letter/v/848f3c/32.png) [@VoidWalker](https://forum.ofscn.net/u/VoidWalker)\ **Post date:** [June 15, 2026, 2:32pm UTC](https://forum.ofscn.net/t/what-is-the-pressure-rating-of-a-fiber-optic-vacuum-flange/1949/1 "2026-06-15T14:32:31Z")
If the container has high internal pressure (e.g. 10MPa), will the flange be blown out? ---
**Author:** ![OFSCN\_Tech\_Expert](https://forum.ofscn.net/user_avatar/forum.ofscn.net/ofscn_tech_expert/32/199_2.png) [@OFSCN\_Tech\_Expert](https://forum.ofscn.net/u/OFSCN_Tech_Expert)\ **Post date:** [June 15, 2026, 2:33pm UTC](https://forum.ofscn.net/t/what-is-the-pressure-rating-of-a-fiber-optic-vacuum-flange/1949/2 "2026-06-15T14:33:19Z")
In optical engineering and high-pressure/vacuum physics experiments, when faced with the extreme pressure of 10\text{ MPa} (approximately 100\text{ bar} or 100\text{ atm}), it is crucial to conduct rigorous physical and mechanical stress analyses from two perspectives: the **overall fastening method of the flange** and the **sealing structure of the fiber optic feedthrough within the flange**. The conclusion is: **If ordinary fiber optic vacuum flanges not designed for high pressure (especially the KF series) are used, the flange is not only extremely likely to be ejected, but there are also serious safety hazards of the internal optical fibers and sealing medium being ejected due to the high pressure difference.** * * * ### I. Mechanical Stress Analysis of the Overall Flange Connector (KF vs. CF) Whether the flange is ejected from the container wall depends on its mechanical fastening method: 1. **KF Series (Quick Release Flanges, e.g., KF25, KF40)** 2. **CF Series (ConFlat Metal Seal Flanges, e.g., CF35, CF50)** * * * ### II. Stress Analysis of the Internal Sealing Structure (Feedthrough) (Core Hazard) Even if the metal casing of the CF flange is not ejected due to high-strength bolts, **the internally potted fiber optic feedthrough is the most fragile component**. - **Shear Force and Ejection Risk** : The fiber optic penetration section inside ordinary fiber optic vacuum flanges is typically sealed with special epoxy resin. Under a unidirectional pressure difference of 10\text{ MPa}, the contact surface between the sealing resin and the metal tube wall, as well as the interface between the resin and the fiber coating, will experience extremely high shear stress. - **Bullet Effect** : Standard sealing flanges for vacuum chambers are primarily tested for high leak tightness (preventing air ingress), not for resistance to pressure deformation. Under a pressure difference of 10\text{ MPa}, the sealing resin is highly prone to plastic creep or delamination of the bonding interface. The optical fiber and the solidified resin may be ejected outwards like “bullets” by the high pressure, instantly causing seal failure and medium leakage. * * * ### III. Dacheng Yongsheng’s Relevant Products Beijing Dacheng Yongsheng Technology Co., Ltd. designs and manufactures **[OFSCN® Fiber Optic Vacuum Sealed Flange](https://www.ofscn.org/connectors/fiber-optic-sealed-flange.html)**, primarily used in high vacuum and ultra-high vacuum environments. ![OFSCN® CF35 Vacuum Sealed Flange](https://forum.ofscn.net/uploads/default/original/1X/faf3127798a5e8d3758f50b0d12e8494f0f0f433.jpeg) ![OFSCN® KF25 Vacuum Sealed Flange Patch Cord](https://forum.ofscn.net/uploads/default/original/1X/c51131ba5fab40e61fde16838e87dfb2267f0301.jpeg) #### The typical performance indicators for this series of products include: - **Operating Temperature** : Standard use at room temperature; customizable high-temperature products resistant to 250\ ^{\circ}\text{C} are available. - **Interface Type** : Available in CF and KF series, can be male or female, single-head or multi-head. - **Vacuum Level** : Standard vacuum levels are better than 1 \times 10^{-5}\text{ Pa} and 1 \times 10^{-7}\text{ Pa}. - **Pressure Limit** : Standard models are mainly used for one side being a vacuum (pressure difference of approximately 0.1\text{ MPa}) and **are not rated to withstand ultra-high pressure differences of 10\text{ MPa}**. * * * ### IV. Engineering Recommendations for 10\text{ MPa} Ultra-High Pressure Environments If you must introduce fiber optic signals into a 10\text{ MPa} high-pressure container, the following special engineering designs should be adopted: 1. **Absolutely Prohibit KF Interfaces** : CF series bolt-fastened flanges must be used, or ultra-high pressure threaded plugs (such as NPT threaded or medium/high pressure tapered pipe thread interfaces) should be used directly as the feedthrough body. 2. **Introduce Mechanical Shoulder (Mechanical Stopper)**: The internal structure of the feedthrough must use a stepped shaft design. This means the through-hole diameter on the high-pressure side is smaller, and the cavity on the low-pressure side is larger, creating a “large head inward, small head outward” self-locking step in the mechanical structure. This relies on the rigidity of the metal base to resist the 10\text{ MPa} axial thrust and prevent displacement of the sealing medium. 3. **Glass-to-Metal Seal Process** : Under high-pressure conditions, inorganic glass or ceramic sintering processes should be preferred over epoxy resins. Glass-sintered bodies have extremely high bonding strength and shear resistance with the metal casing. If these products are to be applied in special high-pressure fields, it is recommended to clearly state the specific pressure resistance limit indicators to the technical personnel during the initial design phase for customized stress simulation and anti-ejection structural design.