What are vacuum flanges?
Flanges are an important part of a vacuum system; they achieve and maintain the seal between the viewport and the vacuum chamber.
We manufacture three different vacuum flange styles at Torr Scientific, these are CF, KF and ISO flanges. Each has their advantages and disadvantages, and choosing the right option for your vacuum setup is hugely important.
So, in this article, we will be looking at the question: what are the benefits and differences between these types of flanges?
What is a Conflat®flange?
Multiple viewports with a CF flange in assorted sizes
The Conflat®(CF) flange is the most common choice of flange for vacuum systems.
It is fully constructed from metal, which means it can reach higher bake‑out temperatures than the alternative, an O‑ring (used for KF and ISO flanges). The O‑ring is constructed from elastomer and therefore melts at lower temperatures than the copper gasket used with CF flanges.
Copper gaskets work due to the ‘knife edge’ on a flange. This is a thin‑raised border that ‘bites’ into the gasket when under pressure, leading to the gasket compressing and distorting to fill the space, creating a seal.
Torr Scientific manufacture these gaskets from copper, as it is a highly malleable material, making it perfect for this purpose. They are made even softer with our annealing process, to allow for a leak‑tight seal with less force.
The CF flange is sealed with bolts, allowing for a more robust sealing than with clamps.
This style of flange is classified as ‘sexless’, meaning both parts are identical. However, it is important to pay attention to which holes are tapped for a successful installation.
Here at Torr Scientific, any product containing a flange will be available with a Conflat® flange.
What is a klein flansche flange?
Multiple viewports with a KF flange in assorted sizes
The name for the KF flange comes from ‘Klein flansche’, which is German for ‘small flange’.
This flange is sealed using a tapered circular clamp, featuring a centring ring and an O‑ring. O‑rings are constructed from a flexible elastomer, which when compressed expands to fill the space between the flange, the Centring ring is metallic to provide structure to the seal. Due to the user‑friendliness of the clamp, this is considered the quick‑release flange. This is in opposition to bolts, which can be more complicated to assemble or disassemble, and copper gaskets which are one‑time use only. The KF flange can be considered a “sexless” flange as both sides of the seal are identical.
This style of flange is available with many Torr Scientific’s smaller products, from the KF16 up to the KF50.
Multiple viewports with an ISO flange in assorted sizes
What is an ISO flange?
The ISO flange was designed to fit the vacuum flange standards set by the International Organization for Standardization. Therefore, this style of flange is named after the organisation. There are two sub‑types of the ISO flange, these being the ISO‑F and the ISO‑K.
An ISO-F style viewport
The ISO‑F is comparable to the CF flange, as it is sealed using bolts, and is also similarly “technically” sexless. However, for both flanges it is important to pay attention to which holes are tapped.
ISO ‑K style viewport
The ISO‑K seal in comparison is comparable to the KF flange. Although, they differ with the specific mechanism. The ISO‑K flange is sealed with claw clamps versus the circular clamp used by the KF flange.
Vacuum flanges at Torr Scientific
As shown through this article, Torr scientific offer a variety of flanges that fit into our vacuum viewports. Deciding which is best for your project can depend on the necessary vacuum levels, temperature bake-out requirements and the size of the flange for your chamber. Our team of experts can help you match your project with the ideal vacuum flange.
As well as the flange style, for a vacuum viewport you will also need to decide upon the optic and weld ring material.
Additionally, we also have blank flanges available in each flange style. These are removable seals for vacuum chambers, to close off the opening without requiring a viewport.
You can view our optical materials options on our website and we have kovar or non-magnetic options for the weld rings.
To enquire about our vacuum viewport please reach out to our sales team!
