From Dry Gas Seals Handbook


As discussed in chapter 3, a barrier seal is an integral component of the dry gas seal assembly, installed outboard of the dry gas seal (see chapter 3 figures). The barrier seal, sometimes referred to as a separation seal, separates the gas seal from the compressor shaft bearings. A separation gas (typically nitrogen or air) is injected into the barrier seal, whose primary function is to prohibit the flow of bearing lubrication oil or oil mist into the gas seal. The barrier seal also serves as the last defense in the event of a catastrophic failure of the primary and secondary gas seals.

In the early years of gas seal applications, labyrinth seals were the only available option for the prevention of lube oil migration into the gas seal, and they proved to be quite effective. The current state-of-the-art barrier seal is the segmented carbon ring seal (fig. 4-1), which has replaced labyrinth seals in most barrier seal applications. Segmented carbon ring barrier seals offer the advantage of substantially lower separation gas consumption because of their much smaller shaft clearance compared to labyrinth seals.

Figure 4-1: Segmented carbon ring barrier seal

Segmented carbon ring barrier seals are typically comprised of two sets of circumferential rings, an inboard ring and an outboard ring, contained within a housing (fig. 4-2). Each ring consists of several carbon segments that are held together by a garter spring around the circumference of the ring. The inboard and outboard rings are held in place axially...

Products & Services
Dynamic Seals
Dynamic seals include oil seals, hydraulic and pneumatic seals, exclusion seals, labyrinth seals, bearing isolators, and piston rings. They create a barrier between moving and stationary surfaces in applications such as rotating shafts and pistons rings.  This is a general search form; more detailed search forms are available.
Labyrinth Seals and Clearance Seals
Labyrinth seals and clearance seals are minimum-leakage seals that protect machine elements from contamination through a noncontact method. They operate on the principle of positive clearance and do not rub on shafts or housing. 
Bearing Isolators
Bearing isolators are dynamic seals designed to protect bearings from outside contaminants.  They are comprised of a rotor (rotating) and stator (stationary) member.
V-ring Seals
V-ring seals are all-rubber seals used primarily to exclude dirt and other contaminants. They are stretched over shafts and seal against the side of housing or another machine component.
Hydraulic Seals and Pneumatic Seals
Hydraulic seals and pneumatic seals include piston seals, rod seals, U-cups, vee, cup, and flange packings.

Topics of Interest

Overview Using dry gas seals in a centrifugal compressor requires a support system designed to supply sealing gas to the seal as the working fluid for the running gap. These gas seal support systems...

Glossary B-G balance diameter: The diameter that separates the high (seal gas supply) pressure area from the low (seal vent) pressure area of the primary gas seal ring. This is typically sealed with...

Overview Thousands of centrifugal compressors were manufactured before the advent of dry gas sealing technology. Most of these compressors are equipped with oil film seals (fig. 6-1). Figure 6-1:...

Centrifugal compressors in process gas service require shaft sealing to prevent the process gas from traveling down the shaft and escaping the compressor case into the atmosphere. Multistage,...

Secondary Gas Seal Vent As explained in chapter 3, seal gas for a tandem gas seal is injected between the inner labyrinth seal and the primary gas seal. A very small amount of the sealing gas passes...

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