MECHANICAL SEALS
A mechanical seal is a set consisting of two sub-assemblies that provides sealing efficiency between the rotary part and the stationary part and is generally used to seal shafts in pumps, agitators, etc.
The basic principle is common to all mechanical seals: provide sealing efficiency between two moving faces, lubricated by a liquid film, the so-called primary sealing.
• The film maintained by the rotation comes from the medium conveyed by the machine or is an auxiliary fluid.
• An insignificant part of the film may flow out of the friction faces: this flow is called the consumption of the seal.
• The friction, at the level of the film, produces calories that heat the friction faces, the film itself and the surrounding fluid.
• To ensure optimum seal face service life, the film must be stable and liquid.
• To prevent it from vaporising, the fluid to be sealed should have a sufficient pressure at the level of the seal faces.
Depending on the service conditions, the nature of the fluid and the industrial applications, there are three types of seals (two-component or cartridge seals in single or dual configuration). Depending on the applications, unbalanced (U) or balanced (B) may be used.
Secondary sealing is ensured by O-rings, elastomer bellows, welded or hydroformed metal bellows that provide leakproof connection between the friction faces and holders.
Depending on the design, other adaptation elements may be associated to the sub-assemblies (sleeves, flange, cover, drive ring, etc.)
What fluid is the mechanical seal designed to seal?
It is necessary to know the characteristics (abrasive, corrosive, volatile, etc.) and additional information about the fluid, such as its chemical formula, concentration, density, composition in the case of a mixture, crystals and solids, toxicity, corrosiveness (pH), volatility (vapour pressure) and viscosity.
What is the pressure acting on the mechanical seal?
This information is required to select a balanced seal (B) > 10 bar or an unbalanced seal (U) < 10 bar.
What is the rotational speed of the mechanical seal?
A mechanical seal must be dynamically stable at its rotational speed. Geometric defects in the machine (such as misalignment between the stator and the rotor, for example) lead to an unstable interface film at high speeds.
Above 20 m/s, stationary mechanical seals should be selected as they can accommodate greater geometric misalignment because they are not subject to centrifugal forces. To avoid generating heat and to promote the interface film, the choice of materials is dependent on the speed.
What is the operating temperature of the mechanical seal?
All components of the mechanical seal must remain intact throughout the entire operating temperature range.
Does the customer require any approvals, standards or directives?
Our mechanical seals can be supplied with approvals, standards or directives such as FDA, CE 1935/2004, WRA or ATEX.
Changes to the CE 1935/2004 standard following the entry into force of the decree of 5 August 2020
As part of our commitment to quality and safety, we ensure that all seals incorporated into our equipment comply with the requirements of the Decree of 5 August 2020 on rubber materials and articles intended to come into contact with foodstuffs.
Since 1 July 2025, new restrictions on the use of certain substances in elastomers, notably EPDM and FKM/Viton, have come into force. In order to anticipate and ensure full compliance with this regulation, the LATTY GROUP has implemented appropriate solutions to meet the requirements of this decree.
