Mechanical seal pump: features and benefits

News 19 August 2024

A mechanical seal pump is a popular choice due to its reliable performance and ability to operate in harsh environments, making it ideal for many industrial and commercial applications.

Its main strength is a design that allows fluids to be kept separate in two distinct environments, preventing any communication between them. In electric pumps, the mechanical seal allows the rotating shaft to come into contact with the fluid without causing leakage. For this reason, the sealing systems are installed between the shaft and the pump housing, ensuring friction resistance and effective pressure control.

Let’s now examine this type of pump in detail, its benefits and its main characteristics.

Mechanical seals on pumps: operation

A mechanical seal pump, such as those present in CDR Pompe’s CCL line, represents an evolution from previous pumping systems, overcoming their limitations in strength and productivity. In this type of pump, the mechanical seal acts as an interface between the static part (the housing) and the dynamic part (the shaft) of the pump.

The rotating section, which connects to the shaft, is sealed by an O-ring, a ring seal made of elastic materials, available in different sizes. This gasket is designed to adapt to deformations and ensure an effective seal.

Mechanical seal systems for pumps generally include three points of contact: two on the static part and one on the dynamic part, near the rotating shaft, which is particularly critical. This last element is essential for the effectiveness of the system and includes a surface with two bearings, one fixed and one rotating, designed to reduce friction. The bearings are kept under pressure and stabilised by a spring, thus preventing leakage of liquid.

To ensure proper operation and prevent wear, bearings must be constantly lubricated with a fluid film during use. The distance between the bearings must be very precise, about 1 micron, to allow frictionless fluid movement and prevent leaks.

Single or double mechanical seal pump

A mechanical seal pump can be either single or double, like the models in our UCL line.

The main difference between a single seal and a double seal mechanical pump lies in the number of sealing surfaces and their arrangement.

Here’s an overview of the differences:

Single mechanical seal pump

Number of sealing surfaces: it has only one pair of mechanical sealing surfaces.
Structure: the seal consists of a single pair of sealing faces, one mounted on the pump body and the other on the shaft.
Applications: Suitable for applications where the fluid pressure is relatively low and the risk of leakage is contained. It is generally used in less aggressive environments or with less corrosive fluids.
Maintenance and costs: usually simpler and less expensive to install and maintain than double sealing. However, if the single seal fails, it can lead to direct fluid leaks.

Double mechanical seal pump

Number of sealing surfaces: it has two pairs of mechanical sealing surfaces.
Structure: it has two sets of sealing faces, mounted in series, which work together to ensure a more secure seal. One pair of sealing faces is in contact with the pumped fluid, while the other is in contact with a washing or ventilation chamber.
Applications: suitable for applications in high pressure environments or with highly corrosive, toxic or expensive fluids. Double sealing is often used when it is necessary to reduce the risk of leakage or when safety is critical.
Maintenance and costs: more complex and expensive to install and maintain than the single seal, but offers additional protection against leaks. If one of the sealing pairs fails, the other provides additional protection.

The advantages over pumps with traditional systems

Compared to a stuffing box seal, which requires periodic adjustments or replacements due to friction on the seal, a mechanical seal pump offers numerous advantages.

It is more resistant and consumes less energy, and also has other significant benefits, including:

Reduction of leaks: fluid leaks are minimal and occur mainly in the form of steam.
Shaft protection: does not damage the pump shaft, ensuring greater durability and reliability.
Less maintenance: it requires less maintenance thanks to the automatic adjustment of the internal springs.
Energy efficiency: consumes less energy than stuffing box seals.
Reduction of contamination: less contamination of bearings and reduced risk of equipment corrosion.
Vacuum seal: it also guarantees the seal of the vacuum, reducing air intake.

The adoption of mechanical seals therefore reduces water consumption and operating costs, contributing to economic savings and greater sustainability.

Comparison of mechanical seal pumps and drive pumps

At CDR Pompe, we produce both mechanical seal pumps and magnetic drive pumps, each with its own specific characteristics and advantages.

Mechanical seal pump

Our mechanical seal pumps are designed to handle chemical liquids, abrasive fluids and dirty industrial liquids.

Benefits:

Absence of metal adjustment mechanisms: suitable for various industrial sectors.
Corrosion resistance: they require quick and economical maintenance.

Disadvantages:

Potential leakage: possibility of leakage to the external environment.
Greater maintenance: shorter duration compared to magnetic drive and greater maintenance interventions, especially on the mechanical seal

Magnetic drive pump

Magnetic drive pumps are designed without a mechanical seal, using a magnetic joint divided into two parts to isolate the pumped liquid from the atmosphere. They are ideal for pumping hazardous liquids, as they are free from external leakage, but require clean liquids.