A Detailed Guide on Mechanical Seals

by Mike H. Marketeer

Mechanical seals have an important role to play in centrifugal pump systems. They work as the devices that protect the pump system's efficiency by preventing fluids from leaking and keeping the environmental pollutants from getting into the system. Mainly, mechanical seals are used on centrifugal pumps to detect leaks, lubricate the secondary seals, and manage the environment.

Mechanical Seals

A mechanical seal can be defined as the way of confining a liquid within a vessel such as rotating pumps, mixers, and so on, where a rotating shaft passes through a fixed housing or the housing revolves around the shaft.

A mechanical seal keeps fluids in and pollutants out of the spinning shaft on a pump or mixer. They are intended to prevent leakage between a rotating shaft and its housing, under severe temperature conditions, shaft speed, and severe pressure. Mechanical seals are classified as either single-acting or double-acting. There is just one sealing gap in a single (active) mechanical seal.

Mechanical seals consist of two flat sides which are mounted perpendicular to the shaft. One side is attached to the seal chamber housing. The main seal is provided by the opposite face, which rotates inside the shaft. Between the gaskets, the face materials are held by fluid pressure and axial mechanical force. This contact keeps the fluid inside the pump and prevents leaks.

Different Types of Mechanical Seals

Mechanical seals for centrifugal pumps are available in a variety of styles and configurations. Some of the most commonly used ones are:

1.     Balanced seals

2.     Unbalanced seals

3.     Pusher seals

4.     Non-pusher seals

5.     Conventional seals

6.     Cartridge seals

Balanced Seals

Balanced mechanical seals are the ones in which the forces acting on the faces of the seal are balanced. The lower face load allows for more accurate lubrication of the sealing faces and longer seal life. Balanced mechanical seals for handling liquids with poor lubricating capacity and hydrocarbons with high vapor pressure as they can withstand larger pressures across their faces and create less heat.

They are ideal for higher operating pressures and are also a suitable choice for working with liquids that have minimal lubricity and high volatility.

Unbalanced Mechanical Seals

Unbalanced mechanical seals are widely used as a less expensive alternative to the balanced mechanical seal. Unbalanced mechanical seals are utilized in extreme settings when there are vibrations, shaft misalignment, and the problem of fluid cavitation. Unbalanced seals have a substantially shorter mean duration between failures and have less product leakage due to better control of the face film.

Unbalanced seals should not be used in most hydrocarbon or high-pressure applications.These mechanical seals are affordable, allow for reduced fluid leakage, and are extremely stable. However, unbalanced mechanical seals only work at low pressures, and the seal can break if the fluid force surpasses specified limitations causing the lubricating film between the faces to squeeze out.

Pusher Seals

Pusher mechanical seals maintain contact with the seal faces by traveling axially along the spinning shaft or sleeve. Pusher mechanical seals are available in a broad range of sizes and configurations making them one of the most common seals to be used. They are also less costly and offer to seal at extremely high pressures, but the main drawback to these seals is that they can cause fretting of the shaft.

Pusher seals rely on one or more springs to keep the seal closed. The springs in the mechanical seal might be in either the rotating or stationary part.

Non-pusher Seals

Non-pusher or bellow mechanical seals do not need to travel axially to maintain contact with the seal faces. Non-pusher seals rely on metal or elastomeric bellows to keep the seal closed and are suitable for both low and high temperature and low and high-pressure applications. The bellows utilized in these seals can function in corrosive conditions.

Conventional Seals

Conventional seals are basic mechanical seals that must be positioned properly and adjusted correctly on the pump's shaft or sleeve. They are used on regular service machinery and are less expensive than other seal types. Conventional seals need proper operator expertise to function as they are fitted as independent components.

Cartridge Seals

Cartridge mechanical seals are the seal type that combines all of the seal components into a single unit. Unlike other traditional seals, cartridge seals do not need an elaborate setup during installation. There are little to no chances of assembly mistakes in cartridge seal, hence they require low maintenance as well.

Why Choose Mechanical Seals?

Mechanical seals are critical components of every machine or pump. The pump shaft or sleeve are not harmed by modern cartridge seal designs and prevent leakage which can cause damage to a pump. Mechanical seals contain inboard springs that allow them to self-adjust when the faces wear whichreduces their day-to-day maintenance. Mechanical seals have lightly loaded faces that require less power to operate than other conventional shaft seals. Normal operation reduces bearing contamination since the lubricant is not impacted by seal leakage and washes out.

Mechanical seals must be of high quality and well-made for them to function properly in a pump. It is critical to use the proper seal from a good manufacturer for the correct purpose and get your mechanical seals maintained and repaired regularly for a longer pump life and better efficiency.

Mechanical Seal Solutions From a Professional

To get reliable mechanical seal solutions in Texas, check out the engineering services from Robco of America. The mechanical seal repair experts provide mechanical sealing repair services and specialize in mechanical pump seal parts, valve packing, mechanical pump packing, and more.  Their trained professionals can help you with their seal repair or replacement services, engineered industrial parts, and fluid sealing solutions.

For more information, call them at 800-662-0585.

About the Author

Glenn Jacob has been a mechanical seal division expert for the past 20 years and has been in charge of coordinating new product developments and managing the engineering department. He has been providing technical assistance to distributors and the sales force with his expertise in engineering workflows. Glenn has been continuously writing about the evolving technologies in STEM and providing industry insights on how to make engineering processes smoother and more efficient.

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Created on Dec 9th 2021 02:45. Viewed 231 times.

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