Seals

Types of Seals
 

Introduction

The mechanical seals in centrifugal pump systems are essential. These components keep fluids inside the pumps and unwanted debris out, ensuring the longevity of the pumping systems. 

For example, a notary seal is a tool used by a notary to authenticate legal and technical papers, while a security seal is intended to prevent things from being opened without authorisation or detect and notify the existence of tampering.

Users and operators must take responsibility for the upkeep of the mechanical seals. For this reason, it's crucial to learn everything you can about mechanical seals, from how they work to the conditions necessary for installation to common causes of their failure.

Here, a failures evaluation method on mechanical seal losses in the complex is consolidated in an effort to assemble the numerous failures that are seen with mechanical seals.

Seal Types 

1. Axial Shaft Seal

Like radial shaft seals, axial shaft seals (or face seals) are used to stop process fluids from leaking along rotating shafts and elements and to keep contaminants out of the system. These seals are installed on the shaft and rotate with it; they consist of a stationary and rotating component, a spring-loaded seal, and a secondary seal (e.g., an O-ring) and are able to withstand slight variations in placement and shaft movement.

2. Radial Shaft Seals 

Lip seals, or radial shaft seals, are used to seal the bearing elements of rotating shafts and other parts and to prevent pollutants from entering the equipment or system. These stationary seals prevent leakage around the periphery of the spinning component, and they typically have a metal inserts and an elastomeric membrane with a spring-loaded closing lip.

3. Labyrinth Seals

Labyrinth seals have an inner and an outer ring with a grooved route in between to prevent process fluids from leaking out or getting in. These seals prevent leaks from moving parts without making physical contact with them.

4. Cartridge Seals 

Cartridge seals are mechanical sealing systems that include a shaft sleeve, seal, and gland plates, all of which are preassembled and ready to use. These units come in single, double, and tandem formats, each of which allows for speedy installation and removal.

5. Bellow Seals 

For reciprocating machinery, bellow seals serve as both a primary dynamic seal and a spring. These gadgets can be constructed from metal, plastic, or elastomeric bellows, and they provide a secondary static seal.

6. O-Rings 

O-rings, or packing, are a type of circular, ring-shaped mechanical gasket that has both static and dynamic uses. When compressed, an O-ring forms a leak-proof seal that can endure high temperatures and pressures and is designed to fit into a groove or housing between two parts.

7. Gaskets 

Gaskets are used to seal joints and prevent leakage; they are often made of flat, elastomeric or similarly flexible material. Secondary seals in static applications can be found in a variety of device types and sizes.

8. Balanced mechanical seal

The term "balanced mechanical seal arrangement" is used to describe a system where the forces applied on the seal faces are equal. Lower face loading allows for more uniform lubrication of the seal faces, which in turn increases seal life.

9. Tandem Seal

This seal is not meant to provide a controlled environment like a double seal would, but rather to act as a backup in case the inner seal fails.

A closed reservoir is used to lubricate the outer seal by flooding the cavity between the inner and outer seals. The substance acts as a lubricant for the inner seal.

10. Pusher Seals

One or more springs are used in pusher seals to maintain the seal closing forces. Mechanical seals may use springs in either the revolving or stationary parts. Pusher type seals have the advantage of being able to provide fixing at extraordinarily high pressures, but they have a drawback in that the elastomer under the crucial seal face might be subjected to wear as the face advances and along shaft/sleeve during operation.

11. Water pump Seals

Due to water's lack of lubricity, it is crucial that water pump seals for applications such as spas, swimming pools,  irrigation, heating systems, and shower pumps be made from durable materials.

12. Diaphragm Seals

Diaphragm seals, which often feature parallel springs, find widespread use in a variety of rotating shaft machines.

13. Air Seals

Air seals were developed to prevent leaks in spinning shafts without requiring any physical touch. Dry powder and slurry uses are typical settings for these seals. Minimal volumes of air or inert gas are used for protection against product loss, leaks, and contamination. The positive pressure and reliable seal are created by restricting this air.

What are seals used for in engineering
 

To prevent leakage between the hydraulic cylinders moving parts, engineers install engineering Seals at the cylinder's interfaces.

The seals are used in dynamic applications, typically with rotating or reciprocating motions and at high speeds.

For fluid sealing, they are used in hydraulic cylinders. They are located within the cylinder head, sealing against the cylinder bore to prevent fluid from bypassing the head. As a result, the cylinder can be expanded or contracted by increasing the pressure on one side of the piston.

When pressures are changing rapidly, the seal is put to use.

Washers used to seal fasteners are made of multiple components, including a metal backing and a vulcanized elastomer lip. Assuring constant, perfect compression conditions between the housing components to prevent the deterioration of the sealing lip, they perform a static function on flanges or threaded connections.

When using integral seals, a machining groove in the mating sealing flanges is not necessary. The elastomer is either mechanically or chemically bonded to a frame edge that is distinct from the flange, ensuring the seal remains in place.

These Seals are installed on moving or oscillating sections of machinery to prevent foreign matter like dirt and water from getting inside.

What are seals.
 

Industrial seals are installed at component interfaces to prevent leakage, maintain pressure, and deflect contamination. A static or dynamic interface is a common place to install an industrial seal. The connection between an engine block and cylinder head, as well as the entry point for bolts and screws, are also examples of static interfaces.

Static seals are often created with adhesives and gaskets. Sealants and gaskets work together to create a static seal. The seal between the piston and cylinder is an example of a linear dynamic interface, while the seal between the bearing housing and the axle is an example of a rotary dynamic interface.

Usually, mechanical seals have two flat surfaces that are perpendicular to the shaft, but we'll get to air seals in a minute. One side of the housing for the seal is fixed.

What are the advantages of seals
 

1. Compatible with any liquids Substances such as acids, salts, and abrasive particles

2. Disappointingly crooked/non-concentric handle.

3. Take on extreme variations in pressure, temperature, and speed, as well as bidirectional shaft rotation.

4. There is no pressing concern about the shaft's condition. Dimensions, shape, hardness, and composition of the finish

5. The seals ensure that there will be no mishaps caused by liquids leaking unexpectedly. Additionally, they lessen the possibility of slips and falls. The seal lessens the prospect of poisonous chemicals leaking out of the pump. For this reason, mechanical seals improve operational security.

7. Shaft wear is not a result of normal operation

8. Reliability that lasts for a long time in operation

9. Positive sealing for use with perishable foods, toxic materials, and radioactive liquids

10. Pump failure is less likely to occur when there is less fluid loss in the machine. Therefore, you avoid spending money on upkeep and repairs. It helps to lower overhead expenses.
 

FAQs: Seals
 

Q. What are the different types of seals?
Ans. Here are the basic types of Seals:

1. O-Ring

2. Labyrinth Seals

3. Water pump Seals

4. Axial shaft Seals

5. Cartridge Seals

6. Radial Shaft Seals

7. Balanced Seals

8. Unbalanced Seals

9. Pusher or Non-Pusher Seals

10. Gaskets

11. Bellow Seals

Q. How to select a mechanical seal?
Ans. Here are some Considerations

1. Design Options for Seals

2. Specifications of Seals

3. Reliability & Emission considerations

4. Liquid Characteristics

5. Pressure

6. Temperature

7. Liquid 

8. Manufacturing Details

Q. What are seals in industry?
Ans. In the Mechanical industry, mechanical seals are used in pumping systems, to contain pressure, and to keep out contaminants, among other applications. Sealants rely on adhesion to be successful, while gaskets use compression to seal.

In the Engineering Industry, to prevent leaks at the points of entry or release of a drive shaft, mechanical seals are installed. An engineer can use a wet seal and embossing seal to authenticate documents.

Q. What are the two main categories of seals?
Ans. Here are the two main categories of Seals

1. Pusher Seals

2. And Non Pusher Seals