Classification of Mechanical Seals
The utility of mechanical is multifaceted. Not just it acts as a check valve, but also as a slider bearing. Thus, it prevents liquid underpressure from leaking out of the pump or drawing air into the pump in vacuum conditions.
Mechanical seals when improperly installed can fail frequently. They can be classified into several categories. Here, we will study the classification of mechanical seals by arrangement.
Types of mechanical seal arrangement
- Arrangement 1
It can be defined as one mechanical seal in a seal chamber. Therefore, it is also known as a single seal. You have one set of seal faces. The seal is exposed to fluid in the pump as well as the seal chamber.
The main goal of a mechanical seal is to control the amount of process fluid in the seal chamber from reaching the atmospheric ide in the seal.
Arrangement 1 is one of the most commonly used arrangements in industrial applications because it is cost-effective and easy to use. You need a simple piping plan to apply it. You do not have any operator to monitor it.
Arrangement 1 is small in size, and it can fit any centrifugal pump design.
- Arrangement 2
In this arrangement, two seals are arranged in series. The purpose of the inner seal is to seal the fluid in the chamber. If any leakage happens, it flows into a cavity between these two seals. The cavity between the two seals contains a buffer fluid. The buffer fluid is maintained at a lower pressure than seal chamber pressure. acc
The outer seal seals the buffer liquid and any accumulated process leakage under low-pressure conditions.
The outer seal operates under full pressure and temperature in case the inner seal fails. Thus, total redundancy is guaranteed.
- Arrangement 3
In this arrangement also two seals are used. But here, the barrier fluid between seals keeps a pressure higher than the seal chamber pressure.
Here, both inner, as well as outer seal, will seal the barrier fluid.
In this arrangement, the seal is less dependent on the properties of the process fluid in the process.
The seals can operate when there is any liquid present in the seal chamber. There is no process leakage here because the barrier fluid is maintained at a higher pressure as compared to the seal chamber pressure.
Barrier fluid will leak to the atmosphere across the outer seal. It will leak into the process across the inner seal.
All these three arrangements have positive and negative aspects. One has to choose an arrangement that is fit for the process.
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