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Step-by-Step Instructions for Installing Mechanical Seals in Centrifugal Pumps
Did you know mechanical seals play an important role in ensuring peak performance and maximum pump lifespan?
Mechanical seals prevent the leakage of fluid into the atmosphere from the critical connection point between the impeller and the casing.
To state the obvious, mechanical seals not only help maintain the proper pump pressure but reduce the chances of pump failure.
The mechanical seal offers valuable benefits when used in a centrifugal pump, but do you know how to install a mechanical seal in a centrifugal pump?
In this article, let’s dive into the details of mechanical seals, and then we will look into some handful of steps you need to install or replace mechanical seals in a centrifugal pump.
What Is A Mechanical Seal?
Mechanical seals are a crucial component to install in any centrifugal pump system. By removing impurities and preventing fluid leakage, mechanical seals help maintain the integrity of the pump systems.
Primarily, mechanical seal systems are installed in pumps to identify leakage, lubricate secondary seals, and regulate the sealed environment.
Correctly installed mechanical seals are significant to maintain pump performance and increase the pump's overall lifespan.
Different Types Of Mechanical Seals
There are different types of mechanical seals available for different processes and types of pumps. Below are some of the common types:
- Balanced Seals
- Unbalanced seals
- Pusher seals
- Non-pusher seals
- Conventional seals
- Cartridge seals
How Does A Mechanical Seal Work?
A mechanical seal needs contact between two smooth and flat seal faces where one rotates with the shaft and the other stays stationary with the casing.
These mechanical seal faces are properly sealed to their mounts [O-rings or gaskets] with the use of secondary seals. Furthermore, these surfaces are mechanically energized and flexible to contact so that they can reduce static and dynamic misalignments and wear.
When preventing leakage through the seal faces, the seal requires fluid lubrication, resulting in low vapor leakage.
How To Install Mechanical Seal In Centrifugal Pump?
Cut The Power:
The first step is to turn the power off of the centrifugal motor. Do this by shutting down the main power supply and double-checking that the machine cannot be restarted.
Remove The Fluid:
Next close the inlet and outlet isolation valves followed by draining the pump casing to drain the pump housing.
Disconnect The Pump:
Carefully disconnect and detach the centrifugal pump situated beyond the housing using a wrench. Make sure to keep unscrew bolts safe, as they will be needed later to reattach the centrifugal pump.
In the case of the “back pull-out” design pump, detach it by removing the spacer element in the pump coupling. After that, remove the casing bolts and slip the pump residue away from the casing.
Whereas other than the “back pull-out” design pump, complete disconnecting of the pump will be needed. Disconnect the coupling between the pump and the motor shaft.
For a close-coupled design pump, remove the entire pump or motor, as well as remove the casing bolts and casing.
Remove The Impeller:
The mechanical seal is generally situated behind the impeller on the centrifugal pump shaft. Dismantle the pump impeller that is either screwed or bolted onto the pump shaft. To remove the screwed impeller from the shaft, hold it with a wrench, then unscrew the impeller by turning it clockwise. In contrast, to remove the bolted impeller, hold the pump shaft in place to remove the bolt.
Remove The Seal:
The first step is to detach the mechanical seal. The two rotary and stationary seal parts can be accessed directly. One is attached to the impeller, while the other is attached to the motor shaft. Detach the seal off from both these places using set screws.
Replace The Seal:
This is one of the important steps when replacing the mechanical seal in a centrifugal pump. Install a new mechanical seal on the pump shaft by carefully sliding the components of the replacement seal. Next, press the stationary part into the housing or seal chamber bore using an O-ring or gasket material and reattach the rotating element back onto the shaft in the right way.
Screw On The Impeller:
Hold the shaft with the use of a wrench and screw the impeller by using the new impeller O-ring or seal. Another way is to use the impeller bolt and a new O-ring or seal to fix the impeller to the end of the shaft.
Reconnect Pump Casing:
By using the original casing bolts, reconnect the pump casing.
For back pull-out design pumps, glide the rear extension component against the installed casing. Make sure to check the pump alignment after the ninth step below.
For close-coupled design pumps or non-back pull-out design pumps, reassemble the casing using the casing bolts.
In the end, in every pump type and design, tighten the casein bolts as stated in the pump Installation, Operation, and Maintenance (IOM) manual.
Reconnect The Centrifugal Pump:
In case of back pull-out designs, reattach the spacer to the existing coupling hubs and back extension design mounting feet to the base plate of the pump.
After adjusting the pump and motor, reassemble the pump. In the case of close-coupled pumps, reconnect the inlet and outlet piping, and for non-back pull-out pump and motor designs, replace and re-bolt the pump on the base plate, reconnect the coupling, and readjust the pump and motor.
Restart The Pump:
Check out if the pump casing is refilled properly or not by opening the isolation valves at the inlet and outlet. Some pump designs require venting; hence, it's important to refer to the pump Installation, Operation, and Maintenance manual.
Moreover, after attaching the pump and motor couplings, it is always recommended to check the motor rotation and then reconnect the coupling to restart the centrifugal pump.
Take Proper Safety Precautions:
Lastly, it's crucial to check out the safety precautions in the pump operating manual. Always use the pump IOM and install a mechanical seal to the centrifugal pump according to the specific instructions mentioned in the manufacturer’s manual.
Do not miss to check the alignment of the pump and motor as misalignment is one of the major reasons behind the mechanical seal failure.
When Is The Right Time For Mechanical Seal Replacement?
Mechanical seals are vital components for centrifugal pumps as they help prevent fluid from leakage. As stated above, mechanical seals are situated between the pump casing and the impeller, which allows the impeller to rotate without fluid leakage. These mechanical seals get worn out due to many reasons and eventually will need replacing.
When a centrifugal pump starts struggling to maintain the correct pump pressure, mechanical seal failure can often be the reason behind that. Apart from this, when a pump starts consuming fluid more than normal, it can also be the reason behind the mechanical seal failure.
Under such circumstances, it becomes necessary to replace the mechanical seal or avoid more damage to the pump and its performance.
There you have it. Mechanical seals play a vital role in the proper functioning of centrifugal pumps; therefore, it’s necessary to install the mechanical seal on centrifugal pumps correctly.
In addition to this, selecting the right mechanical seal for your centrifugal pump is equally important. Here at Popular Pump Seals, we offer a quality range of mechanical seals for centrifugal pumps.
We have years of experience in manufacturing and supplying the best industrial pumps and mechanical seals for a wide range of industries and their applications. Reach out to our experts today to get the best mechanical seal for a centrifugal pump.
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