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There are many factors that affect mechanical seas installed in pumps adversely and even cause them to fail.Let's talk about two of them in this article.
1. Fierce pump vibration and measures to eliminate it
Aggravate vibration of the mechanical seal is often not caused by the mechanical seal itself, but the unreasonable design of the pump shaft, the insufficient machining accuracy, the overly-large parallelism of the backrest wheel, and the overly large radial force.
Measures to eliminate pump vibration include: when auxiliary equipmens such as pumps, motors, bases, and on-site pipelines are installed on site, strict checks must be made to eliminate vibration sources.
2.Causes of and relevant measures to tackle pump cavitation
The inlet of the impeller of the centrifugal pump is the place where pressure in the pump is the smallest. When pressure here is equal to or lower than saturated vapor pressure of the liquid being conveyed by 1pt at the working temperature, the liquid will boil and vaporize, resulting in a large number of bubbles. At the same time, the bubbles originally dissolved in the liquid will also be precipitated. These vapors flow with the liquid to the impeller where the pressure is higher and the bubbles condense again.
During operation of the pump, when pressure at local position in the pump drops to the saturated vapor pressure of the water at corresponding temperature for some reasons, the water begins to vaporize to generate a large number of bubbles, and the bubbles move forward with the water flow. When the bubbles move to the higher pressure part,they quickly condense and collapse. This process generates noise, vibration and erosion of the flow-through components. This phenomenon is called cavitation of the water pump.
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After cavitation of the water pump occurs, there will be air bubbles in the water, which will adversely affect the mechanical seal:
1) Air bubbles will impact the outer surface of the mechanical sealing surface, causing damage to the mechanical seal;
2) There will also be air bubbles in the flow film of the fitting surface of the rotary face and stationary seat, resulting in dry friction which easily damage the mechanical seal device.
3) After cavitation occurs, other parts of the pump will vibrate, which will cause the mechanical seal to vibrate too much, and eventually lose the sealing effect.
The measures to eliminate cavitation at the pump inlet are as follows:
1. Improve the anti-cavitation performance of the pump to meet relevant requirements.
2. The pump should be operated below the allowable aspiration height.
3. The impeller should be made of anti-cavitation materials, such as: 2Cr13, rare earth alloy cast iron, high nickel-chromium alloy materials, etc., which have much better anti-cavitation ability than ordinary cast iron.
1. Fierce pump vibration and measures to eliminate it
Aggravate vibration of the mechanical seal is often not caused by the mechanical seal itself, but the unreasonable design of the pump shaft, the insufficient machining accuracy, the overly-large parallelism of the backrest wheel, and the overly large radial force.
Measures to eliminate pump vibration include: when auxiliary equipmens such as pumps, motors, bases, and on-site pipelines are installed on site, strict checks must be made to eliminate vibration sources.
2.Causes of and relevant measures to tackle pump cavitation
The inlet of the impeller of the centrifugal pump is the place where pressure in the pump is the smallest. When pressure here is equal to or lower than saturated vapor pressure of the liquid being conveyed by 1pt at the working temperature, the liquid will boil and vaporize, resulting in a large number of bubbles. At the same time, the bubbles originally dissolved in the liquid will also be precipitated. These vapors flow with the liquid to the impeller where the pressure is higher and the bubbles condense again.
During operation of the pump, when pressure at local position in the pump drops to the saturated vapor pressure of the water at corresponding temperature for some reasons, the water begins to vaporize to generate a large number of bubbles, and the bubbles move forward with the water flow. When the bubbles move to the higher pressure part,they quickly condense and collapse. This process generates noise, vibration and erosion of the flow-through components. This phenomenon is called cavitation of the water pump.
After cavitation of the water pump occurs, there will be air bubbles in the water, which will adversely affect the mechanical seal:
1) Air bubbles will impact the outer surface of the mechanical sealing surface, causing damage to the mechanical seal;
2) There will also be air bubbles in the flow film of the fitting surface of the rotary face and stationary seat, resulting in dry friction which easily damage the mechanical seal device.
3) After cavitation occurs, other parts of the pump will vibrate, which will cause the mechanical seal to vibrate too much, and eventually lose the sealing effect.
The measures to eliminate cavitation at the pump inlet are as follows:
1. Improve the anti-cavitation performance of the pump to meet relevant requirements.
2. The pump should be operated below the allowable aspiration height.
3. The impeller should be made of anti-cavitation materials, such as: 2Cr13, rare earth alloy cast iron, high nickel-chromium alloy materials, etc., which have much better anti-cavitation ability than ordinary cast iron.
