The often-forgotten and crucial component in a pump system is the mechanical seal, which prevents fluid from leaking into the immediate environment. Leaking mechanical seals due to improper maintenance or higher-than-expected operating conditions can be a hazard, housekeeping issue, health concern, or even an EPA issue. It is important to implement practices and conditions to ensure the proper operation and longevity of your mechanical seals to prevent leakage and subsequent downtime or safety hazards.
Here are some things that you can do to ensure a longer life for your pump seal:
1. Understand your Conditions
Pressure, temperature, and speed are all factors that can contribute to a worn seal or increased leakage rate. Knowing the application conditions will help better select the right mechanical seal. The mechanical seal may perform steadily in fixed application conditions, however, if system variables are introduced, they may have drastic effects that can reduce your seal’s durability. The published limits a seal can withstand are more accurate for a continuous operation where there are more constant conditions. These limits are not as precise with a cyclic operation.
Combining process variables creates varying degrees of conditions that a seal may need to adjust for such as vaporization, freezing, or extreme heat that needs to be dissipated. Applications that operate under higher pressures, higher temperatures, faster speeds, and thicker pumped fluid makes maintaining a pump’s efficiency more difficult. Having a mechanical seal that is more robust and resistant to condition changes may be the key to keeping repair downtime at a minimum if you have a more difficult fluid transferring process.
2. Know Seal Face durability with Liquid
The fluid being pumped is in most cases is the lubricant for the mechanical seal. The fluids, depending on the application, are susceptible to temperature and pressure changes. Similar to the condition factors, the liquid is the main variable, with vast degrees of physical and chemical states that need to be understood. Liquids can range in thickness, purity, volatility, toxicity, and can even be explosive depending on the temperatures, pressure, and chemical compatibility.
Greater seal face pressure and deflection capabilities decrease the chances of having to replace or repair the seal. Lowering the damage sensitivity can be obtained by selecting the right combinations. Hard/Hard mechanical seal faces are better for dirty fluids, but vulnerable to higher damage if the fluid film is lost. Hard/soft mechanical seal faces can hold up longer after periods of lost fluid film before seal faces become damaged. It is important to understand the limits that the pump system will be exposed to based on the application, and how that will affect the liquids state along with how that seal can sustain expected performance.
3. Know the reason for Seal Face Wear
Excessive leakage is typically a symptom of a worn seal face. There can be other more serious issues with your pump, such as bad bearings or a bent shaft.
If worn from abrasive contact, the rubbing edge of the seal will show signs of physical distress such as grooves and even chips. Some seals also need a flushing system to remove the heat that is developed. Serious issues may occur if this process is interrupted or stopped.
4. Reduce Vibration
Try to operate your pump in its BEP (Best Efficiency Point). When you deviate from this it can cause pump cavitation This will cause vibration which can deteriorate the seal. Operating at maximum flow can be deadly to the pump.
Excessive vibration can cause deterioration of components within the seal such as the O-rings, bellows, polymer or wedges, or metal parts such as springs, drive pins, or set screws.
5. Proper Lubrication
Mechanical seals rely on the fluid film between the seal faces to reduce heat and friction. The fluid being pumped in most cases provides this lubrication as it comes into contact with the seal faces. Maintain your seal by not operating in a dry run. Install a Dry Run Monitor or flow sensor that will alert users when there is not sufficient fluid within the system. Continuous applications tend to be more stable with mechanical seal reliability than cyclic applications for this exact reason.
Mechanical seals on average are rated to last a minimum of a span of two years. Obviously as stated earlier this is largely dependent on the variables, conditions involved, and the limits to which you run at. Knowing your system and how it will function and what to look for when problems occur can go a long way in maintaining a mechanical seal. Selecting the right one can be a time-consuming and complicated process, Anderson Process has the knowledgeable experts to help guide you towards providing a solution that helps your system perform at maximum efficiency.