Choosing a mechanical seal on a pump requires careful consideration. Engineers must identify the type of fluid being handled, as well as measure the pressure and temperature involved. It’s also important to check the shaft size to ensure compatibility. The seal type and material should be selected to match both the pump and the fluid, which is essential for protecting the equipment and preventing leaks. When selecting component mechanical seals or a lowara pump mechanical seal, users should prioritize safety and confirm that the seal will perform effectively in its intended environment.
Key Takeaways
Find out what kind of fluid you have and its features first. This helps you pick a seal that works well and stops it from breaking too soon.
Measure the pump’s shaft and gland size very carefully. Good measurements make sure the seal fits tight and helps stop leaks.
Pick the seal type that matches how you will use it. Single seals are easier to use. Double seals stop leaks better when fluids are dangerous.
Choose seal materials that can handle the pump’s heat and chemicals. This makes the seal last longer and work better.
Take care of the seal and install it the right way. If you follow the rules, you can avoid mistakes that make the seal break.
Key Factors for Selecting a Mechanical Seal on a Pump
Picking the right mechanical seal for a pump is important. You need to look at a few key things. Engineers should know about the fluid, the working conditions, and the size of the parts. Each thing helps the seal work well and keeps it safe.
Fluid Properties and Compatibility
The kind of fluid in the pump matters a lot. Different fluids can change what seal you need. Some fluids are water, chemicals, oil, and solvents. Others are slurries, which mix solids and liquids like sand or clay. Gases like air, natural gas, and nitrogen also need special seals. Suspensions have solid bits in liquids, like pigments or dyes. Thick fluids like creams and gels need strong seals. Abrasive stuff like sand or metal pieces can wear out seals fast. Corrosive fluids, like acids, can damage seals too. Hot fluids, like melted metals or oils, need seals that can take heat.
The fluid’s chemicals must match the seal’s material. For strong chemicals, ceramic or special metals work best. Picking the right material keeps the seal safe and makes it last longer.
Tip: Always know what liquid is in the pump. Check if it has solids, rough bits, or harsh chemicals. This helps stop the seal from breaking too soon.
Pressure and Temperature Limits
Pressure and temperature inside the pump are very important. The seal must handle the highest pressure. Some rules, like API 682, say seals should take 315 to 615 psi. The pressure can make the seal hot and wear out faster.
Some seals can take heat from 200°C to over 400°C. Special seals for refineries can handle up to 700°F. These seals work in pumps, compressors, and mixers with hot fluids.
Seals must be made for the pump’s top pressure.
Tubes and seal parts must not break under pressure.
High heat needs seals that do not melt or break down.
Note: Knowing the liquid’s heat and pressure helps you pick a seal that will not break in tough spots.
Shaft and Gland Dimensions
You need to measure the pump parts to fit the seal right. The shaft size, chamber size, length, and depth all matter. Good measurements stop leaks and problems.
Measurement Type | Description | Tool |
|---|---|---|
Shaft Diameter | Find the width of the shaft where the seal goes. | Caliper or micrometer |
Seal Chamber Diameter | Measure the inside of the chamber for the seal. | Caliper or micrometer |
Axial Length | How long the seal face is along the shaft. | N/A |
Gland Depth | How deep it is from the outside to the seal plate. | Depth gauge or caliper |
Stuffing Box Face to Bearing Center | How far from the box face to the bearing. | Ruler or tape measure |
Shaft Runout and End Play | Check if the shaft moves or wobbles. | Dial indicator |
Operating Conditions | Info about heat, pressure, fluid, and speed. | N/A |
It is smart to measure the chamber and shaft size. Use charts from the maker or industry to check sizes. Think about how fast and how hard the pump works. These steps help the seal fit tight and work well.
Tip: Good measurements stop problems when you put in the seal. They also make sure the seal fits the pump just right.
Types of Mechanical Seals for Pumps
When you pick a mechanical seal for a pump, you need to know the main types. Each seal type works best in certain jobs. The next parts show how each seal is different and where it is used.
Single vs. Double Mechanical Seal
Single mechanical seals have one set of sealing faces. Double mechanical seals have two sets in a row. You choose based on the fluid, safety, and where the pump is used.
Feature | Single Mechanical Seal | Double Mechanical Seal |
|---|---|---|
Design | Simple and cheaper | More parts, two seals together |
Leakage Prevention | Good for safe fluids | Stops leaks better, good for dangerous fluids |
Maintenance Requirements | Needs regular checks and changes | Needs buffer fluid and more care |
Safety and Reliability | Not as safe for risky fluids | Safer because of extra seal |
Double mechanical seals stop leaks in harmful fluids. They keep people and nature safe. Many places use double seals for health and safety.
Application | Reason for Double Mechanical Seals |
|---|---|
Petrochemical Plants | Used for dangerous and smelly fluids |
Chemical Processing | Handles strong fluids with different heat and pressure |
Pharmaceutical Manufacturing | Keeps things clean and stops germs |
Pulp and Paper | Works with rough fluids in big pumps |
Power Generation | Seals strong pumps with lots of pressure |
Tip: Double mechanical seals are best for chemical plants, oil refineries, medicine making, rough fluid pumps, food factories, and pumps with high heat or pressure.
Balanced vs. Unbalanced Seal
Balanced seals and unbalanced seals work in different ways. Balanced seals lower the pressure on the seal faces. This means less leaking and longer life. Unbalanced seals push harder on the faces. They are good for pumps with low pressure.
Mechanical seals control how much fluid leaks. The space between the seal faces matters. Balanced seals keep the space small, so less fluid gets out. Unbalanced seals may leak more because the faces press together more.
Balanced seals are for pumps with high pressure. Unbalanced seals are for pumps with low pressure. Engineers pick the seal by looking at the pump’s pressure and fluid.
Note: Balanced seals help stop leaks and work well in hard jobs.
Pusher vs. Non-Pusher Seal
Pusher seals use a moving part like an O-ring or wedge to keep tight. Non-pusher seals use a bellows that bends but does not move back and forth. Each type is good for different pumps.
Feature | Pusher Seals | Non-Pusher Seals |
|---|---|---|
Sealing Mechanism | Moving O-ring or wedge keeps the seal tight | Bellows bends to seal, does not move back and forth |
Adaptability | Works in many pump jobs | Good for strong chemicals and high heat |
Maintenance | Needs more care because of moving parts | Needs less care because it does not move |
Wear Compensation | Adjusts for wear and heat changes | Not as good at adjusting for wear |
Application Suitability | Works with rough fluids and many jobs | Best for pumps with strong chemicals |
Pusher seals are good for rough fluids. They change shape when the pump gets hot or worn. Non-pusher seals need less care. They fit pumps with lots of shaft movement or when the shaft is not straight.
Feature | Description |
|---|---|
Static Secondary Seal | Stops damage from moving parts |
Flexible Component | Bellows or similar part helps the seal fit many jobs |
Application Suitability | Good for pumps with lots of shaft movement or big pumps |
Tip: Non-pusher seals help lower care in chemical pumps. They are best when the pump handles strong chemicals or high heat.
Choosing Seal Materials
Elastomers and Metal Parts
Elastomers and metal parts are important in a mechanical seal. Elastomers are soft and bendy, so they help stop leaks. Metal parts are strong and hold everything together. Engineers pick elastomers by looking at the fluid and heat in the pump. The table below lists some elastomers, what they do, and where they work best:
Elastomer Type | Properties | Applications |
|---|---|---|
FFKM | Handles strong chemicals and big temperature changes | Used for top jobs that need high performance |
Buna | Good for many uses | Used in most regular seals |
EPDM | Stands up to heat and weather | Used outside and in water systems |
Viton (FKM) | Great with chemicals | Used in chemical plants |
Aflas | Handles chemicals and heat | Used for special, hot jobs |
HNBR | Works well with heat | Used in moving parts |
XNBR | Very tough and strong | Used for hard jobs |
Metal parts must not rust or break down fast. Duplex stainless steel is very strong in tough chemicals. Metals with lots of chromium help stop rust, especially if there is chloride or hydrogen sulfide.
Tip: Always make sure the elastomer and metal can take the chemicals and heat in your pump.
Face Material Selection
The seal face materials touch each other and stop leaks. Picking the right face material helps the seal last longer. Here are some common choices:
Carbon: It is slippery and handles heat changes. Carbon faces work when the pump gets hot or has small scratches.
Ceramic: It is very hard and does not wear out fast. Ceramic faces are good for rough fluids and strong chemicals.
Silicon Carbide: It is even harder than ceramic and slides better. Silicon carbide faces last a long time in tough jobs and can be fixed.
When the pump gets hot, the face material must move heat away. If it cannot, it might bend or crack. The best choice depends on how thick the fluid is and the pressure in the pump.
Matching Materials to Fluid and Conditions
Picking the right seal materials for the fluid and job keeps the pump safe. Engineers look at a few things:
Criteria | Description |
|---|---|
Operating conditions | Check the heat, pressure, shaft speed, and how heavy the fluid is. |
Fluid compatibility | Make sure the seal will not get ruined by the fluid. |
Seal material compatibility | Follow rules for safe water or food if needed. |
Thermal expansion | Pick materials that grow at the same rate as the pump parts. |
Leakage tolerance | Choose seals that meet safety and leak rules. |
Cost and life cycle | Pick seals that last long and do not cost too much. |
Pump type | Some pumps need special seals for their shape. |
For example, EPDM is good for most chemicals. Viton is better for oil-based fluids. PTFE and FKM work with many man-made fluids. Engineers use charts to help pick the best material for each job.
Note: The right seal material keeps the pump safe, saves money, and stops leaks.
Common Mistakes When Selecting a Mechanical Seal
Ignoring Application Details
Some engineers do not check every part of the job. They might forget to look at the fluid, heat, or pressure. This can make the mechanical seal break and stop the pump. If a pump runs with no fluid, the seal can get ruined fast. Too much shaking can wear out the seal and move its parts. Picking the wrong seal material can cause leaks and damage.
Mechanical seals often break when people miss key details. Running dry, shaking, and wrong materials all cause trouble.
A checklist can help stop these mistakes. It should list the job’s heat, fluid, speed, and pressure. Using a checklist helps match the seal to the job.
Choosing Incompatible Materials
Picking the wrong seal materials can cause big trouble. Some elastomers get bigger when they touch some chemicals. This makes more rubbing and stops the seal from working. Chemicals can break down seal parts and cause leaks. The wrong chemicals can make elastomers crack and break.
Chemical mismatch often makes seals fail in pumps.
EPDM is best for water and soft chemicals.
FKM works well with oils and strong cleaners.
BUNA-N is good for oil-based fluids.
Elastomers can break from heat, chemicals, or being squeezed too hard.
Engineers must pick seal materials that fit the fluid in the pump. This keeps the seal strong and stops leaks.
Overlooking Installation and Maintenance
Bad installation and poor care can make seals wear out fast. Common mistakes are hitting couplings onto the shaft, putting the seal on wrong, and using dirty seal faces. Shafts that do not line up and bolts that are too tight also cause problems. Using the wrong seal size or type can make the seal fail.
Installation Error | Impact on Seal Performance |
|---|---|
Shaft not lined up | Makes the seal shake and wear |
Dirty seal face | Causes leaks |
Bolts too tight | Breaks seal parts |
Wrong seal size | Stops the seal from working right |
Regular care helps seals last longer. Checking, cleaning, and changing seals on time keeps them working. Maintenance teams should follow a plan to find problems early and save money.
Regular care is very important for seals. Checking and cleaning helps seals last longer in pumps.
Picking a mechanical seal for a pump takes a few steps. Engineers need to:
Pick seal materials that work with the liquid’s heat.
Check if the liquid is thick or rough.
Make sure the seal type follows safety and leak rules.
Think about how well the seal stands up to chemicals and wearing out.
A checklist helps make sure the seal fits right, the materials match, and the pump works well. Talking to experts can help with tricky systems and new ideas. Doing these things keeps pumps safe and working well.
