Lubricating circulating pumps is essential for their efficient and reliable operation. Proper lubrication reduces wear on components, prevents overheating, and extends the life of the pump. This comprehensive guide covers everything you need to know about lubricating circulating pumps.
Overview of Lubricating Circulating Pumps
Circulating pumps move water or other fluids through closed loops in heating, cooling, and industrial process systems. They operate under high pressures and temperatures, making lubrication vital. Here’s a quick overview:
- Most circulating pumps have oil lubricated bearings that require periodic lubrication. Gear and magnetic drive pumps may have grease lubricated bearings.
- Pump manufacturers provide lubrication instructions specific to that pump. Always follow OEM guidelines for type, amount, and frequency of lubrication.
- Key components to lubricate are the pump bearings and shaft seal. For gear pumps, also lubricate the gear teeth.
- Use high quality oil and grease made specifically for pump applications. Match viscosity and composition to OEM specs.
- Over and under lubrication can both cause problems. Maintain proper lube levels and replace aged oil and grease.
- Monitor lube condition and check for signs of contamination, loss of viscosity, overheating, and other issues indicating lubrication problems.
Now let’s look at how to properly lubricate the key components of circulating pumps.
Lubricating Pump Bearings
Circulating pump bearings enable the pump shaft to spin smoothly. There are two main types of bearings:
Sleeve Bearings: Depend on a film of oil between shaft and bearing for lubrication and cooling. Require periodic oil changes and level checks.
Anti-Friction Bearings: Use rolling elements like ball bearings. Grease lubricated and sealed, may have permanent lubrication.
Here are tips for properly lubricating pump bearings:
- Use oil or grease specified by manufacturer. Match viscosity, composition, and additive package.
- Change sleeve bearing oil at recommended intervals, based on operating hours or schedule. Check/top-off oil level regularly.
- Grease lubricated bearings per manufacturer instructions, usually 1-2 times annually or every 2000-4000 hours.
- When adding or changing lube, clean and flush bearings first to remove contamination.
- Ensure shaft and bearing housing surfaces are smooth. Roughness damages oil films.
- If oil level drops rapidly or bearing overheats, investigate for leaks or other problems.
- Dispose of used oil properly.
Lubricating the Shaft Seal
Shaft seals prevent pumped fluid from leaking along the pump shaft. There are two types:
Mechanical Seals: Have stationary and rotating seal faces that form a tight, lapped contact. Require external flush fluid.
Packing Seals: Compressed non-hardening packing rings around shaft. Need periodic tightening and repacking.
Lubricating guidelines for shaft seals:
- Use clean oil of proper viscosity, as specified by the seal manufacturer. Light oil is commonly used.
- Mechanical seals require adequate flush fluid flow and pressure. Ensure lines are clear and operating properly.
- Packing seals are lubricated by the pumped fluid. Make sure packing is moistened. Add external lubrication if needed.
- Watch for signs of dry-running, overheating, and leaks indicating inadequate lube.
- Replace seals at recommended intervals or if damaged or worn.
Lubricating Gear Pumps
External gear pumps use meshing gears to move fluid. Proper lubrication of the gear teeth prevents wear and surface pitting.
- Use wide temperature range gear oil. EP additives help withstand heavy loads.
- Maintain oil level at manufacturer’s indicated position on dipstick or sight glass.
- If pump is intermittent duty, run briefly periodically to coat gears with fresh oil.
- Change gear oil yearly or per OEM change schedule.
- If gears show accelerated wear or pitting, inspect oil for contamination.
- Use magnetic drain plug to capture metal particles, an indicator of internal wear.
What Oil or Grease Should I Use?
Choosing the proper lubricant is critical. Consider the following:
Oil vs Grease: Oil flows easily to lubricate and cool. It requires containment and changes. Greases adhere and stay in place. They withstand water washout.
Base Oil Type: Common types include mineral, PAO synthetic, esters, and PAG. Mineral oil is economical but less durable. Synthetics perform better under high temps and pressures.
Viscosity: Select viscosity based on bearing clearances and operating conditions. Higher viscosity provides thicker oil film but is harder to pump and circulate.
Additives: Look for EP, anti-wear, anti-oxidant, anti-rust, and other additives to handle high loads, corrosion, and breakdown.
Always check manufacturer specifications for the proper lubricant type, viscosity grade, additive package, and other requirements. Using the incorrect lubricant can lead to major problems.
Recommended Lubricants by Pump Type
Here are typical oil and grease recommendations by pump type:
- Centrifugal Pumps: ISO VG 32-68 mineral or synthetic bearing oil. High viscosity gear oil for gear-driven pumps.
- Positive Displacement: ISO VG 32-150 mineral or synthetic oil. PAO or PAG gear oil. NLGI No. 2 lithium complex or polyurea grease.
- Metering Pumps: ISO VG 15-220 mineral or synthetic oil. NLGI No. 2 lithium or polyurea grease.
- Magnetic Drive: ISO VG 32-100 synthetic oil or NLGI No. 2 polyurea or food-grade grease.
- Canned Motor: ISO VG 32-68 mineral or synthetic oil. API Group I or II turbine oil.
Again, always follow the lubrication recommendations provided by the pump manufacturer.
Lubrication Equipment
Having the right tools makes lubricating pumps easier and cleaner. Here are some common lube equipment choices:
- Oil Pump/Grease Gun: For extracting old oil and injecting new oil or grease. Pistol grip or lever style.
- Metering Valves: Dispense precise amounts of oil or grease for single point lubricators.
- Sample Ports: Allow oil samples to be taken for analysis without opening pump housing.
- Filter Carts: Pump oil through fine filters to clean contaminants. Remove water, acids, and particles.
- Oil Analysis: Checks oil condition, contamination, and wear particle levels to optimize oil change intervals.
- Grease Meters: Measure grease consumption at single point lube locations. Track relubrication schedule.
Investing in quality lubrication tools improves the reliability of your pumping systems and reduces maintenance headaches.
Best Practices for Pump Lubrication
Follow these tips and best practices to properly lubricate your circulating pumps and keep them running reliably:
- Always follow pump manufacturer OEM lubrication instructions for type, amount, method, and intervals.
- Use high quality oil and grease designed for pump applications. Match viscosity, base oil type, and additives to specs.
- Regularly inspect components. Look for leaks, sludge, rust, foam, odor, and other signs of lubrication issues.
- Sample and test oil condition at recommended intervals to optimize change intervals.
- Keep lubricants clean and dry. Contamination damages bearings and gears.
- Ensure adequate flow for mechanical seal flush plans. Check plan pressure.
- Lubricate conservatively. It’s better to under lubricate than over lubricate.
- Document lubrication activities including products used, amounts added, levels, and change dates.
Proper lubrication seems simple but is critical for circulating pump reliability and longevity. Following best practices will extend pump life, reduce repairs, and save money.
Table Summarizing Key Lubrication Information
Pump Type | Bearing Lubricant | Seal Lubricant | Gear Lubricant | Frequency |
Centrifugal | ISO VG 32-68 oil | Light mineral oil | Gear oil if applicable | 6-12 months |
Positive Displacement | ISO VG 32-150 oil or NLGI #2 grease | Light oil or pumped fluid | PAO or PAG gear oil | 1-6 months |
Metering | ISO VG 15-220 oil or NLGI #2 grease | Light oil | n/a | 1-4 months |
Magnetic Drive | ISO VG 32-100 synthetic oil or NLGI #2 grease | Light oil | n/a | 6-12 months |
Canned Motor | ISO VG 32-68 oil | n/a | n/a | Monthly |
Frequently Asked Questions
Below are answers to some frequently asked questions about lubricating circulating pumps:
Q: How often should I lubricate the pump bearings?
A: Follow the pump manufacturer’s recommendations for lubrication frequency. This varies by bearing type and pump runtime hours. Typical intervals range from twice per year for intermittent duty pumps to monthly for pumps in continuous operation.
Q: What if I can’t find the OEM lubrication specs for my pump?
A: Choose a premium quality oil or grease designed for pump applications. For oil, an ISO VG 32-68 mineral or synthetic should work for most bearing applications. Use an NLGI No. 2 lithium complex grease for greased bearings. Strictly follow lube change intervals.
Q: What are signs that a pump is under or over lubricated?
A: Under lubrication causes overheating, noise, binding, leaks, and wear. Over lubrication leads to oil churning, overflow, and seal deterioration. Routinely check oil level and condition to catch problems.
Q: Does the pump need to be turned off before lubricating?
A: Yes, you should always stop the pump before adding oil or grease. For greased bearings, you must stop the pump to access the fittings. Adding oil requires stopping the pump to get an accurate level reading.
Q: Do I need special tools to lubricate pumps?
A: An oil pump, grease gun, and metering valves make lubricating easier, cleaner, and more precise. You may also need filter carts or oil analysis equipment. But basic hand tools may suffice for DIY lubrication on small pumps. Use funnels to refill oil.
Q: How do I dispose of old pump lubricating oil safely?
A: Used oil and grease should be recycled. Do not pour down drains or discard in regular trash. Take it to an oil recycling center, waste disposal site, or hazardous waste collection event in your area. Store waste oil in marked containers until ready for disposal.