What is an OH1 pump？

If you work with industrial centrifugal pumps regularly, you’ve probably come across the “OH1” model—and let’s be honest, it’s really easy to mix up with other types. Many engineers know centrifugal pumps transport fluids, but if you ask them what makes an OH1 pump unique? Most of them will struggle to answer. And don’t even get me started on procurement teams—misunderstanding the model all but guarantees ending up with the wrong equipment. But here’s the thing: OH1 pumps are workhorses in industries like oil, power, and chemicals. They’re a classic overhung pump under the API 610 standard (the global design code for centrifugal pumps), and once you get the basics down, they’re actually pretty straightforward. Let me walk you through the key details.

1. First, Let’s Clarify—What Exactly Is “OH1”?

OH1 is a specific type of “overhung centrifugal pump” defined by the API 610 standard. Let’s break down the designation: “OH” stands for “Overhung” (that makes sense, right?), and the “1” indicates it’s a single-stage, end-suction pump. In plain terms, here’s what that means: the impeller (the part that moves the fluid) is fixed to only one side of the pump shaft, the bearing housing is integrated directly with the pump body, and the bearings support just one end of the pump—hence the “overhung” name.

API 610 categorizes centrifugal pumps into major groups: OH (Overhung), BB (Between-Bearing), VS (Vertical Suspended), and more. Within the OH group, there are sub-models like OH1, OH2, and OH3—each with its own features. OH2 is a two-stage overhung pump (ideal for high-pressure applications), and OH3 adds extra components to balance axial forces. But OH1? It’s the simplest of the bunch. No fancy extra features—just a focus on medium-to-low head applications. That’s why it’s the most versatile overhung pump in most industrial settings—no need to overcomplicate things when you don’t have to.

2. Design of OH1 Pumps: 4 Practical Advantages

Why do so many industries rely on OH1 pumps? The key lies in their design, which solves real-world problems. Here are their most standout features:

• Compact, Space-Saving Build: The bearing housing and pump body are cast as a single piece, so no extra supports are needed. I’ve seen it firsthand: an OH1 pump with the same flow rate is easily 30% shorter than a double-suction pump. This is a lifesaver in tight spaces like petrochemical plants or power plant boiler rooms, where every inch matters. No need to rearrange pipes or expand the space—just slot it right in.
• Reliable Sealing, Excellent Leak Prevention: Leaks are a major headache, especially when handling flammable media like crude oil or corrosive chemicals. OH1 pumps come standard with mechanical seals (some models can be upgraded to double-ended seals), and the seal faces are usually made of silicon carbide and graphite—tough enough to withstand high temperatures and wear. Under normal operation, leakage is less than 5 milliliters per hour—far better than old-fashioned packing seals. I once worked with a chemical plant that switched to OH1 pumps, and their leak-related shutdowns dropped by nearly 80%.
• Bearings That Don’t Require Constant Attention: They use double-row cylindrical roller bearings, which grip the shaft tightly and handle both radial and axial forces. Plus, the bearing housing has a built-in lubricating oil circulation system, keeping things cool through splash lubrication. Regular centrifugal pumps need oil top-ups every 3 months, but OH1 pumps? You can stretch that to 6–12 months. That means fewer shutdowns—easily 2 to 3 fewer per year. For factories running 24/7, this is a huge boost to productivity.
• Energy Efficiency: The impeller features a backward-curved blade design, optimized by engineers based on fluid mechanics to minimize turbulence inside the pump. The pump’s flow channels are also polished to reduce resistance. I once saw test data showing that an OH1 pump is 8–12% more efficient than a regular overhung pump at the same flow rate. Let’s do a quick calculation: if you’re moving 100 cubic meters of water per hour, that’s 20 kWh saved per day. Over a year, those savings add up to a significant amount.

3. Where to Find OH1 Pumps: 4 Key Industries

This pump isn’t just well-designed—it also fits perfectly into specific working conditions. Here are its most common application scenarios:

• Petrochemical Industry: They’re everywhere in refineries, mainly used to transport low-viscosity media like crude oil and gasoline. Take the crude oil storage area, for example: you need to move oil to the distillation tower without leaks, and the OH1 pump’s compact size fits perfectly between dense pipelines. Plus, its flow rate is extremely stable (with an error of less than 2%), so the distillation tower never gets too much or too little feed—no unexpected shutdowns.
• Power Industry: Thermal power plants and biomass power plants use OH1 pumps to supply water to boilers. Boilers need a steady flow of medium-pressure water, and OH1 pumps meet this need perfectly. I once worked with a 300 MW unit that had two OH1 pumps—one in operation, one on standby. They can withstand temperatures up to 180°C, and their efficiency helps reduce the plant’s overall energy consumption.
• Water Treatment Industry: Municipal sewage plants and industrial wastewater facilities love using them to transport clean water or low-concentration sewage. The pump body is usually made of 304 or 316L stainless steel, or corrosion-resistant cast iron—so it won’t rust from chemicals in sewage. And its end-suction design is far less likely to clog than submersible pumps—no fibers get wrapped around the impeller. It’s perfect for small-to-medium water treatment plants with a processing capacity of 50–500 cubic meters per hour.
• Pharmaceutical Industry: Food-grade OH1 pumps are essential here. They meet GMP (Good Manufacturing Practice) standards, with ultra-smooth inner walls (roughness Ra ≤ 0.8 μm) so liquid medicine won’t stick to them. The seals are also made of food-grade rubber, so no contamination of materials occurs. I’ve seen them in vaccine labs and pharmaceutical factories, mainly used for mixing and transporting liquids in production lines.

4. How to Choose the Right OH1 Pump: 5 Unmissable Tips

Choosing an OH1 pump isn’t hard—just follow these five steps:

• Start with the Fluid to Be Transported: If you’re handling high-temperature media (like hot oil over 120°C), choose a model with a cooling jacket—otherwise, the bearings will burn out. For high-viscosity media (like lubricating oil over 50 cSt), go for a model with a larger impeller inlet—too small an inlet will lead to insufficient flow. For acidic media (like hydrochloric acid), skip regular stainless steel and use Hastelloy (a corrosion-resistant alloy). I once saw a factory use a standard OH1 pump for acid, and it only lasted 6 weeks.
• Don’t Skimp on Flow Rate and Head Margins: Never choose a pump based on your “exact” flow rate needs—add a 10% margin. For example, if you need to transport 80 cubic meters per hour, choose a model rated for 90 cubic meters per hour. As for head (the pump’s output pressure), remember to account for pipeline resistance: if you’re moving water 15 meters high through 100 meters of pipe, you’ll need a pump with a 25-meter head (the extra 10 meters is to overcome pipeline resistance). Insufficient head will cause the pump to run overload and fail quickly.
• Consider the Installation Environment: If installing outdoors, choose a model with a rain cover—water getting into the bearing housing will damage the bearings. For tight spaces (like a 1-meter-wide room), opt for a horizontal short-shaft model—total length under 1.2 meters. If there’s a vibration source nearby (like a compressor), add a shock pad—vibration damages seals faster than anything else.
• Energy Efficiency Matters: Pumps with first-class energy efficiency save 15–20% more electricity than those with third-class efficiency. Running 8 hours a day, that’s nearly 10,000 yuan in annual electricity savings. Spending a little more upfront on a high-efficiency model is definitely worth it.
• Choose the Right Accessories: For toxic media like methanol, upgrade to double-ended seals plus a seal fluid system—this prevents leaks. If you want to monitor equipment status remotely, install vibration sensors and temperature transmitters. When bearings start to wear, the vibration value will reach 4.5 mm/s, triggering an early alert so you won’t face sudden failures.

5. How to Maintain an OH1 Pump: 3 Simple Tips (No Expert Needed)

Many people complain that pump maintenance is a hassle, but OH1 pumps are really low-maintenance—just do these three things:

• Daily Checks (5 Minutes Max): Every week, feel the bearings—if they’re over 70°C, change the lubricating oil. Every month, check the seal—if leakage exceeds 10 milliliters, replace the seal components. Every quarter, clean the inlet filter—clogged filters reduce flow. You don’t even need to disassemble the pump for these tasks, saving half the time compared to maintaining a double-suction pump.
• Troubleshooting: Start with the Basics: Reduced flow? First check the inlet pipe—clogs are usually the culprit. Then inspect the impeller—single-stage impellers are easy to replace. Increased vibration? Check the bearing clearance (replace bearings if clearance exceeds 0.1 mm) and the pump shaft—single-stage shafts can be straightened if bent, unlike multi-stage shafts which need full replacement. Leaking seals? Check the seal face—scratches can be fixed by grinding, no need to replace the entire seal assembly.
• Annual Deep Maintenance: Once a year, take apart the bearing housing and replace the lithium-based grease—don’t overfill it, just fill it to 1/2 to 2/3 of the bearing housing volume (overfilling causes overheating). Tighten the bolts connecting the pump body to the base—loose bolts cause misalignment of the pump shaft. Apply a layer of epoxy resin to the impeller and seal cavity to prevent rust. All these tasks can be done on the ground—no crane required.

Conclusion

At the end of the day, the OH1 pump is just a solid, practical tool. It doesn’t have the fancy features of multi-stage pumps, but it excels in what it’s designed for—medium-to-low head applications, stable flow, and easy maintenance. For businesses, this means fewer headaches and lower total cost of ownership over the equipment’s lifetime.

If you’re still on the fence—maybe you’re unsure which material is right for your fluid, or how to integrate the pump into your existing system—don’t worry. Our team at Teffiko deals with this stuff every day. Whether you need help with selection, installation support, or post-installation troubleshooting, we’ve got you covered. No need to guess—just reach out.