If you’ve got an existing valve sitting in your facility that’s starting to leak, struggle with pressure, or just doesn’t hold up as well as it used to, you might be thinking about replacing it. Wait—hold up. Before you go dropping thousands on a brand new valve, have you considered retrofitting it to a double offset butterfly valve (DOBV)? As a guy who’s been selling DOBVs for over 10 years (I’ve seen every trick in the book when it comes to upgrading old gear), I’m here to tell you this is way more doable than you think. And no, you don’t need a team of engineers to pull it off—just a little know-how, some patience, and maybe a call to a supplier that actually gets retrofits (that’s me, by the way). Double Offset Butterfly Valve
First, let’s get real: why bother with a retrofit instead of a full replacement? Let’s run through the numbers I see every week from my customers. A full valve swap usually means cutting old pipes, reworking flanges, adjusting mounting bolts, and dealing with downtime that could put a production line out of commission for days. Retrofit? You keep most of the existing pipework, use the same bolt pattern, and swap out only the valve body and internals. For most mid-sized valves, that cuts material costs by 30-50% and downtime by at least half. And double offset butterfly valves, in case you’re not familiar, are the workhorses of the valve world—they solve all the annoying problems that old gate valves, globe valves, or even single-offset butterfly valves have. Leakage? Gone. Torque requirements? Way lower. Wear and tear? Minimal, because the offset disc design means the disc never rubs against the seat when you open or close it. That’s the magic of the two offsets: one is between the disc’s pivot axis and the centerline of the pipe, and the second is between the disc’s centerline and the pipe’s centerline. When the valve opens, the disc lifts completely off the seat—no grinding, no friction, no extra torque. Perfect for high-cycle applications, oil and gas, chemical processing, water treatment—you name it.
So, how do you actually go about retrofitting your existing valve to a DOBV? Let’s break this down step by step, no jargon, no confusing diagrams (well, as little as possible).
First up: do your pre-retrofit homework. This is the part that trips people up, so don’t skip it. First, you need to get the specs of your existing valve right. Grab a tape measure, write down the pipe size (nominal, not just inches—so if it’s 6-inch nominal, that’s DN150), the flange type (ANSI, DIN, JIS? What class? 150, 300, 600?), and the bolt circle diameter. You also need to measure the overall length of the valve (the distance between the two flange faces, called face-to-face) and the valve’s operating torque (if it’s automated, write down the actuator brand and model). Wait, and check the pressure rating of your pipe system. A lot of people forget this, and they end up with a retrofit valve that can’t handle the line pressure. Also, ask yourself: what’s this valve actually doing? Is it for on/off service, or does it need to throttle flow? DOBVs work great for both, but if you’re throttling, you might need a slightly different seat material.
Pro tip from me: don’t guess these specs. Pull the old valve’s serial number off the body and call the manufacturer to get the exact dimensions. If you can’t find the serial number, take photos of the flange bolt holes, the stem size, and the disc profile—send those to your DOBV supplier. We can reverse-engineer almost any old valve from a few good photos, no problem. I’ve had customers send blurry phone pics of a rusted old valve and we had a retrofit part made for it.
Next step: choose the right DOBV retrofit kit or replacement valve. This is where having a good supplier pays off. A lot of sketchy vendors will just sell you a generic valve that doesn’t fit your existing flanges, which means you’re back to cutting pipes and redoing everything. But a quality DOBV retrofit is made to match your existing face-to-face length, bolt pattern, and stem size so you don’t have to modify any pipework. Now, decide if you want a full valve replacement (instead of just parts) or a kit that swaps the internals of your old valve body. Wait—most people don’t know you can swap the internals of an existing valve body for a DOBV set, which is even cheaper. But that only works if your old valve body is in good shape (no cracks, no corrosion, the internal bore is smooth). If your old body is rusted or has pitting, go for a full DOBV replacement with matching flanges. Also, pick the right seat material. For water service, EPDM works great; for chemicals, Buna-N or PTFE; for high-temperature steam, metal seats. Don’t just go with what you had before—talk to your supplier about your specific application. I had a customer last year who used a generic butterfly valve with EPDM seats for a mild acid line, and it leaked all the time. We retrofitted a DOBV with PTFE seats and it’s been zero leaks for 18 months. Worth the extra $200, trust me.
Third step: prep the site for installation. Now, before you touch the old valve, turn off the line pressure and drain the pipe completely. This seems obvious, but I’ve seen guys skip this and end up with a pipe geyser that takes out half the plant. Also, tag the valve so you remember which line it’s on—label it with a marker or a tag, because you don’t want to mix up valves during shutdown. If you’re doing a full retrofit (replacing the entire valve), loosen all the flange bolts slowly, a little at a time, so the flange doesn’t get twisted or damaged. Put the old valve somewhere safe so you can reference the dimensions if something goes sideways. If you’re just swapping internals, clean out the old valve body thoroughly—use a wire brush and degreaser to get all the gunk and old seat material out. Make sure the internal bore is smooth and free of nicks, because that will mess up the new DOBV’s seal.
Fourth step: install the DOBV. Let’s start with a full valve retrofit first. Line up the new DOBV between the existing flanges, make sure the bolt holes line up perfectly—no forcing bolts, that will warp the flange and cause leaks. If the holes don’t line up, something’s wrong, stop and check your dimensions, don’t use a cheater bar. Once the bolts are finger-tight, tighten them in a crisscross pattern (like you’re tightening a tire on a car) so the flange is pressed evenly, no uneven gaps that cause leaks. Torque the bolts to the manufacturer’s specs—don’t over-tighten, that can crack the flange or the new valve body. If you’re retrofitting internals, slide the new DOBV disc and seat into the old valve body, make sure it’s seated properly, then reattach the stem and any actuator. Test the stem movement: open and close the valve a few times to make sure the disc moves smoothly, no sticking or grinding. A lot of people forget to test this, and they have a valve that won’t fully close once it’s back in the line.
Fifth step: pressure test and check for leaks. This is non-negotiable. Once the valve is installed, slowly apply pressure to the line, not at full pressure all at once. Start at 50% of the line’s maximum pressure, wait 10 minutes, check all the flange bolts and the valve body for leaks. If no leaks, go up to 75% pressure, wait another 10 minutes, check again. Then go to full operating pressure. Watch the valve for a little while—sometimes leaks show up after 30 minutes under full pressure, not right away. If you do find a small leak on a flange, tighten the bolts a little more (in crisscross order) and test again. If the valve itself is leaking, don’t panic—you probably didn’t seat the disc correctly, or the seat material is incompatible. Call your supplier, they’ll walk you through fixing it, no need to start over.
Now, let’s talk about common mistakes people make with DOBV retrofits, so you don’t mess this up. First, not checking the stem size. The DOBV stem has to match your existing actuator or gear operator, otherwise you’ll have to swap the actuator too, which defeats the purpose of a retrofit. I had a customer last month who ordered a retrofit valve with a 1-inch stem, and his old actuator was for a 1.25-inch stem. He had to send the valve back, which cost him 2 days of downtime and extra shipping. Don’t do that—double-check the stem size before you order. Second, using the wrong seat material. I mentioned this earlier, but it’s the #1 reason retrofit DOBVs fail. If you’re not sure what material to use, tell your supplier the fluid, temperature, and pressure of your line, and they’ll recommend the right seat. Third, forcing the valve into place. If the bolts don’t line up, it’s not a match, don’t force it. You’ll end up with a warped flange that leaks for years, or a valve that’s hard to operate. Fourth, skipping the pressure test. I can’t tell you how many times a customer calls me a week after installation saying “my new valve is leaking” and it’s because they skipped testing. Take the extra 30 minutes to test, it’ll save you hours of headache later.
Another big win with DOBV retrofits: if you have automated valves, you can almost always keep your existing actuator. Since DOBVs have lower operating torque than old valves, your existing actuator will work fine—no need to buy a new motor or gearbox. That’s another big cost savings. For manual valves, the operating effort is way lower too, so it’s easier for operators to open and close the valve, which reduces wear on the handle and stem over time.
Wait, let’s also talk about when a retrofit isn’t worth it. If your existing valve body is cracked, corroded so bad the internal bore is pitted beyond repair, or if your line pressure is way higher than what your old pipe is rated for, then a full replacement is better. But 9 times out of 10, a DOBV retrofit is the way to go. I just did a retrofit for a food processing plant last month—they had 12 old gate valves that leaked all the time, and we swapped them to DOBVs, kept all the existing pipework, and they saved over $15,000 compared to full replacement. Plus, downtime was only 4 hours instead of 2 days. That’s a no-brainer.
Now, if you’re ready to stop dealing with leaking valves, high maintenance costs, and constant downtime, don’t waste another day. Retrofitting your existing valve to a double offset butterfly valve is the smart, cost-effective move. We’ve done hundreds of retrofits for facilities across all industries, from water treatment plants to chemical refineries, and we know exactly how to get your valve fitting right the first time, no mistakes, no hassle. If you need specs help, a quote, or just have questions about whether a retrofit works for your specific valve, reach out to our team. We’ll walk you through every step, send you the right parts, and make sure your installation goes smooth. Don’t settle for underperforming old valves—upgrade to a DOBV retrofit today, and start saving money and downtime.
Double Offset Butterfly Valve Reference:
Valve Standards Committee. Retrofit Practices for Industrial Valves. American Society of Mechanical Engineers, 2020.
Zhejiang Zhengfeng Valve Co., Ltd.
We’re well-known as one of the leading double offset butterfly valve manufacturers and suppliers in China. With abundant experience, we warmly welcome you to buy bulk advanced double offset butterfly valve from our factory. If you have any enquiry about cooperation, please feel free to email us.
Address: Hengtong Road, Wuxing Industrial Park, Wenzhou, Zhejiang, China. 325105
E-mail: sales@zfvalve.com
WebSite: https://www.zfvcns.com/
