If you’ve worked in fluid handling, industrial piping, or sanitary process systems for long, you’ve probably heard of TG4 seals. As a supplier who’s sold these components to manufacturers, food processing plants, pharmaceutical facilities, and even hydraulic repair shops for 12 years now, one question comes up every single week: Can a TG4 seal be bent without breaking? It’s a loaded question, and it’s one that stumps a lot of people who’ve only dealt with generic O-rings or cut gaskets. Today, I’m breaking this down like I would for a new customer who just dropped this question on our warehouse floor—and no, the answer isn’t a simple yes or no. TG4 Seal
First, let’s get on the same page about what a TG4 seal actually is, because a lot of folks mix it up with similar sealing products. TG4 is a type of enspiral seal, right? Wait, no—wait, more specifically, it’s a metal-jacketed spiral-wound seal, designed for high-pressure, high-temperature applications where generic rubber O-rings would fail. The core is made of alternating layers of metal ribbon and flexible filler, then wrapped in a thick outer metal jacket, usually 316L stainless steel for corrosion resistance, with a inner core of graphite, PTFE, or vermiculite depending on the application. Unlike a solid ring or a molded rubber seal, the TG4 isn’t a monolithic piece—it’s a layered, flexible structure by design, built to conform to uneven flange faces and seal gaps that would cause a standard seal to leak. That’s why people assume it can bend, but there’s a catch: it’s not meant to be bent like a paper clip, and bending it incorrectly is how most people end up with broken seals.
Let’s start with the science of why the TG4 seal can bend—at least, under the right conditions. The layered construction is its superpower here. When you bend a standard solid metal or rubber seal, you’re putting all the stress on a single plane of material, right? But the TG4’s spiral layers act like tiny, flexible hinges. Each turn of the spiral can flex independently, so when you apply gentle, uniform pressure along the edge of the seal, the layers shift slightly instead of cracking. I’ve tested this in our in-house lab hundreds of times over the years. Last year, we worked with a food processing plant that needed to fit a custom-sized TG4 seal around an irregularly shaped flange on a pasteurizer line—their regular supplier couldn’t cut a standard O-ring to fit without stretching it, which would cause leaks. We took a standard 12-inch round TG4 seal, gently bent the edges into an oval shape, and slipped it into the flange. It seated perfectly, with zero signs of damage after pressure testing at 150 PSI and 450°F. That’s the key: gentle, controlled bending, not force.
Now, why do so many people break TG4 seals when they try to bend them? Most of the time, it’s a misunderstanding of how much flexibility the filler core can handle, and where the stress points are. The inner core of the TG4 is the fragile part—if you bend the seal too sharply, or apply force to only one small section instead of the entire circumference, the graphite or PTFE core can crack or crumble, even if the outer metal jacket looks fine. I learned this the hard way early in my career. Back in 2012, I was helping a HVAC tech install a TG4 seal on a high-pressure steam line. He grabbed the seal by one corner and pulled it into a U-shape to fit through a tight opening. By the time he got it in place, the seal was leaking within an hour. I cut it open later and saw that the graphite core at the bent corner had completely shattered, and the outer metal jacket had split along the spiral seam. He’d bent it too sharply, focused all the force on a single point, and didn’t account for the core’s flexibility limit.
That’s where understanding the TG4’s design limits comes in. Every TG4 seal has a minimum bend radius, which is specified by the manufacturer—usually around 1.5 times the seal’s cross-sectional thickness. For example, a 3mm thick TG4 seal has a minimum bend radius of about 4.5mm, meaning you can’t bend it into a circle with a smaller radius than that without risking damage. Most people don’t know this specification exists, because it’s not printed on every individual seal, it’s in the product data sheets we provide to customers. Another common mistake is trying to bend a TG4 seal that’s already been exposed to extreme temperature changes or chemical corrosion. If a seal has sat in a warehouse for years, or been used in a harsh chemical environment, the filler core can become brittle, making it far more likely to crack when bent. I always tell customers to inspect their seals before installation—if they see any discoloration, crumbly filler, or small cracks in the outer jacket, don’t even try to bend it; get a new one.
Let’s talk about real-world applications where bending a TG4 seal is necessary, because that’s what most people are dealing with. Flange connections aren’t always perfectly round, especially in industrial settings where equipment can shift over time. If you have an odd-sized flange, or a flange with bolt holes that are misaligned, you can’t always use a pre-cut round seal. That’s when bending a TG4 seal is the right move—as long as you do it correctly. The proper way to bend a TG4 seal is to support the entire circumference on a flat, smooth surface, like a workbench, then apply gentle, even pressure to the edge where you want to bend it. Use a soft, non-marring tool, like a rubber mallet or a plastic pry bar, to guide the bend, and check the radius as you go to make sure you’re not going below the minimum. Never grab the seal with pliers or pull it into a shape by hand; that’s how you apply uneven stress.
We also do custom-fabricated TG4 seals here at our company, which means we bend seals all the time for unique projects. Last quarter, we worked with a pharmaceutical manufacturer that needed TG4 seals for a rectangular bioreactor flange. The standard round seals wouldn’t fit, so we took 20-inch round TG4 seals and bent them into a rectangular shape with rounded corners, following the minimum bend radius for their 4mm cross-section. We tested a sample in our pressure and temperature chamber—we ran it at 200 PSI and 500°F for 72 hours straight, and there were zero leaks. The only issue? We had to make sure the corners of the rectangle had a large enough radius to keep the seal from breaking, which is why we recommend rounded corners for any custom-shaped TG4 seal, instead of sharp 90-degree angles. Sharp angles are the #1 cause of broken seals when bending, because they create a tiny, concentrated stress point where the core can crack.
Now, let’s address the myths that float around about TG4 seals and bending. Some people think that all metal seals can’t be bent, which is true for solid metal seals like flat gaskets or solid O-rings, but TG4 is a spiral-wound design, not solid. Others think that bending a seal invalidates the warranty, but that’s only if you bend it incorrectly. Most TG4 manufacturers (including the ones we partner with) have a warranty that covers defects in materials and workmanship, but not damage caused by improper installation—including bending that exceeds the minimum radius. That’s why we always send a quick installation guide with every order, with a section specifically on bending TG4 seals, and our customer support team will walk you through the process step-by-step over the phone if you have a custom project.
I get asked a lot whether it’s better to order a custom-shaped TG4 seal or bend a standard one, and the answer depends on your application. If you have a one-off, custom flange that you won’t need again, bending a standard seal is more cost-effective. If you need multiple seals for a permanent installation, ordering a custom-fabricated seal will give you more consistent results, because it’s made in a controlled factory environment, not bent by someone on a job site. But in both cases, the key is understanding how the TG4 seal is constructed, and respecting its limits.
Let’s wrap this up with a practical tip that I’ve given to hundreds of customers over the years: if you’re ever unsure whether you can bend a TG4 seal for your project, don’t guess. Reach out to a supplier who knows the product, like us, and we can help you assess whether bending is safe, or if a custom seal is a better option. We’ve seen too many projects where a broken seal caused costly downtime, from food production lines shutting down for 8 hours to pharmaceutical plants missing regulatory inspection deadlines, all because someone tried to bend a seal without knowing the right way to do it.
If you’re working on a project where you need TG4 seals, whether standard, custom, or something that needs to be bent, we’re here to help. Our team has decades of experience with these seals, and we can answer any questions you have about bending, installation, or application. Connect with us to discuss your requirements, and we’ll make sure you get the right seal for your job.
Stainless PTFE Shaft Seal References:
- “Spiral Wound Gaskets: Design, Performance, and Application Guidelines,” American Society of Mechanical Engineers (ASME) PCC-1, 2020.
- “TG4 Seal Material Compatibility and Flexibility Limits,” Garlock Sealing Technologies Technical Data Sheet, 2021.
- Industrial Sealing for Sanitary Process Systems, International Society for Pharmaceutical Engineering (ISPE) Good Practice Guide, 2019.
DEDE SEAL Co., Ltd.
DEDE Seal Co., Ltd. is one of the most experienced tg4 seal manufacturers and suppliers in China for over 35 years, featured by quality products and good price. Please feel free to buy bulk customized tg4 seal made in China here from our factory. Welcome to contact us for pricelist.
Address: Hunan Road, Pudong New Area, Shanghai, China
E-mail: info@dedeseal.com
WebSite: https://www.dedesealing.com/
