You’re installing трубные фитинги. You need them to hold pressure. You need them to not leak. You need to know which one to pick.
This article covers two things:
- What single and double ferrule actually do
- Which one fits your pressure, vibration, and tube condition
First, Know What You are Really Asking
When you ask “what’s the difference”, you’re actually asking “what should I buy?”
A ferrule is basically a metal ring that has two main jobs. First, it helps to seal things, making sure there are no leaks. Second, it provides a good grip, so the tube it’s attached to won’t accidentally pull out.
Single ferrule: one ring does both jobs.
Двойной наконечник: two rings split the work. Front ferrule seals. Back ferrule grips.
Single Ferrule: Cheap, Good Enough, Hard to Mess Up
One ring does both sealing and gripping.
Why you might pick it:
- Pressure under 3,000-5,000 psi
- No vibration
- Tight budget
- You are not a specialist installer
Good for:
General industrial
Water, air, low pressure hydraulic
Repair and replacement market
One sentence: Get the job done. No frills.
Double Ferrule: Expensive, Vibration-Resistant, Hard to Install
Two rings. Front ferrule seals. Back ferrule grips. Split the work.
Why you might pick it:
- Pressure above 6,000 psi
- Vibration is present: pumps, engines, compressors
- Chemical plants, oil & gas, power generation
- You need peace of mind: “I bought the good one”
Good for:
Instrumentation panel builders
Chemical and oil & gas projects
OEMs exporting to Europe or Asia
Systems that run 24/7
A Real Warning: Tube Matters
Here’s something most articles don’t tell you.
Double ferrule fittings require bright annealing tubes, while single ferrule fittings work with acid-pickled tubes.
We once had a customer, who purchased acid-pickled tubes. Since most customers require double ferrule fittings and the customer didn’t emphasize on the tube they use. We sent them double ferrules and the ferrules ended up useless.
Learn from this.
Before you order, check your tube. Is it bright annealing or pickled? If you don’t know, ask your tube supplier. Or send us a photo.
Get it wrong and nothing seals. No matter how good the fitting is.
Another Warning: Know What You Are Buying
Here is another mistake we see all the time.
Both single and double ferrule fittings can be assembled on the tubes directly, while flare fittings can’t. We once had a customer who ordered flare fittings. They thought that’s what they needed. However, after we sent the fittings, they realized that they needed an extra flaring machine to assemble the fittings onto the tube. They sent me the video about what kind of fittings they required. The fittings in the video indicated that they were double ferrule fittings that can be assembled onto the tube directly.
Learn from this.
Before you buy, ask yourself: “Do I have the tooling for this fitting?”
Double ferrule: wrench only
Single ferrule: wrench only
Flare fittings: need a flaring machine
It takes only ten seconds and it will save a lot of time at the end.
Quick Comparison Table
| Dimension | Single Ferrule | Двойной наконечник |
| Ferrule count | 1 | 2 (front and back) |
| Номинальное давление | 3000-5000psi | Over 6000 psi |
| Vibration resistance | Good | Excellent |
| Wrong installation ways | 2 | Over 14 |
| Tube required | Pickled | Bright annealing |
| Reusability | Limited: once compressed, seal degrades | Yes, replace ferrule, reuse body and nut |
| Best for | Low to medium pressure, no vibration | High pressure, pumps, engines, instrumentation |
Installation: 3/4 Turn vs 1-1/4 Turn
Single ferrule and double ferrule install differently. Here’s the exact difference.
Single ferrule:
- Push tube all the way in
- Hand-tighten the nut
- Mark the nut at 6 o’clock
- Tighten with a wrench 3/4 turn (from 6 to 3 o’clock)
Double ferrule:
- Push tube all the way in
- Hand-tighten the nut
- Mark the nut at 6 o’clock
- Tighten with a wrench 1-1/4 turn (from 6 to 9 o’clock)
Why does this matter？
Because if you under-tighten, the fitting leaks. If you over-tighten, you crush the tube or damage the ferrule.
No torque wrench needed. Just a marker and a wrench. Mark the nut. Turn to the mark. That’s it.
This is the DIN 2353 standard method. Used worldwide. Works every time, regardless of lubrication or thread condition.
Why Most Customers Choose Double Ferrule
Double ferrule has been the industry standard for over 50 years. Swagelok and other top brands use it.
In oil, gas, chemical, and power plants, where safety matters, double ferrule’s vibration resistance and reliable sealing make it the obvious choice.
But here is what most suppliers don’t tell you.
In the double ferrule design, the back ferrule has one job: grip the tube. To grip, it must bite into the tube surface. That means the gripping edge must be harder than the tube.
We harden the gripping edge of every back ferrule.
Not the whole ferrule. Just the edge that bites. Why? Because if you harden the whole thing, the ferrule becomes too stiff. Installation torque goes up. You have to fight the wrench. Most people don’t want that.
Standard hardening: only the gripping edge. Works for 95% of customers.
Custom hardening: full edge hardening. Some customers ask for it. We do it. Just know the fitting will feel different when you install it. Tighter. Heavier.
Here is a picture of a back ferrule with custom full-edge hardening. The customer wanted every edge hardened. We made it happen.
Часто задаваемые вопросы
Q1. Do you have your own factory?
Yes. Own factory. No middleman markup.
Q2. What if it leaks?
First things first, make sure the installation is done right. A lot of leaks happen because the tube isn’t fully inserted, or the ferrule is put in the wrong way. We test every batch under pressure before we send it out, so it’s probably something with how it was set up.
Q3. Can you add my logo to the fittings?
Yes. Laser marking. Body and ferrule. Your logo, part number, or heat number.
Q4. What else do you make?
Needle valves, ball valves, tube fittings, ferrules, manifold valves. One-stop instrumentation fittings supplier.
Final Thoughts
Let me keep this simple.
Single ferrule and double ferrule, there is no such thing as which one is better. They just do different jobs.
Single ferrule is for low pressure. No vibration. Limited budget.
Double ferrule is for high pressure. Pumps running. Engines vibrating.
The most common mistake? Using a single ferrule on a vibrating line. It leaks. You get angry.
Second most common? Wrong tube. Double ferrules on pickled tubes won’t seal. No matter how good the fitting is.
Ask yourself two questions before you order: What’s my pressure? Any vibration?
Pick the right fitting the first time. No leaks. No returns. No headache.
Looking for a reliable ferrule fitting supplier?Try NPTLOK.
We make both single and фитинги с двойным наконечником. Нержавеющая сталь и латунь. ДНЯО, BSP, or metric threads.
Own factory. No middleman. Full traceability. MTC with every batch.
Visit www.npt-lok.com or email yolanda2021@npt-lok.com.
Tell us what pressure and tube size you’re working with. We’ll recommend the right fitting. No upsell. Just straight talk.
Want to give our samples a try? We have a minimum order quantity of 10 pcs, so it’s a good idea to test them before placing a larger order.
