Cone-and-thread fittings make a tight, reliable seal
The image above highlights the key components of the IPT fitting.The cone and thread fittings are desgined to withstand medium and high pressure environments.
When you have a fluid system running at above-normal pressures, you need something sturdier than the standard Swagelok tube fitting. For great performance under pressure, we have the IPT series. We offer two types of IPT fittings: The medium pressure fittings are designed for up to 20,000 psig or 1378 bar and the high-pressure fittings for up to 60,000 psig or 4134 bar.
These cone-and-thread fittings are designed specifically for the oil and gas, chemical, petrochemical, water jet cutting and blasting, and aerospace industries.
A good angle
The threaded tubing ends with a cone at a 59-degree angle. It fits into the primary seal surface, which has a 60-degree angle. All manufacturers use the same interference angle between the male cone and female body, which allows for interchangeability. This is one of the rare times Swagelok gives a green light to mixing its components with those from other manufacturers.
A collar surrounds this area. A threaded part, called a gland, creates a load on the collar to ensure a seal on the tubing. This is another area where standard procedure departs from the standard Swagelok tube fitting. Instead of prescribing a fixed number of turns for proper tightening, IPT fittings require a specific amount of torque.
Another key element in IPT fittings is a weep hole at the collar. It's a quick way to detect leaks and verify proper installation. Even steam leaks are easy to spot by applying a bit of Snoop leak detector at the weep hole. When removing the collar and gland for maintenance, the weep hole also releases trapped pressure to avoid a "live loaded" thread. But never use the weep hole to bleed the system or vent system pressure. This could cause a pressure-injection injury to your employees.
The medium-pressure and high-pressure components have the same basic design, but the parts are not interchangeable. The high-pressure version has a larger collar and gland, and the collar sits inside the gland when assembled. The high-pressure design also uses thicker wall tubing to compensate for threads.
Both the medium-pressure and high-pressure versions have anti-vibration assemblies available. That's useful when the fittings are placed near a compressor, for example. Again, the assemblies are not interchangeable. An easy way to spot the high-pressure version is its additional slotted collet, which must be pointed in the right direction for assembly. (The medium-pressure slotted collet can be oriented in either direction.)
The special cold-drawn tubing used with IPT fittings is also different from the standard used in other applications. It's harder and has thicker walls in order to allow cutting away material for threads with a tap-and-die set. In a sense it's really a very small pipe. We'll gladly rent you the tools to do the coning and threading, or we can do it for you if you tell us the dimensions you need.
Another difference from ordinary tubing is the outer diameter, which is slightly smaller than the nominal tube OD.
The harder steel and thicker walls also come into play when bending the tubing. The bend radius must be larger, at least 1.25 inches for quarter-inch tubing. (Keep that in mind when planning out your installation, as you'll need some extra space.) Don't try using a hand tube bender; use the bench-top version as you will also experience greater spring back.
Even extra-tough tubing is softened by heat. That means high temperatures (greater than 93.33º C) will have an impact on the pressure rating of the connection. At 204º C, the pressure rating drops to 93 percent of normal for strain-hardened 316 stainless. At 537º C it drops to 84 percent of normal.
If you've properly installed your IPT fittings, you can take them apart and reassemble them up to five times. But it's important to make sure the cone stays perfectly smooth. If the cone doesn't fit tight against the body, you won't get a proper seal. Tubing can be re-coned if you aren't sure, though be aware that doing so can shorten the length of the tubing.
So don't let the pressure get to you the IPT download has even more information on all the types of IPT fittings and ordering information.
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