Tube Fittings

A socket weld is a pipe attachment detail in which a pipe is inserted into a recessed area of a valve or fitting, and then fillet welded between its outside diameter and the fitting end. Generally used for piping whose nominal diameter is 2 inches (50 mm) or smaller.

DESIGN CONCEPT:

Weld fitting design offers smallest envelope, lightest weight and strongest joint among all other mechanical fitting joints. Navy test results showed an average welded joint has a durable fatigue life up to 150% higher than mechanically attached fitting joints. No wonder this concept is widely used in commercial and military programs worldwide. The weld fitting end design has the simplest geometrical contour with an integral T-ring. It provides alignment for the fitting and tubing and is also a filler material for welding. Fitting and tubing ends shall be cleaned prior to welding; one of the simplest cleaning methods is to spray acetone to the joint and it will quickly evaporate. Weld fittings are easily to be welded by Orbital weld tooling with electronic memories to reproduce accurate repeated weld each time. It minimizes X-ray inspection to a large degree. Different tooling is available for bench production weld or portable welding. The unified welded joint provides a positive fluid sealing.

DESIGN ADVANTAGES:

• Unified weld joint offers positive sealing.
• Offers smallest envelope, lightest weight and strongest fitting joint.
• Electronic memories produce accurate repeated weld each time.
• Weld tooling requires lowest maintenance cost by replacing tungsten only.
• Integral T-ring offers self-alignment for fitting and tubing butting to support proper welding.

TOOLING
Various welding equipment manufacturers offer Orbital Weld tooling and training.

Features
VCR fittings offer the high purity of a metal to metal seal, providing leak-tight service from vacuum to positive pressure.
The seal on a VCR assembly is made when the gasket is compressed by two beads during the engagement of a male nut or body hex and a female nut.

Plating
VCR female nuts are silver plated. Avoid chemical processes used for cleaning, electropolishing, and passivation that will remove plating. If the plating is damaged or removed, thread galling may occur, damaging fitting components and preventing a proper seal.

Testing
The VCR fitting design has been helium leak tested to a maximum leak rate of 4 x 10-9 std cm3/s with silver-plated and copper gaskets and to a maximum leak rate of 4 x10-11 std cm3/s with unplated gaskets.

Ultrahigh-Purity Processing
A variety of VCR face seal glands and bodies is available with controlled surface finishes, electropolished, and specially cleaned to meet ultrahigh-purity system requirements.

ISO-KF Flanges and Fittings allow quick release and tight connections from 10 to 50 mm nominal diameters. With 2 flanges coupled together by a cente-ring ring with a O-ring and a clamp (Fig. 1 & 2), this kind of connection provides many advantages such as: Easy and quick mounting

• Assembly without any tools
• Unlimited orientation
• Easy interchangeability

A vacuum flange is a flange at the end of a tube used to connect vacuum chambers, tubing and vacuum pumps to each other. Several vacuum flange standards exist, and the same flange types are called by different names by different manufacturers and standards organizations.

The ISO standard quick release flange is known by the names Quick Flange (QF), Klein Flange (KF) or NW, sometimes also as DN. The KF designation has been adopted by ISO, DIN, and Pneurop. KF flanges are made with a chamferred back surface that attached with a circular clamp and an elastomeric o-ring that is mounted in a metal centering ring. Standard sizes are indicated by the nominal inner diameter in millimeters for flanges 16 through 50 mm in diameter.

• DN16KF
• DN25KF
• DN40KF
• DN50KF

The ISO large flange standard is known as LF, LFB, MF or sometimes just ISO flange. As in KF-flanges, the flanges are joined by a centering ring and an elastomeric o-ring. An extra springloaded circular clamp is often used around the large diameter o-rings to prevent them from rolling off from the centering ring during mounting.

The ISO large flanges come in two varieties. The ISO-K (or ISO LF) flanges are joined with double claw clamps which clamp to a circular groove on the tubing side of the flange. The ISO-F (or ISO LFB) flanges have holes for attaching the two flanges with bolts. Two tubes with ISO-K and ISO-F flanges can be joined together by clamping the ISO-K side with single claw clamps which are then bolted to the holes on the ISO-F side.
ISO large flanges are available in sizes from 63 to 500 mm nominal tube diameter.

• DN63LF (63.5 mm)
• DN100LF (102 mm)
• DN160LF (160 mm)
• DN200LF (200 mm)
• DN250LF (254 mm)
• DN320LF (316 mm)
• DN400LF (400 mm)
• DN500LF (500 mm)

For ultra-high vacuum applications, there are ConFlat (CF) flanges that use a copper gasket and knife-edge flange to achieve the vacuum seal. Conflat flanges operate down to 10-13 torr (10-11 Pa) pressure and can be heated to 450 °C for bake-out. North American flange sizes are given by flange outer diameter in inches: 1
("mini"), 2¾, 4½, 6, 8, 10, 12, 13¼, 14 and 16½. In Europe and Asia, sizes are given by tube inner diameter in millimeters.

• DN16
• DN40
• DN63
• DN100
• DN160
• DN200
• DN250