GB2134614A - Pipe connection - Google Patents

Abstract

The invention relates to a pipe connection for thin-walled line pipes typically of high-alloy stainless steels, in particular for water and heating installations, wherein the pipes are connected with a press fitting (2) of the same type of material, the ends of which are constructed as ring beads (3). The fitting surrounds the pipe ends (1) with a force fit with sealing rings (4) arranged in each ring bead (3). There is also a metal sleeve (5) provided between at least one of the pipe ends (1) and the inner surface of the press fitting (2). <IMAGE>

Description

SPECIFICATION A pipe connection The invention relates to a pipe connection, particularly for thin-walled line pipes for water, usually containing chloride. Such pipes, especially those for water as heating installation are often made of high-alloy stainless steels.

A pipe connection of the above type is described in published German Patent Application No. 27 25 280 as a press fitting. Two pipe ends are connected with a press fitting of the same type of material the ends of which, constructed as ring beads, surround the pipe ends and hold a sealing ring thereagainst. A jointing clamp is used to connect the pipe ends by pressing the press fittings including sealing rings onto the pipe ends.

In connecting stainless steel pipes using press fittings of the same type of material and with nonmetallic sealing rings, e.g. of butyl rubber, corrosion damage can occur in the region of the seals inside the rings beads through crevice corrosion and pitting, and at temperatures above approximately 450C also through stress crack corrosion. The risk of such damage is greater where the pipe in question carries water containing chloride. These types of corrosion damage are due to the fact that by penetration of water into the region between pipe ends and press fittings and the diffusion off of water vapour through the sealing ring in the ring bead, water components, amongst which chlorides are of particular significance, are accumulated. Chloride ions are specifically damaging substances for the types of corrosion mentioned.

The present invention seeks to relieve the problems i.e. posed by this form of corrosion damage. To this end the invention provides a pipe connection between thin-walled line pipes comprising a press fitting, each end of which encircles the end of a said pipe, and holds a sealing ring thereagainst, wherein a metal sleeve is disposed between the fitting and at least one of the pipe ends.

The preferred material for the sleeve is copper.

One of a plurality of sleeves may be used, a plurality spaced along the fitting, and encircling one or both pipe ends. Thus, a single sleeve may extend substantially the length of the fitting to cover both pipe ends, or separate sleeves may be used on each end. One sleeve on only one end can be satisfactory.

The invention will now be described by way of example and with reference to the accompanying drawing wherein: Fig. 1 shows a longitudinal section through one part of a pipe connection according to the invention; and Fig. 2 shows a cross-section along line A-A of Figure 1.

The press fitting 2 which has ring bead 3 and sealing ring 4 inserted therein, is pressed onto the end of the pipe 1. A copper sleeve 5, of which the wall thickness is no more than of 0.5 mm, is located between the press fitting and the pipe end.

The fitting is pressed onto the pipe end with the jaws 6 of a jointing clamp, not shown.

The copper sleeve in the press fitting on the pipe provides: a) an active, electrochemical (cathodic) corrosion protection of the stainless steel, since in the waters in question copper has a more negative (basic) corrosion potential than the stainless steel, b) a more extensive sealing in the connection.

The water vapour diffusion to and through the non-metallic sealing ring is reduced as consequently is the accumulation of water components associated therewith in the region of the ring bead.

1. A pipe connection between thin-walled line pipes comprising a press fitting, each end of which encircles the end of a said pipe, and holds a sealing ring thereagainst, wherein a metal sleeve is disposed between the fitting and at least one of the pipe ends.

2. A pipe connection according to Claim 1 wherein the pipe ends and the press fitting are made of the same type of material.

3. A pipe connection according to Claim 2 wherein said material is high alloy stainless steel and the sleeve comprises copper.

4. A pipe connection according to any preceding Claim wherein a sealing ring is held in a ring bead at each end of the fitting, and wherein the fitting is a force fit on the pipe ends.

5. A pipe connection according to any preceding Claim wherein the metal sleeve surrounds both pipe ends.

6. A pipe connection according to any of Claims 1 to 4 wherein a metal sleeve is disposed between the fitting and each pipe end.

7. A pipe connection between thin-walled line pipes substantually as described herein with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION A pipe connection The invention relates to a pipe connection, particularly for thin-walled line pipes for water, usually containing chloride. Such pipes, especially those for water as heating installation are often made of high-alloy stainless steels. A pipe connection of the above type is described in published German Patent Application No. 27 25 280 as a press fitting. Two pipe ends are connected with a press fitting of the same type of material the ends of which, constructed as ring beads, surround the pipe ends and hold a sealing ring thereagainst. A jointing clamp is used to connect the pipe ends by pressing the press fittings including sealing rings onto the pipe ends. In connecting stainless steel pipes using press fittings of the same type of material and with nonmetallic sealing rings, e.g. of butyl rubber, corrosion damage can occur in the region of the seals inside the rings beads through crevice corrosion and pitting, and at temperatures above approximately 450C also through stress crack corrosion. The risk of such damage is greater where the pipe in question carries water containing chloride. These types of corrosion damage are due to the fact that by penetration of water into the region between pipe ends and press fittings and the diffusion off of water vapour through the sealing ring in the ring bead, water components, amongst which chlorides are of particular significance, are accumulated. Chloride ions are specifically damaging substances for the types of corrosion mentioned. The present invention seeks to relieve the problems i.e. posed by this form of corrosion damage. To this end the invention provides a pipe connection between thin-walled line pipes comprising a press fitting, each end of which encircles the end of a said pipe, and holds a sealing ring thereagainst, wherein a metal sleeve is disposed between the fitting and at least one of the pipe ends. The preferred material for the sleeve is copper. One of a plurality of sleeves may be used, a plurality spaced along the fitting, and encircling one or both pipe ends. Thus, a single sleeve may extend substantially the length of the fitting to cover both pipe ends, or separate sleeves may be used on each end. One sleeve on only one end can be satisfactory. The invention will now be described by way of example and with reference to the accompanying drawing wherein: Fig. 1 shows a longitudinal section through one part of a pipe connection according to the invention; and Fig. 2 shows a cross-section along line A-A of Figure 1. The press fitting 2 which has ring bead 3 and sealing ring 4 inserted therein, is pressed onto the end of the pipe 1. A copper sleeve 5, of which the wall thickness is no more than of 0.5 mm, is located between the press fitting and the pipe end. The fitting is pressed onto the pipe end with the jaws 6 of a jointing clamp, not shown. The copper sleeve in the press fitting on the pipe provides: a) an active, electrochemical (cathodic) corrosion protection of the stainless steel, since in the waters in question copper has a more negative (basic) corrosion potential than the stainless steel, b) a more extensive sealing in the connection. The water vapour diffusion to and through the non-metallic sealing ring is reduced as consequently is the accumulation of water components associated therewith in the region of the ring bead. CLAIMS

1. A pipe connection between thin-walled line pipes comprising a press fitting, each end of which encircles the end of a said pipe, and holds a sealing ring thereagainst, wherein a metal sleeve is disposed between the fitting and at least one of the pipe ends.

2. A pipe connection according to Claim 1 wherein the pipe ends and the press fitting are made of the same type of material.

3. A pipe connection according to Claim 2 wherein said material is high alloy stainless steel and the sleeve comprises copper.

4. A pipe connection according to any preceding Claim wherein a sealing ring is held in a ring bead at each end of the fitting, and wherein the fitting is a force fit on the pipe ends.

5. A pipe connection according to any preceding Claim wherein the metal sleeve surrounds both pipe ends.

6. A pipe connection according to any of Claims 1 to 4 wherein a metal sleeve is disposed between the fitting and each pipe end.

7. A pipe connection between thin-walled line pipes substantually as described herein with reference to the accompanying drawings.