In order to provide for special requirements such as corrosion resistance, it is common practice to make entire valve and tubing structures from a material which has the necessary properties. This is tolerable if the material is not too expensive, or if the nature of the installation is such that it can absorb the expense. Often, however, a relatively expensive material, or one which is difficult to employ, must be used. For such installations, it would be good practice, if possible to utilize less expensive material for strength and structure, and the more expensive material only as a liner and seal.
Pipe linings are, of course, well known in the art. Slush coatings, and wiped-on coatings are known for both the inside and outside walls of pipes. Also, plated coatings are known. A problem with many of the prior art expedients is that they often have faults and leaks, and in some installations this can lead to expensive and dangerous situations.
It is an object of this invention to provide tubings and fittings which have cast-in-place liners that are unlikely to have faults or leaks, that are cast into jackets of relatively inexpensive materials such as organic plastic materials.
Another object of this invention is to provide coupling assemblies for such tubings and fittings, that are expedient to prepare and install.