US 5,741,458 A · Method of forming a water heater tube

Abstract

A process for the fabrication of a thermoset water heater tube is described. By shifting to a thermoset rather than a thermoplastic, a much higher heat distortion temperature is achieved when compared to standard thermoplastic materials such as polypropylene, polyethylene, ABS or PVC. The stress crack resistance is also higher as is the dimensional stability. These desirable properties can be achieved by using a lower cost material, in contrast to a more expensive thermoplastic, and solves the problem of water heater tube failure when dry firing conditions are present. The invention utilizes thermoplastic processing conditions, with subsequent crosslinking to form a thermoset. This combines the best features of both types of materials: (1) the ease of thermoplastic processing; combined with (2) the desirable physical properties of a thermoset.

Claims26

Dependent claims

A process for forming a thermoset hollow cylindrical water heater tube having one belled proximal end without wall thinning from a constant thickness portion of the tube and an opposed distal end, comprising without regard to order of steps (a) through (e):

(a) belling the proximal tube end comprising the steps in the following order of:
(i) inserting the proximal tube end through a female die and having a portion of the tube projecting the female die, the female die surrounding a first outer diameter of the tube and having a projection adapted to cooperate with a recess of a male die;
(ii) heating at least a portion of the tube projecting from the female die sufficiently to make such projecting portion pliable enough to form;
and
(iii) belling the proximal tube end by insertion of the projecting tube portion into an annular recess of the male die and the cooperating recess of the male die and the projection of the female die by closing the female and male dies;
(b) heating a portion of the tube at an inflection region between the proximal and distal ends of the tube and bending the tube;
(c) at least partially sealing the distal end of the tube;
(d) crosslinking the tube;
and
(e) drilling at least one hole into a wall of the tube.

7 more elements

Dependencies are inferred from the claim text.

Method of forming a water heater tube

Life of this patent

Method of forming a water heater tube

Life of this patent

Abstract

Claims26