What is the production process for high-pressure hoses?

What is the production process for high-pressure hoses?

There are numerous types of equipment for manufacturing high-pressure hoses, a wide variety of raw materials, and complex production processes. However, in recent years, the production process for high-pressure flexible hoses made primarily from plastics or thermoplastic elastomers has been somewhat simplified; yet, due to the relatively high cost of these alternative materials, rubber-based formulations still dominate. So, what is the primary production process for high-pressure hoses?

High-pressure hose manufacturing process:

1. For high-pressure hoses, a mixer is used to blend the inner, middle, and outer rubber layers. An extruder then extrudes the inner hose, which is applied over a soft or rigid core coated with a release agent.

2. For high-pressure hoses, the middle-layer adhesive is thinly pressed using a rolling mill, an isolating agent is applied, and the material is wound into rolls; it is then cut to the specified width according to process requirements.

3. When winding or knitting copper‑plated steel wire on a winding machine or a knitting machine, simultaneously wrap an intermediate‑layer adhesive sheet between every two layers of copper‑plated steel wire. The starting and ending points of the wound wire.

4. Reapply the external adhesive on the extruder, and wrap it with a lead or cloth vulcanized protective layer. High-pressure hose.

5. Vulcanization is achieved through sulfur curing or salt-bath vulcanization.

Common problems with high-pressure hoses

1. External adhesive layer failure:

(1) The table outside the hose has cracks.

The primary cause of cracks appearing on the outer surface of the hose is that, in cold conditions, the hose bends.

(2) Bubble rings appear on the outer surface of the hose.

The cause of bulging on the outer surface of a hose is either substandard manufacturing quality or improper use during operation.

(3) The high-pressure hose is intact, but significant oil seepage has occurred.

The hose has suffered extensive oil penetration, but no rupture was detected. The cause is that, as high-pressure oil flows through the hose, the inner bridge becomes eroded and abraded, leading to widespread penetration into the wire‑reinforced layer.

(4) Severe degradation of the hose’s outer rubber layer, accompanied by microcracks on the surface, is a sign of natural aging. As aging and deterioration progress, the outer layer undergoes continuous oxidation, forming an ozone‑resistant surface coating that thickens over time. When the hose is gently bent during use, small cracks may appear. In such cases, the hose should be replaced.

2. Failure of the inner rubber layer in the high-pressure hose:

(1) The rubber layer inside the hose is hard and cracked. The primary reason is that plasticizers are added to rubber products to make the hose flexible and pliable. However, if the hose overheats, these plasticizers may leach out.

(2) The rubber lining inside the hose has severely deteriorated and is visibly swollen. This severe degradation and swelling are caused by incompatibility between the hose’s rubber material and the hydraulic system fluid, leading to chemical deterioration of the hose. 3. Faults indicating damage to the reinforcement layer.

(1) The hose ruptured; wire braiding was found near the rupture. In cases of rust‑induced hose failure, the outer rubber layer was stripped away for inspection, revealing wire braiding and rust in the vicinity of the rupture. This is primarily due to moisture or corrosive substances, which weaken the hose’s structural integrity and lead to rupture under high pressure.

(2) The hose reinforcement layer is free of rust, but exhibits irregular silk‑like damage.

The hose ruptured, with the external adhesive peeling off. The reinforcement layer showed no signs of rust, but it was irregularly separated along its length, primarily due to high-frequency impact forces acting on the hose.

4. Failure caused by rupture of the high-pressure hose at the outlet:

(1) One or more hoses are ruptured, with clean, well-defined cracks, while the remaining sections remain in good condition.

This phenomenon is primarily caused by excessively high system pressure, which exceeds the hose’s pressure‑rating capacity.

(2) Torsion during hose rupture

This phenomenon occurs because the hose is excessively twisted during installation or use.

5. In summary, based on the foregoing analysis, the following precautions should be observed when using high-pressure hoses in the future:

(1) Hose routing should, as far as possible, avoid heat sources and be kept well clear of the engine exhaust pipe. If necessary, use conduit or protective shields to prevent hose degradation due to heat.

(2) When hoses are routed in a crossed configuration or subjected to operational stresses, protective devices such as hose clamps or springs should be used at points where friction with machine surfaces may occur, to prevent external damage to the hoses.

(3) When bending a high-pressure hose, the bend radius must not be too small; it must be at least nine times the outer diameter. At the connection between the hose and the fitting, there must be a straight section that is at least twice the outer diameter of the hose.

(4) When installing high-pressure hoses, do not overtighten them; even if there is no relative movement at the hose ends, the hose must remain slack. A tensioned hose will expand under pressure, leading to a reduction in its strength.

(5) Do not twist the hose during installation. Even slight twisting can reduce its strength and cause the fitting to loosen. When assembling, tighten the hose onto the fitting rather than tightening the fitting onto the hose.

(6) If the hose consists of major components, it is recommended to inspect or replace it periodically.