Hoses

In the high-pressure washer industry, proper hose care and maintenance is not only essential for full service life, it is also necessary to ensure the safety of any washer operator. A hose blowout doesn’t just mean an extra mess to clean up or a new hose to buy. During a blowout, high-pressure water, in many cases at high temperature, escapes from the hose and can possibly injure the operator or anyone nearby. This added safety concern is why it is of the utmost importance to know when a hose should go.

Hose Construction
In the high-pressure washer industry, the hose is one of the most abused pieces of equipment. One reason for this is that the hose is deceptively simple, and many operators erroneously feel that it can withstand various kinds of inappropriate treatment. However, the hoses made for the high-pressure washer industry are complex enough to warrant more care. After all, you wouldn’t run over your electric pump, would you? The high-pressure washer hose is basically constructed of three layers:

• The innermost layer consists of the inner tube of the hose.
  This is the part that is exposed to cleaning solvent or water, and it is usually constructed of an oil-resistant synthetic rubber, such as neoprene or nitrile blend. These materials can withstand exposure to a variety of solvents and high temperatures (- 40°F to 250°F) and are thus well suited for their application.
• The middle layer contains the hose reinforcement.
  This may consist of 1- or 2- wire braid, usually constructed of high tensile steel, or 1 or 2 braids of high strength yarn. The wire reinforcement is possibly the most important part of any hose, for it keeps the hose in one piece while it is being subjected to high pressures. It is not surprising that many causes of hose blowout can be traced to a break in the wire reinforcement.
• The third layer of the hose is the hose cover.
  Like the inner tube of the hose, the hose cover is also constructed of durable material, usually carboxylated nitrile. This is usually pinpricked to allow super heated water permeating the tube to escape, thereby preventing blisters from forming on the cover. Further hose specifications include abrasion, oil and fat resistance.

Suitable material may also be incorporated over the inner tube and/or over the wire reinforcement to anchor the synthetic rubber to the wire.

Hose fittings are either the European ball-type quick disconnect or the threaded type. The former is more convenient (and subsequently more expensive), but is more prone to developing leaks because of the greater number of valves it contains. The threaded fitting, although more time-consuming to connect, is cheaper, more fail-safe, and less prone to leaking.

Hose Failure
Hose failures usually occur within 3 to 4 feet of the gun or wand end of the hose. Needless to say this is an uncomfortably close distance to the operator. However, most of the problems that lead to a blowout can be avoided. In discussions with several hose manufacturers, it became apparent that the biggest cause of hose blowouts was abuse. Therefore, certain steps can be followed for proper hose care and maintenance to avoid many of the problems that lead to blowout.

Improper Coupling
One reason many hose blowouts occur so close to the wand end is improper coupling of the connector to the hose. Consequently, one of the main safeguards which can be followed when operating a hose is to make sure the fitting with the spray gun has been properly executed and that the crimp setting for the hose has been accurately determined. The crimp setting is determined by crimping and assembling, then measuring the crimped outer diameter. The hose manufacturer’s recommendations should always be followed for the type and size of coupler to be used.

Goodyear recommends that skive be required for all hose couplings as added insurance against coupling failure. With skive, a hose is shaved down to the wire reinforcement, and the fitting is crimped directly over the wire. It should be noted that the outer crimp diameter will be smaller with skive than without. This method of coupling is thought to be safer because it gives a higher coupling tensile, meaning the coupling is less likely to come off.

Strain relievers (also known as kink guards) are devices, which can be put on the end of the hose to relieve the pressure behind the fitting. These will also help prevent problems by reinforcing the wand end of the hose.

Excessive Kinking
Excessive kinking of the hose can cause damage to the wire reinforcement, thereby weakening the hose and making it more susceptible to failure and blowout. Excessive kinking often occurs when an operator treats the hose like a rope and uses it to pull the pump along during cleaning operations. This puts excessive strain on the connection at the pump and can also cause an unreasonable amount of kinking when; for example, the operator uses the hose to pull the pump around corners. This is a particular concern with less flexible varieties of thermoplastic hose.
Bend restrictors, which slide over the hose, can help prevent problems due to excessive kinking. These will help extend the service life of the hose by distributing stress over the entire hose length. In addition, live swivels can be put at the nozzle end to prevent excessive kinking due to manipulation of the spray gun.

Flattening
The wire reinforcement braid can also be damaged when the hose is flattened from a vehicle. Driving over a high-pressure hose seems to happen a lot, and unfortunately, these hoses were not made for this kind of abuse. When a hose is flattened in this manner, the wire braid usually gets broken. This may weaken the hose enough to cause a future blowout. Vehicle flattening causes more damage when the hose is empty because there is no internal pressure to help withstand the pressure of the vehicle.

Another problem that stems from hose flattening occurs when a flattened piece of hose is cut off and the remaining hose is fitted with an improper coupler. As mentioned above, improper coupling is one of the main reasons hose blowouts occur at the wand end. The problem with damage resulting from kinking or flattening is that failure does not occur immediately. In fact, damage may not be visible at all.

Hose Abrasion
Hose abrasion can be a problem if the cover of the hose abrades down to the wire reinforcement, exposing the reinforcement to rust or deterioration. One of the ways in which abrasion can occur is by excessive dragging of the hose. This situation can be resolved easily – simply avoid dragging the hose over rough surfaces. Abrasion can also result from the pressure cycle of the pump. Due to the piston action of the pump, pressure fluctuations occur which cause the hose to move slightly along the floor. This problem can be overcome by smoothing out the pressure cycle of the pump with a pulse hose or pressure actuator.

Improper Operation
Hose failure can also be attributed to improper operation. Hoses should only be used at their temperature and pressure rating as well as the temperature and pressure ratings of the pressure cleaner to which they are connected. Excessive temperature can cause the rubber material of the hose to harden and subsequently crack whereas excessive pressure can cause damage to the hose material as well as increase the internal temperature. It should also be pointed out that damaging pressure buildup could occur if the spray gun is shut off while the pump is still running.

The materials with which it is constructed determine the working temperature and pressure of a hose. In addition, the working pressure is also determined by the inner diameter of the hose. Obviously, then a hose can be constructed to meet a variety of temperature and pressure ratings, and, indeed this is why there are such a variety of hoses on the market. To purchase a hose suited for your purpose, you need to know the application, pressure, temperature and kind of machine for which it will be used.

Improper Application
The hose should always fit the application. Some hoses are not made for steam service, so if a steam-service hose becomes defective, it should be replaced with the same, not with any other hose that is on hand. As tempting as this might be, hoses should never be switched from one machine to another unless the two are identical in operation and application.

Improper Care
As with other pieces of equipment, hoses should be properly cleaned after each use. Because of the pinpricks in the hose cover, the exterior of the hose is particularly vulnerable to solvents. These tiny holes can allow fluid to enter the hose from the outside. Therefore, hoses should never be allowed to sit in pools of liquid, as some solvents can permeate the hose through the pinpricks and degrade the wire reinforcement.

Hoses should also be winterized properly. If water is allowed to remain in the hose under freezing conditions, it is likely to expand, causing damage to the tube or reinforcement. In addition, the metal fittings may freeze and be damaged.

Further Precautions
It should be kept in mind that water always exists at the weakest point. Therefore, a leak does not always occur at the site of the problem. In fact, a hose may be leaking at a point far away from the source of the trouble. This not only means that a hose problem is that much harder to solve, it also means that a particular problem may be much worse than is first apparent. For example, a pinprick leak may be due to a hole in the tube or it could be caused by a bad fitting. Either way, if the source of the problem cannot be determined and/or solved, the hose should not be used.

If the preceding guidelines are followed, and barring that, a routine inspection is carried out before every hose use, then a hose blowout is likely to be circumvented. As a result there will be less operator hazard involved when running a high pressure cleaner and the lifetime of your high pressure washer hoses will be extended.