The ferrule used with two-piece fittings allows greater flexibility in hose selection and connection, including 1SN, 2SN and multi-spiral hoses which allow for multiple two-piece fitting and ferrule options to accommodate the specific application.
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Stainless 316 two-piece hose fittings are the best selection to ensure corrosion resistance and long service life, especially in chemical and offshore applications. In these critical applications where 316 stainless is used, the end user may require the hose fitting manufacturer provide material traceability.
Two-piece hose fittings are used for these critical and exceptionally high pressure applications, particularly when there is the possibility of extreme hose vibration and/or pressure surges. When severe conditions are present near the fitting components, two-piece hose connections are highly important for providing a powerful assembly of the fitting and hose.
In these high pressure applications the hose is sometimes inside/outside skived (or 2 skive), creating a metal to metal connection on both the inside and outside of the hose.
The development of hydraulic machinery was accelerated by World War 2 after engineers discovered the size, weight and self-lubricating nature of hydraulics made them preferable to traditional gear driven components and incorporated them into various military machines. Ongoing advances of flexible hydraulic hoses in the following few decades led to further development of a wide range of new, high-powered machines which incorporated hydraulic technology.
There are many advantages of hydraulic power - hydraulic machines generate powerful, low speed torque that allows the operator to manage speed and movement with extreme accuracy. A single hydraulic pump can power many different machine functions at varying power levels at the same time. Hydraulic powered machines can also operate safely in high risk areas where there is flammable dust or vapour.
In simple terms, a hydraulic hose uses the transfer of fluid to transmit force. Fluids transmit force effectively because they don&#;t compress ... force applied at one end of a hydraulic hose travels to the opposite end with little loss of power.
Hydraulic hoses consist of four basic parts - an inner tube which carries the fluid which is typically reinforced with a sheath of wire or textile encased in another outer layer that provides protection from weather, abrasion or chemicals and the steel fittings that connect the hose to the machine or attachment.
Hydraulic hoses are often custom-made for specific applications. In most cases, hydraulic hoses are designed to be a certain size, length and thickness and have customised connectors that attach them to the relevant component of the machine.
Every hose has a specific rating for the type of fluid they are designed to carry, working temperature ranges and pressure limits. Usually they are printed on the hose or fittings.
Over the past five years there have been nearly three times as many workplace incidents in Australia linked to hydraulic pressure than incidents involving electric shocks!
Because hydraulic systems tend to run at very high pressures and temperatures, hydraulic hoses pose hazards associated with heat and stored energy as well as crush hazards such as falling loads if a hydraulic system fails.
If a hydraulic hose or hose fitting does fail, the major potential risks are:
1. Injection Injury
Injection injuries occur when a jet of hydraulic fluid pierces the skin and enters the blood stream.
This generally occurs at close range and requires the fluid to be under pressure. Injection injuries are a potential hazard on machines where the hydraulic hoses run in close proximity to the operator, such as on a vehicle-loading crane, and to an operator or maintenance professional conducting maintenance or inspecting leaks anywhere on a machine whilst the system is pressurised.
Due to the toxicity of most hydraulic fluids, this type of injury requires immediate treatment and may result in the need for multiple debridement operations and potential amputation, or worse.
The consequences of a hydraulic injection injury are substantial, a factor which needs to be taken into account when considering risks and controls as part of a risk assessment.
Link to HT-HYDRAULICS
2. Burns
A hose burst resulting in the release of hydraulic fluid may cause burns to both the operator and bystanders in the immediate vicinity. Containing a fluid burst is especially important in these situations. When assessing the risk, the proximity of operators, as well as bystanders should always be considered.
3. Whiplash/Striking
Whiplash occurs when an unrestrained hose fails and the hose moves rapidly (whips) back and forth until the hydraulic energy is fully released. The whipping hose not only increases the likelihood of contact with hot hydraulic fluid but the hose itself can also cause striking injuries, including concussions, lacerations and broken bones.
The most common point for failure in a hydraulic hose is at the fitting, where corrosion and stress related damage is most likely to occur.
All hydraulic hoses have a limited lifespan and this can be influenced by a variety of factors including over flexing, twisting, kinking, stretching, crushing or compromising the links or surface. Sharp changes in operating temperatures can also compromise hoses as will sudden variances in internal pressure.
Using the wrong size, type or weight of hose can also cause it to break down. Hoses should be replaced before they fail especially if they are being used on heavy machinery, in braking systems or on safety critical machines. Old or damaged hoses often show swelling, cracking, blisters or bubbles when worn but may show virtually no signs at all.
The current Australian Standard for Safety of Machinery (AS.: clause 6.2.10 Pneumatic and Hydraulic Hazards) states that pneumatic and hydraulic equipment shall be designed so that no hazardous fluid jet or sudden hazardous movement of the hose (whiplash) results from leakage or component failures. Safe Work Australia specifically includes High Pressure Fluid in the Hazards Checklist in the &#;Managing Risks of Plant in the Work Place Code of Practice".
Hydraulic hose safety is an important facet of the plant risk assessment process and Plant Assessor includes the following questions for any item of plant that has a hydraulic systems:
Assessors need to answer these questions and capture suitable comments and photos in the event that a deficiency needs to be further identified, examined and rectified.
Question 1 is straight-forward: the item of plant either does or does not have hydraulic hoses. There is no remedial action required if the answer is &#;No&#; and questions 2 and 3 can be answered as N/A.
When answering Question 2, the assessor needs to consider the following:
As usual, when conducting an inspection, assessors should err on the side of caution and, where warranted, take and upload photos and make relevant comments in the risk assessment report.
When answering Question 3 the assessor needs to consider the following:
At Plant Assessor, we are focused on helping people take control of their machinery safety, and are only too happy to help you consider how best to manage risks associated with hydraulics and any other aspects of your machinery.
For more information on Plant Assessor, please contact us and visit www.assessor.com.au
Disclaimer: This information is intended to provide general information on the subject matter. This is not intended as legal or expert advice for your specific situation. You should seek professional advice before acting or relying on the content of this information. Please contact us for further assistance.
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