How To Order A Metal Hose
To properly design a flexible metal hose assembly for a particular application, certain parameters must be determined first. Sometimes you may have a drawing with all of this information already on it but if you don’t we have a nifty way to remember what information we need to quote and fabricate your metal hose assembly. To help remember them, we have arranged them to form the acronym “S.T.A.M.P.E.D.”
- S Size or diameter of hose and end fittings. Also overall length of hose assembly.
- T Temperatures to which the assembly will be exposed to.
- A Application the hose will be used in.
- M Material of hose core and braid as well as end fittings.
- P Pressure requirements of hose assembly. Includes pressure spikes, pulsation and vacuum.
- E End fitting type required. Threaded, Flanged or Custom Machined.
- D stands for DELIVERY; testing, quality, packaging, and delivery requirements
- What is the inside diameter of the hose?
- Is the outside diameter critical?
- Minimum live length required (amount hose between braid bands) ?
- What is the overall length of the hose assembly?
- What is the temperature of the medium being conveyed inside the hose?
- What temperatures will the hose be subjected to in its installed environment?
The temperatures both inside and outside of the hose can have a major impact on the working pressure of the hose. As the temperature gets hotter the material gets weaker so a hose rated at 500 psi @ ambient will not reach 500 psi at 1000°F. Each alloy has its own derating factor based on temperature.
- What type of application will the hose be used in?
- Is there any movement in the hose while in the installed position?
- Does this hose replace another hose? If yes then why are you replacing it?
- Does the hose require abrasion protection or firesleeve on the outside?
- Will the hose experience harsh chemicals that may require special alloys to be used?
- What materials do you want your hose assembly made from?
- The medium going through your hose can determine what alloy is required.
- What material do you want your end connections made from?
- Is the medium wet or dry? Is it sharp or abrasive?
- What is your working pressure of your hose assembly?
- Is your working pressure rated at ambient or working temperatures?
- Are there any pressure spikes we need to know about?
- What pressure would you like the pressure test to be preformed at?
- What type of connections do you want on the end of your hose assembly?
- Are there any specifications your end connections need to be certified to?
- If custom machined, do you have a drawing of the end connector?
- Are you supplying the end connections or are we procuring them for you?
- What date do you want your hose delivered by?
- Do you have time constraints where you need a RUSH hose assembly?
- Does a custom crate or container need to be made for shipping your hose?
- Is this an international or domestic ship location?
Additional Hose Information
Flexible metal hose and braid is manufactured in sizes from 1/4″ up to 12″ in diameter. Typically it comes with a single layer of braid or if you need a higher pressure rating you can add a second layer of braid. Typically the smaller the hose diameter the higher the pressure it can withstand. The exact opposite happens as you get larger in diameter. The larger the diameter the lower the maximum pressure rating is.
The reason flexible metal hose assemblies are widely used in a variety of industries is because of the extreme temperature range they can perform well in. For example a cryogenic application like liquid hydrogen or oxygen transfer hoses where temperatures can get down to -320°F.
In contrast by using a flexible metal hose assembly you can reach much higher temperatures than a PTFE or rubber hose. This is because of the materials the hose is made from. Stainless steel can tolerate temperatures much higher and lower than a PTFE or rubber hose assembly.
What Alloy’s Are Available
Flexible metal core and braid comes in a variety of different alloys. Each alloy of core and braid is tailored to a specific application. Typically the core and braid comes in 321ss, 316ss, Alloy 400 (Monel) and Nickel 625. The standard braid alloy is 304 stainless steel, however this can also be substituted with 316ss, Alloy 400 and Nickel 625.
In general, 321 stainless steel is used for higher temperature applications while 316L stainless steel is used in corrosive environments. The low carbon content and the addition of molybdenum provides the protection from salt and other chemicals used in manufacturing.
The diameter of the hose and number of layers of wire braid determines the maximum allowable working pressure of a flexible metal hose. The temperature of what’s going through the hose or the environment its in can also affect the MAWP of a flexible metal hose.
For example a 1/4″ ID flexible metal hose with 2 layers of braid can handle 6000 psi working pressure while a 12″ flexible metal hose with 2 layers of braid handles 325 psi working pressure. Furthermore, if the temperature goes up past 300°F we would need to downgrade the pressure rating based on the higher temperature.