Frequently Asked Questions

METAL HOSE

What are the differences between working pressure, test pressure and burst pressure?

NAHAD (National Association of Hose and Accessories Distributors) and EJMA (Expansion Joint Manufacturers Association) calculations are used to derive theoretical burst pressure. Industry standard, ASME Boiler and Pressure Vessel Code, Standard Code for Pressure Piping, etc., recommend a 4:1 safety factor for maximum working pressure. Thusly, maximum working pressure is 1/4 the theoretical burst pressure. The maximum test pressure is 1.5 times the maximum working pressure.

What is the difference between annular and helical hose?

Annular hose construction is a series of full 360-degree corrugations consisting of a root radius, sidewalls, and a crest radius. Each convolution is a complete entity unto itself. Helical hose construction is a single, continuous corrugation that travels along the longitudinal axis of the hose.

Why do some of your competitors list working pressures in their catalogs that have to be reduced 20% to be of any value?

Some of our competitors list maximum working pressures based on calculations performed using the material properties of raw steel strip. These working pressures only apply to corrugated tube with no fittings and are of no value to the customer. Our maximum working pressures are based on the properties of the annealed materials actually used in the finished products - the products our customers use every day. Thus, no reduction in pressure rating is necessary for fitting attachment welds.

What is the difference between live-length and overall length?

Overall length is the maximum length of the assembly including the end fittings. Live-length is the portion of the assembly that is flexible.

How do I know which hose will work best in my application?

Chances are, except in the most extreme cases, there are several hoses that will meet or exceed the parameters of your application. The most common determining criteria are pressure, temperature, motion, media, and flow. We recommend using the hose with the greatest safety margins that is within your budget. Contact the Engineering Dept. at US Hose, the only hose manufacturer with truly engineered products for your applications, to find out what your options are.

 

COMPOSITE HOSE

Why does composite hose elongate?

Composite hose elongates as the materials used are not vulcanized together by heat treatment. US Hose composite hoses are manufactured from tightly wound thermoplastic fabrics and films wound around a pressure stabilized inner wire helix. All materials are reinforced with an outer wire helix. All these materials working together provide a exceptionally strong and durable flexible transfer hose with a superior service life.

What is the temperature rating of US Hose composite hose?

Our standard oil and chemical hoses are rated for 212 degrees Fahrenheit, depending on media, pressure and handling. Whereas our range of cryogenic hose is suitable for as cold as Liquified Natural Gas. For more specific information, please contact the US Hose Product Management or Engineering Department.

What is the maximum pressure ratings of US Hose composite hose?

With the wide range of hoses we manufacture ranging from vapor recovery to cryogenic service, pressure is dependent on size and service condition. Generally speaking, our standard oil and chemical hoses are rated between 200 to 250 psi with a minimum 4 to 1 safety factor and our cryogenic hose is rated up to 350 psi with a 5:1 safety factor. For more specific information, please contact the US Hose Product Management or Engineering Department.

 

TEFLON® HOSE

Exactly what is Teflon®?

Teflon is a resin discovered by E.I. Dupont in the late 1930's, but was not commercially developed until after WWII. It is now extruded or molded by its licensees. Teflon® is a trade name for several different kinds of flouroplastics, all of them having in common extreme chemical resistance as well as a higher heat range than other plastics. In addition Teflon does not seem to decompose the way other plastics and synthetic rubbers do, no shelf life has yet been determined for Teflon®. Some Teflon® items have been in service for over 30 years without any signs of deterioration. A few of the most common formulations are PTFE a.k.a. polytetrafluoroethylene, PFA a.k.a. perfluoroalkoxyl and FEP a.k.a. Fluorinated Ethylene Propylene.

Which fitting attachment method is best for Teflon hose assemblies, crimping or swaging?

In the end, the most important factor is whether or not the finished assembly performs to the accepted industry standards. Both methods are used successfully when fabricating qualified aerospace and industrial assemblies. However there are several advantages to the crimping, lower tooling costs, ease of assembly, faster production rate, scrap reduction, etc…
Therefore crimping is the more widely used.

What is the difference between dash and true bore sizes.

Dash size is common terminology used to refer to the inner diameter of a hose. This was a system developed to identify the hose size in a part number. A two digit number is used to represent the relative I.D. in sixteenths of an inch. However, dash sizes do not match to the actual inner dimension of the hose. The actual I.D. is smaller. For example, -04 hose has an actual I.D. of .187, -05 hose has an actual I.D. of .250. If the exact inner dimension is required be sure to ask for true bore hose size.

This can cause some confusion but when in doubt contact our customer service department and we will be happy to assist you in making the proper choice.