One of the first things people learn when they enter the hose industry is the acronym known as ‘S.T.A.M.P.E.D’. It has been used for decades, to provide an easy to remember method for operators to make the best recommendation of a hose assembly for various application challenges. There are a variety of factors that go into these recommendations/selections, including availability of materials, and cost considerations.
As the global economy shifts back towards pre-pandemic levels, coming up with a solution for a hose assembly which can be fulfilled in a timely basis, is more challenging than ever. Given the various safety concerns related to hose applications, a hasty selection based solely on delivery times, could lead to harmful situations. Care should therefore be taken to provide the best recommendation options possible, despite on-hand product challenges brought about by labor and material shortages.
By Brent Lilly, Vice President of Sales & Marketing, PT Coupling
The acronym ‘S.T.A.M.P.E.D’ is used to help with the proper selection of a hose and/or fitting. To reduce the chance of failure, Size, Temperature, Application, Material, Pressure, Ends, and Delivery are all considered in the selection process. Operators take extreme care when utilizing Chemical Resistance Chart, and application specifics, such as: materials being transferred at various temperatures, working pressures, and vacuum/discharge needs, to determine the best hose selection (Tube/Cover Rubber/Plastics/PVC/Inner Wire & Linear Materials).
One of the things often missed during this selection process is a focus on the ‘E’ in the acronym. The same level of care is not often used to determine the ‘Ends’ of a hose; more specifically the couplings, reducers, and adapter materials. This can be problematic since the Ends are in constant contact with the material passing through the hose. In addition, assembly failures can occur within the hose and fitting interface, especially if care is not taken to ensure the proper metal alloy is selected for the fittings.
Metal is defined as pure substances existing in elemental forms, as found in Periodic Tables, whereas an alloy is defined as metallic compounds created through a mixture of two or more metals and non-metals, to create a new material.
Below is a recommended process to follow when making fitting recommendations:
Fitting Selection Steps:
1.Starting with a worksheet to utilize, the end user or operator will transfer the information from their application ‘S.T.A.M.P.E.D.’ data collection. On a worksheet, the operator should list the name of the material being transferred through the hose. If this material is a chemical, take care to see if more than a ‘trade name’ or ‘brand name’ can ascertained. The operator may need to request MSDS data for the chemicals/chemical blends and percent of solution being transferred.
2. Utilize a Chemical Resistance Chart for the selection of fitting metals, and alloys construction. The operator should scroll down until they locate the ‘Material Name’ listed on a worksheet; they are usually listed on the tables alphabetically.
a. On a worksheet, list every metal, or alloy shown as having ‘A/1/excellent’ or similar interaction properties with that ‘Material Name’.
b. Then list separately every metal, or alloy, shown as having a ‘B/2/good’ or similar interaction properties with that ‘Material Name’. Save these lists to compare with the fitting options selected to determine which material the fitting should be made of.
3. Identify the end configuration that the fitting requires to complete the connection from the hose to the port/manifold/loading arm/valve it will be attached to:
a. Male or Female
b. Threaded (NPT, BSP)
f. Tri-clove Sanitary
g. Beveled Seat Sanitary
h. Stub/Welded End
i. And a variety of other options
4. Determine if a fitting requires a gasket to be used in the application. Operators should also take care to select the proper gasket material (polymer, or rubber, or metal/alloy). If the fitting does require a gasket, follow Step #4a. and 4b. below, if it does not, move to Step #5.
a. Utilizing a ‘Rubber/Polymer Chemical Resistance Table’, on the worksheet, list every rubber/polymer/plastic material shown as having ‘A/1/excellent’ or similar interaction properties with that ‘Material Name’.
b. Then list separately every rubber/polymer/plastic material shown as having ‘B/2/good’ or similar interaction properties with that ‘Material Name’.
c. If the gasket is a metal/alloy, then use the same methods/tables from your selection Step #2.
d. Save these options for use when the gasket is selected to determine which material the gasket should be made of.
5. Determine the attachment method you will use for fitting retention, and assembly integrity:
a. Bands & Clamps
b. Sleeves or Ferrules
Once an operator has completed these steps, they are ready to fabricate and test their assembly, utilizing NAHAD’s HSI recommendations for testing and qualifying hose assemblies prior to placement into service.
A Deeper Dive into Metals and Alloys
Common industry names are used to describe various metals and alloys. However, the quality of any particular manufacturer’s fittings, adapters and reducers, can vary tremendously.
Common names for fitting materials are: Aluminum, Brass, Carbon Steel, Stainless Steel, and other more exotic metals. However, there are various specifications each manufacturer uses to blend the mixture of material content. This means that various other ‘filler materials’ used to create a finished product, can be shifted and altered to control costs, leading to remarkably different, often inferior product performance; the manipulation of these material can even lead to dangerous conditions. It is pertinent to take a closer look at some common fitting materials to explain this a little further.
Something as basic as Aluminum is often used as the material for many common fittings. Aluminum is best known for being lightweight, with strong properties. There are vastly different types of Aluminum which can be used. For instance, A380 grade aluminum is used for lawn equipment housings, gear cases, household parts, etc. Whereas A356-T6 aluminum is used for pressurized parts, aircraft components, and structural parts, etc. So, one cannot say that Aluminum is identical from one manufacturer to the other.
Stainless Steel is made up from the combination of iron, carbon, chromium, nitrogen, aluminum, silicon, sulfur, titanium, nickel, copper, selenium, niobium, and molybdenum. The combination of these materials create a product which is extremely resistant to corrosion and penetration/degradation by chemicals; it also has an added performance strength. Each of these materials can be altered as a percent of blend used, with the net result being controlled/lowered costs.
There are a variety of factors that go into the selection of attachment method one chooses to utilize when fabricating an assembly. No one method is better than the other; it is all based on the unique conditions of assembly usage, fabrication environment (power or no power available), equipment investment (hand tools, power tools, production capacity tools), a desire to repair or replace certain assemblies (repair = bands/clamps, replace = sleeves/ferrules), desired assembly operating pressure rating (consideration made for ‘Safety Factors’ of working to burst pressures), and last but not least volatility of application itself (proximity to people of hazardous material transfers, regulatory agency requirements often are factors requiring the precision of a crimped assembly-sleeves/ferrules). It should also be noted that the main difference between a sleeve and ferrule, is that the ferrule has an interlocking area for additional retention properties, as illustrated in Figure 1.
Brass has experienced added emphasis in the state of California recently. Brass is comprised from a mixture of copper and zinc to make it harder or softer depending on the blend. Other metals such as aluminum, arsenic, and lead are added as alloying agents to improve machinability and corrosion resistance. Manganese and nickel are added in various percent to create various shades of color ranging from gold to brown. Recent trends are calling for Lead Free Brass, so the formulation of this will change over time, until it is entirely without lead.
Fitting Manufacturers each have established their own acceptable levels of material content mixes. Manufacturers confirm content through the use of a highly specialized type of equipment known as an Optical Spectrometer. Optical Spectrometers use light waves to identify the percent of each element that makes up the alloy, cross-checked against the material specification for each batch/casting. In more critical applications such as Government Products, Nuclear Power facilities, and DOT applications these standards are often required to be fully certified as complying with prescribed standards (a document of the certification test). Since all applications do not require certifications, the end user is dependent on the reputation and consistent standards of the fitting manufacturer to provide the highest quality of material content possible. Therefore, the selection of fitting supplier is as critical as the complete assembly recommendation.
About the Author
Brent Lilly is the Vice President of Sales & Marketing for PT Couplings, an Enid, OK. Based manufacturer of Hose Fittings, Fitting Attachment Systems, Adapters & Reducers, Accessories, Government/Mil Spec Products, Transportation Product Systems, and Hose Management Systems. He has over 38 years’ experience in the Hose industry with a variety of Engineering, Sales, and Marketing positions. Brent is currently serving a term on the NAHAD (The Association for Hose and Accessories Distribution) Board of Directors and has long been a member of the NAHAD Standards and Education Committees. He has presented a variety of topics relating to his areas of knowledge and expertise, at several National Conferences and Trade Shows.