How to Select Hydraulic Hose Using STAMP? | Parker Hannifin Guide

Hi, I'm Mike from The Parker Store. Selecting hydraulic hose may seem simple, but there's more to it than you think. It's important because Incorrect hose can fail prematurely, causing expensive downtime or worse, damage to people or property. To help remember what to consider when selecting hose, we have the acronym STAMP. The words that form the acronym STAMP are: size, temperature, application, media, and pressure. By using the STAMP method, we are better prepared to spec spec the correct hose. Think of it this way: before you spec it, stamp it. To begin the stamp selection method, we need to answer the question of hose size. Like water through your garden hose, hydraulic hose has oil dashing through it. The speed the oil is traveling at is called velocity, and in the United States, it's measured in feet per second. Oil moving too fast generates heat, and heat in a hydraulic system is a sign of inefficiency. Oil moving too slowly will result in lower pressure and poor performance. So what does oil velocity have to do with hose size? Everything. Look at this cross-section of hose. This hole here is the inside diameter, or abbreviated ID. A hose ID that is too small will create a high velocity, and if it's too large, the oil will move too slowly. So how do we decide the right size? If you are replacing a hose, the original equipment is probably the correct size. In the US, hydraulic hose ID is measured in 1/16 of an inch and are standardized in 4/16, 6/16, 8/16, etc. Instead of using fractions, the size is abbreviated as a dash number or dash size. So that 4/16, which is 1/4, becomes -4. 6/16 is -6, or 3/8 of an inch, and 8/16 is -8, or 1/2 an inch. One way to remember this is the velocity of the oil is dashing through the hose depending on its dash size. If you want more technical details on proper hose size and velocity, look in the Parker Hose Products Catalog 4400. And open to the page with a flow capacity nomogram. The next letter in the Stamp Hose Selection Method is T for temperature. Selecting a hose for the proper temperature is important if you want to maximize the service life of the hose. Don't make the mistake of only identifying the temperature of the oil or fluid inside the hose. What if the equipment is operating in the desert or at the North Pole? When considering temperatures, you'll actually be thinking about two different temperatures. First is the fluid or temperature inside of the hose, and second is ambient temperature, or the temperature in the environment outside of the hose. For example, think of a hose in an engine compartment. The fluid flowing inside the hose may actually be lower than the ambient temperature of the environment. Select a hose that has a working temperature equal to or greater than both the fluid and ambient temperatures. The third letter in the Stamp Hose Selection Method is A for application. Hydraulic hose is used in hundreds, if not thousands, of applications. The correct hose size and temperature are essential, but now we need to identify unique factors specific to the applications to get maximum service from the hose. With so much to consider for each application, What's the most important to identify? Well, there are two key elements to be aware of for each application. They are impulse and duty cycle. Duty cycle is how frequently the hose is exposed to full pressure of the application. Impulse in an application happens when there's a sudden surge of pressure and the hose is exposed to a brief pressure spike. The type of steel wire reinforcement is important— braided or spiral. Without getting too technical, spiral steel wire reinforcement is better for high impulse duty cycle than braided reinforcement. The trade-off is flexibility. That's why you'll see spiral reinforced hose on heavy-duty bulldozers. They don't need as much flexibility as that hose can handle extreme impulses. Depending on your application, you may also need hose that has a tough cover to withstand abrasion, or one with a short bend radius to install in an application where there isn't much space. Whatever your application, speak with the professionals at your Parker store. Maximizing hose service life for every application is what we're here for. The fourth letter in the STAMP hose selection method is M for media. Now, we're not talking about entertainment media like an MP3 or WAV file., but fluid chemical compatibility. Construction of hydraulic hoses begins with what is typically called the inner core tube, then the reinforcement layer and outer jacket are added. This inner core tube must be compatible with the fluid, otherwise it may dissolve contaminating and damaging your entire system. In the back of the Parker hose products catalog 4400, are chemical compatibility tables. Identify your fluid for your application and then verify that it's compatible with the inner core tube and perhaps the outer core jacket. Media concerns are not limited to just the hose, but you should also verify that the metal and any type of O-ring or sealing components on the hose ends. Every material that comes into contact with the media is suspect. This may be another area that you want to speak to a professional from your Parker store to identify the best choice. The letter P in the Stamp Hose Selection Method is for pressure. Before we go any further, don't make the mistake of only identifying what the pressure relief valve or maximum working pressure is. Much like temperature, you need to identify two pressures: the system pressure and pressure spikes, or impulse pressure. Select a hose that has a working pressure equal to or greater than both the working and impulse pressures. The fittings attached to each end of the hose must also be properly selected. For example, a 5,000 PSI hose that has 3,500 PSI hose ends attached is not compatible to withstand 5,000 PSI of pressure. The hose assembly in this case is rated for the lesser of the two pressures, which is 3,500 psi. Remember this: you identify the highest pressure of the system and match the lowest pressure component. So that's the STAMP method: size, temperature, application, media, and pressure. Remembering this simple acronym will help you select the proper assembly components for any application. Providing you with an efficient, durable, and most importantly, safe operating system. Remember that Parker Store Professionals can help you select the right components for your application, and we're also a great resource for product information, training, and advice. Thanks for taking the time to learn about the Stamp Method. Have a great day.