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  • How to determine your NPT thread size

    How to measure for the NPT sizing chart Male connections rely on the outside diameter (OD) measurement, while female connections can use OD or inside diameter (ID.)

    An 1/4” NPT connection size doesn’t have any 1/4” measurements where you think they would be. In fact, the connection’s outside diameter measures a little more than 1/2" wide.

    Did I just blow your mind?

    Well, take a deep breath and hang on for a bit while we discuss the different factors that go into determining the NPT size of a pipe connection. Or, if you are the impatient type, skip ahead to the chart below.

    First off, NPT stands for National Pipe Thread, but you probably already knew that from other research or this article. NPT is a standard pipe connection designed specifically to create a fluid-tight seal between valves, pipes and fittings. Their tapered thread design makes them one of the most common general-use pipe threads available.

    The threads are deeper at the end of the pipe and shallower at the base (moving away from the end of the pipe). This is done while maintaining a 60° thread angle, to ensure that the threads pull tight but are still uniform.

    A look at the taper and thread angle of an NPT gauge connection. An NPT connection's threads taper and become shallower as they move toward the base.

    But back to the main topic. There is no direct naming relationship between the measured diameter of a pipe’s threads and the corresponding NPT size. A 1” NPT male connection has an outside diameter (OD) of about 1.3”. An 8” pipe has an OD of about 8.6”.

    The measurements are “trade sizes.” That means they are uniform sizes according to the diameter of the pipe or fitting that they can be used with. And that makes it easy for the fella at your local hardware store to identify what ball valve will fit your piping.

    Sadly that doesn’t help when people are trying to measure something for themselves and come up with a completely wrong size, which in turn translates into the wrong NPT connection. That happened a couple of days before we posted this article and was the impetus behind my writing on the subject.

    What I can do for you is give you a table to compare your measured size to the corresponding NPT size. Just measure the outside diameter (OD) or inside diameter (ID), as illustrated in the picture above.

    The OD measurement for a male connection should be taken near the base of the threads, farthest from the end of the part.  An ID measurement for female connection should be taken as close to the opening as possible while remaining within the threads. An OD measurement for a female connection is more difficult, but sometimes may be taken by measuring outermost edge of the threads at the pipe opening.

    NPT Chart with ID and OD measurements

    Other facts about NPT you should know

    NPT measurements are sometimes referred to by different names: FIP (for Female Iron Pipe), MIP (Male Iron Pipe), MPT (Male Pipe Thread), FPT (Female Pipe Thread) and IPT (Iron Pipe Thread).

    Although NPT connections do seal better than straight thread connections, they do require a pipe sealant to ensure the connection is air-tight. This is thanks to minute differences in pipe and fitting, which can create gaps that cause leaks.

    A solution that doesn’t require sealants comes in the form of NPTF (National Pipe Thread - Fuel) threading. The threads on those connections are crushed together during tightening, creating a strong seal.

    NPT and NPTF threads can be used interchangeably, so long as an appropriate sealant is used. NPT and NPS (National Pipe [Thread] Straight) are NOT interchangeable.

  • The Many Faces of DuraChoice Gauges

    gauge face sizesYou can find out more about DirectMaterial's Gauges by clicking on the above image.

  • Industrial Vocabulary List

    Remember those vocabulary lists we all had to study in elementary school? They are the reason we know the difference between “brake” and “break” or the definition of “myriad.”

    Chances are that you already knew a few of the words when Mrs. Crabapple handed out your first grade reading assignments. Some were probably new, though, and that was the point. The vocabulary list was designed to improve your fluency in language.

    In this article, we are going to go over a few of the terms and acronyms common to the parts sold at DirectMaterial.com. Consider it an industrial vocabulary list to improve your fluency in industrial “parts-ese.” You may already know some, but you might just learn something.

    We will add to the industrial vocabulary list as time goes on, so if something is particularly perplexing, feel free to write us at service@directmaterial.com. We’ll answer your question and may add that term to our list so others can find a quick answer.

    NPT NPT threads draw in close as they continue down the pipe.

    NPT (National Pipe Thread) - Often abbreviated NPT, this is one of the most common acronyms you will find when talking about industrial piping in the United States. National Pipe Threaded parts have a tapered thread, which pulls tight as it continues along the pipe. This allows the pipe to maintain a fluid-tight seal.

    NPT is used on DirectMaterial.com along with a pipe diameter to denote the connection size of a particular part.

    OEM (Original Equipment Manufacturer) - Generally speaking, OEM means that the part is manufactured by one company but sold under another company’s name, possibly with the seller’s name and logo.

    In other cases, the part is not branded at all, such as DuraChoice’s PAG158B pressure gauge.

    If someone buys a machine with that pressure gauge in it, he just knows that the machine manufacturer provided the part and is not presented with multiple brands. In other cases, resellers want to sell parts without giving up their supplier advantage.

    PTFE (Polytetrafluoroethylene) – Say that three times fast. Polytetrafluoroethylene is a hydrophobic compound of carbon and fluorine designed to allow the low-friction passage of water and other fluids. In fact, it has the lowest coefficient of friction of any solid. It is also very non-reactive, meaning that it can be used in piping with corrosive chemicals.

    Together, those two factors make it an ideal material for seats and seals in many of the valves on this site. The low friction coefficient the means opening and closing of valves is easier and causes less wear than if they the seals were made of another substance.

    RPTFE (Reinforced Polytetrafluoroethylene) – Similar to the description above, but with added fillers. Those fillers range from glass fiber, to carbon and graphite. Each filler adds different chemical properties when mixed with PTFE. Carbon substantially improves wear and deformation strength, while changing the compound’s electrical properties. Glass fiber, on the other hand, only improves resistance to wear only slightly, but maintains the PTFE’s electrical characteristics well.

    PSI (Pounds Per Square Inch) – Basically, it’s what the name implies – the force of one pound applied to one square inch of space. It is the most common measurement of pressure in the United States of America and can be found on most gauges sold here. All of the gauges regularly stocked by DirectMaterial.com have PSI scales.

    The term should not be confused with SI (the abbreviation for the International System of Units) which uses units called Pascals. The conversion rate is 1 PSI to 6,894.757 Pa.

    Read more about pressure measurement in this blog post.

    Bar – No, it’s not just the place you go to grab a beer after a long day’s work.

    It is a unit of pressure equal to 100,000 Pascals (see previous entry). This is considered to be about the atmospheric pressure of sea level and meteorologists often use the bar scale as a matter of convenience. That relates to barometric pressure, although that may also be presented in hectopascals, which convert to 1/1,000 of a bar.

    The bar scale can often be found on dual scale pressure gauges.

    WOG (Water, Oil, Gas) – It may sound like a caveman’s name (“Wog hungry. Me go find mammoth burger shack”), but WOG refers to the pressure a valve can handle, measured in PSI at ambient temperatures. Ambient temperatures run from -20° and 150° F for brass valves to -10° to 100° F for stainless steel bodied valves.

    All valves perform differently at extremely high or low temperatures. WOG is just shorthand to indicate that the pressure rating decreases for those materials outside the bounds of normal temperatures.

    ISO 9001 – You will find that certification on the DuraChoice products for sale in the DirectMaterial.com store. The term ISO 9001 certified does not refer to a product, but to the company that manufactured that product.

    A company can be ISO certified if it meets the quality management standards set out by the International Organization for Standardization. Those qualities include a strong customer focus, the motivation of top management and a dedication to continual improvement.

    If a company meets the requirements for ISO 9001 certification, it signals that the company has a focus on quality from the top down.

  • On Pins and Needle Valves

    Precision is the watchword when it comes to needle valves.

    Much like the globe valves we talked about last week, needle valves are control valves. They share some of the same design features and have similar benefits.

    Both allow the operator to change flow rate and use a threaded rotating stem to adjust that rate. The difference is precision.

    Needle Valve Diagram Needle valves are similar in design to globe valves. The primary difference is the valve seat and the needle shape.

    Needle valves are valued for their use in calibration because they can be so finely tuned. The valves can also provide positive shutoff, so that gauges and other measurement instruments may be installed or removed safely.

    The valves are used in a wide variety of industries, including petrochemicals and biofuels.

    A needle valve gets its name from its business end: a conical, needle-like plunger that fits exactly into a valve seat. As the stem rotates, the needle is raised or lowered into the seat, increasing or decreasing flow as it moves. The change in needle position is minimal with each turn, allowing fine tuning of flow.

    The fine threading of the valve stem gives it great mechanical advantage, meaning it can be sealed with minimal force from the operator. The downside of that ease of operation, however, is that its open or closed nature cannot be determined by visual inspection alone.

    The seat is designed to fit the needle exactly, providing a seal that can operate at high pressure ratings.

    The DuraChoice needle valves that DirectMaterial.com sells are rated at 10,000 psi at normal operation temperatures.

    Part of the reason needle valves can take so much pressure is their size. The valve’s opening, or “orifice”, is generally small, compared to the rest of the valve’s body. While this makes the valve great for high pressure projects, it means the valve’s flow rate is relatively low.

    However, this is not usually a problem when you consider how the valves are used. They work well for processes which require precise control of gas flow. At DirectMaterial.com, we sell a lot of needle valves along with vacuum gauges, for use in projects like gas lasers or to regulate the filling of voltage regulator tubes.

    Needle valves are common in engines with carburetors because of they can be used to finely dial in fuel. That precision is important, because too much fuel will begin to flood the engine causing the fuel/air mixture to suffer and killing the motor. If there is not enough fuel flowing into the carburetor, the engine is forced to work harder, making it less effective and possibly causing damage over time.

    Needle valves can be found in utility equipment used to measure water or natural gas consumption. Because the rate of delivery is kept constant by the valve, there is little unintended variation. The valves are also used at distribution points as well, to regulate the flow delivered into the system. Operators at the production level are able to determine how much gas, water, etc., to put into the system, lowering or raising it as the need arises.

    They may also be used as “bleed” valves in residential water heater systems to relieve pressure on the water flowing through the heater.

  • Globe Valves: The Control You Need

    This blog is going global. OK. Technically, since it is on the internet, it has always been worldwide. But this week, we are going to talk about globe valves.

    Globe Valve Animation Click the photo for an animation showing how globe valves work.

    As alluded to in last week’s article, globe valves are a kind of control valve which allow the operator to increase or decrease flow, usually by turning a hand wheel. Turning the hand wheel rotates the valve’s stem, which raises or lowers a plug into a valve seat.

    The distance between the plug and the valve seat determines the amount of flow through the valve. The greater the distance, the greater the flow.

    Globe valves get their name from their body shape, which was once consistently spherical. As technology has changed, so has the body’s exterior shape. Globe valves now come in a number of different looks, not all globe-like.

    The internal shape and function, however, is much the same as it has always been.

    You can picture a typical straight line, or “Tee” pattern, globe valve’s interior – like the ones that DirectMaterial.com sells - as a kind of flattened “S” shape. The letter’s center point is the valve seat and the stem descend vertically through it to that point. The fluid or gas enters through the lower end of the letter and then travels up until it meets the midsection. If the plug is in place, the flow stops at the midpoint. If not, it continues through at a rate determined by the plug.

    The globe valve’s ability to throttle a substance’s flow makes it useful as a control valve. Globe valves are used in operations which require frequent changes in flow rate. Unlike the gate valve we talked about last week, any wear on the plug or the valve seat should be uniform, making a leak less likely, even after extended use.

    In normal operation, the direction of flow comes from under the plug. In high temperature operations, the direction of flow may be changed so that flow comes from the opposite direction. Doing so keeps the stem at a constant higher temperature, which decreases the chance that it will contract and lift the plug off of the valve seat.

    One drawback of globe valves is greater flow restriction. The twists and turns of the valve along with a narrowed channel through the valve seat opening conspire to increase flow resistance. That makes pressure drop a factor in some applications.

    Check back next week to learn about needle valves, an even more precise type of control valve.

  • Gate Valves: Holding back the horde (Figuratively speaking)

    When I think about gate valves, I think about castle warfare.

    Stop giving me that blank stare and let me explain.

    Castle Gate Think of this when you think of a gate valve, you know, without the holes.

    You’ve probably seen it in medieval war movies. Some great horde is bearing down on the castle. Archers man the walls. The villagers scurry in fear.

    The call goes out. “Close the gates!!!!”

    An iron barrier with wedge-shaped points slams down into holes designed to receive them, keeping the barbarians at bay.

    That’s kind of what happens when you turn the handle on a gate valve … you know, on a MUCH less dramatic scale.

    Gate valves, which are also known as sluice valves, function by lifting or lowering a moveable “gate” to fully allow or stop the flow of liquids or gasses. They are best used in systems where full shutoff is the norm and long service life is required. Gate valves are some of the most commonly used valves in the petroleum industry.

    These are two main parts of a gate valve A hand wheel operated gate valve

    Although there are other designs, most gate valves are operated via hand wheel. That hand wheel drives a spiral grooved stem, moving the rectangular or disc shaped gate. The wheel may take several turns to fully close the valve, making the action relatively slow compared to a ball valve or another shutoff valve.

    But that can be an advantage. Since flow is introduced gradually, the damaging effects of fluid hammer are greatly reduced.

    Because of the hand wheel, the gate valve’s exterior may resemble the water spigot you connect your garden hose to.

    Do not confuse the two, though. Spigots are a kind of control valves, which you can use to increase or decrease flow.* Gate valves are designed as shutoff valves and should not be used as control valves, although they often are in non-industrial settings.

    In industrial uses, gate valves are supposed to be fully open or fully closed.

    Why? Well, that’s because when a gate valve is left in a half open position, the gate edge is exposed to the flow passing by. That may not mean much for non-viscous fluids like water in the short term, but the gate can be warped or may erode over time. The wear would be concentrated on the lower section of the gate, making the valve seal less effectively.

    However, when the valve is completely closed, the gate provides a solid surface to stop flow with the disc’s edges protected in the gate’s seating area.

    An undamaged gate valve will provide positive shutoff under pressure.

    Another advantage of gate valves is minimal pressure loss, since the gate is usually made to the diameter of the piping connection. That full port design means less restriction of flow.

    Gate valves stems come in two main types, rising and non-rising. Rising stems are useful in visually determining whether the valve is open or closed, because the stem will be higher when open. Non-rising stems are often used when there is limited space available and the rising action of the stem would make the valve more difficult to operate.

    DirectMaterial.com has DuraChoice gate valves with non-rising stems in both brass and stainless steel. You can see our full selection, including PVC stop valves, here.

     

    * Tune in next time for a discussion of globe valves, a type of control valve similar to the water spigot.

     

  • What are pressure ratings?

    How do pressure ratings work?

    On its face, a pressure rating seems like a simple enough statistic. The pressure rating is the maximum pressure a pipe, fitting or valve should be capable of withstanding in a normal conditions.

    Also known as maximum allowable working pressure (MAWP), a pressure rating lets an engineer or plumber determine which part will work best with the system being built. The higher the pressure rating, the less likely the part is to fail due to structural issues during heavy use.

    There are a number of ways pressure can be expressed. We will focus on Pounds per Square Inch (psi), since that is the most common term used in the United States, where we do the majority of our business. You may also see WOG, which stands for “Water-Oil-Gas.” That term denotes the psi that the part can handle at ambient temperatures with any of those media.

    Here are a few things to consider when determining the pressure rating to go with.

    Higher temperatures adversely affect the working pressure of the part. That is, a stainless steel ball valve rated at 1,000 psi can hold that pressure at up to 100 degrees. But it may have a maximum pressure of only 600 psi at 650 degrees.

    And just because the part has a higher pressure rating, though, doesn’t mean that it is the better buy. If it was, DirectMaterial.com would only stock parts rated for the highest pressure and the choices would be a lot simpler.

    However, parts with higher pressure ratings generally cost more. A valve with a 3,600 psi pressure rating will usually have thicker walls than one with a 1,000 psi rating. The cost of the extra material alone will increase the price, as will the difference in materials used and the cost of the part’s development.

    Brass, while less expensive, is not as strong as the more costly steel. So, if a part will work at a lower pressure rating and there are no other factors to consider, like material composition or connection type, buying a part at a lower cost is a no-brainer.

    Whether it’s brass, stainless steel, carbon steel or PVC, DirectMaterial.com has the part you need at the pressure rating you need. Check out all of our great prices by clicking on the drop down menu at the left.

  • So what is a thermowell, anyway?

    Thermowells Thermowells come in many lengths and many materials.

    Thermowells are a lot like hazardous material suits for thermometers. You know? The big white or yellow suits that virus hunters use in a “hot zone” or nuclear engineers use to keep their skin from glowing when they turn off the lights.

    In other words, thermowells keep the bad stuff away from the thermometer so that it has a long and happy service life.

    Installed in a permanent position before the process begins, thermowells are usually one-piece designs which act as a second skin for thermometers. The thermowell transfers the heat or cold from the medium being tested via a hollow tube which the thermometer fits into. The tube is closed at one end and the temperature testing equipment is inserted and removed from the other.

    In many cases, a thermometer can be secured inside the thermowell with a threaded end.

    What are you trying to keep away from the thermometer? Anything that might do damage to them. A thermometer may bend over time due to stresses from high velocity flows or warp because of high pressure.

    And depending on the medium, the temperature testing equipment can corrode or erode over time. If, for instance, the material being tested contains phosphoric or sulfurous acids, then you may want a thermowell made of Stainless Steel 316, as they stand up to corrosion better than other metals, including those often used to make thermometers.

    Thermowell interior The thermometer is screwed into the thermowell with the stem extending down this tube.

    Likewise, if the material being tested has fine particulates suspended in it, the movement of those particulates might wear away at the thermometer.

    Actually, thermowells have another function other than the hazmat suit. You can also see them as the gloves that historians use when touching delicate old paper, when the oil on their hands could damage something important.

    Thermowells help eliminate contamination of the materials being measured by keeping the temperature testing equipment from ever touching it. That means that the thermowell allows the user to service or replace a thermometer without disturbing the process, pressure or temperature.

    DirectMaterial.com sells thermowells in Stainless Steel 304 and Stainless Steel 316, as well as heavy duty Stainless Steel 316 models. They are all one-piece construction and made to fit thermometers with 1/4” diameter stems.

  • Foot Valves offer clean, consistent flow

    Need a hand in pumping particulate-free water? How about a foot?

    DuraChoice Brass Foot Valve Notice that this foot valve consists of a brass check valve and a stainless steel strainer.

    Foot Valves are basically the marriage of a check valve (two varieties of which I wrote about a few weeks ago) and a straining element. They are generally used in conjunction with suction pumps to maintain pressure in a plumbing system while keeping out solids which could gum up the works.

    Although they are often found in water wells, foot valves can be used for many systems where a liquid needs to be pumped from a lower level holding area.

    I will use a foot valve with a spring assisted in-line check valve as an example, since that is the one we sell at DirectMaterial.com. However, you can use other types of foot valve as long as they are installed correctly.

    A suction pump draws the liquid into the foot valve’s strainer and through its check valve system. Because the spring assisted check valve responds to pressure on a continuum, the valve closes quickly when the pump shuts down, trapping the liquid in the pipe and pump before any backflow can occur.

    Retaining the liquid is important, because most pumps need to be primed in order to work. Being primed means that liquid in the pipe is sufficient to create suction through the pump. Without liquid in the pipes, the pump may not be able to create the suction needed to run properly. And that, in turn, could damage the pump.

    Using a household water well as an example, the pump is installed above ground, so that it can be reached for maintenance. Piping with a foot valve at the bottom is placed into the well at a level deep enough to ensure the pump always finds water. Water is pulled up a vertical pipe to the pump’s level and held in place by the closing check valve. Without that check valve, the water would seek its normal level and allow the pump to run dry.

    So, why not just use a check valve without the strainer? Doing so runs the risk of picking up something that could lodge itself in the valve, jamming it into the open position and causing the liquid to drain. Worse, that debris could find its way into the pump causing major damage.

    The strainer’s restriction needs vary with the application. Processes which pull from wells unlikely to contain particulates may use a more open mesh or possibly only a perforated pipe strainer. A foot valve in a water well should have a fairly tight mesh to keep the incoming water as clean as possible.

    The two pieces of the foot valve work in tandem to create cleaner intake, which will means the whole system will run better.

    DirectMaterial.com stocks the aforementioned spring assisted foot valves in both brass and stainless steel.

  • Y-Strainers: Keeping Things Clean

    A customer called in the other day and asked for a Y-Strainer to keep some of the rust from his old water heater out of his pipes. He said that he wanted an easy solution to keep his pipes cleaner and to keep his shower heads from being clogged.

    Stainless Steel Y-Strainer by DuraChoice Y-Strainers can be installed horizontally or vertically with the leg down to catch debris.

    While you can wonder at the wisdom of not just replacing the water heater that sounds like it is on its last legs, this call does give me an opportunity to talk about Y-Strainers.

    Useful for both liquids and gasses, Y-Strainers are an important tool for filtering unwanted particulates out of a line. They are most often used to protect more sensitive equipment like pumps, condensers, nozzles and turbines from particulates that may clog or otherwise damage them.

    “We use them to strain chemicals that are being pumped from a poly tank by a chemical pump,” said Billy Babineaux, the facility manager for FloQuip Inc. “(They are) very convenient for our setups.”

    The Y-strainer helps keep the pump running at peak performance without concerns about clogging.

    DuraChoice Y-Strainer Diagram Notice that the straining element is in a place that can be opened easily for cleaning.

    Much like the Y-Check Valve discussed in a previous article, the strainer is shaped like a lower-case “y” with the descending line of the letter as the main channel. The filter fits into the intersecting leg of pipe and strains all of the fluids or gas that passes through the main channel.

    That filter is usually made from perforated metal or wire mesh and come in a variety of particle retention sizes which are fitted securely to the strainer to prevent “bypass.” DirectMaterial.com offers filter sizes of 20 mesh or 100 micron.

    The Y-strainer can be installed horizontally or vertically, but should always be installed with the filter leg pointing down so that filtered materials can be collected away from the main flow channel. That ensures the flow will not be obstructed as long as the filter leg is cleaned out regularly. How often it should be cleaned out depends on the process and materials being filtered.

    The filter can be accessed easily for cleaning or replacement by simply loosening and removing a plug at the end of the filter leg. Some engineers and designers use a “blow-off connections” added to the downward pointing filter leg to clean the strainer.

    Babineaux said he relies on DuraChoice Y-Strainers for their low cost and reliability. He said he uses DirectMaterial.com for its “great service, prices and products.”

    Founded in 1997, FloQuip Inc. manufactures and maintains chemical injection pumps, solar injection pumps and high volume double diaphragm pumps. The company has offices in Louisiana, Texas and Mississippi.

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