Livingston and Haven Store Blog

  • Bosch Rexroth Air Valve Sizing Guide

    As the internet's premier Bosch Rexroth distributor, Livingston & Haven would like to provide you information that will make air valve sizing as simple as possible.
    Before selecting an air valve make sure it is capable of delivering the necessary flow of air at an acceptable pressure drop though the valve, lines, and fittings to the power device.
    A satisfactory pressure drop through a valve is 10 to 15 psi. A lower pressure drop such as 5 psi should be used to complex circuits. The Cv valve of a component is used to designate the actual flow capacity of that device. The Cv valve can mathematically calculate the actual flow at various pressure drops, operating pressures and temperatures. Under certain standard conditions a flow path with a Cv valve of 1.0 will pass 1 gpm of water with a 1 psi pressure drop. One method that is widely used in hydraulics and pneumatics is using the Cv to calculate the flow of a compressible fluid such as air.
    The most common way to size an air valve is by matching the NPT port size of the cylinder being used; this will result in the most satisfactory application. The NPT cylinder port has a higher Cv valve than the typical valve of the same pipe size.

    Cylinders:

    The rod may be subtracted from the SCFM requirements if the cylinder has an oversize piston rod and the retracting stroke is fastest and is being used to size the air valve.

    Lines and Line Lengths:

    The appropriate time to add the line volume to the SCFM requirement will be when the line lengths between the delivery ports of the air valve and the cylinders significantly exceed 10 ft. in length. Often on small cylinders you will need to add additional SCFM if the line volume exceeds 20% of the cylinder volume. SCFM=Line Volume (cu.in.) x 60 x {Supply Pressure+14.7}/14.7

    Response time consideration:

    If the speed of the system is critical and the cycles per minute required is high, the response time for the valve should be considered. In most applications this will not be necessary.

    Valve fitting restrictions:

    The valve flow and the rest of the system may be restricted if tubing is used instead of standard piping. Apply the following equation to the minimum inside diameter of the fitting to approximate the restriction (I.D.): Corrected Cv= 18 x (I.D.)^2

    Multiple Valve Paths & Complex Systems:

    Pressure drops are additive in a pneumatic circuit where air passes through more than one device in a series. One thing to consider is the Cv valve of the flow control valve in the free flow direction. The drop from set pressure on the delivery side of the regulator determines the capacity of a pressure regulating valve. The regulator may be one or more pipe sizes larger than the directional valve it is supplying.

  • Hydac Filter Element Media & Model Code Changes

    Hydac is continuously researching and testing new filter media looking for ways to reduce pressure drop while retaining or improving filtration rates and dirt holding capacity. The newest filter media, called Optimicron, is now being phased-in to Hydac’s Low Collapse (BN) product line which is used in return and offline filter assemblies. Low Collapse filter elements have a maximum collapse rating of 290PSI differential.

    HYDAC is not changing filter element or filter assembly part numbers. Only model codes will change, from BN4HC to ON. If you receive an element with “ON” in the model code, then the element includes Optimicron technology — example: ordered 0330 D 010 BN4HC, received 0330 D 010 ON.

    Optimicron technology incorporates several performance improvements, with the main one being decrease Delta P. This allows for higher running efficiency, longer intervals between filter changes and lower operating costs. Otherwise, these elements are equivalent in fit, form, and function. Note, high collapse (BH4HC) elements will not be converted at this time. Please see the attached documents for more details.

    TechNews Optimicron Prod Release

  • How Clean is Your Hydraulic Application

    How Clean is your hydraulic system? How is that cleanliness defined? John Edwards talks about what the International Standards Organization and the industry uses to define a systems cleanliness. Cleanliness is crucial to the effectiveness and longevity of any hydraulic application, knowing where you stand is the difference between a successful production and a catastrophic event.

  • Choosing the Right Hydraulic Fluid

    John Edwards, Livingston & Haven’s resident Hydac Expert, talking about different types of fluids for your Hydraulic application and how important it is that you choose a filtration element that is engineered to work with that fluid.

  • How to Measure Filter Element Performance

    John Edwards here, talking about contamination control fundamentals, specifically hydraulic elements and element performance and what makes one manufacturer better than the other. In the industry, most of filter elements are rated using a multi-pass test. That's where in a lab type environment, the manufacturer can put an X number of particles into the system upstream of the filter and then measure the amount of particles downstream of the filter and from that, they can know exactly how many particles are caught by the filter element and from that, determine the efficiency of the filter and that's where beta ratios come from.

    Without getting into all of the calculations, a beta ratio actually lets you know what size particles a filter element may be catching and what efficiency rate it’s doing it at. If you got a filter element that’s catching 99.5% of all the particles that come in, that's pretty good, we call that high efficient, but at thousands of particles per milliliter, it’s still pretty important to get a high efficient high beta filter, also what's important is the beta stability, that actually lets one know how the element performs as it starts to fill it with particles during the life of the filter element. Most all manufacturers will have a good performance when that element is clean but as it starts to fill up in and has pressure pulses, how does it perform, that's beta stabilities, the way we measure that.

    Pressure rating is the amount of pressure drop that it takes for the fluid to get from one side of the filter to the other and the trick is to catch the particles with as low of a pressure drop as possible, that’s also important; and also the collapse rating, some of these filters are using high pressure applications where the differential pressure is pretty high and the core tubes have to be made out of more solid material as not to internally implode or crush inside the filter housing.

  • The Importance of Hydraulic Filtration

    Why do hydraulic applications need to filter? Why is that important? Find out with John Edwards as explains the contamination control and fluid filtration fundamentals that will help you get the most effective service life from your machinery as possible.

  • How to Choose A HYDAC Filter Element

    John Edwards here, talking about contamination control fundamentals and summarizing the steps that we take to properly select the correct filters, putting them in the right place, monitoring the system and making sure to give the customer maximum efficiency and and the least amount of downtime possible. Number one is determine the actual desired target cleanliness level of a system by looking at it as a whole and picking the most sensitive component and defining that target level. Number two is selecting the right medium, high-performance, high efficiency filtration and at what micron level, dependent on the system. Where to filter, whether that’s in the pressure line, return line filter or our research type filter. Selecting a good filler breather, we discussed how important is to have a good filler breather to catch those airborne particles before they make their way into the reservoir. Practicing good contamination control, good housekeeping, not leaving filter caps off in a dusty environment, not stuffing rags in hose assemblies. So, things of that nature and also, verifying the results by either pulling fluid samples on a proactive maintenance type schedule or by some of the various diagnostic equipments that we can supply where the customer on-site can actually do real-time iso-cleanliness levels, trend analysis and any ways we can be proactive to maximize our efficiency.

  • How to Measure Hydraulic Fluid Samples

    John Edwards here, talking about contamination control fundamentals specifically how we measure and quantify in regards to fluid samples. We sell a fluid sample kit here: that comes to you, the customer, in a box, with the bottle and some paperwork, serial number stamped on it. Where you would pull your sample in this sterile bottle, fill out the information. It comes in an already self-addressed, prepackaged return shipping information, goes to the lab within a couple of days. You have a report of fluid analysis that gives you the iso-cleanliness code, also the water content that may be in contamination, if you got a high percentage of water in a high humidity environment, that will affect your lubricity of the system, also a chemical breakdown of what kind of particles are found in it that can be important in your additive breakdown in your oil package, or if you see some rust in the system, or if you find some copper that you know is coming from the the actual component in the system, and it can give you proactive maintenance warning, and then you can also keep trend analysis on machines, if you make improvements, and get emailed the results within a couple days.

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