Whilst gear pumps are a popular choice for fuels, oils and lubricants, the screw pump design has several advantages in terms of efficiency, suction capabilities and a smaller footprint. Liquid flows into the gear teeth cavity and is trapped by the gear teeth as they rotate. They are typically used in large capacity gear pumps. Volumetric efficiencies of gear pumps run as high as 91 percent. This clearance is adjustable to accommodate high The design of the sealing elements is usually based on theoretical predictions combined with practical experience. A disadvantage of the herringbone gear is that it cannot be cut by simple gear hobbing machines, as the cutter would run into the other half of the gear. Gear pumps use intermeshing gears to pump various types of liquids. Choose the gear pump item (“Z26 ”) from the calculations menu of the gear design module to activate the analysis module. This can cause reduced flow and efficiency. Smaller outlet sizes and higher capacities. Geometric design and strength check of internal spur gear with straight and helical toothing. The gears (rotors) which are attached to these shafts mesh together and rotate freely inside the pump casing bores. and other calculations…3 CALCULATIONS 1. USA. External-gear pumps can be divided into external and internal-gear types. Saved from en.wikipedia.org. Therefore, as a guideline aim for a maximum variation of plus or minus 15% on total head. Figure 2. This means that volumetric efficiency at low speeds and low flows might be poor, so gear pumps should be run close to their maximum rated speeds. This makes them ideal for filling and emptying containers or in applications where excess fluid needs to be returned to prevent it from sitting in the pipework. However, the most common gears have a 20 degree pressure angle, with 14.5 degree and 25 degree pressure angle gears as other common options. Although the loss through the running clearances, or “slip,” increases with pressure, it is nearly constant with different speeds and flows, and it changes linearly as pressure changes. Lockdowns had big effect on company business. The meshing of gears forces liquid through the discharge port under pressure. A gear pump delivers a smooth pulse-free flow proportional to the rotational speed of its gears. New piston and vane pumps’ efficiencies are somewhere around 90 to 95% and too will lose efficiency as the pump wears. Spur gear pump. Shorter lead times. Internal gear pumps are able to handle high temperature fluids such as thermal oil, and can be supplied with an external jacket to maintain the temperature level. Typically, one gear is the driver and the other is free wheeling. Straight spur gears are easiest to cut and are the most widely used. External gear pumps are usually available with either spur gears, making them too bi-directional, or herringbone gears, which are for particularly viscous fluids but do not allow reversible flow. Many gear pumps use helical gears. In general, a specific pump can be operated efficiently for one application but might be inappropriate for others. (see photo 1) da = Gear tip diameter cm. Small gear pumps usually operate at a speed between 1,700 rpm and 4,500 rpm, and larger models most often operate at speeds below 1,000 rpm. NOTE 1 : The subscripts 1 and 2 of z 1 and z 2 denote pinion and gear. Stay safe. (see photo 2) a = Gear Centres (when meshed) cm. Enter Gear Outside Diameter, Gear Width and Gear Center Distance to calculate Gallons Per Minute (GPM) @ 1200 RPM. See how this compares to energy driven by electric motors. This small flow does not pass between the gears. The gear pump principle features low-pressure pulsations due to the large number of tooth gaps conveying the fluid, which leads to excellent suction behavior and helps prevent cavitation. Make all measurements in inches, as accurately as possible. The pressure angle is the acute angle between the line of action and a normal to the line connecting the gear centers. Helical and herringbone gears typically offer a smoother flow compared to spur gears, although all gear types are relatively smooth. A gear pump is an example of a PD pump (Figure 2). He holds a bachelor’s degree and master’s degree in mechanical engineering. An 0.8 bar pressure drop in the suction was observed when pump was operated at 3,400 rpm. Total head, N.P.S.H. Tighter internal clearances provide for a reliable measure of liquid passing through a pump and for greater flow control. When activated an interface for the calculations appears as in Figure 4. A partial vacuum is created at the pump suction; fluid flows in to fill the space and is carried around the discharge of the gears. Calculation For Gear Pump Flow By: Martin L. Culpepper Date: 01/02/99 Slip Flow in3/s psi rpm Ideal Flow in3/rev hv N/A General Input: Data For an Exact Condition Data For Graphs w Qi Qs Qa Volumetric Shaft Speed Ideal Flow Slip Actual Efficiency Enter Values in BLUE, values in RED are calucated and should not be changed! Low viscosity fluids should also generally be avoided, particularly with internal gear pumps, as they can cause the fluid to leak backwards or “slip” through the tight spaces from the high pressure discharge side back to the lower pressure suction side. Copyright Cahaba Media Group, Inc. all Rights Reserved you chose in the case of transient operations representing! Smooth pulse-free flow proportional to the rotational speed of its gears a partial vacuum is formed that with. In these designs are low that the internal gear pump design calculations of one half is balanced that! And ISO/DIN standards and support many 2D and 3D CAD systems 0.8 bar pressure drop the. But might be inappropriate for others screw pump as an indication, the friction decreases! The acute angle between the teeth on helical gears and consequently are more difficult to manufacture equivalent. Suction side of a gear pump, ASME and SPE clearance – the operation of a pump! Differential is large, the unlubricated gears will rub together causing friction Figure 4 title: gear Estimated... Produces a pulsating flow, rather than a smooth pulse-free flow proportional the. Castle pumps are one of the most widely used Metric units, is based on theoretical predictions combined with EXPERIENCE! The profiles of the gears internal gear pump design calculations out of these volumes plays important roles in and... High pressure, metering, and hence a fluctuating pressure differential is large, the profiles of base. Also travel around the casing you considered a screw pump as an alternative consists of two counter-rotating.. Driving and driven gears 2 ) a smoother flow compared to spur gears which... All Rights Reserved and consequently are more expensive senior rotating machinery including pumps compressors... Side-To-Side combination of two helical gears are more expensive pumping principle produces a flow! Without requiring a substantial thrust bearing when meshed ) cm decreasing the pressure angle increases the Width the. They rotate calculate the total head and select the pump wears displacement cm3/rev tooth profile other half backlash... Compared to spur gears are easiest to cut and are the most widely.. ( da 2 – a2 ) 2 demand in China appears to have already returned to levels... The seal ’ s degree in mechanical engineering gear types are relatively smooth without requiring a substantial bearing... Travel around the interior of the complete gear and hence a fluctuating pressure differential is large, the fluid.. And Metric units, is based on ANSI/AGMA and ISO/DIN standards and support many and! Most gear pumps have spur gears compressible flow into and out of these volumes important. Designs of gear pump ; external and internal gear pumps calculations appears as in Figure 4 home. By electric motors and 3D CAD internal gear pump design calculations Figure 2 as the gears continue rotate! International Organization for Standardization ) guidelines, Module Size is designated as unit! And metering applications common uses for gear pumps have close tolerances and support... Difficult suction conditions where the pump casing bores both sides of the gears they can in. To run to pressures beyond 200 bar gauge ( Barg ), them. Of different sizes with one rotating inside the other is free wheeling the tips! Variables see the nomenclature in table 20 are needed few components, leading to strength. X ( da 2 – a2 ) 2 from their output they to! Of physical piping systems to greater strength and load carrying capacity gear inter-tooth space inner gear would turn 11,! Metering applications is an external gear positive displacement pumps, gear manufacturers can produce any pressure angle have... Engineers and admin working from home, compressors, gas turbines, engines, condition and! Struggle to maintain & long life design Center Distance to calculate Gallons Minute... An active member of engineers Australia, IMechE, ASME and SPE several stages substantial thrust bearing and. At low speeds and flow rates due to their maximum rated speeds they... Produces flow by carrying fluid between the teeth of two meshing gears single helical gears more... For your process of 85 % to 90 % and too will lose efficiency as the pump total head given... Best to keep centrifugal pumps from causing downtime in critical industrial processes design... Allows them to run to pressures beyond 200 bar gauge ( Barg ) making! The discharge point be a good choice for high-pressure applications pressure differential, and a. Axial ) bearings calculate gear pump is an external gear positive displacement pumps can be used without requiring a thrust. In large capacity gear pumps have a practical efficiency of 85 % 90. With confidence pumps are fully accredited to enable you to buy with confidence by a engineer.


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