Troubleshooting paper machine vacuum systems, Part 3: excess seal water, or a deteriorated base or foundation, are common causes of pump vibration. These problems, and others, can be easily recognized by carefully troubleshooting the vacuum system.Generally, vacuum systems vacuum system Urology A mechanical system used to facilitate and maintain an erection; an erection erector. Cf Penile implant. operate without frequent problems; but when trouble occurs, it may be tough to identify the problem. Often the symptoms--rather than the root cause--get treated. Mill maintenance and production personnel can use this troubleshooting guide to help quickly determine the causes of vacuum system problems and identify the differences between vacuum pump Vacuum pump A device that reduces the pressure of a gas (usually air) in a container. When gas in a closed container is lowered from atmospheric pressure, the operation constitutes an increase in vacuum in this container. problems and problems external to the pump(s). This guide covers the most frequently occuring system problems. When troubleshooting vacuum systems or any operating problem, key questions include "What changed, and when?" and "Is this a problem or a symptom?" The first two articles in this series covered low vacuum levels and high-horsepower motor trip-outs (See the September and November 2001 issues of Solutions!). This article discusses hot pump operation and pump vibration. HOT PUMP OPERATION A liquid-ring vacuum pump operating at 130 [degrees] F and higher may be an indication of a problem; yet this operating temperature does not necessarily damage the pump. Vacuum pumps usually operate at a temperature 10[degrees]-25[degrees]F higher than that of the seal water flowing to the pump. More often, high pump temperature indicates low seal-water flow. Insufficient flow can result from plugged orifices or spray nozzles A spray nozzle is a device that facilitates the formation of spray. When a liquid is dispersed as a stream of droplets (atomization), it is called a spray. The typical purpose of the spray is to maximize the effect of the liquid by increasing the total surface area for better and/or low seal-water feed pressure. As stated in Part 1, low seal-water flow can cause low vacuum levels. Vacuum pumps operating at unusually high temperatures can be a telltale sign requiring investigation. High pump operating temperatures may also occur with proper seal-water flows. Sometimes the paper machine vacuum service is just normally hot, as seen with flatboxes or couch mils on a linerboard lin·er·board n. A type of paperboard used in making corrugated cartons. machine with a steam box. Vacuum steam boxes in the press section am also typically hot. In these cases, the elevated pump temperature is normal. PUMP VIBRATION Vibration in liquid-ring vacuum pumps is an occasional problem, and it is important to understand the causes ,so that a good pump is not replaced. In this article, I won't discuss high-frequency vibrations due to wear in bearings. Mill maintenance and bearing analysis have progressed to the point where bearing problems can often be detected before they become serious. However, note that most liquid-ring vacuum pumps have 16, 18, or 20 blades; this fact is helpful in determining blade-pass frequencies. Other more common, easy-to-recognize problems an cause pump vibration. These include excess seal water or a deteriorated base or foundation. High seal-water flows (2-3 times the standard rating) can cause vibration or "knocking" within the pump. The high seal-water flow may also show up as high horsepower horsepower, unit of power in the English system of units. It is equal to 33,000 foot-pounds per minute or 550 foot-pounds per second or approximately 746 watts. , as discussed in Part 2. The problem of deteriorated bases and foundations is obvious and is normally caused by old age. In these cases, he pump may "rock" at low frequencies. This vibration may increase in pumps with poorly supported vacuum piping. Using common flexible roses at the pump inlet inlet /in·let/ (-let) a means or route of entrance. pelvic inlet the upper limit of the pelvic cavity. thoracic inlet the elliptical opening at the summit of the thorax. can help isolate the pump tom vibration due to the system piping. Pump vibration occurring at the rotation frequency may be due to scale buildup build·up also build-up n. 1. The act or process of amassing or increasing: a military buildup; a buildup of tension during the strike. 2. on the rotor rotor: see generator; motor, electric. .. While normal pump wear may be more uniform and not heavily contribute to vibration, the buildup and removal of scale (calcium carbonate calcium carbonate, CaCO3, white chemical compound that is the most common nonsiliceous mineral. It occurs in two crystal forms: calcite, which is hexagonal, and aragonite, which is rhombohedral. ) is not so uniform, in mills with hard water, routine descaling procedures may not fully remove scale deposits from the rotor These deposits can cause the rotor to be unbalanced and will show up as vibration. Look for vibration just after these procedures take place. A more unusual occurrence is "stalling." A liquid-ring vacuum pump creates a liquid ring due to centrifugal force centrifugal force Fictitious force, peculiar to circular motion, that is equal but opposite to the centripetal force that keeps a particle on a circular path (see centripetal acceleration). of the spinning rotor During startup, this ring of water develops as long as the vacuum pump has a free flow of air from the process. In some systems, a valve may be closed in the vacuum line, minimizing or eliminating the free flow of air to the pump during startup. If the pump does not get good airflow, it may only partially develop the liquid ring. This may show up pulses in the indicated vacuum level. The pump will vibrate slightly or, in some instances, shake enough to rack a concrete foundation. A random knocking sound may also come from within the pump. This problem occurs just after the pump has been started. The solution is to start the vacuum pump with all vacuum system valves open. Areas of the vacuum system with vacuum control valves Control valves are valves used within industrial plants and elsewhere to control operating conditions such as temperature, pressure, flow, and liquid level by fully or partially opening or closing in response to signals received from controllers that compare a "setpoint" to a , such as uhle boxes and suction suction /suc·tion/ (suk´shun) aspiration of gas or fluid by mechanical means. post-tussive suction a sucking sound heard over a lung cavity just after a cough. pickups, am candidates for stalling if valves am not properly positioned at startup. Often, vacuum pumps am considered "out of sight, out of mind "Out of Sight, Out of Mind" was the 99th episode of the M*A*S*H television series, and the third episode of the fourth season. Written by Ken Levine and David Isaacs and directed by Gene Reynolds, it first aired on October 5, 1976 and was repeated December 28, 1976. ." Yet, with good troubleshooting techniques, quality operating data, and basic system understanding, you can identify and resolve pump problems with minimal effort. Dan Dunn and Dough Sweet are with Paperworx, a Division of Nash Engineering, 140 Highland Ave., Trussville, AL 35173-1461. |
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