The Hard Face
Some ceramics and silicone carbides are attacked by caustic. Check to see if your seal face contains silica. As an example both reaction bonded silicone carbide and 85 ceramic have this high silica content. The product is solidifying between the faces. Most hard faces have poor tensile or shear strength. Excessive vibration will cause cracking at the drive lug location A cryogenic fluid is freezing a lubricant that was put on the face. The elastomer is swelling up under an outside seal face....
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or 62.4 pounds. Therefore, the density of the liquid is 62.4 pounds per cubic foot. This is the density of water at 4 C and is usually used as the standard for comparing densities of other substances. The temperature of 4 C was selected because water Educational CD- has its maximum density at this temperature. In the metric ROM's system, the density of water is 1 gram per cubic centimeter. The Printed Manuals standard temperature of 4 C is used whenever the density of Downloadable Books liquids...
SUBJECT The pump is not producing enough capacity to satisfy the application
This is the second paper in a four part series about pump troubleshooting. Let me begin by pointing out that there are a couple of things you must keep in mind when troubleshooting centrifugal pump problems The centrifugal pump always pumps the difference between the suction and discharge heads. If the suction head increases, the pump head will decrease to meet the system requirements. If the suction head decreases the pump head will increase to meet the system requirements. A centrifugal pump...
Auxiliary Equipment Failure
The seal faces are off center causing a pumping action across the faces. The inlet and outlet ports are not drilled properly. A cartridge double seal has not been centered properly The pressure or level in the tank changes. One of the seals is leaking. The pressure or level change should tell you which one. Not convecting. It was installed incorrectly. The minimum and maximum dimensions were ignored. The flow is not high enough. The gage graduations are too large. No flow through the quench...
The leak occurs only at start up and then stops after a short time
Face distortion. Caused by a high pressure surge that was created when the pump was started with the discharge valve shut. The shaft is bending, and interfering with the seal movement. Occurs because the pump is running with the discharge valve throttled or shut. Operators shut the discharge valve at start up to save electricity and prevent cavitation. The same problem can occur if the pump is started with the discharge valve wide open and because of the lack of discharge resistance the pump...
Tutorial
NPSHA for those who hate that stuffy word Fluide Design Inc. copyright 2006 NPSHA for those who hate that stuffy word This article follows the same approach as the pump tutorial and if you are just starting in this field I recommend you read it first. The dreaded term NPSHA means Net Positive Suction Head Available. Its a term that most people find difficult to relate to in part because they have no idea what value it should have. Before we discuss values and the exact definition of NPSHA, let...
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Congress Event Early Career Forum amp Fair Featuring top industry pros presenting key trends, opportunities, and expectations in the engineering field. Participant in the one-day program or get more insights when you include the second day of sessions. gt gt Learn More B31Q-2006 Pipeline Personnel Qualification Standard This Standard sets requirements for effective pipeline personnel qualification programs addressing covered tasks that impact pipeline safety and management of qualifications of...
Discharge Recirculation
A line is connected between the discharge of the pump and the stuffing box. The high pressure fluid is then recirculated through the stuffing box to the back of the impeller and eventually to the pump discharge. This technique presents several problems for maintenance people If the fluid contains solids and most of them do the centrifugal action of the impeller will concentrate the solids on the inside diameter of the pump volute and it is this dirty fluid that is being recirculated to the...
SUBJECT Why do pump bearings fail 412
What do we mean by good bearing life Most of us change the bearings every time we disassemble the equipment to replace the mechanical seal or the packing sleeve. Is this really a sensible thing to do If you think about it for a minute there is nothing in a bearing to wear out, there are no sacrificial parts. Bearing life is determined by the number of hours it will take for the metal to fatigue and that is a function of the load on the bearing, the number of rotations, and the amount of...
Other Considerations
Vertical pumps require venting or the seal will trap air in the stuffing box, causing high heat at the seal faces. To vent the stuffing box properly, connect a suction recirculation line between the seal flush connection and the pump suction. Vertical pump applications also present a problem for dual seal applications. You will need to provide some method of venting air trapped at the outside seal. Carbon metal composites are a good choice for heat dissipation across the carbon seal face. Try...
Controlling The Pressure In The Stuffing Box Area
Increase stuffing box pressure by installing a recirculation line from the pump discharge back to the stuffing box figure A with a close fitting bushing in the bottom of the stuffing box. Try to avoid positioning the recirculation line so that it aimed at the lapped seal faces or thin bellows seal plate materials. Eliminate the pressure drop between seal faces by using two seals with a higher pressure barrier fluid circulating between them. This is very important in the sealing of chemicals...
SUBJECT Controlling the temperature in the stuffing box area 46
Many fluids are adversely affected by a change in their temperature, and when this reaction takes place seal failure is almost sure to follow. The reaction can take several forms One of the seal components can be destroyed. The elastomer, seal faces, or metal parts will almost always be altered at some degree of change in ambient temperature. Coated hard faces can heat check crack . Carbon fillers can melt and pits can form in carbon graphite faces as trapped air expands and blows out pieces of...
Barrier Or Buffer Fluid
Any time you use two seals in an application you will need a fluid between them. If the fluid between the seals is higher than stuffing box pressure we call it barrier fluid. If it is lower than stuffing box pressure we call it buffer fluid The liquid can be circulated either by forced circulation, a pumping ring or convection. The method that you will use will be dictated by the pressure, pump speed and shaft size. All seal manufacturers have charts available to give you the correct...
Centrifugal Pump Selection How To Pick The Correct Size Pump For Your
We will begin by deciding what operating conditions our pump has to meet and then we will approach pump suppliers to see how closely they can satisfy these needs. Unfortunately no comprehensive theory which would permit the complete hydrodynamic design of a centrifugal pump has evolved in the many years that pumps have been around, so the pump manufacturer will be doing the best he can with the information you supply to him. To clearly define the capacity and pressure needs of our system we...