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Suction Bell Upgrades for Vertical Turbine Pumps
Suction Bell Upgrades for Vertical Turbine Pumps
Dr. Lev Nelik, P.E., APICS
How long should a vertical pump’s suction bell last? That was a question a plant manager asked me during a recent consulting assignment for a power plant. A pump manufacturer’s typical response to such a question is, “it depends.”
Basically, it depends upon the liquid being pumped, the operating point on a curve, the accumulated hours, the materials of construction, and so on. But is there an average value, or does a pump life vary within a very broad range? Is 30 years of life considered a very long time? Is two years unacceptably low?
If a large vertical cooling water or recirculating pump supplies water to the plant, 15 (or more) years of life should be achievable. Anything under five years is too short for most applications. If water comes in from the ocean or a gulf, the pump life (i.e. impeller, casing cone, suction bell) will be reduced, especially if a pump operates off-design, where suction recirculation is particularly damaging and the seawater is known to be very corrosive.
Often, damage to the impeller casing (cone — at immediate proximity to the vanes) is much more severe as compared to the damage of the suction bell (below the impeller) itself. In recognition of this fact, some designs are deliberately configured into a two-piece construction where the impeller casing (cone) is bolted to the suction bell, thus making it simpler to replace. For large vertical turbine pumps, these parts are expensive, and separating a shorter-expectancy-life part from a longer-expectancy-life part is a good idea.
Unfortunately, many designs configure the impeller casing and suction bell into one continuous unit because it is obviously cheaper to produce a single-piece casting. The problem here is that when the casing gets damaged, the entire part must be scrapped and replaced — and the end user pays for that.
When examining such a worn-out casing cone/ suction bell part, an effective upgrade strategy involves modifying the design by separating the part into two pieces and then bolting them back together. An example of such an upgrade was recently done by our repair shop.
Suction bells are usually constructed from iron, which is significantly less expensive than stainless steel but lacks its resistive properties. Upgrading an entire piece is another possibility, but it is often too expensive and really unnecessary. Instead, a two-piece construction will have a new stainless cone, bolted to the old bell and fitted with a stainless flange.
The result is a much better design, with stainless steel providing many more years of operation at enhanced resistance to corrosion and cavitation damage.
And should the lower portion (suction bell) eventually need repair, it can be done, saving time and money by reusing the undamaged stainless upper part.
We cannot change the single-piece past. But we can certainly improve the life of individual components, once the deficiencies of past practices are realized, understood — and corrected.
Oh "Overall Equipment Effectiveness", I've heard about that before! Unfortunately, in many facilities, that's all OEE (Overall Equipment Effectiveness) is to the personnel. Something they heard of, talked about or read about. Many maintenance departments today still do not effectively utilize the OEE tool even though it's widely used among the world class companies.
Oh "Overall Equipment Effectiveness", I've heard about that before! Unfortunately, in many facilities, that's all OEE (Overall Equipment Effectiveness) is to the personnel. Something they heard of, talked about or read about. Many maintenance departments today still do not effectively utilize the OEE tool even though it's widely used among the world class companies.
One of the most costly mistakes that almost every company makes with its pumps is to actually buy the wrong pump. Sadly, this is a situation that occurs with much more frequency than anyone would care to admit. The ramifications are truly enormous—and they are magnified even more in tough economic environments. Efficiency drops. Reliability plummets. Maintenance costs rise dramatically. Even in the best of times, you couldn't afford to gamble on the efficiency and reliability of your pumping systems. Don't start now.
One of the most costly mistakes that almost every company makes with its pumps is to actually buy the wrong pump. Sadly, this is a situation that occurs with much more frequency than anyone would care to admit. The ramifications are truly enormous—and they are magnified even more in tough economic environments. Efficiency drops. Reliability plummets. Maintenance costs rise dramatically. Even in the best of times, you couldn't afford to gamble on the efficiency and reliability of your pumping systems. Don't start now.
There has always been a debate on whether jack screws should remain tight against the side of the machine case after the machine has been moved into position or to back off the screws, so they do not touch. Should jack screws be tight or backed off? The answer is yes and no. In some situations you should leave the bolts tight against the machine and in other situations, it may be better to back off the jack screws.
There has always been a debate on whether jack screws should remain tight against the side of the machine case after the machine has been moved into position or to back off the screws, so they do not touch. Should jack screws be tight or backed off? The answer is yes and no. In some situations you should leave the bolts tight against the machine and in other situations, it may be better to back off the jack screws.
Gear pumps are the most common type of positive displacement pump, ideal for transferring high viscosity fluids such as automotive oils, plastics, paint, adhesives, and soaps. As with any pump, proper operation and regular maintenance are vital to reducing costly pump repairs and maximizing pump efficiency. Below are helpful tips for operating your gear pump and ensuring it achieves a long operating life through regular maintenance. As with any pump, proper operation and regular maintenance are vital to reducing costly pump repairs and maximizing pump efficiency.
Gear pumps are the most common type of positive displacement pump, ideal for transferring high viscosity fluids such as automotive oils, plastics, paint, adhesives, and soaps. As with any pump, proper operation and regular maintenance are vital to reducing costly pump repairs and maximizing pump efficiency. Below are helpful tips for operating your gear pump and ensuring it achieves a long operating life through regular maintenance. As with any pump, proper operation and regular maintenance are vital to reducing costly pump repairs and maximizing pump efficiency.
One of the important ingredients for making and keeping a reliable electrical connection is clean contact surfaces. When initial contact is made between electrical contact surfaces, no matter how smooth and level the surfaces, only a few high points touch. As the contact force increases, more points make contact until at optimum force most of the metal-to-metal contact has been accomplished. Contact theory tells us that these points are actually cold welds.
One of the important ingredients for making and keeping a reliable electrical connection is clean contact surfaces. When initial contact is made between electrical contact surfaces, no matter how smooth and level the surfaces, only a few high points touch. As the contact force increases, more points make contact until at optimum force most of the metal-to-metal contact has been accomplished. Contact theory tells us that these points are actually cold welds.
A standard centrifugal pump impeller is constructed of a group of elongated, solid-walled chambers attached together in the shape of a circular ring. The ring is spun quickly and the liquid that enters the inside end of the chambers is flung out at high speed from the other end. Figure No. 1 shows a section through centrifugal pump wet-end showing regions of low and high pressures.
A standard centrifugal pump impeller is constructed of a group of elongated, solid-walled chambers attached together in the shape of a circular ring. The ring is spun quickly and the liquid that enters the inside end of the chambers is flung out at high speed from the other end. Figure No. 1 shows a section through centrifugal pump wet-end showing regions of low and high pressures.
Get mechanical seals working properly. Mechanical seals are used to keep the bulk contents of rotating equipment such as pumps and compressors from escaping. They do this by sealing the shaft that protrudes from the casing. They require quality installation and operation conditions for a long life. Keywords: precision assembly, barrier fluid, stationary seal, rotary seal, alignment.
Get mechanical seals working properly. Mechanical seals are used to keep the bulk contents of rotating equipment such as pumps and compressors from escaping. They do this by sealing the shaft that protrudes from the casing. They require quality installation and operation conditions for a long life. Keywords: precision assembly, barrier fluid, stationary seal, rotary seal, alignment.
