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  • Pusher Centrifuge Video Transcript

Pusher Solid/Liquid Separation Centrifuge Animation Video

Video Transcript

B&P Process Equipment and Systems LLC is a company with a long tradition of serving the chemical industry. First opened in the 1890s, B&P has been successfully manufacturing and marketing the pusher centrifuge since the 1930s. In fact, B&P, which was known until 1987 as Baker Perkins, was one of two companies worldwide that licensed the original Ter Meer patents for pusher centrifuge design. Six decades later, much has changed in the design and performance of the machines, but B&P is positioned as leader and innovator in the design and manufacturing of the pusher centrifuge has not changed. B&P has manufactured over 700 pusher centrifuges, shipping them to over 5 continents around the world. It is the unique performance and design characteristics of this remarkable machine that make it the number one choice of the market today. 

Superior Process Performance - How
 
In brief, the B&P/pusher-centrifuge.html pusher centrifuge consists of a basket which rotates about the horizontal axis, generating the centrifugal force to separate solids from feed liquor. A hydraulic system powers a piston, this transports the cake along the basket discharging solids on each forward stroke. A closer look at how materials travel through this machine reveals the many special features of the B&P pusher centrifuge. Feed slurry enters through a stationary charging pipe. A rotating funnel accelerates the slurry, depositing it on a wedge slot filtration screen. Solids accumulate on the screen and liquor drains through. The pusher plate rotates with the basket, and reciprocates. On the forward stroke, the plate pushes the solids ahead of it. On the reverse stroke, fresh screen is exposed where more solids collect. The solids form a uniform cake which eventually pushes off the end of the basket. In most applications, the cake can be washed to increase purity. Baffles in the housing surround the basket to segregate washer fluid from mother liquor concentrate. The key to the outstanding performance of the B&P pusher centrifuge, is it's single stage long basket design and slow speed operation. Features in direct contrast to the original European pusher centrifuges which are characterized by short baskets and high speed operation. 

Advantages

There are many advantages to B&P's slow speed design. First, speed is expensive since the basic energy cost of any centrifugal device increases with increasing speed. High basket speeds also significantly reduce the design life of critical components and multiply the risk of machine failure. The B&P slow speed design, in contrast, contributes to much longer machine life, and there are many process benefits to slower speeds as well. Crystal breakage is kept to a minimum. Better liquor drainage results from lower cake compaction. Fewer fines are lost in the filtrate, and lower speeds assure smoother cake movement down the screen. Another advantage of B&P's slow speed long basket design is greater cake capacity. B&P found that by increasing basket length by 20%, they could achieve more than a 20% increase in cake capacity.

This extra capacity occurs because the cake also gets thicker as the screen length increases. Thicker cakes have many advantages over thinner cakes. Fewer fines are lost to the filtrate since the thicker cake acts as its own filter to trap fines. The larger cake cross-section minimizes the axial cake compaction. The thicker cake maximizes wash efficiency, lowering wash costs, and thicker cakes are purer than thinner cakes. The reason for this increased purity is that in any cake, the layer immediately adjacent to the screen is where fines and wet, low purity solids accumulate. The thicker the cake, the smaller in overall proportion this layer becomes and the higher the total cake purity. Clearly, the long basket slow speed B&P design is overall more efficient and more cost-effective than short basket high speed European models. 
 
Why is a Single Stage Design Better than a Multi-Stage Design?

Another type of pusher centrifuge on the market today is the multi-stage design, a design that B&P actually manufactured itself for a time. B&P found the multi-stage design inferior to the single stage design, here's why. In a typical multi-stage design, the cake moves from stage one to stage two, and is washed as it tumbles between stages. Advocates of the multi-stage system claim that the tumbling of the cake promotes wash efficiency. B&P's experience, however, shows that tumbling the cake between stages makes it necessary for impurities to diffuse down toward the screen at each stage. Fines are disturbed and are lost through the screen. In contrast, the undisturbed cake in the single stage B&P machine drains from the top down only once for a smooth displacement wash. Cake capacity, too, is reduced in the multi-stage systems. Since each stage builds a separate cake, the size of the individual screens drastically limits the cake capacity. Cake capacities for B&P pusher centrifuges are substantially greater than those available from European designs. In fact, B&P's model S-18, which is 18 inches in diameter, has 5% more cake capacity than a 630 millimeter European design. B&P's model S-25 has almost 20% more cake capacity than an 800 millimeter unit. And B&P's model S-36 boasts the largest cake capacity of any pusher centrifuge in widespread commercial use today. 

Superior Operating Reliability

But equally as important as the B&P pusher centrifuge's superior capacity and processing performance, is the low-maintenance superior operating reliability built into every machine. In this cutaway of a typical B&P pusher centrifuge, the components colored green rotate together driven by the shiv at the back of the unit. The components which appear red, rotate and reciprocate to provide pushing action. The components colored brown or tan represent the hydraulic system. The wet or processing end of the pusher separates the solids from the feed liquor and washes the solids to improve product purity. 
 
There are two precision tapers. One long precision taper lies where the basket hub mounts on the hollow shaft. The other precision taper provides an exact connection between the pusher plate and the pusher shaft. The length and precision contact of these tapers are very important to rotational stability and operating reliability. Precision slots in the single piece wedge slot screen, capture the solids and drain the liquor. The screen is extremely long-wearing and can simply be turned around to double its useful life. In addition, B&P screens do not require filing or hand fitting to install like most multi-segment screens, and the B&P screen cannot lift or dislodge from the basket.
 
The design of the basket and screen account for the high capacity of the pusher centrifuge. Oblong holes or slots are milled in the basket to provide maximum basket backwash capability. Backwashing preserves the liquor drainage capability by periodically removing any bad crystallization products that would otherwise plug the screen. Milling these baskets slots also reduces the mass of the rotating components without sacrificing required strength. This contributes greatly to long bearing life and rotational stability. The hydraulic end of the machine contains many features that help minimize maintenance costs. The base of the machine provides rugged support as well as a reservoir and housing containing all hydraulic system components. 
 
Since all hydraulic piping and components are contained within the base, the system cannot pump dry if a leak develops. The hydraulic pump is belt-driven from the main motor. The single motor stores the momentum from the rotating basket components and uses it to absorb pressure peaks and power surges from the hydraulic pump. Because all power requirements are satisfied by a single small motor, the B&P pusher centrifuge is extremely energy efficient. Pump suction is submerged, greatly reducing noise levels and eliminating the possibility of air cavitation or entrainment which could reduce pump life. A heavy-duty hydraulic hose on the pump discharge isolates vibrations and absorbs hydraulic shocks on stroke reversal, maximizing component life. 
 
Shafting Assembly

The shafting assembly is the backbone of the B&P pusher centrifuge. B&P's experience with high tonnage heavy-duty abrasive cakes has taught us how much muscle to design into the shafting to provide reliability under demanding conditions. A hollow shaft, colored green, drives the basket and is supported by widely spaced heavy-duty bearings for maximum rotational stability. The pusher shaft and piston inside the hollow shaft provide reciprocating action and support the pusher plate and funnel. This S-36 shafting has three bearings, one just behind the basket, and a double bearing assembly at the transfer bushing. These last two bearings assure the transfer bushing never touches the rotating shaft. 
 
Most normal maintenance operations can be completed with the shafting in place. The shafting is designed so where is confined to the least costly parts by utilizing liners, inserts, bushings, piston rings, and other renewable components. Wearing parts of B&P shafting are readily accessible, and since they are originally manufactured on numerically controlled machine tools, they are completely interchangeable with replacement components.

A History of Reliability & Quality

The B&P pusher centrifuge is a remarkably reliable machine. Over 95 of B&P's largest and most popular model, the S-36, have been ordered since they first became available in 1963. Since then, none of the stressed components, including the basket hub, pusher shaft, hollow shaft, or drive shaft has ever failed in service, and bearing failure is nearly nonexistent. But the outstanding performance, and reliability of the B&P pusher centrifuge are only part of what B&P has to offer. B&P will service and support you from the moment you come to us with a chemical processing challenge, and throughout the life of your B&P pusher centrifuge. Initially, our staff of chemical engineers will analyze your needs and determine the best B&P pusher centrifuge for your individual separation process. Where your separation is a traditional one, like salt from dilute caustic in chloralkali plants, or a specialized one like acid removal from military nitrocellulose, or dilute acid cottonseed dillinting, B&P can modify its pusher centrifuges to meet your special needs. And to help you determine exactly how your specific feed slurry will process in a B&P pusher centrifuge, B&P's 15,000 square foot technology center is always available to you. 

On-Site Evaluation

If you can't ship your sample to be B&P, B&P will bring their test equipment to your plant or laboratory. Based on years of experience, B&P can reliably extrapolate your test results to full-scale plant flows. Once your pusher centrifuge is built to your specifications, B&P has a team of technical service experts ready to assist you in the installation and start up of your machine. Our team will also work with you to plan and maintain an adequate inventory of replacement parts. B&P holds complete records of all the machines we sell, including original specifications and parts numbers. So any time you need a replacement part, just contact us, we'll have complete information on your pusher centrifuge on file. The B&P pusher centrifuge has a reputation as a rugged machine that operates reliably year after year with minimal repairs. However, B&P maintains a crew of experienced service specialists who will be dispatched to help you get your machine back in service should the need arise. B&P can also execute major rebuilding projects on old machines often at no more than a fraction of the replacement cost of the machine. 

No Better Choice than B&P

The long basket slow speed single stage pusher design, exclusive to B&P, will help you produce at minimum cost and maximum efficiency, and the superior operating reliability built into every B&P pusher centrifuge, will keep you on line and making money from the moment of installation and for years to come. B&P's whole approach to equipment supply emphasizes quality equipment, reliable operation, professional service, and unparalleled customer support. For the ultimate in pusher centrifuge design and operation, there's no better choice than B&P.