Re:
Hi Jessica,
I recommend a trowelable epoxy lining. Our Eli-Cote range of wear-resistant mortars are filled with varying percentages of alumina, silica carbide and ceramic beads.
The advantage of trowelable ceramics is that you can apply them quickly and easily to any thickness desired and can patch over particularly worn areas periodically without having to remove a metal liner and replace the whole section.
It is difficult to guage the extension in working life that will be realised by trying an Eli-Cote lining. This is due to many variables e.g flow rate, operating temp etc.
If you are willing to try out one of these wear-resistant linings, or need more technical detail, please do not hesitate to ask.
Regards,
Aram Friedrich
globalresins@hotmail.com
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Wear Reistant Blowing Seals
Hi Jessica,
I don't know of a proprietary blowing seal capable of withstanding the very aggressive conditions you describe. However, there are various methods of protecting the wear surfaces of your blowing seals, but it is a matter of 'you get what you pay for.'
Tungsten coating and Ni-hard liners are options, but I don't think that either of these will give your blowing seals a life expectancy greater than has already being achieved. 95% alumina ceramic, or engineering grade reaction bonded silicon carbide (as opposed to refractory grades), will increase the wear life of your seals significantly.
The bore of a 380mm blowing seal fitted with a fully sintered and diamond ground 95% alumina ceramic lining will wear at a rate of approximately 0.15mm per annum, operating in the conditions you describe, if the ceramic vane sealing blades are changed at 6 monthly intervals.
A diamond ground 95% alumina ceramic should exhibit around 20 - 30 times greater wear resistance than cast iron and a good engineering grade reaction bonded silicon carbide around 150 to 200 times.
With regard to your pneumatic conveying pipe work, I suggest that you consider fully sintered 95% alumina ceramic lined steel pipe.
If you would like to contact me at mike@omegaslate.com, I would gladly e-mail you Powerpoint slide shows on these subjects.
Perhaps, you would like to take a look at the following Web pages for further information on wear and corrosion resistance:
http://www.omegaslate.com/physical.htm
http://www.omegaslate.com/advancedceramics.htm
http://www.omegaslate.com/advancedceramics.htm
http://www.omegaslate.com/producti.htm
For information relating to blowing seals, you might like to take a look at the following Web sites:
http://www.dmn-nwh.nl/
http://www.bushandwilton.com/
http://www.alexw.demon.co.uk/
Regards,
Mike Griffiths. ■
Fina Microsilica
you can use 2 materials to protect your system. Densit and Ceramite.
These materials are the best becouse they contain microsilica in them.
The best methot to stop or deaccelarate the wear is, to protect the system by wear medium.
You can contact to snu@veezy.com.
BR
Semih US ■
Elkem Ceramite
Dear Jessica,
Elkem Ceramite comprises a range of mortar and castables with ultra-high strength and durability. It is designed to give superior performance where wear resistance is critical.
The properties of the various Ceramite grades are highly dependent upon the chioce of aggregates (e.g. bauxite or SiC).
Hence, in order advice you the best choice of Ceramite I would need some more specific information about your application.
Please contact me if you would like further information on Ceramite in order to solve your wear problems.
Best regards,
Aase Hundere
aase.hundere@elkem.no ■
Blowing Seals
Thank you all very much for your prompt replies to my posting.
Please correct me if my interpretation of your offered solutions is incorrect. My understanding is as follows:
1.CEMENT SYSTEMS: Mr. Semih and Mr. Hundere both offered solutions that appear to be aggregate filled cements and I am concerned that the sub-micron to 1mm silica grains that pass though our blowing seals will wear away the cement bonding very quickly, therefore exposing and freeing the hard aggregate that gives the lining product its wear resistance. Surely, this type of product is more suited to protection against soft aggregates rather than very hard, free flowing and sharp silica that will scour the surface of the lining. I suspect that the ability of the cement system to resist penetration from the hard silica grains is severely restricted. The velocity of air pressure and free silica leaking back past the vanes moving through the empty side of the blowing seal is quite high and, in effect, grit blasting of the valve bore and end plates occurs.
The other problem I anticipate is one of installed accuracy, in that we need to run the vane sealing blades very close to the lining system. Ideally, we need to able to ensure and maintain an accurate gap between the vanes and the lining bore/end plates of 0.003" to 0.005".
How are the cement based linings installed and what accuracy can be achieved?
2. EPOXY SYSTEM: Rightly, or wrongly, I envisage the epoxy resin filled system, suggested by Mr. Friedrich, performing similarly to the cement based systems and ask the same questions regarding installed accuracy and the ability of the expoy resin to resist the scouring action and penetration by the silica.
3CERAMIC SYSTEM: Thank you Mr Griffiths for the information and data you have supplied. You are quite specific regarding performance for ceramic systems. However, I have little knowledge of ceramics and, again, I question the ability of the alumina ceramic to withstand the scouring and penetration by our silica.
The authority and detailed nature of your reply to my posting suggests to me that you might have specific experience with silica being handled through blowing seals. Do you have specific instances, real applications, that would give me the confidence that I require to proceed further?
Thank you all once again for your assistance and I hope that I am not considered as being too pedantic.
Jessica Westwood. ■
Re: Blowing Seals
Dear Jessica,
Ceramite is rightfully a cement-bonded castable, however due to its specific combinaiton of microsilica, cement and other addtives in the bondphase one achive a very dense structure.
For your information Ceramite has been used in pipelinings for pneumatic transport of rockwool (fines) and Nepheline Syenite** , (mean particle diamter = 250 microns.) Lifetimes of the pipelines (old pipe line: standard steel) were improved from 1 week to 100-200 weeks.
Ceramite linings are casted and normally prefired. Accuracy +/- 1 %.
If you have further interest for discussion of Ceramite – I would need some more specific information about impact angle, temperature velocity, pipe dimensisons etc.
Best regards,
Aase Hundere
aase.hundere@elkem.no
** Nepheline syenite is a mineral with Mohs hardness 6. ■
Blowing Seals
Thank you Mr. Hundere.
The blowing lines are 150mm bore.
The temperature is no more than 100 Centigrade.
The hardness of the quartz is between 1100 and 1200 Vickers, or 9 on the Moh scale.
The particle velocity is around 80 metres per second.
The bends are 1000mm radius.
I am still not happy that the cement bonding will be hard enough to stand up to the scouring action in the blowing seals, where we need to maintain an accurate and long lasting surface finish.
I have just been informed by one of our engineers that we tried Densit in our blowing lines a few years ago and it lasted 6 hours. Is Ceremite similar to DENSIT.?
Jessica Westwood. ■
Re: Blowing Seals
Dear Jessica,
I can surely understand your scepticism after your previous trial with Densit. However, Densit as Ceramite comprises a range of products. So before we close this discussion I would appreciate knowing the Densit quality which was tested.
Best regards,
Aase Hundere ■
Blowing Seals
Thank you Mr. Hundere.
We tested 2 bends one lined with WEARCAST 1000 and the other lined with WEARCAST 2000. The WEARCAST 1000 lasted approximately 12 hours and the WEARCAST 2000 approximately 6 hours. In both cases, the 150mm NB linings were cast into 8" schedule 40 pulled steel bends. Expanded polystyrene was used to shape the bore, which was offset to achieve a thicker extrados. The sand blew a hole through the DENSIT lining just after the start of the bend, at the initial impact point.
I didn't carryout the tests and the engineer who was responsible at the time is no longer with us. The above data is from our maintenance records of 1996. As you can appreciate, the wear problem has been with us for some time. Cast basalt failed in 3 days, soft rubber lasted 2 weeks and I can't find any references to tests carried out with alumina or silicon carbide ceramic linings in our maintenance records.
I have found information published by DENSIT specifying that WEARCAST 2000 looses a minimum of 115 cubic cm's when subjected to a flow rate of 350 grms/min of 0.18mm quartz sand travelling at a velocity of 33 metres/sec, at a 45 degree angle of incidence, over a 18 hour test period. WEARCAST 1000 losses 60 cubic cm's under the same wear regime.
Jessica Westwood.
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Blowing Seals
Hi Jessica,
Quartz, with a hardness of 1100-1200 Vickers, travelling into a pipe bend at a velocity of 80 metres per second is almost too aggressive for a 95% alumina ceramic bend lining system. 95% alumina ceramic is suitable for lining the straight pipes, though. For bend linings, you would need to consider using a 99% alumina ceramic or an engineering grade reaction bonded silicon carbide with a hardness of 3500 Vickers and an average grain size of less than 10 microns, which should be capable of handling your quartz at velocities slightly in excess of 100 metres/sec.
95% alumina ceramic is suitable for lining your blowing seal rotor bore, end plates, vanes sealing blades and the rotor shafts that rotate in the stuffing boxes. The hardness of a 95% alumina is normally around 1100 Vickers, but the pressure of the quartz on the wear surfaces of the lining system is minimal. Blow-back velocity in the non-product side of the blowing seal will be quite low if the clearance between the rotor vane sealing blades and the rotor bore/end plate linings is not allowed to exceed 0.010".
A good wear resistant 95% alumina ceramic will have an average grain size of <10 microns and a 99% alumina can have an average grain size of 3 to 5 microns. The practical effect of reducing grain size is the narrowing of the glass bonding matrix that holds the alumina grains together in the formed ceramic. The wider the grain boundary, the easier it is to erode the bonding matrix which, inevitably, results in the release the hard alumina grains from the ceramic. Generally speaking, reducing the size of the bonding matrix results in a more wear resistant ceramic with increased fracture toughness - providing the ceramic is fully sintered.
If we take a 99% alumina tile, 95% alumina tile and a mild steel tile, all with a 6mm thickness, and subject each in turn to 10 concentrated high velocity (120 metres/sec) sand blasting operations, with the sand flow at 90 degree to the tiles, we find that 50% the mild steel sample tile thickness has been eroded, a hole has been blasted straight through the 95% alumina tile after 8 blasting operations, and the wear face of the 99% alumina tile has been indented by approximately 1mm.
The ability of the 95% alumina ceramic tile to resist the effect of the high velocity sand impingement and the consequential surface crushing of the glass bonding matrix, is improved immensely with the reduction of the blasting nozzle angle of incidence. Reducing the blasting nozzle angle of incidence reduces the sand pressure on the wear surface of the ceramic and crushing of the bonding matrix ceases.
I understand your concerns regarding lining system selection and performance and your need to make the right decisions. The vast majority of the 'day to day' wear problems that I am involved with are caused by quartz. I can put you in touch with companies who have solved wear problems as aggressive as yours with advanced ceramics.
Mike Griffiths. ■
Re:
Hello,
with these service conditions (in particular in view of the particle velocity at around 80 metres per second), two materials would be appropriate:
1.) alumina ceramic
2.) even more suitably, silicon carbide ceramic, but this involves higher costs.
A high wall thickness (1") has to be chosen.
Details on these ceramic lining materials are outlined on our website http://www.scholten-gmbh.de
Please do not hesitate to get in touch with us for further details.
regards
Dr. Jürgen Scholten
Th. Scholten GmbH & Co., Germany ■
Re: Blowing Seals
Originally posted by Jessica Westwood
Thank you Mr. Hundere.
We tested 2 bends one lined with WEARCAST 1000 and the other lined with WEARCAST 2000. The WEARCAST 1000 lasted approximately 12 hours and the WEARCAST 2000 approximately 6 hours. In both cases, the 150mm NB linings were cast into 8" schedule 40 pulled steel bends. Expanded polystyrene was used to shape the bore, which was offset to achieve a thicker extrados. The sand blew a hole through the DENSIT lining just after the start of the bend, at the initial impact point.
I didn't carryout the tests and the engineer who was responsible at the time is no longer with us. The above data is from our maintenance records of 1996. As you can appreciate, the wear problem has been with us for some time. Cast basalt failed in 3 days, soft rubber lasted 2 weeks and I can't find any references to tests carried out with alumina or silicon carbide ceramic linings in our maintenance records.
I have found information published by DENSIT specifying that WEARCAST 2000 looses a minimum of 115 cubic cm's when subjected to a flow rate of 350 grms/min of 0.18mm quartz sand travelling at a velocity of 33 metres/sec, at a 45 degree angle of incidence, over a 18 hour test period. WEARCAST 1000 losses 60 cubic cm's under the same wear regime.
Jessica Westwood.
Hello Jessica,
It may be a viable option to try a soft material in this application. Our K-Tex abrasion resistant rubber is widely used on silica sand processing plants. The top temperature limit of K-Tex is around 70 degrees C. What is the normal operating temperature of your system? another option would be our K-Alox high alumina ceramic but installed in a larger radius bends, can your system cater for larger radius bends? Ideally, we would like to look at your conveying system in total so that we can identify possible modification to reduce the high wear that is taking place. I look forward to your reply.
Robin Kiddie
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Wear Resistant Bends.
Dear Jessica,
In my opinion, instead of attempting to develop a wear resistant surface, you should consider a bend design that allows for accumulation of the material being transfered in the bend.
These solutions require some trial and error and some engineering effort. However it looks like you have dedicated a sizable effort on the issue.
There are off the shelf designs but at the moment I can't give you a link to their site.
Let me know if you need more info on this subject.
Antonio Reis
http://www.vitrom.com ■
Pipe Bends
Thank you Mr. Kiddie,
We have tried soft rubber and it lasted approximately 2 weeks in our bends.
Thank you for your offer. We have decided on a line of action and I may be back in touch if we are again unsuccessful.
Regards,
Jessica Westwood. ■
Pipe Bends
Thank you Mr. Reis,
We have tried the bends you describe, they were called Blo Bends, but they didn't last very long either.
Regards,
Jessica Westwood ■
Re:
Dear Mrs. Westwood,
In pneumatic conveying lines wear and abrasion increasing very fast with the particle velocity.
In simplistic terms the relationship between erosion and velocity can stated as
Erosion=constant x velocity**N
where the exponent N can varies between 2 and 6. As a guideline, it is generally accepted N=3 for the most industrial applications.
If possible, I would propose to set the conveying velocity down to moderate values (between 18 - 25 m/s). As I understand, your particles are very fine, therefore 18 m/s should be sufficient.
Try first to eliminate the roots of your problem (high velocity) and then think about "normal" wear protection.
Best regards
Klaus Schneider ■
Re:
Dear Jessica,
In my opinion, unless you decrease the velocity of the particles to bellow 50 meters per second it will be very difficult to provide a solution to your problem.
If you must maintain the current process parameters, than it seems practical that the design efforts are towards minimizing the cost of the replacement parts. As an idea, in the impact zone of the turns, a flat wear plate can be installed. One would replace the wear plate when needed and the plate will become a consumable in the process. ■
Re:
I totally agree with Herr Schneider, you must have the reduction in conveying velocities as your priority. You should consider having a stepped bore conveying line installed, in conjunction with ensuring that adequate spacing exists between the bends in the system (typically 5m +), in order to ensure that the powder can be fully entrained before reaching the next bend in the system. A stepped bore system will not only reduce the velocities, but also the pressure drop in the line - which should help to reduce the level of air leakage (and hence leakage / wear past the tips of the blowing seal feeders).
If you want to talk over this option in more detail, please feel free to contact me.
Regards
Richard Farnish ■
Velocity Reduction
I agree that lowering velocities will result in reduced wear.
I came across a 300mm nominal bore ceramic lined rotary valve last week and it exhibited a wear problem that I feel is relevant to this discussion.
I have attached a jpeg of the rotary valve, which is used to feed very abrasive stone dust into a pneumatic conveying system. The rotor has hardened steel sealing blades along the periphery and sides of each rotor vane, and alumina ceramic bore and endplate liners are fitted. During normal operating conditions, each of the hardened steel rotor vane sealing components wore by just over 4mm in approximately 4 weeks. The wear on the ceramic end plates is negligible, as can be seen in the photograph.
There are situations where it is not feasible, usually within existing plant layouts, to adopt larger diameter pipe bores and long sweeping bends. Silica can cause wear in plant and equipment at quite low velocities; a sand storm can do a good job of removing the paint and rust from a vehicle in a relatively short period of time. - whichever way you look at it, swirling air and sharp sand is an abrasive combination.
Attachments
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Re:
A client has purchased a ceramic lined rotary valve for an abrasive application. The rotor is fitted with wear resistant hardened steel blades (see attatched photograph), but the plant will not be operational for 2-3 months. On reading the previous message I am concerned about the ability of the rotor to cope with the abrasive material being handled.
The 12" diameter valve is fitted to a sand drier cyclone and is discharging into an 8" pneumatic conveying pipeline.
My question is: If the rotor vanes wear as quickly as those mentioned in the previous posting, is there a viable solution to the problem?
Regards
Dave
Attachments
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Re:
Mr Truman,
Having seen the image of the rotary valve (but lacking any information regarding the bulk solid or operating conditions for the installation), I would like to make the follwing comments:
Firstly, the wear of the seals will be at its highest rate at the position in the rotary valve where the air leakage velocity is at its highest. This point will be just before the tip reaches the vessel outlet on the "clean" side of the rotary valve (i.e. the air pressure will have reduced as it leaked past successive tips). It would appear that your rotary valve has no provision for venting from the body, which would serve to vent away most of this leaked air prior to it reaching the upper regions of the valve body. This approach will not eliminate the wear, but may give a slight increase in service life (all this being subject to info on the material, air pressures, etc.).
An alternative, is to use two rotary valves (one above the other), where the upper valve meters the abrasive material at a lower rate than the valve beneath (which provides the "air lock" function into the system). Obviously, the lower valve must be able to feed the bulk solid away at a higher rate than the valve above can fill, such that the lower valve does not run "full" - hence wear is reduced. Adequate venting will still be required of course!
Wear in the upper rotary valve will have little consequence since it is simply a metering device and the lower valve will have a longer service life.
Hope this helps out!
Regards
Richard Farnish
The Wolfson Centre for Bulk Solids Handling Technology
Univ. Greenwich, London
http://www.bulksolids.com ■
Re:
I agree with Richard, regarding the theoretical effect of non-product side air venting on rotor vane wear. High wear rates in rotary valves are usually caused by high velocity, and hard grit laden, air leaking past the non-product side vanes; the air venting reduces the pressure and, therefore, killing the air velocity - in theory, at least. However, in practice, there are still many vented rotary valves that have needed to be ceramic lined in order to achieve a viable operating life.
I suspect that the chances of rapid wear of the sides and periphery of your client's valve rotor vanes are quite high. It is likely that the wear pattern will be as severe as the application depicted by the valve photo in my previous posting, depending on the conveying system pressure.
The solution is quite painless and quite quick to implement. 6mm thick alumina ceramic vane sealing blades can be fitted. The effect of fitting ceramic vane sealing blades should be to decrease the vane wear from, say, 4 mm per month, to something in the order of 0.08 mm per 6 month period. I am not saying that this rate of wear life increase is cast in stone, but I have seen similar wear life rate increases achieved, many times, with valves handling of high silica powders.
The attached jpeg shows a valve fitted with ceramic lined rotor vanes.
Attachments
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Wear Resistant Materials
I graph below gives and indication of the relative wear life of various valve lining materials, against cast iron.
Attachments
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Re:
Just as an aside, if vent lines are installed it is extremely important that they are sized according to the air leakage rate of the rotary valve. It is important to appreciate that the vent line is (in effect) a pneumatic conveying line in its own right, and must be sized to enable material to be entrained in the air stream, but also such that excessive back pressure does not exist such that its function is impaired. It is not unusual for some types of operational problem to be traced back to inadequate sizing of the vent lines. It is attention to the details, like this, in a system that can have a major impact on overall performance an equipment longevity.
Regards
Richard ■
Re:
Quite so, Richard. However, this is another area where practice can out do theory in certain circumstances. A small amount of moisture can cause a build-up of powder that might result in a blockage of the air vents. Air vent blockage is not so much of a problem with free flowing materials, such as sand, but it can be with powders that readily absorb moisture and set like concrete when they dry out.
It is a very good ideal to air vent RV's that are to be used with abrasive powders. ■
Re:
What is the maximum temperature that ceramic lined rotary valves can be used at?
Regards,
Henry ■
Rotary Valve Bearings
I have a an annoying problem with rotary valve bearings and am wondering if there is a simple answer.
My problem is the frequent seizure of outboard bearings. Is there a proven way of keeping the dust away from the bearings? ■
Re:
Henry,
Have you considered air purge seals?
Regards
Richard Farnish ■
Re:
Henry,
I have encountered this problem too. I have used the method shown on the enclosed drawing on a number of valves and it seems to work pretty well. Best of all, it is cheap and doesn't need any modifications to the valve!
I hope this is of some use to you.
Regards
Dave
Attachments
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Re:
Originally posted by Henry
What is the maximum temperature that ceramic lined rotary valves can be used at?
Regards,
Henry
Henry,
In theory, the ceramic components could work quite happily in temperatures up to 1350 degrees Centigrade; however, I am not aware of any ceramic lined rotary valves working at anything like this sort of temperature.
The ceramic lining systems can be bonded into a rotary valve and, were the operating temperature is too great for organic adhesives, they can be welded in position.
The problem in using advanced ceramic in high temperature rotary valves is one of successfully accommodating the multiple differential expansion rates of the valve body, cement grout, ceramic lining and the rotor, without over stressing the ceramic components.
Best regards,
Mike. ■
Re:
I have had extensive experience with abrasion of rotary valves. Ceramic lining works very well to prevent wear of the valve but MUST be used with very effective shaft sealing.
The MID TWA extreme duty ceramic lined valve has been installed in plant handling slate with a high silica content. A standard rotary valve lasts only a few days in this environment. Even a ni-hard valve only lasts 6 weeks. We installed a TWA ceramic lined valve with mechanical shaft seals and the valve lasted for 14 months before refurbishment was required. This only cost a fraction of the price of a new valve.
The main problem with ceramic lined normal valves is the cast iron end covers wearing away as the product passes the gland packer seals. These seals are very old technology and should not really be used on rotary valves. The MID mechanical shaft seals virtually never leak, never require maintenance and are utterly reliable, even on extremely abrasive products.
For more information see:
www.mid.uk.com
Alex Marshall. ■
Re:
Hello Mr. Marshall,
I have been looking for mechanical seals that virtually never leak and are utterly reliable for quite some time. I would be grateful if you would explain the main differences between your mechanical seal and the more common mechanical seals that don't work very well in stuffing boxes?
Thank you.
Jessica. ■
Re:
Normal stuffing box seals rely on a compressible gland packing that is forced to expand by a follower. This squeezez the shaft and expands onto the housing making a seal. This is effective when sealing liquid systems but has real problems when used on a dry system, especially if the product is fine. The product gets under the packing and starts to wear away the shaft, causing scoring. Usually the shaft then has to be sleeved to repair it.
The MID mechanical seal is totally different. It uses two chilled iron rings which are ground and lapped together as a pair. They are extremely hard- around 700 Brinell. The two rings are forced together by a spring on each side which pushes the rings together. This seals the shaft and also stops product from getting between the rings.
We use mechanical seals on extremely fine products, similar in size to face powder and they work very well. The valves we have working on slate, when returned for refurbishment after 14 months, usually have the same seals put back in the valve as they are unworn even after being in a very extreme environment for shaft seals.
Please call me on +44 (0)115 9382154 or email alex.marshall@mid.uk.com and I can forward some pictures to give you a better idea.
Alex Marshall, MID. ■
Re:
Thank you, Mr. Marshall,
I am intrigued and would like to find out more about your chilled cast iron mechanical seals. I can understand how such a seal might work with talcum powder, but I am not sure why it works so well when called upon to seal air pressure in the presence of an abrasive mineral such as a sharp grained silica powder. We use class 40 grey cast iron, with a hardness of around 250 Brinell, for our RV bodies. 700 Brinell equates to between 650 to 750 on the Vickers hardness scale (I don't have hardness conversion tables to hand at the moment, so I can't be exact). We have used alumina ceramic mechanical seals, with harnesses of 1100 and 1500 Vickers, without much success. We are currently using reaction bonded silicon carbide mechanical seals, which have a 3500 Vickers hardness, and these appear to be lasting quite well.
Is there something different in the design of your RV's that is likely to account for the excellent wear life of your cast iron mechanical seals? Does the abrasive powder, passing through your valves, get near the mechanical seals, or is an auxiliary method of deflecting the powder away from the seals used?
I don't understand why chilled cast iron seal faces are so resistant to abrasive wear within a RV stuffing box application, particularly as the seal face hardness is only 3 times greater than regular grey cast iron. It is difficult to see, with abrasive powder sloshing around the rotor shaft seals, why they are so effective. Using a closed rotor and a decent gap between each side of the rotor and the end plates, I can envisage a situation where powder, or at least not much powder, is not getting to the seals. Is this the reason why your mechanical seals work so well?
Regards,
Jessica. ■
Re:
The MID mechanical seals work by using the very close tolerance lapped faces of the seals to prevent product from getting anywhere where wear is a problem.
The TWA does have a closed end rotor but when used in a pneumatic conveying application (as most are) the product tends to be blown all around the casing of the valve, including the area around the shaft seals.
We also fit our seals to standard valves with open ended rotors and there is no difference in performance. The main difference between all of our rotaty valves and everyone elses is we weld our rotor blades to a tube instead of the solid shaft- this means we can fit the seals inside the tube and so avoid the product flooding the seals.
The seals are used extensively on ash handling plant and never need maintaining- we even get calls to see whether we can retro-fit our seals to other types of equipment such as screw conveyors etc.
If you would like to talk to one of my customers handling slate about the seals and the TWA rotary valve then please contact me. Even better, I can send you some photos if you can forward your email address.
Alex Marshall, MID.
alex.marshall@mid.uk.com
+44(0)115 9382154 ■
Silica Wear
Dear Jessica.
we have handled iron ore fines fom sub micronic to 1 cm , carbon steel bends lasted less than one day, using 304 stainless steel , the 0.7 inch tk pipe lasted 1 month , using martensitic overlays the pipe lasted 3 years. using austenitic matrix oriented crome carbide overlays the pipe is believed to last 16 years.
We are further developing the alloys to further increase the application at high temperatures and reduce cost , 150 mm pipe is one of the standard pipe sizes alrready in use. If you are still interested I will be glad to supply further information.
By the way we eliminated the long radius bends and installed x teebends , to reduce the impact and installed replaceable bottom impact plates to simplify maintenance .
Regards
marco ■
Re:
Jessica,
You may try out with High Alumina more than 90% Alumina product for the same. If you need furhter information you may visit our site www.hofmannindia.com or write to us on sunil@hofmannindia.com
Thanks
Sunil ■
Rotary Valve Seals
Jessica .
would you consider redesigning the seal ?
I used to work for HYL steel technology , and I used to design their dossifier valves , ths rotary valves do not use mechanical seals . they rely in a stuffing box with redundant o rings and gas/grease injection.
they work with iron ore and sponge iron for more than one year between repairs.
Regards
marco ■
High Wear Rates
Hi Jessica,
I am interested to learn what course of action U have decided to try.
In the cement industry, we do have pneumatic conveying wear but not as bad as yours...we use Basalt normally but ceramics are used in bad applications esp. where interstical wear/cutting can occur esp. with fine materials.
Cheers
James ■
Convert To Low Velocity?
I have read your post and the replies with interest (and can sympathise with your problem). Perhaps the best way forward is to deal with the cause - the extremely high velocity. My company have developed a Dune Phase System which transfers granulates at approximately 2-3 m/sec and this eliminates any wear problems (and product damage).
The technology looks like a conventional lean phase system and existing systems can easily be converted without changing the piping. The only problem is that it will not cope with powders which can plug and form a seal in the pipe because of dust present in the mixture. If it has the consistency of fine sand then it will be ok.
A test rig is available in the UK should you wish to use it. The following pic shows a Dune in a pipe :
http://img56.photobucket.com/albums/...dFrame2b.jpg
Send me a private message and I will provide further details if you are interested. ■
Wear
Dear jassica
I am sure we can solve your problem. We work with wear problems and check our home page. www.danalco.dk
Will you please send me your drawings and some more information, I will send our suggestions.
It is very normal in hardfacing no materials can sustain impact and abrassion. We have a technique to meet these conditions.
I can give you maore details as we do`nt want to open it to all.
It our bread & butter.
with regards
chodavarapu ■
Untitled
Hello,
We pneumatically convey a dry fine silica powder and are suffering heavy wear in our pipe systems and in our blowing seals. We are refurbishing each blowing seal, 8 in total, between 10 and 14 times per annum with hard metal liners.
Does anyone know:
1. of a wear resistant blowing seal with the potential to significantly increase operational life beyond that of our current seals?
2. a wear resistant pipe or lining system that will improve the operating life of our pneumatic conveying pipe work? We are using heavy gauge steel pipe at the moment, which lasts around 4 weeks on average.
Thank you.
Jessica Westwood. ■