14th October 2001, 9:48
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.
14th October 2001, 17:28
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.
15th October 2001, 10:10
WEAR REISTANT BLOWING SEALS
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 email@example.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:
For information relating to blowing seals, you might like to take a look at the following Web sites:
15th October 2001, 16:58
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 firstname.lastname@example.org.
16th October 2001, 7:57
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.
16th October 2001, 9:37
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.
3 CERAMIC 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.
17th October 2001, 13:36
Re: Blowing Seals
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.
** Nepheline syenite is a mineral with Mohs hardness 6.
17th October 2001, 15:32
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.?
18th October 2001, 10:05
Re: Blowing seals
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.
19th October 2001, 9:09
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.
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