Thank you for visiting Dos Santos International

Welcome to Dos Santos International, LLC where we are the world’s foremost authority on high angle conveyor applications and design of sandwich belt type high angle conveyors. We invite you to learn more about our most reliable and economical solution for your steep angle and vertical high-tonnage conveying requirement, our Snake Sandwich Conveyor.

DSI was founded on its extensive worldwide experience in sales, engineering, and construction of bulk materials handling systems and equipment. This has included major contributions that have expanded the range of bulk handling and transport solutions. Most notably advances in sandwich belt high angle conveyors have led to their worldwide utilization. DSI’s expertise spans a wide range of materials handling systems and equipment including high angle conveyors, high powered, high capacity, high lift slope conveyors and long overland conveyors utilizing the very latest technology.

Dos Santos International is the ideal consultant and supplier for this technology and we welcome you to browse our pages and learn more about our expertise and worldwide presence. We look forward to the opportunity to fulfill your materials handling needs.

Joseph A. Dos Santos Qualifications in Sandwich Belt High Angle Conveyors

Background - Origins of Sandwich Belt High Angle Conveyors, Innovations of J. A. Dos Santos

The sandwich belt concept was first introduced in the early 1950’s (1&2).  Then, known as “conveyor with cover belt”, it was used at the boom conveyor of a bucket wheel excavator, in a German lignite mine.  The “cover belt” was laid over and pressed onto the conveyed material so that the conveying angle could be increased, thus increasing the excavated bench height.  Other various cover belt concepts soon followed. These systems did not achieve a lasting success.  By end of the decade they were largely abandoned.

The first lasting success in sandwich-belt conveyors was achieved in the 1970’s with development of the Loop Belt for self unloading ships.  The Loop Belt, a C-shaped vertical elevating system, demonstrated that very high volumetric rates could be achieved using all conventional conveyor components and equipment including smooth surfaced rubber belts.  An inner belt is supported along a convex curve path of troughing idlers, while an outer belt wraps around the bulk material and the inner belt.  Hugging pressure on the bulk material is by radial pressure derived from the inherent tension of the outer belt and the convex curvature of the C-profile. Very wide belts, to 3048 mm (120”), are used to elevate various bulk materials continuously from the ships holds to the deck.  A discharge boom conveyor then transfers the bulk to shore.  Though used in many self-unloading ship applications, the Loop Belts did not develop further technically or commercially.  Limited to a C-shaped elevating profile they did not find many land based applications.

In 1979 the Bureau of Mines, United States Department of the Interior, funded a major study entitled “High Angle Conveyor Study”(1).  The purpose; to advance the state-of-the-art in high angle conveying; to develop high angle conveying systems that would reduce the haulage costs in open pit mines.  The study was awarded to a prominent U.S. engineering company.  Joseph A. Dos Santos- Project Engineer was assigned to the Study.

The Bureau of Mines Study was the beginning of the Dos Santos long involvement in and significant contributions to the development of high angle conveyor technology.

The study considered all high angle conveying methods.  It became clear to Dos Santos that the Sandwich-Belt concept offered the most promise for success.  Equally clear; it was the least understood.  His in-depth study and research produced the comprehensive theory of Sandwich-Belt High-Angle conveyors entirely rationalized in the conventional conveyor technology.  The prophecy: “A sandwich belt high angle conveyor system, utilizing all conventional conveyor components and equipment, subject to the conventional rules of their design, will result in the performance characteristics of a conventional conveyor system, that is, low cost, high reliability.”  The two volume “High Angle Conveyor Study” report, published in 1981, included the Dos Santos theory and various sandwich belt conveying methods by Dos Santos, pursuant to the theory.  Drawing from the success of the Loop Belt, Dos Santos Sandwich Belt systems included its best features but offered versatile profiles that could follow any high-angle path.

The Snake-Sandwich High-Angle Conveyor was cited as the preferred method and it was submitted for patent in 1981.  The Sandwich Belt High-Angle conveyor research and development was published more concisely in the 1982 landmark article “Evolution of Sandwich Belt High-Angle Conveyors” by Dos Santos and Frizzell(2).

Dos Santos Sandwich Belt High-Angle Conveyors Installations Record 1982-1997

Now recognized as a leading authority in the application and design of high-angle angle conveyors, J. A. Dos Santos was sought by a major U.S. manufacturer of conveyor systems and equipment.  He was offered the opportunity and challenge, to develop his innovations into commercial reality.  In 1982 Dos Santos accepted the challenge.   

By mid 1983, in only 9 months, Dos Santos designed, built and started-up the first large scale prototype sandwich belt high-angle conveyor pursuant to his published theory.  The unit featured 1524 mm (60”) wide belts, 35 meters (115’) length and adjustable incline angle, from 30º to 60º.  It was powered by variable speed DC drives.  An immediate success, the prototype demonstrated high angle conveying of widely varying materials, from light weight wood chips to heavy, course ores, at rates to 2900 t/h (3200 STPH).  This Dos Santos invention, originally referred to as “Mechanically Pressed Sandwich Conveyor”,(1&2) features fully equalized pressing rolls to hug the conveyed material and develop its internal friction.  It was patented in the U.S. and abroad in 1986.

Commercial success came slow initially, with only 7 units installed before 1990.  By 1997 however more than 80 units were in operation world wide.  These are located in the six civilized continents, in thirteen countries.  The installations vary widely in profile from compact C and S shapes, as small as 3.6 meters (12’) lift and 8.6 meters (28’) length, to long undulating profiles as high as 175 meters (574’) lift and 454 meters (1490’) length.  High conveying angles vary from less then 30º up to 90º (vertical).  The range and versatility of the Dos Santos designs is dramatized in Figure 1, where some of the various profiles are displayed at a common scale.  Materials handled vary widely in properties from light weight wood chips in pulp and paper applications to heavy course ores at copper and iron mines.  Belt widths from 500 mm (20”) to 2134 mm (84”) elevate the various materials at widely varying rates from .3 to 4250 t/h.  These sandwich belt high-angle units serve many industries including grain distribution, pulp and paper, municipal waste treatment and disposal, trans-shipment (including self-unloading ships and barges), power generation, construction and tunneling, and mining and processing.

Numerous published articles by Dos Santos document the progress in sandwich-belt high-angle conveyors from 1982 to 1997(3-38).

Figure 1: Various profiles of Dos Santos sandwich belt installations (to a common scale) dramatize the versatility

DSI Snake Sandwich High-Angle Conveyors Since 1997

In 1997 Dos Santos International was founded on the experience and accomplishments of its name sake, Joseph A, Dos Santos.  Dos Santos International presented an opportunity to return to the roots of the sandwich belt conveyors.  The many sandwich belt installations by Dos Santos, from 1982 until 1997 fully proved the technology and are a great success yet, the “Mechanically Pressed Sandwich Conveyor” was not the preferred system and did not fulfill the “prophecy”, requiring use of non-standard, special pivots and equalizer bars in the pressing mechanisms.  The “Snake-Sandwich” high-angle conveyor, the preferred system, fulfills the prophecy utilizing all and only conventional conveyor components and equipment.  There are no special pressing mechanisms.  Material hugging pressure is fully derived as radial pressure due to the inherent belt tension on a profile of alternating convex curves.

Progress in high-angle conveying continues at Dos Santos International.  The DSI Snake-Sandwich, the preferred method, now incorporates the vast experience of its inventor.  This includes improved inflection zones that insure continuity of hugging throughout the profile.

In 1997 and 1998 the partnership of Dos Santos International and EleVeyor Associates engineered, manufactured and installed three additional sandwich-belt systems, to elevate sludge, at waste water treatment plants in the U.S.A.

A DSI Snake, elevating iron ore, in a U.S.A. mine process plant, followed in 2001.

The latest DSI Snake was commissioned in July of 2003 at a steel mill in northern Spain.  Part of the carbon injection systems to the blast furnaces the Snake elevates raw coal the grinding systems.

Dos Santos published articles (39-43) continue to document the progress.

DSI Snake-Sandwich High-Angle Conveyor

The DSI Snake-Sandwich Conveyor is the only system to use only conventional conveyor equipment, components and smooth surfaced belts.  The system consists of two endless belts that share a common carrying path where the material is sandwiched between them.

Material is loaded onto the bottom belt between narrow skirts to achieve a well-centered material stream.  The top belt joins the bottom belt at the sandwich entrance where the material is captured and hugged between the belts prior to increase of the conveying angle.  Conservative rules of design ensure a modest material cross-section allowing ample, material free, edge distance so that leakage will not occur, even under the most aggravated belt misalignment conditions, or during occasional limited overload.

Beyond the entrance, the carrying sandwich, with material, begins its ascent (angle increase) along an inverted, vertical convex curve.  Here, the upper troughed belt is supported along and against closely spaced inverted troughing idlers.  The bottom belt imparts a radial pressure, due to its inherent belt tension and the engineered curved profile, suspending and hugging itself and the conveyed material, firmly yet gently, against the inverted troughed upper belt.  In this manner the material is continuously elevated to and through the first inflection zone of curvature reversal.  Beyond the first inflection zone the carrying belt sandwich with material enters another adjacent, opposite, vertical convex curve where the lower belt is troughed and supported, along and against closely spaced upright troughing idlers.  The top belt imparts a radial pressure, due to its inherent belt tension and the engineered curved profile, hugging itself and the conveyed material, firmly yet gently, against the troughed bottom belt.  Special variable troughing idlers, properly located and field adjusted, insure continuity of hugging through the inflection zone.

Additional adjacent, opposite, vertical curves with inflection zones between them allow engineering of the overall profile for the best path from loading to discharge.  At discharge, the belts separate to their respective head/drive pulleys where they are deflected and returned along independent paths to their respective tail, take-up pulleys.

In its simplest C-shaped profile the carrying path is along a single convex curve with no inflection zone.  In its simplest S-shaped profile two adjacent, opposite, convex curves are joined by a single inflection zone. By exploiting the inherent belt tension to impart a radial pressure, the DSI Snake Conveyor insures a firm hugging pressure to develop the internal friction in the sandwich, precluding any material slide back.  In fact, the safety factor against material slide back is well known as it is determined or selected when engineering the profile.  The DSI Snake Sandwich conveyor uses all and only conventional conveyor equipment and requires no mechanical devices to apply a hugging pressure.

Dos Santos Bibliography

  1. Mevissen, E.A., Siminerio, A.C. and Dos Santos, J.A., High Angle Conveyor Study by Dravo Corporation for Bureau of Mines, U.S. Department of the Interior under BuMines Contract No. J0295002, 1981, Vol.1,291 pages, Vol.II,276 pages.
  2. Dos Santos, J.A. and Frizzell, E.M., Evolution of Sandwich Belt High-Angle Conveyors. CIM Bulletin. Vol.576, Issue 855, July 1983, pp. 51-66.
  3. Dos Santos, J.A., Sandwich Belt High Angle Conveyors - Applications in Open Pit Mining
    • Presented at the 1983 AMC (American Mining Congress) Mining Convention, San Francisco, CA, Sept 11-14, 1983, published in proceedings.
    • Presented at the SME-AIME Fall Meeting, Salt Lake City, UT, October, 1983, published in proceedings.
    • Published in Bulk Solids Handling, Vol. 4 (No. 1), March 1984, pp. 67-77
  4. Dos Santos, J.A., Sandwich Belt High Angle Conveyors - HAC® - Evolution to Date. Bulk Solids Handling, Vol. 6 (No. 2), April 1986, pp. 299-314
  5. Dos Santos, J.A., High Angle Conveyors-HAC for Open Pit Mining. Bulk Solids Handling, Vol. ? (No. ?), September 1986, pp. 575-589
  6. Dos Santos, J.A. and Stanisic, Z. "In-Pit Crushing and High Angle Conveying in Yugoslavian Copper Mine.
    • Presented at the Mining Latin America, Int. Mining Convention, Nov. 17 - 21, 1986, Santiago, Chile, published in proceedings
    • Published in International Journal of Surface Mining 1, 1987, pp. 97-104
  7. Dos Santos, J.A. "High Angle Conveyor-HAC Provides Shortest Route to Train Loading Silos", Coal Prep 87, April 27-29, 1987, Lexington, Kentucky, U.S.A.
  8. Dos Santos, J.A., Sandwich Belt High Angle Conveyors - Broad Horizons.
    • Presented at CoalTrans ‘86, Amsterdam, The Netherlands, June 10-12, 1986, published in proceedings
    • Published in Bulk Solids Handling, Vol. 7 (No. 2), April 1987, pp. 229-239
  9. Dos Santos, J.A. and Wrede, K. L., High Angle Conveying Applications for Coal and Other Bulk Solids.
    • Presented at the Third Western Regional Conference on Precious Metals, Coal and Environment, Rapid City, South Dakota, USA, September 23-26, 1987, published in proceedings, pp. 215-226
  10. Dos Santos, J.A., McGaha, J.R., Modern Continuous Haulage Systems and Equipment.
    • Presented at Simposium Nacional de Seleccion de Maquinaria,Fundacion Gomez-Pardo, Madrid, Spain, December 15-17, 1987, published in proceedings (11 pages)
  11. Dos Santos, J.A., High Angle Conveyors-HAC’s for Surface Mining.
    • Presented at AMC MineExpo International ’88, Chicago, IL, USA, April 24-28, 1988, published in proceeds  (9 pages)
  12. Dos Santos, J.A., HAC’s for Pulp and Paper and Other Industries.
    • Presented at TAPPI Annual Meeting ’88, Atlanta, GA, USA, September 19-22, 1988, published in proceedings (6 pages)
  13. Dos Santos, J.A., McGaha, J.R., Modern Continuous Haulage Systems and Equipment. Bulk Solids Handling, Vol. 9 (No. 3), August 1988, pp. 303-308
  14. Dos Santos, J.A. Interview by Jon Jacobs, High-Angle ‘Hugging Conveyor Proposed for Port Operations. Bulk Transpo ’89, New Orleans, LA, USA, September 27, 1989
  15. Dos Santos, J.A., McGaha, J.R., Modern Continuous Haulage Systems and Equipment.
    • Presented at Western Surface Coal Mining Conference, Gillette, WY, USA, November 3-5, 1989, published in proceedings, pp. 85-91
  16. Dos Santos, J.A., McGaha, J.R., A Boost for Continuous Haulage in the Nineties. MinTech’90, The Annual Review of International Technology and Development, Sterling Publications Ltd, London, UK, January, 1990, pp. 137-141
  17. Dos Santos, J.A., High Angle Conveyors-HAC’s, A Decade of Progress Yields a Rock Solid Future. Bulk Solids Handling, Vol. 10 (No. 3), August 1990, pp. 267-270
  18. McGaha, J.R., Dos Santos, J.A., State of the Art Conveyor Support for the Nineties.
    • Presented at Mechanical Handling Engineers Association Conference, Birmingham, UK, submitted October 1990 (12 pages)
  19. Dos Santos, J.A., High Angle Conveyors-HAC’s for Surface Mining in the 90’s.The Institute of Mining Electrical and Mining Mechanical Engineers, Doncaster, UK, November, 1990 (22 pages)
  20. Scott, D.W., Dos Santos, J.A., Straight Up – The Best Way To Go
    • Presented at The AMC (American Mining Congress) Coal Convention ‘92, Cincinatti, OH, USA, May 3-5, 1992, published in proceedings (12 pages)
  21. Dos Santos, J.A., Sandwich Belt HAC®s Broad Horizons – 1992. Bulk Solids Handling, Vol. 12 (No. 3), September 1992 (8 pages)
  22. Dos Santos, J.A., Stanisic, Z., In-Pit Crushing and High Angle Conveying in Yugoslavian Copper Mine. Bulk Solids Handling, Vol. 12 (No. 4), October 1992, (9 pages)
  23. Dos Santos, J.A., Continuous Haulage in the 1990’s. World Coal, UK, April 1993, pp. 24-31
  24. Dos Santos, J., High Angle Conveyors - HAC®s from Mine to Prep Plant and Beyond. Bulk Solids Handling, Vol. 13 (No. 2), May 1993 (7 pages)
  25. Dos Santos, J.A., Continuous Vertical Haulage.
    • Presented at Mine Hoisting ’93 Confernce, Royal School of Mines, London, UK, June 1993
    • Published in Bulk Solids Handling, Vol. 13 (No.3), September 1993 (6 pages)
    • Published in Mining Technology, London, UK. September 1994, pp. 238-243
  26. Dos Santos, J.A., High on Angles Low on Problems, High Angle Conveyors in the Cement Industry. International Cement Review, October 1994 (3 pages)
  27. Dos Santos, J.A., In Pit Crushing and High Angle Conveying in Yugoslavian Copper Mine.
    • Presented at Mine Haulage Solutions Royal Scandinavian Hotel, Dusseldorf, Germany, March 27-29 1994
    • Published in World Mining Equipment, (11 pages)
  28. Dos Santos, J.A., McGaha, J.R., Modern Continuous Haulage Systems and Equipment. Bulk Materials Handling Number, Journal of Mines, Metals and Fuels, Calcutta, India, May-June 1994, pp. 84-94
  29. Dos Santos, J.A., Cement Plants Fed Continuously by HAC’s. World Cement Bulk Materials Handling Review, 1994 (4 pages)
  30. Dos Santos, J.A., HAC’s in Harmony with the Environment. International Bulk Journal, Dorking, Surrey, UK, Submitted July 21, 1995 (15 pages)
  31. Dos Santos, J.A., Sandwich Belt HAC’s Elevating Solid Waste.
    • Presented at The Eleventh International Conference on Solid Waste, The University of Pennsylvania, November 12-15, 1995
    • Published in The Journal of Resource Management and Technology University of Pennsylvania, Philadelphia, PA, USA, 1995 (8 pages)
  32. Dos Santos, J.A., McGaha, J.R., Modern Continuous Haulage Systems and Equipment- 1995.
    • Presented at  BeltCon 8, Johannesburg, RSA, October 24,-26, 1995, published in Proceedings (15 pages)
  33. Dos Santos, J.A., Sandwich Belt HAC’s Broad Horizons- 1996. Port Technology International, London, UK, September 1996 (11 pages)
  34. Dos Santos, J.A., HAC®s - Elevating Gold.
    • Presented at Randal Gold Conference- 1996, Lake Tahoe, NV, USA, published in proceedings
    • Published in Bulk Solids Handling, Vol. 16 (No.3), July/September 1996, pp.361-366
  35. Stanisic, Z and Dos Santos, J.A., In-Pit Crushing and High Angle Conveying at Copper Mine Majdanpek - Performance to Date, Future Expansion.
    • Presented at Fifth International Symposium on Mine Planning and Equipment Selection, São Paulo, Brazil, October 22-25, 1996,
    • Published in proceedings, by A. A. Balkema, Rotterdam, 1996, pp. 487-491
    • Published in Bulk Solids Handling, Vol. 17 (No. 1), January 1997 (5 pages)
  36. Dos Santos, J.A., HAC High Angle Conveyors, Quarry to Bunker. World Cement Bulk Materials Handling Review 1996, UK, pp. 34-40
  37. McGaha, J.R., Dos Santos, J.A., Modern Continuous Haulage Systems and Equipment – 1997. Bulk Solids Handling, Vol. 17 (No. 3), July/September 1997, pp. 379-390
  38. Dos Santos, J.A., The Cost/Value of High Angle Conveying.
    • Published in Bulk Solids Handling, Vol. 18 (No. 2), April/June 1998, pp.253-260
    • Published in World Mining Equipment, Vol 22, (No. 7), September 1998, pp. 46-49
  39. Dos Santos, J.A. , Butterworth, B., Odin, J.P., Pelissou, J.P., The Square Belt/Square Conveyor for Today\'s Environment.
    • Published in Bulk Solids Handling, Vol. 18 (No. 3), July/September 1998, pp.463-467
    • Published in World Mining Equipment, Vol 23, (No. 5), July/August 199, pp. 30-31
  40. Dos Santos, J.A., Endless Elevating Options with Snake Sandwich Conveyors. Bulk Solids Handling, Vol. 19 (No. 2), April/June 1999, pp.199-202
  41. Dos Santos, J.A., Sandwich Belt High Angle Conveyors according to The Expanded Conveyor Technology.
    • Presented at the SME-AIME Annual Meeting, Denver, CO, 1999, published in proceedings
    • Published in Bulk Solids Handling, Vol. 20 (No. 1), January/March 2000, pp. 27-37
  42. Dos Santos, J.A., Dos Santos International –Company Profile.  Bulk Solids Handling, Vol. 21 (No. 2), March/April 2001, pp. 216-219