conveyor equipment manufacturers association...joint screw conveyor and bucket elevator section...

THE VOICE OF THE CONVEYOR INDUSTRY OF THE AMERICAS

JOINT SCREW CONVEYOR & BUCKET ELEVATOR SECTION MEETING 7:30 a.m., Monday, March 12, 2018 Naples Grande Beach Resort, Naples, FL AGENDA

1. Call to Order and Roll Call 2. Approval of the Minutes of September 20, 2017, Minute-Amendments:

CEMA TR 2015-1 Risk Assessment, Std. 300-013 Seal Bolting Pattern For Oversized Shafts

3. Screw Conveyor Safety Video/Pub Inventory (Kimberly MacLaren) 4. Review Engineering Conf./Fall Meeting Items (Committee)

a. Std. 300-001, Helicoid Flight OD Tolerance Survey

(attached) b. Std. 300-019, Standard 2 and 3-Bolt Coupling Shaft

Dimensional Standards for 3-5/16", 4-7/16", and 4-15/16" Shaft Diameters. (attached)

c. Standard 300-013 - Seal Bolting Pattern For Oversized Shafts. (attached)

d. #350 Update - Cosmetic Changes on hold, Material List, Std. 300-019 2 & 3-Bolt Coupling Shaft Dimensional Standards additions.

e. Draft-1 Inclined and Vertical Screw Conveyors, Added to 'Members ONLY Page'. (attached)

f. Bucket Elevator Book - Errata List Review g. CEMA TR 2015-1 Risk Assessment - CEMA SC 2004-01, Risk

Assessment Information needs to be added. h. OSHA and NFPA and 'How they relate to Bucket Elevators'.

Need Volunteers to provide related regulation code and possible subcommittee.

i. Bucket Elevator IOM - Volunteers, formulate plan of action CEMA Materials Master List

5. Membership Committee Representation (Kimberly MacLaren) 6. Other Business - 30" and 36" Dimensions in Std. #350, Add to

affected #300 Standards. 7. Election of Officers 8. Next Meeting of the Section - September 18-19, 2018, Chicago

O'Hare, Chicago, IL 9. Adjournment

Noel Bell, Chair Tom Young, Vice Chair/Secretary

5672 Strand Ct., Suite 2 • Naples, Florida 34110 Tel: (239) - 514-3441 • Fax: (239) - 514-3470

www.cemanet.org

Conveyor Equipment Manufacturers Association

MINUTES Joint Screw Conveyor and Bucket Elevator Section Meeting

Wednesday, September 20, 2017 7:00 a.m.

Chicago, Illinois

1. Meeting was Called to Order and Roll Call was taken, roll call attached.

2. Approval of the Minutes of March 13, 2017, Meeting

3. Screw Conveyor/Bucket Elevator Sales/Inventory

4. Review Engineering Conference Minutes

a) Helicoid Flight O.D. Tolerance - Survey was not completed, it will be resent out by

CEMA (Naylu) and submitted to the ORs at the upcoming Annual Meeting for

approval.

b) Seal Bolting Pattern Oversized Shafts - With completion of the dimensional standards

for larger than current CEMA standard, associated seal dimensions were necessary

to accompany the shafts. Naylu resent out survey after receiving only two

submissions. She was able to complete the survey and provided results to Noel Bell

to be reviewed by committee after this meeting and then it will be sent to ORs at

Annual Meeting for approval to be added to standard.

c) Dimensional Standards for 3-15/16", 4-7/16", and 4-15/16" Shaft Diameters - This

item has been completed and approved by the ORs. This information is ready to be

added to the CEMA dimensional standards #300 and #350 for 30" and 36" conveyor

sizes.

d) #350 Graphics and Photos Update - After Engineering Conference, a conference call

was setup for 8/25 to review all of the graphics and cosmetic changes. A large

amount of the graphics were submitted by Martin Sprocket & Gear / KWS Mfg ,

however review was not completed. Plan of action by end of call was to have

completed by Fall Meeting, however; that goal was not met and has been moved to

the Annual Meeting. It will be reviewed by KWS and recommended to ORs at Annual

Meeting for approval to be uploaded to Store after meeting.

e) Inclined & Vertical Screw Conveyor Best Practices - David Stronczek developed the

rough draft to be reviewed/edited by the engineers at the Engineering Conference.

This document will be added to the CEMA Members ONLY Project page so they can

have access to it before the Engineering Conference. An email will be sent out to

Conveyor Equipment Manufacturers Association 5672 Strand Ct., Suite 2 • Naples, Florida 34110

Tel: (239) - 514-3441 • Fax: (239) - 514-3470 https:// www.cemanet.org

ORs and Engineers advising them to review document. Their target approval date on

this document is the 2018 Fall Meeting.

f) CEMA TR 2015-1 Risk Assessment - Bill Mecke and Andrew Morton of KWS

volunteered to add a statement regarding risk assessment to the safety technical

report TR 2015-1 by referencing Paragraph 5.16 of ANSI B20.1. This verbiage was

shared with the group and is to be submitted to Andy Solis, CEMA Legal Counsel for

review, then onto the ORs for approval at the Annual Meeting. Please supply ANSI

B20.1 as reference to compare. Ask ORs to share with their attorneys and be ready

to share any suggestions at the Annual Meeting before approval.

g) OSHA and NFPA and 'How they relate to Bucket Elevators?' - OSHA - it was

mentioned in the bucket elevator engineering conference that new OSHA regulations

mentioned at GEEPs will directly affect the way elevator platforms are constructed.

Specifically, the way workers are "tethered" to the elevator will need to be examined.

Andrew Beadle of Universal Industries helped to provide the specific regulations in

which this verbiage is found. This will be an important topic at the next engineering

meeting, as all manufacturers of platforms will likely need to modify the construction

type. NFPA - It was mentioned in the summer engineering conference that a closer

look needs to be taken at recent documentation related to NFPA regulations and

human elevators. Some of this regulation may make its way into bucket elevator

construction. Need volunteers at this point to provide related regulation code, and

possible formation of a subcommittee to address.

h) Bucket Elevator IOM Manual - Members of the engineering committee discussed the

need of an IOM manual for bucket elevators. Bucket elevator committee will need to

ask for volunteers to assist with this, and formulate a plan of action and timeline to

complete this project. This item will likely be addressed at the summer engineering

conference.

5. Membership Committee Report - It was reported that as of the Annual Meeting, there were

134 member companies with an additional 3 new member (two are screw conveyor)

companies since that meeting and a total of 6 companies (5 resignations/1 termination)

leaving membership bringing our membership total to: 131 member companies as of

9/15/2017. At this time there are no new additional prospective members for this section.

6. Next Meeting of the Section - CEMA Annual Meeting, Naples Grande Hotel, Naples, FL

March 12, 2018

7. Other Business

a) 'Bucket Elevator Book' Errata. After the initial release of the book for sale, it was

brought to CEMA's attention that there may be some Errata in the publication that

need to be reviewed and possibly corrected. A committee of three, consisting of:

David Stronczek, Warren Knapp, and Drew Beadle will compile a summary of

suggested Errata to be reviewed by the ORs at the Annual Meeting. They would

like a decision made to develop an Errata sheet for this publication or a new printing

done to include the Errata.

b) CEMA 'Materials Table' Master List - Naylu has requested that the Screw Conveyor

Section assist her on the current 'master list' of Materials Table that is listed in the

current 7th Ed. Belt Book. This list should match with tables that are in standards

#350 and #550, and they are not. There are some materials that are not listed in

one publication but in the other and some that have the incorrect information in one

publication but the correct in another. She would like some assistance on in

correcting this list. List will be readied for Annual Meeting.

c) Election - Vice Chair/Secretary - With the Vice Chair position becoming vacant, Noel

Bell advised the Section that Thomas Young, Timken Drives, LLC, has volunteered

to be nominated for the position. It was unanimously voted for him to take over this

position.

8. Adjournment - The meeting adjourned at 7:50 a.m.

Submitted by,

David Stronczek, Acting - Vice Chair/Secretary

CEMA Standard 300 ‐ 2015 – Screw Conveyor – Dimensional Standards

1

F G H

Plus Minus Inner EdgeNominal

Outer EdgePlus Minus Min. Max.

1 1/2 6H304 2 9 (10) 1/16 3/16 1/8 1/16 1/2 1/4 1.505 1.516 7/8 3 17/321 1/2 6H308 2 9 (10) 1/16 3/16 1/4 1/8 3/4 1/4 1.505 1.516 7/8 3 17/321 1/2 6H312 2 9 (10) 1/16 3/16 3/8 3/16 3/4 1/4 1.505 1.516 7/8 3 17/32

1 1/2 9H306 2 9 (10) 1/16 3/16 3/16 3/32 3/4 1/4 1.505 1.516 7/8 3 17/321 1/2 9H312 2 9 (10) 1/16 3/16 3/8 3/16 3/4 1/4 1.505 1.516 7/8 3 17/32

2 9H406 2 1/2 9 (10) 1/16 3/16 3/16 3/32 3/4 1/4 2.005 2.016 7/8 3 21/322 9H412 2 1/2 9 (10) 1/16 1/4 3/8 3/16 3/4 1/4 2.005 2.016 7/8 3 21/322 9H414 2 1/2 9 (10) 1/16 1/4 7/16 7/32 3/4 1/4 2.005 2.016 7/8 3 21/32

2 12H408 2 1/2 11 (10) 1/8 5/16 1/4 1/8 1 1/4 2.005 2.016 7/8 3 21/322 12H412 2 1/2 11 (10) 1/8 5/16 3/8 3/16 1 1/4 2.005 2.016 7/8 3 21/32

2 7/16 12H508 3 11 (9) 1/8 5/16 1/4 1/8 1 1/4 2.443 2.458 15/16 3 21/322 7/16 12H512 3 11 (9) 1/8 5/16 3/8 3/16 1 1/4 2.443 2.458 15/16 3 21/32

3 12H614 3 1/2 11 (9) 1/8 3/8 7/16 7/32 1 1/4 3.005 3.025 1 3 25/32

2 7/16 14H508 3 11 (9) 1/8 5/16 1/4 1/8 1 1/4 2.443 2.458 15/16 3 21/323 14H614 3 1/2 11 (9) 1/8 3/8 7/16 7/32 1 1/4 3.005 3.025 1 3 25/32

3 16H610 3 1/2 11 (9) 1/8 3/8 5/16 5/32 1 1/2 1/4 3.005 3.025 1 3 25/323 16H416 3 1/2 11 (9) 1/8 3/8 7/16 7/32 1 1/2 1/4 3.005 3.025 1 3 25/32

18 3 18H610 3 1/2 11 (9) 3/16 3/8 5/16 5/32 1 1/2 1/4 3.005 3.025 1 3 25/32

Diameter Tolerance (in)

Thickness (in)

Pitch Tolerance

(in)

Bushing Bore Inside Diameter

(in)

A

14

16

Spacing 1st Bolt Hole

(in)

Centers 2nd Bolt Hole

(in)

Nominal Bolt Hole Size

(in)

6

9

12

Listed Screw

Diameter and Pitch

(in)

Coupling Diameter

(in)

Size Designation

Pipe Size

SCH 40 (in)

Length [ft (in)]

B C D

Standard 300-001

Helicoid Conveyor Screws

owner

Highlight

CEMA Standard 300 2015 – Screw Conveyor – Dimensional Standards

14

Bolt Stud

6 1 1/2 1 5/8 4 1/2 5 5/8 8 1/8 9 3/4 1 1/2 1 3/16 4 1/2 7/16 3/8 1 3/41 1/2 1 5/8 6 1/8 7 7/8 9 3/8 13 1/2 1 5/8 1 1/2 1/4 4 1/2 7/16 1/2 2 5/8

2 2 1/8 6 1/8 7 7/8 9 3/8 13 1/2 1 5/8 1 1/2 1/4 5 1/8 5/8 9/16 1/2 2 5/82 2 1/8 7 3/4 9 5/8 12 1/4 17 1/4 2 1 5/8 1/4 5 1/8 5/8 9/16 5/8 2 3/4

2 7/16 2 9/16 7 3/4 9 5/8 12 1/4 17 1/4 2 1 5/8 1/4 5 5/8 5/8 9/16 5/8 2 3/4

3 3 1/8 7 3/4 9 5/8 12 1/4 17 1/4 2 1 5/8 1/4 6 3/4 3/4 5/8 2 3/42 7/16 2 9/16 9 1/4 10 7/8 13 1/2 19 1/4 2 1 5/8 5/16 5 5/8 5/8 9/16 5/8 2 7/8

3 3 1/8 9 1/4 10 7/8 13 1/2 19 1/4 2 1 5/8 5/16 6 3/4 3/4 5/8 2 7/8

16 3 3 1/8 10 5/8 12 14 7/8 21 1/4 2 1/2 2 5/16 6 3/4 3/4 5/8 3 1/43 3 1/8 12 1/8 13 3/8 16 24 1/4 2 1/2 2 3/8 6 3/4 3/4 5/8 3 1/4

3 7/16 3 9/16 12 1/8 13 3/8 16 24 1/4 2 1/2 2 3/8 6 3/4 3/4 3/4 5/8 3 1/43 3 1/8 13 1/2 15 19 1/4 26 1/4 2 1/2 2 1/4 3/8 6 3/4 3/4 3/4 3 3/4

3 7/16 3 9/16 13 1/2 15 19 1/4 26 1/4 2 1/2 2 1/4 3/8 6 3/4 3/4 3/4 3/4 3 3/4

24 3 7/16 3 9/16 16 1/2 18 1/8 20 30 1/4 2 1/2 2 1/2 3/8 6 3/4 3/4 3/4 3/4 4 1/8

20

Shaft Diameter

(in)

D (in)

9

12

14

18

FMinimum

(in)

G (in)

H (in)

J (in)

L (in)

M (in)

Screw Diameter

(in)

K Diameter

AMinimum

(in)

B (in)

C (in)

EMinimum

(in)

Standard 300-013

U-Trough End Plates


21

Standard 300-019

Coupling Shafts

1 1/2 11 1/2 7/8 3 17/32 3 3/42 11 1/2 7/8 3 21/32 3 3/4

2 7/16 12 3/4 15/16 3 21/32 4 7/83 13 1 3 25/32 5

3 7/16 17 1/2 1 1/4 4 29/32 7

F(in)

A(in)

B (in)

C (in)

E (in)

D (in)

Screw Conveyor PROPOSED 2-Bolt Coupling Shaft, Larger than CEMA Standards

b12tmb

Rectangle

b12tmb

Text Box

1 1/21 17/32

1 9/32

1 5/32

Screw Conveyor PROPOSED 3-Bolt Coupling Shaft, Larger than CEMA Standards

b12tmb

Text Box


27

Standard 300-022

Coupling Bolts with nuts

Shoulder Length Tolerance = + 1/8 in / - 0

The coupling bolt shoulder length will be, at a minimum, the same as the outer diameter of the pipe. This will allow the nut to reach the end of the threads / start of the shoulder on all shaft sizes. The nut should be snug against the shoulder of the bolt without over tightening.

Warning: Over tightening the nut could exceed the tensile stress of the bolt.

Coupling Diameter

(in)

Pipe Size (in)

Pipe O.D.(in)

A(in)

B (in)

C (in)

D (in)

1 1/2 2 2 3/8 1/2 3 5/8 2 3/82 2 1/2 2 7/8 5/8 3 5/8 3/4 2 7/8

2 7/16 3 3 1/2 5/8 4 3/8 7/8 3 1/23 3 1/2 4 3/4 5 1 43 4 4 1/2 3/4 5 1/2 1 4 1/2

3 7/16 4 4 1/2 7/8 5 1/2 1 4 1/2

Joint Screw Conveyor & Bucket Elevator Section DRAFT1‐Screw/Bucket Elevator Inclined/Vertical Screw Conveyors‐Committee USE ONLY, No distribution w/out CEMA permission. October 1, 2017

Screw Conveyor / Bucket Elevator Section

Inclined/Vertical Screw Conveyors DRAFT ‐ 10/01/2017

David Stronczek, Martin Sprocket & Gear

Screw conveyors arranged to convey bulk materials up an incline are often utilized due to

minimum necessary equipment and space utilization. Many alternate conveyance arrangements require

multiple conveyors to first move material horizontally, and then vertically respectively.

While inclined screw conveyors offer many benefits, some considerations must be taken for

proper application and operation.

As the angle of incline increases there may be a significant loss in efficiency, often dependent on

the type of material conveyed. Several direct consequences arise from this loss in efficiency:

1.) As the incline increases the overall expected capacity may be drastically reduced.

2.) The required horsepower of the unit increases.

Various reasons cause these effects. As the angle of incline increases, there is a reduction of the

effective angle of the flight as it pushes against the material. See Figure X.X. At certain angles of incline

and screw pitch values, a portion of the helical flight is virtually on the horizontal plane; this reduces the

forward action of the flight, resulting in loss of efficiency, in addition to material turbulence and

trembling.

The losses in effective capacity due to improper flight/angle/pitch combination may ultimately

result in a larger than expected cross‐section of material within the screw conveyor. This increased cross

section is especially important when considering an obstruction such as an intermediate hanger bearing.

The turbulence and tumbling of material will also likely result in the need for increased horsepower

(power that is not really useful in the conveyance of the material).

Inclined screw conveyor efficiency may also be detrimentally affected by the geometry of a

standard U‐trough. A U‐trough design contains void space over the rotating screw, resulting in material

fallback during operation. This furthermore exasperates increased cross‐sectional loading and material

turbulence, resulting in further loss of efficiency.

Figure X.X exhibits a theoretical conveyor capacity of a screw conveyor at various angles of

incline for standard designs, modified designs, and for vertical designs. The capacity curve shows that

even conveyors modified for incline service experience minimum theoretical capacity between angles of

25° and 65°. The angle of minimum capacity in this range is not specified; it greatly depends on material

characteristics, flight pitch, speed, housing geometry, etc.


As shown in figure X.X, there are several modified design considerations that may increase the

overall efficiency of inclined screw conveyors:

1.) Omit utilization of “standard” screw components (IE full pitch screws, U‐Troughs, standard

speed etc.) in applications >25°, preferably over 15°.

2.) Usage of close clearance between trough and screw:

a. CEMA std. clearance of ½” between flight outside‐diameter may allow for material to

fall back between this gap. Reducing this gap can prevent material from falling through

this open space. Note that it is important to consider deflection value of screw if

reducing clearance, to avoid possible rubbing on trough.

b. This gap can be reduced in one of several ways:

i. Adding a liner material between the trough and screw O.D.

ii. Increasing the flight diameter to close the gap.

3.) Increase the speed over normally calculated horizontal screw conveyor of same size.

a. When performing a standard horizontal screw calculation, consider adding rpm to the

final calculated value to overcome the loss in efficiency from the incline.

b. The increase in speed of screw rotation imparts a greater forward material velocity,

which may aid in in pushing material past an intermediate hanger bearing. Despite the

increase in agitation and turbulence of the material, the net result may be an increase in

capacity.


c. Performance gain from a speed increase may greatly depend on material characteristics.

Note that some materials may aerate and/or fluidize at increased speeds, resulting in a

net loss of capacity. Please refer to the material characteristics chart for further

information.

4.) Usage of short pitch (IE 2/3 or ½ pitch) if the material handled permits.

a. See figure X.X. (image showing pitch angle versus incline to be inserted) The helical

flight modified in this manner places the carrying face of the flight closer to a vertical

position relative to the incline. This results in less material fallback, and a more effective

angle of the flight as it pushes against the material.

b. Reducing the pitch of the screw will create the added benefit additional flights, creating

more “walls” to help reduce material fallback.

c. Reducing the pitch of the screw in a horizontal conveyor reduces the overall capacity, as

each volumetric flight pocket is smaller. This must also be considered in an inclined

variant, typically requiring an increase in speed to overcome this.

d. Attention to the material type must be paid when reducing pitch. Specifically on smaller

diameter screws, one must ensure that the lump size of the material isn’t too large for a

reduced pitch.

e. (image showing pitch angle versus incline to be inserted)

5.) Omitting of hangers to reduce obstructions in flow.

a. Elimination of a hanger bearing is usually achieved by increasing the length of a

standard screw.

i. Larger than standard screws must consider increased deflection, possibly

resulting in the need for a larger pipe size. Take careful note when increasing

pipe size to ensure the reduction in cross‐sectional carrying area allows for the

desired material capacity.

ii. Note that hanger obstruction is one of the most common problem areas for

inclined screw conveyors. Elimination of a hanger when possible not only

removes a possible failure mode, but potentially decreases maintenance of a

wear area in the coveyor.

iii. In some applications at appropriate rpm, screws may be close‐coupled and

clocked for an extended length, and ride on a liner. Contact your conveyor

manufacturer before pursuing this option.

iv. (Possibly add image showing reduction in capacity due to increased pipe size)

6.) Use of tubular trough style versus U‐trough to reduce void area at top portion of flight O.D.

a. On specifically aggressive inclines or high speeds, material may fall backwards over the

O.D. of the flight at the void area of a U‐trough. Closing off this area with a tubular style

trough reduces the gap between the flight O.D. and trough, assisting in the reduction of

material fallback.

b. (Possibly add image showing tubular trough versus U‐trough)


It is worth noting that the theoretical capacity and horsepower of an inclined screw conveyor

may be greatly dependent on material characteristics, and often cannot be accurately predicted.

Materials that can accumulate on pipe/screw surfaces, aerate, and fluidize pose challenges and can

greatly affect the expected performance of an inclined conveyor. As such, it is important to consult a

screw conveyor manufacturer with detailed application data to allow for proper design of a product that

will meet the end‐users needs.

Horsepower of inclined screw conveyors – This section can remain the same in reference to the

calculations. Modify final paragraph discussing drive arrangement:

When considering the drive arrangement of an inclined screw conveyor, it is important to recognize that

material will typically fall due to gravity to the bottom portion of the inclined unit. Noting this, one

should use a robust high quality seal for the proper material application. For the same reasons, the drive

on an inclined screw conveyor should always be mounted at the top end of the incline when possible;

mounting of the drive unit on the bottom end may result in material infiltration into the drive unit. If a

drive unit must be mounted on the lower end, usage of a bulkhead style end plate or roller chain drive

may allow separation of drive components from the conveyed material. Additionally, one should always

consult the conveyor/reducer manufacturer for proper oil levels when mounting on an incline.

Vertical Screw Conveyors

A vertical screw conveyor is used to convey materials upward in a vertical path. Vertical screw

conveyors are sometimes referred to as “lifts” or “elevators”, but such names are ambiguous. Vertical

screws have the advantage being compact, and can often fit into much a much smaller footprint that

equipment such as a bucket elevator. There can be additional benefits with the usage of vertical screws:

Relatively low cost compared to other systems of elevating material

No special maintenance required from staff already familiar with screw conveyor systems

Screws and housings are often standard screw conveyor components

Can be manufactured to contain dusty materials

Vertical screw conveyors can handle many of the bulk materials shown in the material table Chapter 2,

column V. Generally this includes all materials listed with the exception of those containing large lumps,

is extremely dense, or is excessively abrasive:

1.) Lump Size – Material with large variance in particle size, or excessively large lumps tend not to

properly convey in a vertical screw. In general, free‐flowing material that does not degrade will

work suitably in a vertical screw. Friable material along with extremely fine powders that aerate

will often have issue working properly in a vertical screw.

2.) Extremely Dense Material – Very dense material that has little to no compressive capability may

not convey properly due to the fully loaded condition and speed at which a vertical screw

operates.


3.) Abrasive Materials – Due to the high speeds and full contact of the material to the screw,

abrasive materials may rapidly degrade components, along with prematurely wearing seals and

drive components.

A vertical screw is constructed in fairly similar fashion to a horizontal screw, with a few notable

exceptions. A typical unit consists of rotating conveyor screw in a tubular housing with a variant inlet

type, along with a discharge at the upper end. The drive is preferably located at the top of the screw (for

similar reasons discussed in the inclined screw section), but may be mounted on the bottom if necessary.

The top bearing for the screw shaft must be able to handle both radial and thrust loading. Note that in

the case of a top‐mounted drive, the screws opposite end shaft may either be external with a seal and

bearing, or mounted on a dead‐shaft to fully enclose the end of the screw. Several types of intake

arrangements are possible:

1.) Gravity Inlet Hopper (insert updated 3D rendering for all inlet styles) – The gravity inlet hopper is

typically arranged as shown in figure X.X. It funnels material by gravity to the lower end of the

vertical screw. While the hopper can be fed manually by dumping sacks or other containers,

they are often fed from another device uniformly. Successful use of this inlet type is greatly

dependent on the material type; it is recommended to contact a screw conveyor manufacturer

should this style be necessary.

2.) Straight Intake – This inlet type is generally interfaces a feeder screw conveyor to the vertical

screw at 90°. The horizontal screw is used to force feed the material into the vertical. A hanger

bearing is generally used at the end of the horizontal conveyor, at the intake of the vertical. This

type of intake is most frequently used with free flowing material that won’t prematurely wear,

and doesn’t easily degrade from being force fed. Note that the drive on the horizontal feed

screw can only be mounted on the inlet end for this intake arrangement. For a straight intake,

the hand of the screw for most efficient operation is as follows:

a. A vertical elevator with a straight inlet will have all the same hand of screws for infeed,

vertical, and take‐away screws, right or left (Right‐Right‐Right or Left‐Left‐Left).

3.) Offset Intake – This type of intake connects to the vertical casing at a 90° angle, however is

offset from the center of the vertical as shown in figure X.X. The advantage of the offset intake is

that the shaft of the horizontal feed screw extends past the vertical casing, eliminating the need

for a hanger bearing. This allows the external bearing on the horizontal screw to carry the thrust

load as well as the radial load of the screw. The horizontal screw may also be driven from either

the inlet or discharge end in this arrangement. In the case of an offset intake, it is important that

the correct combination of vertical to horizontal screw hands are chosen for the most efficient

operation:

a. Right‐Left‐Left – A vertical screw elevator that is offset to left of the intake will have a

left hand screw and should be fed by a feeder with a right hand screw. The take‐away

conveyor should be a left hand screw (Right‐Left‐Left).


b. Left‐Right‐Right – A vertical screw elevator that is offset to the right will have right hand

screw and will be fed by a feeder with a left hand screw. The take away conveyor will

also have a right hand screw (Left‐Right‐Right).

The method by which a vertical screw conveyor is fed is extremely important, as some materials

behave differently than others. Take for example very light materials: A gravity fed hopper inlet would

not function well, as the high rotating speed of the vertical screw would act as a fan, and blow material

back away from the intake. This can be addressed by leaning the vertical screw to a slight incline, and

allowing for the hopper intake to remain on top of the vertical screw. In general, a uniformly force‐fed

horizontal conveyor is generally the superior feed method for efficient operation.

Note that vertical screw conveyors do not perform well in batch‐type operations. The unit functions

somewhat like a pump, in that it must be “primed” or filled until material begins to discharge. Material

will also not fully discharge from a vertical screw; some material remains in the system upon stopping

the infeed. As such, degradable organic materials such as food products are not recommended for use in

vertical screw conveyors, as contamination may occur over time. This can however be counteracted by a

complete wash‐down of the internal components post operation.

Vertical Screw Speeds

This section is good

Capacities of Vertical Screw Conveyors


Vertical Screw Conveyor Housings and Casings


Discharge Arrangement

Discharge of material in a vertical screw is achieved through an opening similar to that of a

horizontal conveyor. The discharge spout may be connected to an elbow or other type of discharge to

move material into a subsequent conveyor or process.

To ensure positive discharge of material, vertical screws are often affixed with “kicker paddles”,

other flat paddle‐type or reverse flights to foster complete discharge of the material. Even so, there are

times when it is advisable to provide a safety overflow. This is usually an opening diametrically opposite

and above the discharge spout, arranged to spill the material if the discharge spout becomes clogged

and unable to handle the normal material flow.

Hanger or Stabilizer Bearings


Intermediate hanger or stabilizer bearings usually are necessary in vertical screw conveyors

when extended heights of lift are required, to eliminate excessive screw deflection and “whip.” These

hanger or stabilizer bearings are positioned between the sections of the screw and are supported

between the housing flanges. The particular kind of hanger or stabilizer bearing to use is determined by

the characteristics of the material being handled.

Some materials travel upward in a mass and would experience obstruction by an intermediate

stabilizer or hanger bearing. One such material is cottonseed. With it, hanger bearings are not used.

Certain other materials tend to center the screw within the housing, thus eliminating the need for

stabilizer bearings. Some lighter duty materials can also allow for wear‐shoe made out of a material such

as UHMW; this is simply a flight that extends slightly past the O.D. of the screw to assist in centering and

eliminating “whip.”

Horsepower look good; no need to modify. Does group want to add more detail on specific vertical screw

drive arrangements? Need feedback at this point.

conveyor equipment manufacturers association...joint screw conveyor and bucket elevator section...

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