all american resources, inc. aari · 2010-02-10 · the gearbox used on a centrifuge is a two stage...

Copyright © 2004 Barbara L. „Bobby” Baker

All American Resources, Inc.

The information provided in this material is meant to provide general information

for personnel not familiar with general centrifugation terms and operational

functions. It was not compiled to serve as technical training or as an operations

manual.

Exclusive U.S. Agent for Hutchison-Hayes Separations, Inc.

All American Resources, Inc. was started by Barbara L. “Bobby” Baker in 1999 with 15 years of site

service experience and 25 years of business experience. The goal then and now is to provide 24/7

Equipment, Service and Supply sourcing support for Project Managers, Site Supervisors and Maintenance

Engineers on Industrial related Field Service Projects. On site service expertise includes Remediation,

Separations, Waste Minimization and Product Recovery.

AAAllllll---AAAmmmeeerrriiicccaaannn RRReeesssooouuurrrccceeesss,,, IIInnnccc... Exclusive U.S. Agent for Hutchison-Hayes Separations, Inc.

38466 B. Baker Lane, Gonzales, La. 70737

Website: aacentrifugerentals.com

[email protected]

Office: 225-928-9406 Fax: 225-208-1261 Mobil: 713-410-6178


Click on rig for slide show and

technical information on 5500.

AARI


Industrial Process Site

Mob in/Rig up Site Tips

Confirm that the equipment you will be using is Explosion Proof

(NEMA 7) and meets all OSHA safety standards including noise

standards. Hutchison Hayes rental equipment does meet these

standards.

Save time and acquire proper rig up permits prior to the

equipment‟s arrival at the site.

Make sure a crane is designated for the site so off loading of trucks

can be performed without delay. Bring slings to use for the proper

(safe) lifting of equipment. Nine out of ten times the plant

operators do not have the proper rigging for handling the weight of

centrifugal equipment.

Use a quality liner (NOT VISQUEEN) for leaks and spills under

all tanks and process equipment. Check with facility on their site

requirements prior to mobilization.

Place boards under all equipment in order to 1) be able to clean

underneath and prevent/control vibrations from centrifuge.

Spot all equipment before rigging up hoses, wire, etc. so that all

support rig up equipment such as crane, trucks, etc. can be

released.

Run hoses in a neat and orderly fashion so they will not be a trip

hazard. Use wire on cam locks not duct tape. Use high

temperature hoses at all times in industrial applications. Use low

temp hoses only on polymer, fresh water feed for polymer systems,

and/or coolers on back-drives. Build walkways over hoses in high

traffic areas.

Centrifuge Project at

major refinery.

Processing sludge

material from tank farm

turnaround. Nine month

project, recovering oil,

producing paint filter

solids for disposal and

water for in plant

treatment prior to

discharge.


Make sure tees, valves, and drains are connected to hoses at one

end to anticipate change out of hoses and changes in the process

flow diagram and for de-con at the end of the project.

Always have washtub(s) on location along with blank cam lock

plugs for exchanging hoses.

SAFETY FIRST

Run wire 10 feet off the ground. Carefully check points where

wiring comes in contact with metal. Take steps to prevent wiring

from being rubbed of its insulation by checking all metal contact

points that could result in electrical shock or an explosion.

Ground the generator with an 8-foot ground rod buried in the

ground with only 2 inches extending above the ground.

Note: If no generator is on this job site then the equipment must be

grounded in the same manner or possibly the plant will allow you to

ground to their facility grounding system.

ALWAYS MAKE SURE YOU ASK FIRST. Make sure everything

is grounded with #6 ground wire are as indicated by facility personnel

in charge of electrical approval. Flag all electrical wire with proper

electrical caution tape.

1. Make sump on lowest corner of location and rig up pump to pump off

excess rainwater or spills.

2. Use the appropriate Caution tape to flag off the entire location.

3. Checking rotation should only be done after you have received proper

permits.

4. Acquire proper work permits to rig up and install equipment.

5. Hold safety tailgate meeting prior to rig up and review all MSDS

information on chemicals to be used and materials to be processed.

6. Check all safety equipment and personal protection gear to make sure

it meets OSHA and Facility Safety Standards.

7. Never leave one person on a job site. Remember the TAKE TWO for

safety rule.

8. Pre-screen materials with a shaker/tank system prior processing to

avoid plugging and equipment damage due to trash and debris.


9. Confirm that the proper power and panel connections for the

equipment to be used have been met.

Basic centrifuge terminology follows with these headings:

Decanting Centrifuge

Operational Information

Centrifuge Feed System

Screw Conveyor/Solids

Discharge

Screw Conveyor/Effluent

Weirs

Effluent Weirs

Centrifugal Force

Variable Speed

Feed Flow Rate

Pool Depth

Weir Plate Adjustment

Differential Speed

Conveyor Speed

Conveyance Speed

Gearbox Ratio

Decanting Solid Bowl Centrifuge Operational Information

Industrial decanting centrifuges process liquid/solid slurries at a high

g force generated by the rotation of the centrifuge bowl. Higher

specific gravity solids are augured from the solids portal into holding

boxes and liquids are discharged from a separate effluent point.

Generally speaking the particle size distribution for the solids

involved in industrial separation activities are well under the 100-

micron range.

Centrifuge Feed System

The centrifuge is fed through a pipe, which is inside a hollow shaft

connected to the screw conveyor or scroll. The feed slurry enters a

compartment located inside of the conveyor. It is then accelerated

through feed ports into the inside of the bowl section. Centrifugal

forces accelerate the solids, they are collected on the inside diameter

of the bowl wall and the liquid forms a concentric annulus and fills

the bowl to the level of the effluent weirs.


Screw Conveyor/Solids Discharge

The screw conveyor is connected through a splinted coupling to a

gearbox and turns slightly slower than the bowl assembly. The helix is

angled in a manner to remove the settled solids toward the small

diameter (beach or conical section). These solids are then conveyed

along the inside diameter of the bowl to the solids discharge port.

Screw Conveyor/Effluent Weirs

The liquid flows around the screw conveyor and exits through effluent

weirs located on the large diameter (cylinder) end of the bowl. Solids

that settle to the inside diameter of the bowl are discharged with the

liquid across the effluent weirs. These solids tend to be in the

5 micron and lower range. Ninety five percent of all particles above 5

microns should be removed in this process but heat and chemical

enhancements may be necessary to achieve this goal in some streams.

Model 5500 High G Decanter

Telescoping

stand

12’ auger section

solids discharge

Effluent

discharge

Line.


Effluent Weirs

Effluent weirs that are adjustable control the amount of liquid inside

the bowl. The maximum volume or pool depth forms an annulus

diameter, which is smaller than the solids discharge diameter. The

liquids always flow to the cylinder end.

Centrifugal Force/G-Level

A good example of centrifugal force would be the high speed mid way

rides that cause an outward force on your body as it rotates. The

intensity of the force is dependent upon the rotational speed.

The force tending to move the object or particle away from its

rotational centerline is expressed as “G-Level”. This is a function of

the bowl speed and bowl diameter. The following formula is used to

calculate G levels.

Bowl RPM (2) x Bowl Diameter (ft)

6000

Fixed Gearboxes are installed on “mechanical” centrifuges

The gearbox used on a centrifuge is a two stage planetary gearbox. It is

mounted on the centrifuge-rotating unit and is rotated at the bowl speed.

Machines have to be turned off and gearbox settings reset to alter this

setting.

Variable Speed – Hydraulic controls on bowl and/or scroll

External hydraulic and electric controls can be installed to allow for a

change in settings on the bowl and/or scroll speeds. If not speed is fixed by

the design of the motor RPM and sheave sizes.


Machine Variable Settings

Speed (RPM), feed flow rate (GPM), pool depth, gearbox ratio, differential

speed, conveyor speed and conveyance speed.

Speed (RPM)

1. Increases or decreases the G level

2. Increases or decreases the differential speed and resonance time of the

settled solids (how fast the settled solids are removed by conveyor).

3. Alters the particle size distribution in the cake (solids) as follows:

a. Higher speed settles more solids inside the

diameter of the bowl and fewer solids in the

effluent (product). In classification this makes a

finer cut (more G‟s to settle solids, higher G seconds).

b. Lower speed settles less solids in the bowl thereby

Sending more in the effluent.

4. Increases or decreases cake moisture.

Feed Flow Rate

1. Increase of the flow reduces the time the slurry is in the bowl

(residence time).

This will usually:

a. Increase the amount of solids in the effluent phase.

b. Sometimes it will affect the solids moisture content.

c. In classification (partial size segregation) it will decrease the

separation efficiency of the machine and coarsen the cut.

2. Decrease in the flow increases the time the slurry is in the bowl

(residence time).

This will usually:

a. Decrease the amount of solids in the effluent phase.

b. In classification it will increase the separation efficiency of the

machine and make the “cut” finer.


The flow rate is adjustable while the machine is in operation. Flow rate

should not vary more than 2-3% or it will effect the particle size distribution

in classification of particles.

An increase in the flow rate will also increase the pool depth due to the

effect of the head, which overflows the weir plates.

Pool Depth

The weir plates on the liquid end of the machine control the pool depth. By

increasing the pool depth i.e. going from 1” to 2” we increase the pool

volume (deeper pool). The same occurs when you reduce the pool level you

reduce the pool volume.

Weir Plate Adjustment

The effects of pool depth follow:

Decrease (going from 3” to 2”) in pool depth reduces the time the slurry is in

the bowl (residence time).

This will usually:

a. Decrease the amount of solids in the effluent phase.

b. In classification it will increase the efficiency of the machine

and make the cut finer.

c. Deeper pool will decrease the length of beach (conical end of

bowl) not covered by the pool. Typically this will increase the

moisture of the discharged cake solids.

Note: Pool depth cannot be adjusted while the machine is in operation.

Gearbox Ratio

Typically the gearbox ratio is fixed. It is a function of the design of the

gearing and usually comes in 20, 40, 116, 130, and 140:1ratios. The higher

the gearbox ratio (i.e.: 130 versus 40:1) the lower the differential speed.

The gearbox ratio affects the differential speed and controls how fast or slow

the settled solids are inventoried inside the machine. In other words how

quickly the solids are conveyed out of the machine.


The higher the differential speed the faster the settled solids (rejects) are

removed. In classification it can affect the particle size distribution.

Differential Speed

The difference in passed between he bowl (driven by the motor) and the

conveyor (driven by the gearbox). The operating speed determines the

differential speed on a fixed ratio gearbox.

Typical effects on the material streams are as follows:

1. High Differential Speed

a. Usually produces wetter solids “cake”.

b. Tends to decrease soils in effluent due to lower residence

time of solids in the bowl.

c. In classification it can increase the solids in the effluent

due to the turbulence of conveyance (a stirring effect).

2. Lower Differential Speed

a. Usually produces a drier solid “cake”.

b. Tends to increase solids in the effluent stream due to

longer residence time of soils in the bowl.

c. In classification it can decrease the solids in the effluent

due to less turbulence of conveyance (less stirring effect).

Note: In classification some products are not affected by the

change in differential speed.


HH-5500 fully hydraulic centrifuge

Conveyor Speed

Conveyor Speed is the rotating speed (RPM) of the conveyor. This speed is

determined by subtracting the differential speed (DS) from the bowl speed

(BS).

To find the speed of the conveyor use the following formula:

BS – DS = Conveyor Speed

Where BS + Bowl Speed and DS = Differential Speed

Conveyance Speed

The linear rate at which the solids are moved along the inside diameter of

the bowl is called the Conveyance Speed. This rate is a function of the

differential speed and conveyor lead (pitch).

Conveyance speed can be calculated as follows:

Formula: DS x CL = inches/sec. Conveyance speed

60

Where: DS = Differential Speed CL = Conveyor Lead

Example: DS = 23 RPM, CL = 12”

23 x 12 = 4.6”/sec

60


Note: When making changes to a machine change one variable at a time to

determine the effect on the process before proceeding.

In case you did not know…….

We can provide parts and service on all

major centrifuge models. If you are

operating your own centrifuges contact

us for a quote and rates for a rental

while it is being worked on.

Hutchison Hayes Model 5500

decanter on telescoping stand at

major refinery site.

This was a six month tank

bottoms waste minimization

project (with oil recovery spec

of 5% or less BS&W).

Heat and oil/water separator

were utilized to enhance the

separation of the discharged

oil/water stream.


External issues that affect the Centrifuge Process 1. Proper sizing of pumps, lines and connections to prevent plugging,

excessive head pressure and build-up/settling of dense materials

during pumping.

2. Proper shaker system (pre-screening apparatus) to remove all trash

that might lead to plugging and/or equipment damage.

3. Containment for the shaker overflow.

4. Agitated mix tank to enhance homogeneous feed for processing.

Note: If the material to be processed is a slurry/sludge containing water,

solids and hydrocarbons then heat and/or chemicals may be utilized to

enhance the oil recovery process. A heated effluent stream containing water

and hydrocarbons should “break” into two streams when pumped through an

oil/water separator or pumped to heated frac tank.

At the break you may get residue of oil in the water phase and a little water

in the oil phase but 5% or less BS&W should be easily reached with this

procedure until emulsions are encountered. Tricanters (3-phase centrifuges)

separate water/oil/and solids and the streams are kept separate as they leave

the bowl. With a decanter (liquid/solid) these streams are separated in the

bowl but are discharged through the same port.

Operating standards for heating materials must be reviewed by utilizing the

material‟s MSDS guidelines. The use of heat and/or chemicals in

conjunction with Special Projects work must always be coordinated with

Plant Representatives, Environmental and Safety personnel.

AAAllllll---AAAmmmeeerrriiicccaaannn RRReeesssooouuurrrccceeesss,,, IIInnnccc... Exclusive U.S. Agent for Hutchison-Hayes Separations, Inc.

38466 B. Baker Lane, Gonzales, La. 70737

Website: aacentrifugerentals.com

[email protected]

Office: 225-928-9406 Fax: 225-208-1261 Mobil: 713-410-6178

all american resources, inc. aari · 2010-02-10 · the gearbox used on a centrifuge is a two stage...

Documents