Report on the Gulper, Rammer and Nibbler Development · 2015-12-17 · The Rammer and Nibbler Page 1 1.0 Introduction and Background Water for People (WFP) is a United States registered

The Rammer and Nibbler Page i

Report on the Gulper, Rammer and

Nibbler Development

The Kampala Sanihub Project

March 2014

Submitted by:

Water For People, Uganda

Plot 9, Olumi Close, Kitante, Kampala

The Rammer and Nibbler Page ii

EXECUTIVE SUMMARY

Water for people’s Sanitation as a business program’s research and development arm, the

Kampala Sani-Hub Project began collaboration with the Water Research Council (WRC) in

South Africa, under the Sanitation Research Fund for Africa (SRFA), to better understand the

process of developing new sanitation technologies which meet the needs of the market. The

project is based in Kampala, Uganda, where, amongst other technologies, the primary focus

is on the development of low cost semi-mechanical pit emptying devices such as the Rammer

and Nibbler and a decentralized faecal sludge treatment plant.

The research on the Rammer and Nibbler was conducted at the Kampala Sanihub led by two

Researchers, Sam Malinga and Herbert Atayo who are both Engineers. This research was

undertaken to develop better devices that could pump thick sludge, cleaner, go deeper and are

affordable to entrepreneurs wishing to start a pit emptying business. Slump cone tests were

carried out to determine the consistency of wetness and fluidity of a synthetic sludge which

would be used to estimated shear strength of synthetic sludge. Shear strength of 100pa,

500pa, and 2kpa were selected to determine the pumping limit of existing pumps. Synthetic

sludge comprising of 85% top soil and 15% kaolin clay were prepared for pump testing for

respective shear strength calculated.

Pump testing was performed on the Gulper, Rammer, and Nibbler. The parameters evaluated

include; time taken to prime, insertion and removal from the pit, and output within 30

seconds. The results showed that the Rammer was capable of pumping sludge of up to 500pa

shear strength with a greater discharge than other devices.

The design improvements were carried out on both the Rammer and Nibbler. For the

Rammer, the donkey tail was incorporated, both the fixed strut and internal rising bar were

made modular to allow the device to enter deeper into a pit, and inner fixed cylinder bend

was reduced to 25° to limit flow restrictions. The Nibbler design improvements were made

on the chain, delivery, discs, and smooth chain movement.

The technologies were demonstrated to the operators and desktop survey was carried out to

gain feedback on these devices. This report also contains further recommendations to be

made to the devices.

The Rammer and Nibbler Page iii

TABLE OF CONTENTS

EXECUTIVE SUMMARY ....................................................................................................... ii

LIST OF TABLES .................................................................................................................... vi

LIST OF FIGURES .................................................................................................................. vi

LIST OF ABBREVIATIONS .................................................................................................. vii

1.0 Introduction and Background ............................................................................... 1

1.1 Main Objectives of the Research ................................................................................ 2

2.0 Existing Emptying Methods ................................................................................. 3

2.1 Rudimentary Emptying ................................................................................................ 3

2.2 Cesspool Emptier ......................................................................................................... 3

2.3 Gulping ........................................................................................................................ 3

3.0 Testing Existing Devices on Synthetic Sludge ..................................................... 4

3.1 The Gulper ................................................................................................................... 4

3.2 The rammer ................................................................................................................. 4

3.2.1 Handle .................................................................................................................. 5

3.2.2 The internal rising bar .......................................................................................... 5

3.2.3 The Fixed Strut ..................................................................................................... 5

3.2.4 External rising bars ............................................................................................... 5

3.2.5 Fixed Cylinder ....................................................................................................... 5

3.2.6 The hose Pipe ....................................................................................................... 5

3.2.7 Outer Rising Cylinder ........................................................................................... 5

3.3 The Nibbler .................................................................................................................. 6

3.4 Slump Cone Tests ........................................................................................................ 6

3.4.1 Procedure of slump cone tests ............................................................................ 6

3.4.2 Results of slump cone test ................................................................................... 7

3.5 Preparation of Synthetic Sludge ................................................................................ 10

3.6 Pump Testing ............................................................................................................. 10

3.6.1 Procedure ........................................................................................................... 10

3.6.2 Results and Discussions of the Pumping Test .................................................... 11

3.6.3 Test Analysis of the Gulper ................................................................................ 13

3.6.4 Test Analysis of the Rammer ............................................................................. 13

3.7 Test Analysis of the Nibbler ...................................................................................... 14

4.0 Development of the Improved Rammer and Nibbler ......................................... 15

4.1 Development of the Rammer ................................................................................... 15

4.1.1 Introduction ....................................................................................................... 15

4.1.2 The Mechanism and principle of operation ...................................................... 15

The Rammer and Nibbler Page iv

4.1.3 Prototype development ..................................................................................... 15

4.2 Design improvements ............................................................................................... 16

4.3 Design ........................................................................................................................ 16

4.3.1 Pipe sizing ........................................................................................................... 16

b) The height of the Rammer ..................................................................................... 17

4.3.2 Total Volume to be occupied by sludge ............................................................. 17

4.3.3 Mass, m .............................................................................................................. 18

4.3.4 Weight, W .......................................................................................................... 18

4.3.5 Fabrication materials ......................................................................................... 19

4.4 Development of the Nibbler ..................................................................................... 21

4.5 The development of the second generation Nibbler ................................................ 21

4.6 The operating principle ............................................................................................. 21

4.7 Design analysis of the Nibbler ................................................................................... 22

4.8 Design improvements ............................................................................................... 24

4.9 Test performance on synthetic sludge ...................................................................... 24

5.0 Operators feedback ............................................................................................. 25

5.1 Feedback on the Rammer ......................................................................................... 25

5.1.1 Challenges of the Rammer ................................................................................. 25

5.2 Feedback on The Nibbler .......................................................................................... 25

5.2.1 Challenges of the Nibbler................................................................................... 25

5.2.2 Way forward for the Rammer ............................................................................ 26

5.2.3 Way forward for the Nibbler ............................................................................. 26

6.0 Further development ........................................................................................... 27

6.1 Peddler ...................................................................................................................... 27

6.2 New Valves ................................................................................................................ 27

7.0 Conclusions and Recommendations ................................................................... 28

7.1 Conclusions................................................................................................................ 28

7.2 Recommendations .................................................................................................... 28

References 29

Appendices 30

Appendix A: Pictures of pump testing of the Gulper ........................................................... 30

Appendix B: Pictures of pump testing for the Rammer ....................................................... 31

Appendix C: Launching of new devices and getting operators feedback ............................ 32

Appendix D: Field testing the Rammer during the sanitation week ................................... 33

APPENDIX E: OPERATOR FEEDBACK QUESTIONNAIRE ........................................................ 34

The Rammer and Nibbler Page v

The Rammer and Nibbler Page vi

LIST OF TABLES

Table 1: Design Chart for Slump cone ...................................................................................... 9

Table 2: Results based on 100pa .............................................................................................. 12

Table 3: Results based on 500pa .............................................................................................. 12

Table 4: Bill of materials ......................................................................................................... 19

LIST OF FIGURES

Figure 1: The Rammer prototype 2 ............................................................................................ 4

Figure 2: Mixing top soil and kaolin clay .................................................................................. 6

Figure 3: (a) Gently removing slump cone and (b) Slump allowed to settled for 30s ............... 7

Figure 4: (a) Measuring the slump and (b) Collapsed Matrix ................................................... 7

Figure 5: shear strength from slump reading versus water content ........................................... 9

Figure 6: Hooking the barrel to lower it into the pit ................................................................ 11

Figure 7: Weight of sludge to be lifted shaded black .............................................................. 13

Figure 8: Portion of sludge to be lifted .................................................................................... 14

Figure 9: Force acting on the handle........................................................................................ 19

Figure 10: Force diagram ......................................................................................................... 22

Figure 11: disc.......................................................................................................................... 22

Figure 12: Nibbler testing ........................................................................................................ 24

Figure 13: The Peddler Rammer .............................................................................................. 27

Figure 14: New valves design .................................................................................................. 28

The Rammer and Nibbler Page vii

LIST OF ABBREVIATIONS

FSM Faecal Sludge Management

SAAB Sanitation As A Business

SRFA Sanitation Research Fund for Africa

WFP Water For People

WRC Water Research Commission

KCCA Kampala City Council Authority

The Rammer and Nibbler Page 1

1.0 Introduction and Background

Water for People (WFP) is a United States registered non-governmental organisation with

solid presence in Latin America, Asia and Africa (Uganda, Rwanda and Malawi).

WFP brings together local entrepreneurs, civil society, governments, and communities to

establish creative, collaborative solutions that allow people to build and maintain their own

reliable safe water systems. Empowering everyone transforms people’s lives by improving

health and economic productivity to end the cycle of poverty. WFP’s vision is a world where

all people have access to safe drinking water and sanitation, a world where no one suffers or

dies from a water or sanitation-related disease.

WFP is currently implementing the Sanitation As A Business (SAAB) program, a market

based approach to improving access to sanitation, which aims to develop and support

sanitation businesses such as latrine construction and a pit emptying service using a semi

mechanical hand pump known as the Gulper.

The SAAB program’s research and development arm, The Sani-Hub Project began

collaboration with the Water Research Council (WRC) in South Africa, under the Sanitation

Research Fund for Africa (SRFA), to better understand the process of developing new

sanitation technologies which meet the needs of the market. The project is based in Kampala,

Uganda, where, amongst other technologies, the primary focus is on the development of low

cost semi-mechanical pit emptying devices such as the Gulper and a decentralized faecal

sludge treatment plant. Using these innovations, the SAAB program aims to develop business

which adds value at each stage of the sanitation value chain, from capture and storage, to pit

emptying, sludge transport and treatment, through to reuse.

Faecal Sludge Management is one of the greatest challenges facing urban authorities today

with the rate of pit fill up exceeding their capacity both technically and financially to empty

and dispose. FSM is becoming an important issue in Uganda’s urban centers especially in

slums where vacuum tankers cannot access the majority of pits. Batch of latrines can be seen

abandoned in various homes and many other open spaces, and this constitutes a crucial

problem to human beings in particular and the environment in general.

Many evidences show that a key driver towards increased efficiency in FSM is the

involvement of all stakeholders including, the waste generators, waste processors, formal and

informal sectors, financial institutions and private initiatives such as non-governmental and


community based organizations (Kassim and Ali, 2006). These technologies will however

improve pit emptying services to people living in unplanned settlements.

1.1 Main Objectives of the Research

To access the performance limit of existing pit emptying devices

To develop a pump that reaches further in to the pit and is cleaner, quicker and easier

to operate than the Gulper.

To develop a device that can pump thicker sludge.

To get operator and business feedback on the new technologies.


2.0 Existing Emptying Methods

This covers the common methods of pit emptying which include; cesspool empting, Gulping

and rudimentary methods.

2.1 Rudimentary Emptying

The habit of releasing untreated faecal matter into the environment is still persistent; most

households living in unplanned settlements like Naguru Go-down, Kamwokya, Kisenyi,

Kibuli, Bwaise, and Natete have a tendency to construct their pits near drainage channels.

During periods of heavy downpour they crack some holes into the pit and release the faecal

sludge into the flood water and this has caused a lot of health problems in the neighborhoods

and this practice has always been attributed to a lack of affordable pit emptying services.

2.2 Cesspool Emptier

There are about 29 vacuum tank trucks serving Kampala and the neighboring districts of

Wakiso and Mukono. These tanks mostly pump liquid slurry and can only service those

facilities which have a clear path for the truck to pass. This has left many facilities unattended

and thus the birth of the gulping pit emptying business.

2.3 Gulping

As part of WFP commitment towards improved sanitation, SAAB launched gulping business

in December 2012 to improve sanitation in unplanned settlements which cannot access

improved sanitation services either because they unable to access modern cesspool emptier or

the quality of the faecal sludge in their pits cannot be pumped by the cesspool emptier. When

gulping was introduced in Uganda, it received a warm welcome in these unplanned

settlements. It was looked at as a heavenly solution to their problems. After a marketing

campaign, 10 entrepreneurs purchased this technology to create their own pit emptying

businesses. A gulping team consists of at least two people having gulping equipment which

include the Gulper, barrels, protective gear, jerricans, a hook and a pickup truck for

transporting the waste to Bugolobi wastewater treatment plant. Few months down the road

these entrepreneurs came to realize the operational limits of the Gulper; it could not pump

thick sludge which is commonly present at the bottom of pits and does not also go deeper into

the pit. KCCA has refused to legalize the use of the Gulper for pit emptying because of the

nature in which faecal sludge is handled during gulping operation, though they do not oppose

using it.


3.0 Testing Existing Devices on Synthetic Sludge

Synthetic sludge of known shear strength was made to test the existing pumps in a controlled

environment. These tests gave a better understand how the pumps function and fail without

having to work with faecal sludge.

Synthetic sludge was prepared by mixing top soil and kaolin clay. This test embraces slump

cone tests, synthetic sludge preparation, pit set up, and pump testing. The devices tested and

evaluated were the Gulper, Rammer, and Nibbler.

3.1 The Gulper

The Gulper is a simple direct lift pump which operates in a similar way a borehole works. It

is designed to partially empty existing pit latrines of the supernatant layer at the top of the pit.

The standard gulper will reach 1m -1.5m in to the pit.

3.2 The rammer

The Rammer uses direct lift mechanism to pump sludge using outer

rising cylinder and delivers it to the barrel through a hose pipe which

is meant to make the operation of pit emptying cleaner. It can be

extended 3 meters into the pit. The Rammer components include:

outer rising cylinder, fixed inner cylinder with valve, fixed strut,

internal rising bar, external rising bars, cage, butterfly valve, and

handle. Please refer to page 14 of the rammer technical drawings in

relation to the description of the device’s components below.

Figure 1: The Rammer prototype 2


3.2.1 Handle

This is connected on the top of the internal rising bars; the lifting force is applied at this point

to provide up and downward stroke for the outer rising cylinder.

3.2.2 The internal rising bar

The internal connecting bar has a drilled hole at the top where the handle is bolted. The slot

insert with drilled holes is welded at the bottom of internal rising bar.

3.2.3 The Fixed Strut

The fixed strut is connected to vertical extension on the fixed inner cylinder. The strut houses

the inner connecting bar and is where slot is cut for movement of external rising bars. The

plug that closely enters into the fixed strut is fitted to prevent contraction of the slot thus easy

drive of the external rising bars.

3.2.4 External rising bars

The two external rods are bolted externally to outer rising cylinder and slot insert which is

welded on the internal rising bar. It moves the outer rising cylinder up and down.

3.2.5 Fixed Cylinder

This is smoothly bent to an angle of 25° to permit smooth flow of sludge into the hose pipe. It

has fixed buttery valves that control the flow of sludge into the pipe. It also has vertical

connection where the fixed strut is linked.

3.2.6 The hose Pipe

The pipe enables sludge to be directly pumped into the barrel so as to prevent spillage during

transfer of sludge using jerricans.

3.2.7 Outer Rising Cylinder

This is the moving cylinder of the Rammer, which collects sludge and houses the cage and

first butterfly valve. External rising bars are bolted here. As apposed to the gulper which has

no external moving parts, the rising cylinder is pushed into pit sludge, thus allowing thicker

sludge to enter into the device.


3.3 The Nibbler

This is a pit emptying device which is meant to remove thicker sludge which cannot be

removed by the Gulper. It uses the same principle as the rope pumps. It has a motor bike

chain instead of a rope and also has circular discs attached to the chain for picking sludge.

3.4 Slump Cone Tests

This is an empirical method used to determine the consistency of wetness and fluidity of

sludge. This aided in approximation of shear strength of the synthetic sludge which was used

for testing existing pumps.

3.4.1 Procedure of slump cone tests

Top soil of 8500g by dry mass was mixed with kaolin clay of 1500g making top soil 85% by

dry mass and Kaolin clay 15%. The recipe was thoroughly mixed in a bucket as seen in

Figure 2.

Figure 2: Mixing top soil and kaolin clay

Initial 2200g of water was added to the mix to make a simulant mix. After making the

simulant mix, varied amounts of water were added to the matrix and for each addition a

slump cone test was performed. A slump cone test involved filling a standard slump cone of

base diameter of 200mm, top diameter of 100mm and height of 300mm with the synthetic

sludge. The synthetic sludge was well compacted to ensure that no voids were within the

cone. When the cone was fully filled with synthetic sludge, the slump cone was gently

removed. After removing the cone, the cone shaped matrix was allowed to settle for 30

seconds as shown in Figure 3 and subsequently the slump was measured.


Figure 3: (a) Gently removing slump cone and (b) Slump allowed to settled for 30s

The whole procedure of adding water and measuring the slump was carried out until the

matrix collapsed completely.

Figure 4: (a) Measuring the slump and (b) Collapsed Matrix

3.4.2 Results of slump cone test

There was a gradual increase in slump with each addition of water. However there was a lot

of deviation from the theoretical values (Radford 2013). For example, for 18% water content

which corresponded to a theoretical slump of 4.16mm, a slump of 18mm was measured

which was far away from our prediction as shown in the Table 1. This drastic deviation was

as a result of our simulant mix. The top soil used had 8% moisture content; less organic

content, finer particles with a density of 918.2kgm-3 yet the soil for which our modules were

based on had 18% moisture content, a higher organic content and a density of 367.28kgm-3.

Also the bench mark kaolin clay had a density of 999.82kgm-3 with granular particles

whereas the sample of kaolin clay used was powdery with a density of 550.92kgm-3.

Nevertheless different modules which correlated linearly with the simulant parameters were

developed by plotting shear strength from slump reading against water content as seen in

Figure 5.

The results from the slump cone tests were tabulated in an excel sheet which had these

equations (Jamie, 2013) fed in each column to generate values in Table 1.

Water content (total mass basis), equivalent to (1-TS) sw

w

mm

m

mass total

watermassWC

a b


Water content (dry mass basis) s

w

m

m

solids massdry

watermassmc

Conversion factors – water content on dry/total mass basis,mc1

mcWC

,

WC1

WCmc

Embodied water content (total mass basis) – determined by oven drying sample of topsoil

mass total

solids with bound water massWCE

Total water content (total mass basis) – includes embodied water content and water added to

simulant mix

mass total

simulanthin water witmass totalWCT

Normalised WC, based on tests on the 60% kaolin, 40% topsoil (by dry mass) simulant

shown in 'Chart' ETEN B.WC).WCA.WC(1WC

Normalisation parameter – gradient A = 2.25

Normalisation parameter – intercept B = 1.25

Equation to calculate total WC from normalised WC and embodied WC

)A.WC(1

)B.WC(WCWC

E

ENT

Correlation between shear strength and normalised water content

NWCβατ

Regression parameter – intercept α = 67556

Regression parameter – gradient β = 1.7707E-006

Equation to calculate required normalised WC for target shear strength

)log(

)log()log(

NWC

Correlation between slump and shear strength qpτS

Regression parameter – intercept p = 18316

Regression parameter – gradient q = -0.77


Table 1: Design Chart for Slump cone

Addition

Water

added

in g

Cumulative

water

added in kg

Water

content

in kg

Total

water

content

WCt

Normalised

water

content

Shear

strength

from

NWC

Theoretical

slump

Actual

slump

Shear

strength

from AS

1 200 0.2 2.40 0.18 0.02 49653.02 4.16 18 7511.371

2 100 0.3 2.50 0.19 0.03 44182.99 4.55 24 5184.605

3 100 0.4 2.60 0.19 0.04 39384.43 4.98 36 3074.638

4 200 0.6 2.80 0.21 0.06 31454.03 5.92 48 2122.22

5 200 0.8 3.00 0.22 0.07 25285.46 7.02 62 1526.003

6 200 1 3.20 0.23 0.09 20454.36 8.27 80 1098.76

7 200 1.2 3.40 0.24 0.11 16645.86 9.71 90 944.0276

8 200 1.4 3.60 0.25 0.12 13624.56 11.34 140 534.207

9 200 1.6 3.80 0.26 0.14 11213.26 13.19 166 428.9181

10 200 1.8 4.00 0.27 0.15 9277.63 15.28 196 346.2583

11 200 2 4.20 0.28 0.16 7715.17 17.63 214 309.1918

12 200 2.2 4.40 0.29 0.18 6447.19 20.27 231 280.1862

13 200 2.4 4.60 0.30 0.19 5412.88 23.21 254 247.9282

A graph of shear strength against water content

Figure 5: shear strength from slump reading versus water content

2000

500


A graph of shear strength against water content shows a linear relationship. Using the fact

that the more water added, the weaker the matrix became. Synthetic sludge of required shear

strength was prepared using the graph. Intersection of a horizontal line drawn from the

required shear strength to the gradient corresponds to the amount water to be added to the

recipe and read from horizontal axis on water content.

3.5 Preparation of Synthetic Sludge

The three barrels of synthetic sludge of shear strength 100pa, 500pa, and 2kpa were prepared

to test the existing pumps in a controlled environment. From the slump cone tests shear

strength of 100pa, 500pa and 2kpa could be achieved using our recipes. Exactly 85% of our

top soil by dry mass and 15% of our kaolin clay needed 0.32% of water to attain shear

strength of 100pa. For 500pa, 0.27% of water and 2kpa needed 0.23% of water as shown by

dotted lines in Figure 5. The synthetic sludge was made in small portions to make mixing

easier. The mass of 1500g of kaolin clay was measured and poured in a basin and 9239g of

top soil was measured taking in consideration the amount of water embedded in the top soil

and was added to the kaolin clay in the basin. Varying amounts of water were then added. For

100pa each time 4120g of water was added, 3174g for a 500pa and 2410g for 2kpa shear

strength. Three 220L barrels were filled with the varying simulant mixes. The resultant

mixtures in the respective barrels were again re-mixed to ensure uniformity of the matrix as

there was a tendency of soil to settle at the bottom.

3.6 Pump Testing

This was primarily done to establish the range of shear strength over which the available pit

emptying devices could operate.

3.6.1 Procedure

The tests started with the 100pa barrel which was lowered into the pit using chain block

hooked on to a metal frame shown in Figure 6.

The slab was placed on the pit and thereafter a super structure was laid on the slab to mimic a

typical pit emptying operation.


Figure 6: Hooking the barrel to lower it into the pit

The Gulper, Rammer, and Nibbler were tested one at a time. For each device, different

parameters were evaluated; the ability of operators of different weights to operate, time taken

to prime, rate of output, time taken to insert into the pit, time taken to remove the device from

the pit, ease of cleaning, robustness and ease of operation.

When the pumping test was completed for the 100pa barrel, the barrel was removed from the

pit and replaced with the 500pa barrel, after which the testing was repeated. The same

procedure was done for the barrel of shear strength 2kpa.

3.6.2 Results and Discussions of the Pumping Test

This contains all the measured time taken to insert, prime and remove the devices and the

resultant mass of synthetic sludge obtained after 30 seconds of pumping at different shear

strengths as shown in Table 2 and 3.


Table 2: Results based on 100pa

Name of

the pump

Operator Time

taken to

prime /s

Time to

insert

device into

the pit (s)

Mass(g) of

sludge pumped

in 30s

Time to

remove device

from the

pit(S)

Gulper Habert A (60 kg) 16 14 17462 26

Gulper Samuel M (80 kg) 15 14 17888 26

Gulper Habert A & Samuel

M

10 14 27585 26

Rammer Habert A (60 kg) 13 20 16485 (21485

when hose

emptied)

13

Rammer Samuel M (80 kg) 12 20 19460 (31960

when hose

emptied)

13

Rammer Habert A & Samuel

M

10 20 35000 13

Nibbler Samuel M (80 kg) Could not

prime

10 0 15

Table 3: Results based on 500pa

Name of the

pump

Operator Time taken

to prime /s

Time to

insert device

into the pit

(s)

Mass(g) of sludge

pumped in 30s

Time to remove

device from the

pit(s)

Gulper Habert A (60

kg)

Failed after

125s trial

14 Failed 30s

Gulper Samuel M (80

kg)

Failed after

180s trial

14 failed 34s

Gulper Habert A &

Samuel M

Failed after

240s trial

14 failed 33s

Rammer Habert A (60

kg)

Failed 20 failed 25s

Rammer Samuel M (80

kg)

214 20 19460

(pumped by

Habert & Sam)

15s

Rammer Habert A &

Samuel M

22 20 30500 15

Nibbler Samuel M (80

kg)

Could not

prime

12 0 18


3.6.3 Test Analysis of the Gulper

The priming of the Gulper was easy for 100 pa and pumping was tiresome as a person of 60

kg could operate it for a short time and became exhausted quickly. Insertion of the Gulper

into the pit was simple but its removal from the pit was cumbersome and it needed two

people due to accumulation of sludge along the column of the Gulper. Cleaning the Gulper

took four minutes. For 500 pa, the gulper failed to prime even when operated by two people.

This was due primarily to the increase in shear strength of sludge, which the

plunger struggled to overcome, and thus it was difficult for the simulant to

enter into the column. Furthermore, the increase in density of the simulant

increased the load, meaning a greater force was required to lift the simulant

out of the pit.

The portion shaded black in figure 7 indicates the vertical weight of sludge

to be lifted that made the Gulper fail to pump sludge of shear strength

500pa. The propensity of sludge to amass in the column of the Gulper made

pumping hard. Above all, the Gulper does both delivery and suction

(pulling sludge) concurrently thus a bigger force is normally required for its

operation.

Figure 7: Weight of sludge to be lifted shaded black

3.6.4 Test Analysis of the Rammer

Priming the Rammer using 100pa sludge took less time than the one taken by the Gulper

because it had a shorter column to be filled with sludge. Insertion of the Rammer into the pit

was much easier and one person could also remove it from the pit. This was also attributed by

shorter column of the Rammer. Cleaning the Rammer took more time and water than the

Gulper. With 500pa, the Rammer was able to pump. This was because the Rammer does not

pick sludge by suction, instead the downward stroke of the outer rising cylinder pushes into

the sludge, thus forcing it to pass through the butterfly valve and into the cylinder the upward

stroke then lifts the sludge into the inner fixed cylinder as seen in Figure 8. Back flow of

sludge is prevented by the second butterfly valve attached to the inner fixed cylinder.

Continuous up and down motion of the outer rising cylinder causes sludge to accumulate in

the inner fixed cylinder until it is discharged through the hose pipe.


.

Figure 8: Portion of sludge to be lifted

3.7 Test Analysis of the Nibbler

The first prototype which was developed by Steve Sugden was not properly fabricated; the

link chain could not rotate smoothly as the motion constantly got locked at short intervals. It

picked little sludge but could not deliver it and the sludge eventually rolled back.


4.0 Development of the Improved Rammer and Nibbler

This section covers the design and operational improvements carried our on these devices to

address the challenges witnessed during pump tests.

4.1 Development of the Rammer

4.1.1 Introduction

The Rammer was developed by Steve Sudgen using the principle of direct lift: The design

concept was to have the moving parts external for easy cleaning. The improved Rammer

components include: outer rising cylinder, fixed inner cylinder with valve, modular fixed

strut and internal rising bar, external rising bars, cage, butterfly valve, rubber seal, and

adjustable donkey tail. The hose pipe is usually clamped on the outlet of the fixed inner

cylinder and then directed to the barrel for delivering sludge. Thus the operation is improved

as there is no need for fetching the sludge in jerry cans, which often causes spillage. The

suction pipe is submersible depending on the depth of the pit.

4.1.2 The Mechanism and principle of operation

The up and down stroke of the internal rising bar provides power to the external bars for

lifting and lowering the outer rising cylinder. Unlike the Gulper, the development of the outer

rising cylinder means that during the down stroke the outer rising cylinder is pushed into the

sludge and it is forced into the cylinder. This is what enables the rammer to pump thicker

sludge than the gulper. The upward stroke allows the sludge collected in the rising cylinder to

be conveyed into the fixed inner cylinder through upper butterfly valve.

The sludge collected into the fixed inner cylinder keeps on amassing during the upward

stroke and back flow is prevented by the fixed upper valve, thus priming the device. The

upward stroke lifts the collected sludge easily until it reaches point where it starts to transfer

it to the hose pipe where an additional force is required to overcome the column weight of the

sludge that has accumulated. Sludge is then discharged from the suction hose directly into a

barrel.

4.1.3 Prototype development

The Rammer was designed and developed to meet the criteria that it must be:

Able to go further into the pit for at least 3 m

Cleaner during operation and easy to clean

Affordable to entrepreneurs


Capable of pumping thick sludge

Fast and calm to operate

Locally fabricated, materials readily available and easy to repair

Easy to assemble, disassemble and transport

4.2 Design improvements

Adjustable donkey tail which is detachable was designed and incorporated with the

footstool so as to minimize the load applied to the fixed strut that may cause it to

bend.

The internal rising bar was made modular such that it can be extended using a pipe of

diameter 20 mm that is bolted into it. This enables the rammer to reach deeper into a

pit.

Similarly, by using threaded pipes joined using a socket, the fixed strut can also be

extended in 1m sections, thus allowing the device to reach deeper into a pit.

4.3 Design

These are steps taken in developing the Rammer to standard dimensions and for optimum

operation.

4.3.1 Pipe sizing

The pipe sizes were selected considering the following pit latrine parameters for easy

insertion and removal of the Rammer;

The length and width of the slab hole in the pit

The height of the toilet structure

The hole Length, L = 200 mm and width, W = 120 mm. These dimensions are based on the

standard size of a clay brick, which is often used to make the slab hole during casting.

a) The Plastic outer Cylinder;

The PVC pipes of φ = 110 mm and 90 mm could be used for fabrication of this component

part but for this research, 110 mm PVC pipe with thickness of 3.2 mm was used. The choice

of the pipe diameter was to allow The Rammer to be inserted into the pit without needing to

break the slab hole.


b) The height of the Rammer

Cage, PVC rising cylinder and fixed inner cylinder will all have height of 200mm, 530mm,

490 mm but since the inner fixed cylinder enters into PVC rising cylinder, their component

height is 800mm. The fixed strut and internal rising bar protrusion will be of height 1700mm.

Since the Rammer was inserted while slanting the whole component. It will enter well for a

typical latrine door of height 1.8m.

The device has been designed such that should it can be extended deeper into the pit, 1m

modular pipe sections are attached in situ. This prevents the need for the operator to remove

the device before making it longer.

4.3.2 Total Volume to be occupied by sludge

The volume of each pipe section was calculated using equation:

Where v is the volume

d is the internal diameter of pipe

h is the cylinder height

Volume of sludge in the PVC rising cylinder

Volume of sludge in the fixed internal bar

32

f 0.00445m4

0.70.09πv

900mmd

700mmh

Volume of sludge in the suction hose pipe

4

hπdv

2

rv

fv

sv

32

r 0.00447m4

0.530.1036πv

530mmh

103.6mmd


32

s 0.02722m4

60.0762πv

76.2mmd

6000mmh

The total volume to be pump

4.3.3 Mass, m

The mass of sludge being pumped was calculated using equation

Where is density of sludge and assumed to be 1500 kgm-3 (David and Mark, 2012)

Therefore,

Considering the mass of the PVC rising cylinder, cage with valve, external rising bars, and

internal rising bar to be 2 kg since these parts are also lifted.

The total was will be 17.21 kg during each upward stroke

4.3.4 Weight, W

Where g is the acceleration due to gravity, g=9.81ms-2

Therefore the weight to be lifted can be calculated

There is resistance to smooth movement of the pipe and assuming the coefficient of friction

to be for a pipe of ɸ=110 mm

Hence the friction force to be subdued will be

Consequently, the total force will be

Thus, the force applied to effectively pump the sludge should be greater than 171.7N

303614.002722.000445.000447.0 m

vvvv sfrT

Tvm

15.21kg15000.03614m

mgW

168.83N9.8117.21W

017.0

2.87N168.830.017μWf

171.7N2.87168.83FT


This weight is directly transferred to the lifting point on the inner rising bar;

Figure 9: Force acting on the handle

Therefore, L=171.7N and by taking moments about the pivot and considering the length of

the handle to be 1m. Thus, the minimum effort for equilibrium can be calculated

A healthy well-fed labourer over the course of an 8-hour day can sustain an average output

of about 75 watts (Tom, 2007).

The power required, 2.15watts8

0.357.23P

Therefore, most adults should be able to operate the Rammer effectively because the power

requirement is far below the maximum of 75 watts.

4.3.5 Fabrication materials

This contains the list of materials required for fabrication of the Rammer and detailed cost

break down. The materials are readily available in the following markets; Nakasero, Kisenyi,

Kiseka and Bwaise. Pentagon Technical Services is a local agro-process company that is

working with Sanihub Engineers to fabricate and refine the Rammer. Throughout the

technology development, the cost of the device has remained low to limit business start up

costs.

Table 4: Bill of materials

Item Quantity Unit Unit cost (£) Total cost ($)

PVC Rising cylinder

PVC pipe 110 mm, thickness 3.2 mm class

4 0.53 m 28 15

Fixed inner cylinder

Mild steel pipe 90 mm, thickness 1.5 mm 0.70 m 30 21

Butterfly valve 1 each 6 6

57.23NE

0.75E0.25171.7

0.25m

1m

Load (L)

Effort (E)


Mild steel 50 mm, thickness 3 mm 0.30 m 16 4.8

Round bars φ = 7mm 4 m 2.5 10

Rubber seal 1 each 4 4

Fixed support strut

Galvanised Iron 42 mm, 3 M 10 30

Slot plug 0.05 m 10 1

Footstool and donkey tail frame

Triangular foot stool 1 each 6 6

Vertical support 1 each 4 4

Donkey tail handle 1 each 6 6

Others

Internal rising bar 3 m 4 12

External rising bar 3 m 4 12

Cage with rising valve 1 each 10 10

Nuts and bolts 15 each 0.3 4.5

Washers 2 each 0.5 1

Hook 1 each 6 6

Subtotal 153

Hose pipe 6 m 10 60

Clamp 1 each 8 8

Labour (30%) 46

Total 267


4.4 Development of the Nibbler

Thick sludge at the bottom of non-flush pits has for long proved a bottle neck to full pit

emptying service providers. Many attempts have been made to develop thick sludge devices;

however none have successfully been taken to the market. The development of the pit screw

auger never went further than the development stage as it failed with the addition of solid

waste in pits, and required a very high RPM on watery sludge. The belt drive concept did not

also go beyond the concept itself. The Nibbler showed a great potential and was further

refined in South Africa into a gobbler which had two chains and its application was limited

due to its high weight and so many moving parts, the ideas of the Nibbler was abandoned

because of the difficulty in removing the sludge from the discs (David and Mark, 2012).

4.5 The development of the second generation Nibbler

Showing a lot of potential in something that can be refined further into a device of practical

application, more research is being conducted into the Nibbler. The second generation

Nibbler is more like the first generation. It consists of a motor bike chain onto which discs are

welded. The disc-chain assembly is constrained to move through two vertical PVC pipes by a

cylindrical joint at the bottom and a sprocket at the top. The sprocket is welded onto a handle

for turning. Rotating the handle at the top of the device causes the sprocket to rotate, forcing

the disc chain assembly to rotate in the same direction. During this motion, the disc scoops

thick sludge from the bottom of the pit latrine and force it into the rising pipe. When the

sludge reaches the top, it is scraped from the discs by a metallic scrapper into the delivery

hose. Sludge then gradually falls into a bucket underneath.

4.6 The operating principle

The Nibbler uses a the scoping principle as it’s primary means of operation, similar to eating

porridge. Dip your spoon in the porridge, scoop, take to your mouth and remove then back to

the porridge. The Nibbler has multiple circular discs which function using the same principle.

The discs welded onto motor bike chain act like spoons to scoop thick sludge. The discs are

welded offset onto the motorbike chain such that the surface area for scooping sludge is

maximum and also to allow more sludge to be removed from the discs by the scrapper.


4.7 Design analysis of the Nibbler

Figure 10: Force diagram

Figure 11: disc

column PipeRiser Effective disc of Area surface =v

column piperiser in the Volume=v

sludge ofDensity =

where;

vgmg=W

)(Wcolumn riser in the sludge ofWeight

19.62N9.8122g =W

4kg = discs pluschain of mass Total =W

2

assemblychain disc of weight Total =W

disc from sludge removinghen scrapper wagainst rubbing discs ofresult a as Resistance=W

overcome be tosludge of forceShear =W

columnriser in the sludge ofWeight =W

discs pluschain theofWeight = W

turn tohandhuman by appliedEffort = E

2

2

1

1

1

4

3

2

1

N0.05559.810.00565mass

0.00565m20.002827v

0.002827m

4

0.06π

4

πd= Area

3

2

2


Neglecting volume occupied by discs since they are only 2mm thick this is negligible

compare to the riser column of 2000mm and the density of thick sludge to be 2000kgm-3

(David and Mark, 2012)

= 0.0555×2000

=111N

Shear force of sludge to be overcome (W3)

The minimum effort required to be applied by the operator to just turn the handle is 92.793N

A healthy well-fed labourer over the course of an 8-hour day can sustain an average output

of about 75 watts (Tom, 2007).

Power required for operation over a period of 8 hours, 7.29watts8

0.2π92.793P

Therefore power required to operate the Nibbler is 7.92W which is much lower than 75W,

hence most people should be able to operate the Nibbler.

22

3

0.377m377000mm2000 188.5 =

piperiser theoflength disc of ncecircumfere = acts stressshear on which Area

188.5mm60ππddisc of nceCircumfere

columnriser ofLength disc of nceCircumfere =Area

Area stressShear W

92.793N=E

200E=9573.6+5655+3330

200)(E + 30)(19.62 = 30)(319.12 + 30)(188.5 + 30)(111 + 30)(19.62

200)(E + 30)(W = 30)(W + 30)(W + 30)(W + 30)(W

Opoint at moments Taking

319.12N=W

188.5+111+19.62=W

W+W+W=W

(W4) disc from sludge removinghen scrapper wagainst rubbing discs ofresult a as Resistance

188.5N=W

0.377500 =W

500pastrength shear of sludge gConsiderin

area stressshear =W

14321

4

4

3214

3

3

3


4.8 Design improvements

The discs were attached to the chain at the periphery exposing a large surface area for

scooping.

Welding discs on the chain at the periphery instead of the centre also exposed larger

surface of the disc from which sludge could be extracted at the top.

The top of the device was encased to reduce chances of contact with sludge.

It has a scrapper to aid removal of sludge from discs.

4.9 Test performance on synthetic sludge

When the new prototype was tested on 500 pa synthetic sludge, it was able to remove a

justifiable amount of sludge from the bottom and deliver it at top through the delivery

channel without struggle.

Figure 12: Nibbler testing


5.0 Operators feedback

This was carried out to obtain the opinions of existing pit emptying entrepreneurs for which

these devices are developed. This would enable the designers to improve the devices further.

Testing of the two equipment was done during the sanitation week by the 5 entrepreneurs

5.1 Feedback on the Rammer

The operators were impressed with the Rammer’s ability to pump thick sludge. They also

liked the donkey tail design used to aid pumping. They were all willing to return their

Gulpers and top up in exchange for the Rammer. Above all, the Rammer appears to have

been accepted by all operators.

5.1.1 Challenges of the Rammer

Cleaning the hose pipe was hard because the inner part cannot be accessed.

Insertion of the Rammer into some pit latrines was tough. The standard pit slab hole has

dimensions of 200 by 120 mm yet some pits have dimensions lower than that.

There is still escape of watery sludge through the clearance between the two cylinders. A

rubber seal has been installed to prevent this, however a better solution needs to be found

as it does not completely prevent water from escaping between the cylinders.

5.2 Feedback on The Nibbler

It was a very embarrassing moment to get feedback from entrepreneurs in the pit emptying

businesses. The entrepreneurs were excited at the sight of the Rammer, when it performed,

they nodded their heads on approval and they could be heard making praise comments on the

rammer. But when it came to testing the Nibbler, they did not want to know what the Nibbler

was and what it does. It was hard to convince them to test the Nibbler; only one entrepreneur

came closer to the Nibbler as most of them were all pointing at the Rammer.

5.2.1 Challenges of the Nibbler

The disc often got stuck at the point of forcing sludge into the riser pipe and at the

point of entry to the return pipe.

The scrapper caused a lot of resistance and thus made it hard to turn at intervals.

It was very difficult to clean the Nibbler as thick sludge tended to adhere onto the

chain and pipes.


The Nibbler was also very heavy to remove from the pit because both columns were

filled with sludge.

It was very difficult to remove the Nibbler from the pit as it got stuck in thick sludge,

which is also very sticky.

Most thick sludge is located at the base of pit latrines. Because the mechanism does

not allow it to be extended, the length of the nibbler is limited to fitting inside a latrine

superstructure – approximately 1.8m. Thus, the sludge that it is intended to remove

from the base of deep pits is not accessed.

Maintenance of the motorcycle chain could be challenging due to its continual contact

with water.

Negative operator feedback suggests that entry into the market will be challenging and

more technology development is required to prove the value of the device to pit

emptying operations.

5.2.2 Way forward for the Rammer

The outer rising cylinder and fixed inner cylinder of diameters 90 mm and 76 mm

respectively should be used instead of 110 mm and 90 mm so as to enable the

Rammer to be inserted easily into the pits without enlarging the prevailing slab hole.

There is a need to use a foam or rubber material to seal the space between the fixed

inner cylinder and outer rising cylinder, thus preventing watery sludge from escaping

through this clearance.

5.2.3 Way forward for the Nibbler

For smooth operation, the discs need to be welded at 90 degrees to the chain and

should properly align.

A spring loaded scrapper should be used to reduce the resistance when removing

sludge from the disc.

Guides should be introduced onto the lower cylindrical joint to prevent the chain from

deviating off alignment.

Funnel shaped enlargements should be provided onto the pipes at the point of

scooping sludge and at the point of entry onto the return pipe.


6.0 Further development

These are ideas that are to be tested as further developments are made to the devices. There

are high hopes that they can yield positives results, which can be further applied to improve

the performance of the Rammer. These include the peddler driving mechanism and a valve

that when open leaves a clear path for the sludge to pass through.

6.1 Peddler

The Rammer with peddle driving mechanism is away forward designed to easy and fasten the

pumping action because the leg muscles provide greater force and motion generated by

peddling is really swift to allow unimpeded flow of sludge from the pit into the barrel. This

idea is worth trying. However, the actual design of the Rammer will remain unchanged.

Issues to be considered:

To make fixed strut adjustable to permit pumping at different levels.

To put provision of a holder to enable peddler stay firm while

peddling.

Seat to be adjustable to cater for people of different heights.

Figure 13: The Peddler Rammer

6.2 New Valves

Current valves have a bar along the diameter of the pipe, which can trap detritus materials

such as hair and plastic bags. The new valve design should prevent this, and this will be

tested in the near future.

These valves are predicted to allow clear and uninterrupted flow of sludge into the cylinder.

Blockage will be minimal because the valves open at the center and are hinged at the sides.


Figure 14: New valves design

7.0 Conclusions and Recommendations

7.1 Conclusions

From the analysis of pump test results, operator feedback and the field tests, the Rammer is

an improved pump compared to the Gulper. Within WFP, a system is being developed in

which existing entrepreneurs can swap their gulpers for rammers. All new entrepreneurs will

be guided to Pentagon Technical Services to purchase a rammer.

From tests with synthetic sludge, the Nibbler can remove thicker sludge as long as it can flow

but due to its messy operation, entrepreneurs rejected the device. Further development is

required to make the device cleaner and therefore more appealing to pit emptying businesses.

7.2 Recommendations

A marketing strategy should be developed to take the Rammer into the market and also

convince KCCA to legalize its use for pit emptying as it is now cleaner than the Gulper and

its operations are more like the Cesspool emptier.

With the negative perception of the Nibbler by entrepreneurs due to its messy nature, further

developments should be aimed at fluidizing the thicker sludge which could be done by

incorporating a fluidizer into the existing devices or developing a separate fluidizing device

which can re-mould thicker sludge such that it can be pumped by the Rammer.


References

David. S and Mark. O. 2012. Tackling the challenges of full pit latrines, volume 3, and page

28.

Jamie. R, 2013. Slump cone experiment on synthetic sludge (unpublished).

Tom Gibson, Turning sweat into watts, IEEE Spectrum Volume 48 Number 7 July 2011, pp.

50-55.


Appendices

Appendix A: Pictures of pump testing of the Gulper

A – Barrel of synthetic sludge in test pit, B – The Gulper has been inserted for pump testing,

C – Removing the Gulper from the pit, D – Cleaning the Gulper by pumping sludge out

A B

C D


Appendix B: Pictures of pump testing for the Rammer

A – Parts of the Rammer prototype 2, B – The Rammer has been inserted for pump testing, C

– Cleaning hose pipe, D – The assembled Rammer

D C

B A B

A

D C


Appendix C: Launching of new devices and getting operators feedback

A – Showing the Rammer to entrepreneurs, B – The Rammer pumps thick sludge, C –

Explaining the difference between the Gulper and Rammer, D – Nibbler inserted into a pit

A B

C D


Appendix D: Field testing the Rammer during the sanitation week

A – Inserting the Rammer into a pit, B – The pit slab hole small for the Rammer to enter, C –

The Rammer pumps shit, D – The

A

D C

C


APPENDIX E: OPERATOR FEEDBACK QUESTIONNAIRE

Name of device being surveyed

…………………………………………………………………

Tick the boxes where necessary. A score of 1 is the least desirable attribute of the device. A

higher score is a more desirable attribute. Give comments where necessary.

Is it easy to setup the device in the pit?

1Yes No

If yes. What makes it hard to setup?

Does it go deep into the pit?

Yes No

How deep would you like it to go?

…………………………………………………………………………………………………

…………………………………………………………………………………………………

Does it pump thick sludge?

Yes No

Do you easily get tired when pumping using the device?

Yes No

If yes, what do you think makes you to get tired easily?

…………………………………………………………………………………………………

…………………………………………………………………………………………………

How easy do you find it to operate?

1 2 3 4 5

What makes it hard to operate?

......................................................................................................................................................

........................................................................................................................

How easy do you find it to clean?

1 2 3 4 5

Which components do you find hard to clean?

......................................................................................................................................................

........................................................................................................................

Would you swap the device for your gulper?

Yes No

If yes, how much extra would you be willing to pay?

......................................................................................................................................................

........................................................................................................................


Would you like to own one?

Yes No

How much would you be willing to pay for it?

......................................................................................................................................................

........................................................................................................................

What improvements would you like to be done on the device?

......................................................................................................................................................

........................................................................................................................

Thanks for your time

Documents

Report on the Gulper, Rammer and Nibbler Development · 2015-12-17 · The Rammer and Nibbler Page 1 1.0 Introduction and Background Water for People (WFP) is a United States registered