Dosing Presentation 2012

Welcome!
INTRODUCTION TO
DOSING SYSTEMS

PSI ENGG SYSTEMS P.LTD.

WHAT IS CHEMICAL
DOSING
 Chemical conditioning of feed water / steam
condensate cycle, is essential
to prevent corrosion and scale formation

 Dosing can be of two types :
H.P. (High Pressure)
L.P. (Low Pressure)


WHAT IS CHEMICAL
DOSING
Corrosion:

 Corrosive components, especially O2 and CO2 have to be removed,
usually by use of a deaerator.

 Remnants can be removed chemically, by use of oxygen scavenger.

 Feedwater has to be alkalized to a pH of 9 or higher, to reduce
oxidation and to support the forming of a stable layer of magnetite on
the water-side surface of the boiler, protecting the material underneath
from further corrosion.

 This is usually done by dosing alkalies into the feedwater, like sodium
hydroxide (caustic soda) or volatile ammonia.


WHAT IS CHEMICAL
DOSING
Treating the boiler feed water
 The boiler feed water treatment is normally done with
the following chemicals:
 Hardness stabilisers
 Deflocculating agents
 Corrosion inhibitors
 Oxygen binding agents (e.g. hydrazine)
 pH value regulation (caustic soda, ammonia)
 Defoaming agents
Dosing of these chemicals into the tank of boiler
feed water is done using dosing systems


WHAT IS CHEMICAL
DOSING
 H.P. DOSING

 Corrosion rate of M.S. surface is lowest, when pH is between 9 -
10.
 Dosing is therefore done , to maintain pH & reduce scaling
 Generally solution dosed into drum under full boiler pressure


WHAT IS CHEMICAL
DOSING
 L.P. DOSING
 Dissolved oxygen in feed water causes serious
corrosion.

 Hence "oxygen scavengers" or "de-oxygenators" are
dosed into feedwater.
 Dosing done into feed water stream, either at BFP
suction, or at deareator, at low pressures.
 Other chemicals may be also added for pH
adjustment of DM water

WHAT IS CHEMICAL
DOSING
DOSING CHEMICALS
 H.P. DOSING
 Phospate solution (combination of di-sodium and tr-sodium
phospate) is generally used, in concentrations from 2.5 % to 7.5 %.
 Exact dosage rate depends on pH variation of water in drum.

 It prevents scale formation from low remaining levels of hardness
which may have escaped treatment.

 Sodium phosphate causes the hardness to precipitate to the bottom
of the boiler where it can be blown down.


WHAT IS CHEMICAL
DOSING
DOSING CHEMICALS - L.P. DOSING

 Hydrazine Hydrate solution, in concentrations of
about 0.10 % is used for oxygen scavenging
purposes.
 Sodium Sulphite solution, is also used as oxygen
scavenger.
 Ammonia solution (about 1 - 2 %) is also used, for pH
control of feedwater.
 Similarly Morpholine is also used.
 Caustic Soda solution is also used, for pH control of
feed water.
 Other proprietary chemicals are also available for
same purposes. PSI ENGG SYSTEMS P.LTD.

WHAT IS CHEMICAL
DOSING
 Further detail on this complicated subject of
water treatment, is available from water
treatment specialists

 This is very much a matter for expert advice
and professional analysis .


Dosing Systems - Basics
 A metering (dosing) pump is required
to deliver a liquid or solution at
specified rate of flow .
 The logging and control of flow rates
& total quantity delivered calls for
Dosing Systems (also known as
Chemical Injection Skids).


Dosing Systems – Basics -
contd
 These skids typically consist of:
 Storage tanks or solution preparation
tanks, with

Mixers (agitators)

Level Gauges
 Interconnecting Piping
 Pipe Fittings
 Valves
 Instrumentation for flow / pressure
 Control Panels/ Control Systems


contd
 The total assembly is commonly
referred to as DOSING SYSTEM, or,
Chemical Injection Skid.
 A well-designed system should be:
 very compact
 save space and
 be convenient for plant installation as well
as plant operation
 Advanced instrumentation features can be
incorporated into the systems, for compete auto-
control & data logging, through plant interface

contd

Considerable design and detailed
engineering efforts are required
for designing individual
components of the skid, and in
integrating the components into
making a compact and efficient
system.

THE MANY APPLICATIONS OF
DOSING SYSTEMS..


Dosing Systems – Usage
Areas
Dosing Skids are used by a wide cross section of
Industry:
 Oil and Natural Gas Exploration & Refining
 Iron and Steel
 Chemicals processing industries
 Pulp & Paper manufacture
 Thermal Power
 Water & Effluent Treatment
 Food & Pharmaceutical industries
 Personal care products
 Machine building Industry
 Semiconductor manufacturing


Dosing Systems –
Applications
Typical applications include:
 Inhibitor Dosing (Cooling water treatment)
 Phosphate Dosing/ Hydrazine Dosing (Boiler Feed
Water treatment)
 Dye Dosing (Petroleum Industry)
 Lubrication of Rolling Mills (Steel Industry)
 Reagent Dosing (Pharma industry)
 Dosing paper chemicals (Paper Industry)


So what exactly is a dosing
system?

First we see some dosing pump
basics……


Dosing Pump basics….
 The metering pump is a positive displacement
chemical dosing device, with the ability to
vary capacity, manually or automatically, as
process conditions require.

 It features a high level of repetitive accuracy
and is capable of pumping a wide range of
chemicals including acids, bases, corrosive or
viscous liquids and slurries.


Metering pumps are generally used in
applications where one or more of the
following conditions exist:
 Low flow rates in ml/hr or LPH are required
 High system pressure exists
 High accuracy feed rate is demanded
 Dosing is controlled by manual control,
computer, microprocessor, DCS, PLC, or flow
proportioning
 Corrosive, hazardous, or high temperature
fluids are handled

 There are 2 main types of dosing
pumps:
 Plunger Type: The pumping action is
developed by a reciprocating piston which
is in direct contact with the process fluid,
 Diaphragm Type: Piston is shielded from
the fluid by a diaphragm. Diaphragms are
actuated by hydraulic fluid between the
piston and the diaphragm.


Plunger Pump

Hydraulic Diaphragm Pump


Types of Dosing Pumps

Diaphragm Pump
Plunger Pump


Dosing Pump characteristics..
The pumping action is developed by a
reciprocating piston. This reciprocating
motion develops a flow sine wave.


 Unlike centrifugal pumps, flow rate is
not greatly affected by changes in
discharge pressure.


Dosing Pump Drive
mechanism
 The Drive mechanism translates the
rotary motion of the driver into
reciprocating movement. Industrial duty
pumps will submerge this portion of the
pump in an oil bath to assure reliability
during continuous operation.


Flow Adjustment
 Pump flow rate is adjustable by varying stroke
length
 Most metering pumps are supplied with a
micrometer screw adjustment similar to the
one shown here.
 The micrometer can also be replaced by an
electronic or pneumatic actuator to adjust
pump flow rate in response to a process
signal.

Pump Drivers & Adjustment
 The pump is usually driven by an AC
(constant speed) motor.
 Flow control (in manual mode) is done
by rotating stroke adjuster knob, which
varies stroke length, from 0 – 100%
 Flow control (in auto mode) is done by
use of stepper motor to rotate stroke
adjuster

 The metering pump flow vs. Stroke
characteristic curve is linear.
 By measuring flow at 2 stroke settings,
plotting both points and drawing a straight
line through them, other flow rates vs. Stroke
can be accurately predicted.
 The steady state accuracy of a correctly
installed metering pump is generally +/- 1.0%
or better.


 Although a metering pump can generally be
adjusted to pump at any flow rate between 0
and its maximum capacity, its accuracy is
measured over a range determined by the
pump's turndown ratio.
 Most metering pumps have a turndown ratio
of 10:1,which simply means that the pump is
within its accuracy rating anywhere between
10% and 100% of capacity.

•Pump stroking speeds can vary from 75
strokes/min to 200 strokes/min
•Higher stroke speeds reduce pump size & give
higher mechanical efficiency
•Lower stroke speeds only serve to increase pump
size and hence cost
•Newer gland packing materials, and improved
designs (such as “floating cross-head”
construction), lead to near-zero wear and
consequent leakage at higher stroking speeds

Dosing Pump liquid end..
 The liquid end design and materials of
construction are determined by the
service conditions, and the nature of the
fluid to be handled.
 Temperature, flow rate, fluid viscosity,
corrosiveness and other factors are
considered


Dosing System basics…
 In a typical boiler feed water dosing
system:
 The HP Dosing system doses direct

into boiler drum, under high pressure.
 The LP Dosing system doses into the

boiler feed water pump suction line,
or, de-aerator inlet line, under low
pressure


Some boiler installations need 3-pump HP dosing systems, as
shown above. Note the dissolving basket fitted in the dosing tank,
and the top-mounted level switch (to stop pump on low level).

The General Arrangement
drawing (known as GA
Drawing) for a typical 2-pump
boiler feed water dosing
system is shown on the next
slide…..


Dosing System - Components
 Typical components of a dosing
system:
 Dosing Pumps


 Typical components
of a dosing system:
 Tanks


 Typical components
of a dosing system:
 Valves


system:
 Level gauge for tank


system:
 Pressure gauge:


system:
 Pressure Relief Valve:


system:
 Pulsation dampener

 Calibration Column

TYPICAL LP DOSING SYSTEM FOR BOILER DOSING

TYPICAL HP DOSING SYSTEM FOR BOILER DOSING

Manual & Auto-Control
Systems
 What we have seen till now are manually
operated dosing systems, utilizing standard
mechanical dosing pumps.
 These will satisfy the needs of most steady-
state operations
 Auto-controlled systems are responsive to
changes in process conditions, requiring
frequent changes in dosing conditions, done
automatically


Auto-Controlled Dosing

 Auto-control dosing systems need
external logic controllers, which take
signal from process sensors, and adjust
dosing according to pre-determined
values.


Standard Controllers used in Auto-Dosing Systems

Conductivity & pH controllers


Auto-controlled Dosing
 A classic example is a modern
boiler system, where the following
process parameter changes affect
dosing rates:


Auto-controlled Dosing - types
 Flow-proportional method:
 Uses an instrument signal to adjust dosing
rate, based on actual flow of water being
treated
 Instrument signal is generated from a flow-
measuring device
 Commonly used in boiler plants and
cooling water treatment plants


 Parameter Measurement method:
 Measurement of several parameters is
taken from the process
 These are analyzed to make the dosing
decisions
 Dosing decisions made by the central
processor, based on comparison of
readings with programmed control bands


 Parameter Measurement method:
 In a boiler system, parameters such as
dissolved oxygen, pH, and conductivity are
continuously monitored, for dosing
decisions
 This method closely monitors multiple
variables, such as flow rate, dissolved
oxygen content, and adjusts dosing rate
accordingly

Parametric Dosing - examples


Our Chemical Dosing range
 We focus on packaged skid-mounted
dosing systems for cooling water &
boiler feed water treatment.
 This is our core business
 We have been in this business for over
30 years
 A typical system includes metering
pumps, control instrumentation, and all
interconnectingENGG SYSTEMS P.LTD.
PSI pipework.

Some Dosing
Systems
made by
us…


Dosing Systems
(Chemical Injection Systems)
(Chemical feed systems)
Application areas:
 Oilfields
 Boiler Dosing
 Effluent treatment
 Petroleum industry
 Paper Industry
 Heat treatment furnaces

HP Dosing system,
with 2 pumps
& local control panel

User:
Jindal Stainless

LP Dosing system,
with 2 pumps
local control panel
self-cleaning filters
(16 lph 5 bar)

EPC Contractor:
Alstom Projects India
Ltd.

User:
Bokaro Power

Some details of HP Dosing system

LP Dosing system, cap.50 lph / 45 bar
Client: BHEL – PEM Delhi
User: NTPC Aravalli

LP Dosing system, cap.50 lph / 45 bar
Client: BHEL – PEM Delhi
User: Pipavav Power

Control Panel for
LP Dosing system

Client: BHEL – PEM
Delhi
User: Pipavav
Power

Ammonia Dosing system, with 2 tanks 6000 lit. cap., & cont
Dosing Pump cap. 50 lph 45 bar
Client: BHEL Delhi. User: Kalpakkam Nuclear Power Plant

Anti-Scalant
Dosing system,
(CW Dosing)
with tank 5000 lit.
capacity

Dosing Pump
cap. 250 lph 2
bar
Client: BGR
Energy.
User: AP Genco
Kothagudem

IN CONCLUSION….
 We focus on high reliability, high
quality, water treatment dosing
equipment
 Instead of trying to win your

business by being the cheapest, we
focus on giving you the best
possible equipment that your
budget can bear.

THANK YOU
 Dosing is an exhaustive subject
 We have given a brief overview of

the subject
 We will be glad to clarify any

specific queries
 We can custom-design systems for

specific applications

Dosing Presentation 2012

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