The hot water flow controller ensures control of hot water flow to parts of the unitator plant and allows flow during power interruptions to prevent freezing. It has components like switches and relays that control a solenoid valve and ball valve to open or close hot water flow. The cross-sectional area of the outlets must sum to three times the inlet area to minimize splashing from the flowing hot water.

1. AUTOMATIC HOT WATER FLOW CONTROLLER
INTRODUCTION:
The Hot Water Flow Controller is that part of the hot water supply system which
functions to ensure the control of hot water flow onto the Post Crystalizer Unit and
through the hollow shafts of the A Units of the Unitator Plant.
The use of the control unit is informed by the need to establish hot water flow mainly,
immediately electrical power is interrupted. This in effect will impede the speed with
which freeze-up occurs and also reduce the downtime accounted for as a result of having
to wait for frozen process to thaw. Thus, the tendency of the A Unit shafts shearing and
eventually breaking is low since the process could be kept in molten form.
OPERATION AND INSTRUCTIONS
The Hot Water Flow Controller allows or disallows the flow of hot water as may be
demanded during electrical power supply interruption in addition to the set-time on the
timer relay which becomes operational when power is restored. The flow control and
duration can also be determined exclusively through the set-time on the timer relay in
case hot water is needed in a normal operation (i.e. when there is no power outage to
warrant freeze-up).
The function of each component along with a description of control type and operation is
explained in the following table:
S/N NAME CONTROL
TYPE
OPERATION FUNCTION
1 Main Isolator
Switch
Dial Rotational
I=ON, II=OFF
Isolates entire system electrically.
2 Flow ON
Switch
Push Button Press = ON Allows the control unit to be operated
based on the time selected on the timer
relay after the event of an emergency
stop.
3 Emergency
Stop Switch
Push Button Press = ON Isolates the timing element and activates
the Direct-On-Line starter such as to
cause permanent energization of the
Solenoid which results in the closure of
the Ball Valve.
4 Reset Switch Push Button Press = OFF Interrupts electrical power supply to the
timing element such as to cause a repeat
of system operation when switch contact
remakes.
5 Flow ON
Indicator
Green Hot Water Flow On Remains alight the whole time the ball
valve is open for hot water flow to

2. concerned parts
6 Emergency
Stop Indicator
Red Emergency Stop Stays alight until the Flow On Switch is
pressed i.e. when hot water flow should
resume.
7 Contactor K1
K2
Electromagnet
ic attraction
Electromagnet
ic attraction
Energized
switching
2122 = OFF
4344 = ON
Energized
switching
1314 = ON
i) Contacts are actuated for establishing
or interrupting d.c power supply meant
for energizing the 24V solenoid valve
coil.
ii) The 240Vac supply to the Flow on
Indicator
Contacts are actuated for establishing or
interrupting d.c power supply meant for
energizing the 24V solenoid valve coil.
8 Emergency
Stop Relay K3
Electromagnet
ic attraction
Energized
switching = ON
De-energized
switching = OFF
The Relay is used to achieve Direct-
On-Line Starter wiring to ensure
emergency stop and control of voltage
supply to the timing element.
9 Timer Relay Timed-based
Electromagnet
ic attraction.
Energized
switching
1516 = NC
15/18 = NO
It determines the duration of hot water
flow by of means of the selector it bears.
10 Solenoid
Valve
Electromagnet
ic Induction
Energized Coil
= Close
De-energized Coil
= Open
Controls the flow of air into the
electropnuematic actuator.
11 Electropnuem
atic Actuator
Dial Rotational Transmits its rotational motion to the
ball valve causing it open or close.
12 Ball Valve Dial Rotational It opens or closes to allow or disallow
respectively the flow of hot water
through the system onto concerned parts
13 Manual Air
Valve
Dial Rotational It serves as a means of cutting off the air
supply to the electopnuematic valve
such as to ensure a fail-safe idle time i.e.
ensuring the permanent closure of the
ball valve until it is needed otherwise.

3. FLOW ROUTING
The hot water passing through the ball valve is eventually distributed and directed to flow
through the hollow shafts of the A units and through the pipe laid by the Post
Crystallizing Unit (PCU).
To minimize splashing which could result in water ingress into prohibited areas, the
summation of the cross sectional areas of the outlets (i.e. the outlet areas of the pipe by
the PCU and those on the A Unit Shafts) is taken to be three times larger than the cross
sectional area of the inlet (i.e. the cross sectional area of the Ball Valve bore).
Fig: Flow Route Diagram
Considering the diagram above,
Cross sectional area of the Inlet valve = Ain)
Summation of the cross sectional areas of the outlets = A1 + A2 + …… A(n) = A(out)
Given the Mass flow rate:
Avρ = C
Where:
A is the cross sectional area of the passage
V is the velocity of flow
ρ is the density of working fluid being constant

4. Then,
AV = C
Assuming flow rate to be constant in the system,
Then,
Ain Vin = Aout Vout
But in order to minimize splashing, the outlet velocity is taken to be 1/3 of the inlet
velocity.
Hence,
Vin = 3 x Vout
From the Mass flow rate Equation,
i.e. Ain Vin = Aout Vout
Substituting for Vin, we have;
Ain 3 x Vout = Aout Vou
Therefore, Aout = 3Ain
This implies that for a gentle flow to be obtained at the outlet, the summation of the
outlets area must be three times as much as the inlet area.