EBARA GP Operating And Maintenance Manual page 30

directly to the intake ("a") and delivery ("b") lines of the
single pump.
 All the threaded or flanged connections must be well
sealed to prevent air infiltration.
 Supports, anchors, unions, pipes and other system
components must be independent of the set to prevent
creating additional loads or stress. If there are support
brackets on the manifold, use them to fasten the manifold
to a structure in order to reduce the load on the pumps.
 It
is recommended
immediately downstream of the set.
 To avoid transmitting vibrations to the system pipes, it is
recommended to install antivibration joints on the set's
intake and delivery lines.
 Always install a foot valve when installing above-head.
 In order to test the set, install a union tee downstream of it
with an isolating valve and the relative recirculation pipe
connected to the intake tank or towards the discharge.
8.3. CONNECTION TO PRESSURE TANKS (see the
attached drawings fig. D)
It is possible to assemble diaphragm tanks with a capacity of
up to 24 litres on the delivery manifold, depending on the
number of pumps. It is recommended to only install tanks type-
approved according to Directive 2014/68/EU. They must only
be installed on specific G 1 pipe sections ("c"). If using larger
sized diaphragm pressure tanks (precharged or supplied by a
compressor), the connection must be made to the end of the
delivery manifold not used for the connection to the system (for
sets with more than 1 pump). For air cushion type pressure
tanks, the automatic supply must be connected with the G 1/2
intake located on the pump intake line ("d"), which is only
present in sets with fixed speed pumps. In any case, refer to
the tank's instruction manual.
8.3.1. SYSTEM WITH MEMBRANE PRESSURE TANK
For correct operation of the pressurization system, we
recommend the use small size pressure tank. It is necessary to
stabilize any pressure fluctuations during the variation
frequency of the inverter.
Pay attention to the calculation for pre-charge of the pressure
tank. In case of changes in the reference pressure, the pre-
charge of the tank must be adjusted according to the
calculation.
The formula for calculating the pre-charge pressure is the
following:
�� = ( ��
��
where:
P = Pre-charge pressure;
p
P = Setpoint pressure;
s
D = Delta restart pressure.
r
Hydraulic installation (constant pressure)
Caption:
1. Pump
2. Control panel / VFD
3. Gate valve
4. Pressure trasducer / pressure switch
5. Non-return valve
6. Pressure tank
7. Drain off valve (optional)
to install an isolating
− �� ) − 0,5 ������
�� ��
8.3.2. SYSTEM WITH CUSHION TYPE PRESSURE
TANK
The system is schematically represented in the following
image.
valve
ATTENTION
Air supply unit
The device consists of a small container equipped with a float
bottom valve and an air intake valve. The latter, if crossed by a
flow of water, is able to suck air from the outside by the Venturi
effect. This device must be mounted in correspondence with
the holding level of the air cushion.
Principle of operation.
when the pump is running, air enters the feeder through the air
intake valve; the flow stops when the whole feeder is full of air
and the yellow ball is at the bottom closing the connection pipe
with the pump intake. When the pump has stopped, the
pressure from the fluid-mounting tank reverses the flow of
water which, via nipple 4 and pipe 6, pushes the air contained
in the feeder into the fluid-mounting tank (you should hear the
characteristic gurgling sound).
ENGLISH
Caption:
1. Cushion pressure tank
2. Gate valve
3. Pump
4. Air intake nipple
5. Non return valve
6. Pipe line
7. Air supply unit
8. Gate valve
Any difference in installation with respect to the
diagram above precludes the correct operation
of the air supply unit.
6