Nomenclature and Symbology

TAGS:
16-MX-401A-1/2/3/4
2 Nomenclature and Symbology 16-MX-401B-1/2/3/4
16-MX-400 A/B
2.1 List of Abbreviations SHELF SPARE MIXER
h1 [m] Liquid depth
h2 [m] Clearance between mixer centerline and tank floor
h2a [m] Clearance between mixer centerline to DDS
h3 [m] Liquid level above the propeller tip (Submergence)
h4 [m] Clearance between mixer propeller tip and tank floor
h4a [m] Clearance between mixer propeller tip to DDS
h5 [m] Liquid level above the mixer centerline
ld [m] Distance of propeller from the rear wall
la [m] Distance of propeller to DDS
d2 [m] Propeller diameter
AP [m2] Propeller cross area
aW [m] Clearance between propeller and side wall
aP [m] Clearance between contiguous propeller tips
D [m] Outer tank diameter
d1 [m] Inner tank diameter (Liquid)
di [m] Inner tank diameter (Donut tank)
L [m] Total tank length including wall
W [m] Total tank width including wall
l1 [m] Inner tank length (Liquid)
w1 [m] Inner tank width (Liquid)
lC [m] Length of the straight channel (Oxidation ditch)
wC [m] Channel width (Oxidation ditch and donut tank)
R [m] Radius of the round tank
AC [m2] Channel cross area
V [m3] Tank Volume (Liquid)
n [-] No. of mixers or flow boosters
Q [m3/s] Mixing capacity
FP [N] Propeller thrust

Edition 5, 04.12.14 General Rules for mixer and flow booster Installations 9
Positioning in non-aerated tanks

6 Positioning in non-aerated tanks

6.1 Clearances for mixer
Clearance to side walls
For good mixing efficiency the clearance
aw between the mixer propeller tip and the
side wall should be at least 0.5 times the
aw ≥ 0.5 d2 propeller diameter d2.

NOTE
This rule is valid for aerated
aw tanks as well.

Fig. 23 Clearance to side walls mixer

Clearance to tank bottom

In shallow tanks, in tanks with changing
liquid levels or in circulation ditches the
clearance h4 between the mixer propeller
tip and the bottom should be at least 1 time
the propeller diameter d2.

h4 ≥ d2 NOTE
h4
The bottom clearance h4 for
mixer is automatically achieved
by installing the mixer’s guide rail
stop as shown in the mixer
Fig. 24 Clearance to tank bottom mixer typical installation drawings.

Clearance to rear wall

To prevent unbalanced propeller loads, the
ld ≥ 1.5 d2 clearance ld between the mixer propeller
and the rear wall should be at least 1.5
times the propeller diameter d2.

NOTE
This clearance is automatically
achieved when using the
standard ABS guide rail system.
This rule is valid for aerated
ld tanks as well.

Fig. 25 Clearance to rear wall mixer

20 General Rules for mixer and flow booster Installations Edition 5, 04.12.14
 Positioning in non-aerated tanks

6.7 Positioning in rectangular tanks

One unit installed in rectangular tank (1 < l1/w1 ≤ 3)

l1 l1
0.3 l1 0.3 l1

mixer flow booster

w1

0.3 l1 ld ≥ 1.5 d2 0.3 l1 ld ≥ 1 to 1.5 d2

Fig. 38 Positioning in rectangular tank (l1/w1 1 to 3)

The mixer and flow booster must be positioned as shown above, i.e. at 0.3 times l1
from the tank corner with the centerline oriented as shown.
To prevent unbalanced propeller loads, the minimum distance behind the propeller
should be as shown in the above illustration.
The clearance ld between the mixer propeller and the rear wall should be at least 1.5
times the propeller diameter d2 (see page 20).
The clearance ld between the flow booster propeller and the rear wall should be in
accordance with the recommendations on page 21.
The bottom clearance of the mixer propeller centerline h 2 should be 0.25 to 0.33 of the
liquid depth h1.

NOTE
The bottom clearance h4, for flow booster is automatically achieved by installing
the flow booster on the concrete pedestal.
For different installation methods the distance of the flow booster propeller tip h4
should be 0.05 m (2 in) to 0.25 times the liquid depth h1.

Edition 5, 04.12.14 General Rules for mixer and flow booster Installations 31
 Positioning in non-aerated tanks

Two units installed (classic method)

7 – 10°

7 – 10°

mixer and flow booster

Fig. 44 Mixer positioning in round tanks (2 units installed)

The mixer and the flow booster must be positioned as shown above, i.e. with 7° - 10°
orientation right of the tank centerline, to prevent unbalanced propeller loads.
The mixer should be installed on different liquid levels.
The clearance ld between the mixer propeller and the rear wall should be at least 1.5
times the propeller diameter d2 (see page 20).
The clearance ld between the flow booster propeller and the rear wall should be in
accordance with the recommendations on page 21.
The bottom clearance of the mixer propeller centerline h 2 should be 0.25 to 0.33 of the
liquid depth h1.

NOTE
The bottom clearance h4, for flow booster is automatically achieved by installing
the flow booster on the concrete pedestal.
For different installation methods the distance of the flow booster propeller tip h4
should be 0.05 m (2 in) to 0.25 times the liquid depth h1.

Edition 5, 04.12.14 General Rules for mixer and flow booster Installations 37
 Further Rules

7.10 Positioning in aerated tanks with Disc Diffuser System (DDS)

Mixers in tanks with full tank floor DDS coverage

h1

h2a

Fig. 61 Mixer in tank with full floor DDS coverage

h2a ≥ 3d2

When the entire tank floor is covered with the Disc Diffuser System (DDS), the mixer
and aeration system shall not operate together. In this configuration, either the mixer is
switched on and the aeration system is switched off, or vice versa.
In the event that both systems are required to operate simultaneously, refer to page 54
for recommendations.
To avoid damage to any component of the Disc Diffuser System the mixer needs to
have a distance h2a between its centerline and the diffusers surface equal at least 3
times the propeller diameter d2.

NOTE
During the aeration time the mixer has to be switched off.

Edition 5, 04.12.14 General Rules for mixer and flow booster Installations 53
Further Rules

Mixers in tanks with partial tank floor DDS coverage

h1

h2a w1

1.5 d2 la

0.3 l1 2d2

l1
Fig. 62 Mixer in tank with partial floor DDS coverage

la = 2.5 d2 + 2.5m

When the mixer is to be operated in a mixed tank together with the Disc diffuser
system, the mixer must be vertically positioned closer to the bottom i.e. h 2a = 1 to 3 d2.
The front clearance la between the mixer propeller and the disc diffuser system should
be given by the above formula.
To assure trouble free operation the diffuser air pipe mounting brackets must be
designed and supplied in robust SS material. It is recommended that each air pipe
element be equipped with at least 1 SS mounting bracket.
To prevent unbalanced propeller loads caused by air and flow turbulence, the minimum
distance behind the propeller should be 1.5 times the propeller diameter d 2.

54 General Rules for mixer and flow booster Installations Edition 5, 04.12.14