PRINCIPLES OF OPERATION motionless mixers produce mixing or blending of two or more input streams by a series of specially shaped elements. These elements produce multiple divisions and re-combinations of the material so that under laminar flow conditions each element doubles the number of output striations. If we have “m” input streams on “n” elements, the number of output striations is m x 2n. Under turbulent flow conditions the mixing is much further enhanced by elliptical counter rotating vortices on each side of each mixing element. It is important to recognize the input flow rates of materials must correspond to the output ratios required in the mixture. This must be kept in mind when selecting the material pumping system. Low viscosity materials for example may be handled by centrifugal pumps, while high viscosity materials will require positive displacement pumps. Additives to a main product flow must be introduced in a non-pulsating manner in order to avoid a non-homogenous output.

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MIXING ELEMENT CONFIGURATION Most of the turbulent flow applications mixers can be satisfied with 2, 3, or 4 mixing elements. These elements are configured in one of three ways.

STANDARD

This is a very common arrangement and is covered in Data Sheet 102A.

MONO-MAXI

This configuration is used when mixing two materials having a large difference in their specific gravities. By removing the downstream ears and leaving the flat, the latter minimizes spinning of the output stream which in turn minimizes centrifugal separation. This is particularly important when mixing liquids and gases.

DUAL-MAXI

This arrange is used where a very short mixing length is require. At high velocities – particularly with gases – only two mixing elements in this configuration will produce complete mixing of multiple input streams. MOUNTING ORIENTATION Mixing elements may be fixed in place or removable as an assembly. The mixer will be marked with a flow direction indicator such as:

FLOW In this case, the mixer must either be mounted horizontally with the product flow in the direction marked, or vertically with the product flow down. This is to assure that the Mixer will operate as designed. Mixers usually can be mounted in any orientation (vertical or horizontal). The only caveat to this is if there is an additive port or injector and the injected chemical can cause corrosion to the mixer in concentrated form. A typical example would be the addition of concentrated sulfuric acid to water in a steel mixer. recommends that the additive port be placed at the top of the mixer to prevent pooling of this heavier, corrosive acid in the weld crevices of the the additive port, where there is a potential for erosion or damage to the mixer

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MATCH MARKING When two mixers must be connected toge ther, match marks are provided to assure correct operation

Failure to properly align the match marks may severely reduce mixing efficiency. CONSTRUCTION MATERIALS & CONFIGURATION Construction materials include carbon steel, stainless steels, special alloys such as Carpenter 20 and Hastelloy B2, plastics such as PVC and CPVC, FRP (Fiberglass Reinforced Plastic) and combinations such as carbon steel spool pieces with Teflon or Kynar lining. End configurations include plain, prepared for welding, threaded and flanged. Teflon and Kynar lined spool pieces can have elements retained in one of two ways. One way is with element retainer disks of Teflon or Kynar as shown below. In this configuration elements are not removable by the customer.

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Another method which applies to metal elements in a Teflon or Kynar lined spool piece is shown below. In this case, elements are removable as an assembly by the customer.

WAFER MIXERS Wafer Mixers are installed similar to retaining disks. Wafer mixers are sandwiched between two flanges. To simplify installation, often the gaskets are glued to the wafer mixer before installation. The wafer mixer is installed so that any injection orifices (optional) are facing downstream. The flanges are torqued per the standard torque specifications for the flange size and material.

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NOTES ON FLANGES As a general rule, metal mixers have raised face flanges. P.V.C. mixers and FRP mixers on the other hand have flat face flanges. It is poor engineering practice to bolt a raised face flange directly to a flat face flange since dangerous stresses will be placed on the flat face. If, however, installation conditions dictate the joining of a flat to a raised face flange, an appropriate washer must be used to eliminate the stress produced by the raised face.

Note that units configured with a pair of element retainer disks are treated as raised face units. Although the retainer disk is flat, the flange to flange forces are from the spool raised face to mating flange raised face.

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TORQUE PROCEDURE Correct torqueing procedures must be followed to assure uniform stress.

TORQUE SEQUENCE FOR 8 BOLT FLANGES

TORQUE SEQUENCE FOR 12 BOLT FLANGES

SEQUENTIAL ORDER

ROTATIONAL ORDER

SEQUENTIAL ORDER

ROTATIONAL ORDER

1-2 1 1-2 1 3-4 5 3-4 5 5-6 3 5-6 9 7-8 7 7-8 3 2 9-10 7 6 11-12 11 4 2 8 6 10 4 8 12

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TORQUE SEQUENCE

FOR 16 BOLT FLANGES TORQUE SEQUENCE

FOR 20 BOLT FLANGES SEQUENTIAL ORDER

ROTATIONAL ORDER

SEQUENTIAL ORDER

ROTATIONAL ORDER

1-2 1 1-2 1 3-4 9 3-4 13 5-6 5 5-6 5 7-8 13 7-8 17 9-10 3 9-10 9 11-12 11 11-12 3 13-14 7 13-14 15 15-16 15 15-16 7 2 17-18 19 10 19-20 11 6 2 14 14 4 6 12 18 8 10 16 4 16 8 20 12

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The following torque recommendations are to be followed when installing mixers:

Torque Recommendations

Teflon & Kynar Lined Steel Pipe

Pipe Size (in)

Torque (ft-lbs)

1” 8-9

1 ½” 9-12

2” 18-24

2 ½” 23-30

3” 23-30

4”

27-36

6”

35-50

8”

45-60

10”

75-85

12”

95-110

Torque Recommendations PVC Flanges/Pipe

Pipe Size (in)

Torque (ft-lbs)

½” thru 1-1/2”

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2-4 25 5 30 6 40 8 40 10 64 12 95

Torque Recommendations FRP Flanges/Pipe

Pipe Size (in)

Torque (ft-lbs)

2 25 3 30 4 30 6 30 8 45 10 50 12 55 14 55 16 55 18 55 20 55 24 55 30 55 36 55 42 55

When installing PVC & FRP mixers, consideration must be given to the fact that the expansion coefficient is substantially higher than that of steel. Steel expansion coefficient = 7x10-6 inch/inch °F approximately -FRP-expansion coefficient = 20x10-6

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PORTS & SPARGERS In order to introduce additives to the main flow, mixers are often provided with inlet ports at right angles to the main flow axis. These ports may be connected with pipe spargers, which aid in mixing by introducing the additive across the full pipe diameter. The spargers can be fixed in place or removable for cleaning. If the sparger is removable a locating pin is provided to assure correct reassembly. Other sparger arrangements involve a cleanout port which is normally capped or flanged.

Flanged Injector with locating pin shown

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MAINTENANCE Once installed, a motionless mixer requires no routine maintenance since there are no moving parts to repair or replace. If a mixer has been supplied with internals designed for removal by the customer, these internals can be removed for inspection or cleaning. If elements have any special coating such as Teflon or Kynar, greater care must be taken not to damage the protective coating.