In this article, we will learn about the Side Entry Mixers Basic Components
Side Entry Mixer
The side entry mixer converts the mechanical energy (rotary motion) into a fluid motion. Side Entry mixers are very efficient for mixing the product in larger diameter tanks. Side Entry mixers are ideal for floating roof tank where practical considerations preclude the use of top entry mixers.
Purpose of Side Entry Mixers
Side entry mixers widely used for the following purpose
- Homogeneity
- Blending
- Crude Oil Bottom Sludge & Water Control
Homogeneity
A product stored in the tank for a longer time, the product may start to settle (ie., high-density product at the bottom and low density at tank top).
To maintain homogeneity of product to ensure uniform specification throughout the tank. For this reason, the mixer push product throughout the tank with top to bottom “turnover” as well as circulation around the tank, to ensure that the product at the top, middle and bottom remains uniform to specification.
Blending
To mix two or more different products to obtain a homogeneous blend within the specified time period. (ie., a different product with different density, viscosity, etc., blended together to obtain a final product).
The mixer pushes the products throughout the tank with top to bottom “turnover” as well as circulation around the tank, to ensure that the product at the top, middle and bottom blended with the specified time period.
Bottom Sludge & Water Control
As the name indicate the mixer function has to control the bottom sludge, heavy solids and water in the crude oil tank. These types of mixer agitate the sludge/solid particles to mix with the product to maintain suspension.
Side Entry Mixers Basic Components
Impeller
The impeller is the heart of the side entry mixer. Proper impeller design can provide better mixing rate, reduce mixing time and increase the efficiency of the mixer.
Two types of impeller widely used they are
- Propeller Type
- Pitched Blade Type
The selection of impeller is based on the purpose of Mixer (Homogeneity, Blending and BS&W). The impeller of side entry mixers is axial flow type impeller.
Shaft
The shaft has designed as a single-piece construction. Positive fixing and driving of the impellers on the shaft achieved by the use of taper to taper shaft connection with side fitting key and retaining bolt.
The shaft has designed to minimize misalignment, deflection and vibration which all affect the mechanical seal and bearing life. The shaft has hard-chrome plated at the mechanical seal and shut-off areas to increase hardness, thereby shaft wear and tear reduced.
Tank Mounting Flange
The standard manhole size of tank mixer is 24” and 30”. Also, mixer manufacturer provides the tank adaptor flanges suit for all size of tank manhole based on request. The flange provided with swivel assembly for mixer movement in horizontal movement. The swivel assembly comprises a stainless steel polished spherical ball attached to the mixer mounting flange and sealed by an elastomer seal to prevents leakage while the mixer is swivelled in a horizontal plane.
Mixer Driven Type
The side entry mixer driven by two types. They are
- Gear Driven Mixer
- Belt Driven Mixer
Gear Driven Mixer
The flanged motor has connected to the gearbox via a flexible coupling. Normally the gearbox comprises a single reduction hardened high-efficiency spiral bevel gear. The service factor of gear shall be 1.5. The gear and bearing are splash oil-lubricated and enclosed in a large gear case for maximum heat dissipation. The mixer frame is a rigid one-piece iron casting located on the gearbox and the steel mounting flange.
Belt Driven Mixer
A horizontal foot mounted motor fitted above the mixer frame which allows adjustment for correct belt tension. The toothed belt has been used to transfer torque from the motor to mixer shaft. The belt material shall be Fire Resistant Anti-Static High Torque Drive. Tooth Belt correctly sized to transmit motor power.
The pulleys have taper lock bush for ease of removal and are enclosed in belt guard. Drive service factor is 1.5 minimum.
Mechanical Seal
The mechanical seal used to prevent shaft leakage. Side entry mixers are usually provided with a single mechanical seal. If the storage liquid is more toxic and emission not allowed, then double mechanical seal preferred.
Tank Shut-off Device
The tank shut-off device to allow mechanical seal and bearings shall be changed under full tank conditions. The tank shut-off mechanism incorporates tapered metal to metal faces, positively clamped by a bolted flange which both seals products in the tank and securely supports the shaft during bearing or mechanical seal changes. The tapered face has both wear and corrosion-resistant.
Bearings
Bearings are designed for L10 Life. It’s shall be either grease-lubricated or oil lubricated.
Most of the side entry mixers are oil lubricated.
Advantage of Side Entry Mixer
- Capital cost is low when compared with a static mixer
- Tank emptying and cleaning not required for the maintenance of mixer bearing and mechanical seal
- Side entry mixer can handle the viscosity and density change when compared with a static mixer
- The efficiency of the side entry mixer is high when compared with a static mixer