Serva MINI-HEMI High-Energy Mixing System

View Parts List and Assembly Drawing Serva’s High-Energy Mixing Our system was designed for high energy mixing and ease of operation and maintenance. There are many of this family of similar mixing systems working throughout the world. The applications have varied from onshore to offshore and dessert heat to cold climates. The primary components of the mixing system are: Serva MINI-HEMI High-Energy Mixing Injector Cementing metering valve Other components which make up the rest of a complete system are: Mixing tub Recirculating centrifugal pump Mix water centrifugal pump Agitating system Air separator Transfer pump (optional for single pump cementers and required for double pump cementers) These items are discussed in separate documents.

Serva MINI-HEMI High-Energy Mixing Injector

Introduction

The Serva MINI-HEMI a second mixer in the Serva HEMI line and incorporates most of the capability of the full sized Serva HEMI mixer but has been scaled down for lower rates. Like the Serva HEMI, it is a high-energy mixer and does not sacrifice performance. However, it has been designed for the smaller jobs and does not require as much horsepower to operate. A typical application would be a single pump cementer. It is equally as good as a mixer in the recirculating batch mixing mode as it is in continuous mixing (its predecessors were poor batch mixers). Unlike the Serva HEMI, the mixer does not allow the discharge of the densitometer into the mixer. The densitometer output will need to be connected to the mixing tank directly. The bulk flow path is smooth and therefore has a large capacity. Additionally, the water control has an optional remote control to make installations more flexible. The bulk control has always been available with remote hydraulic control.

Description

The slurry mixer is a recirculating type mixer designed to meet the most demanding mixing requirements (however at a slightly lower maximum rate than the Serva HEMI). The mixer design provides easy cleanup and maintenance. The mixer has a 5 ½” union thread half on the inlet for attaching the dry bulk cement metering valve. The recirculated slurry enters the mixing chamber from an outer annular position surrounding the dry bulk cement. The water jets enter the mixing chamber from alternating positions with the recirculation jets. The force of the recirculating jets and the mix water jets is directed inward and mix the dry bulk cement. This provides maximum wetting efficiency.

The operator can easily adjust the water flow from almost zero to maximum. The valve is linear, providing equal increases in water flow per increment of displacement. Maximum water flow is a function of supply pressure. The recirculating mixer design improves mixing and homogenizing of the new incoming slurry with the slurry already in the mixing tank.

Input requirements

• Recirculation flow: 16 bpm minimum with water. Expected back pressure to be 50 psi while operating at 16 bpm. (Note that the SERVApump 5x6 and 4x5 centrifugal pumps can meet this requirement).
• Mixing water: 300 gpm at 130 psi. (Note that the SERVApump 2x3 centrifugal pump can meet this requirement).

• Water inlet 2” npt victaulic
• Recirculation lines are 2” npt victaulic
• Discharge: 5” victaulic
• Inlet for bulk cement: 5.5” suction union

B. Weight: 45kg (100lb)

The above drawing illustrates possible arrangements for the Serva MINI-HEMI mixer with the cement metering valve. Either installation as illustrated above is acceptable. The one on the right is a little simpler but takes up more space in the one direction. It would make cleaning of either the mixer or metering valve relatively straight forward.

Some operators prefer the arrangement at the left with the elbow turned upward. This allows the bulk inlet to be easily turned to any position (to the right, center or left of the cementing truck). The disadvantage of this idea is that metering of cement at low rates may not be as uniform. Having the metering valve inclined to the left or right will give the best metering results.

Bulk Cement Metering Valve Serva has developed a new cement metering valve that overcomes common problems with previous technology. Older technology valves worked reasonably well with clean cement but would develop operation problems when dirty cement was encountered. The new valve greatly improves the ability to handle dirty cement (rocks, weld rod, sack material and other foreign debris) without damaging the valve or becoming difficult to turn. Bearings further enhance ease of operation and life. The body and metering sleeve are heat treated. The rotary operated cement-metering valve adjusts the rate of bulk cement flow. It may be controlled hydraulically with manually operated valve or automatically with a electro-hydraulic valve. In addition, if the hydraulic system failed that is used to operate the valve, the valve is provided with a means to insert a .75 in. steel bar for manually turning. The valve is approximately linear and will provide near equal increases in bulk cement delivery per increment of rotation. A particularly important feature is the ability to meter cement at low flow rates without bridging off (the phenomenon where cement stacks against the opening and therefore prevents further passage of cement). Principle features Hydraulic actuated Position sensor with unitized body Heavy duty assembly clamp – 2 bolt with handle; can be positioned at any angle Valve position scale Heat treated body and valve member Double row ball bearings 3 vacuum breakers Vacuum breaker shield to prevent cement from entering vacuum breaker Bar for operating manually in case of hydraulic failure Mount for hinge which will allow positioning of valve at any desired location