SERVAgroup

SERVAcementing

Mixing Skids

Pump Skids

Pump Truck

Pump Trailer

Bulk Blending

Batch Mixer

Liquid Additive
SERVAacm Auto Mixing System

Dos' and Don'ts'

I. MIXER

  • Do clean after each job by removing the metering valve and washing the dry bulk inlet passage with the wash-up hose
  • Do open water jet after job to allow to drain
  • While displacing, do continue to circulate wash water through mixer and densitometer
  • Do operate the agitator as fast as possible without vortexing fluid in mix tank
  • Do preset the water metering valve to nominal low value before the job - approximately 100 to 120 gpm while putting water in the tub
  • Do not run engine slower than rated speed to make engine last longer (This is a false idea.)
  • Do not mix faster than necessary (usually mixing does not need to be fast while displacing should be)
  • If in manual do not try to adjust both water rate and bulk cement rate. Set water at fixed rate and adjust cement to control density. Control tub level with triplex speed
  • If in automatic, do adjust tub level with mix water valve

II. DIFUSER

  • Do wash diffuser from air vent to clean bottom plate and slurry exit vents
  • Do wash around outside of diffuser with hose inserted into mixing tank opening

III. CEMENT BULK METERING VALVE

  • Do put valve back on mixer after cleaning the mixer after the job (keep it dry)
  • Do open the valve fully at end of job and let bulk air blow out residual cement out of bulk delivery line (from bulk truck) and cement metering valve
  • Do empty valve of excess cement after job
  • Do not wash
  • Do not allow rain or humid air to reach inside the valve
  • Do not allow actuator pressure to exceed 750 psi. If the valve does not turn, clean the valve before using

IV. COMPUTER

  • Do use laptop computer to calculate exact values for density, sack weight, water specific gravity, slurry yield per sack and water requirement per sack
  • Do enter into the SERVAacm the correct slurry design values
  • Do use correct cement sack weight. Sack weight is defined as the weight of 3.6 absolute gallons of dry cement. "Sack weight" is not the package weight
  • Do run the computer simulation (using only density simulation) before the job. If something has been entered incorrectly, the simulation will not develop the correct density. It also checks all lines and components (less the densitometer)
  • Do use the density bump keys to make small changes in density during the job (do not go back to design screen to change design)
  • Do set density a little lower than design (using the bump keys) to compensate for air entrainment - normally 0.1 ppg. Being a little under desired density is less likely to cause a problem than over density
  • Do use polarized sun glasses when viewing screen in bright sunlight. It will eliminate glare or sky reflection on screen
  • Do not weld on unit while computer has power. Disconnect battery and protect wires from welding leads
  • Do not wash with pressure hose
  • Make sure that the Allen-Bradley computer is calibrated exactly as the Micro-Motion densitometer (i.e. the density range and the milliamp signal). It is recommended that the density range be set at 7 to 23 ppg and corresponding to 4 to 20 ma. This requires the densitometer to be ordered from the factory with this calibration or if it is not what is desired, requires special equipment to change its calibration (cannot be done by field personnel)
  • Do check the computer "J-box" (where the computer processor is located) and the Panelview enclosure for moisture periodically (every 3 months for average climates and more often in very humid climates). Replace the desecant material (material that absorbs moisture to protect electronics) if necessary

V. Micro-Motion Densitometer

  • Do thoroughly flush the densitometer after the job
  • After cleaning the mixer, do close the valve to the mixer forcing all recirculation flow through the densitometer
  • Do observe the Allen-Bradley Panel-view screen for density while washing the densitometer. Continue to wash (flush) the densitometer until a density reading of 8.34 ppg is obtained

VI. General comment

  • Always report problems with the unit in writing to people responsible for maintenance on the same day that the problem was observed
  • Do not put off preventative maintenance such as cleaning metering valve, replacing or topping off oil, replacing filters or replacing wires or hoses that have become damaged.