Sand Transportation Systems

 

Overview

Almost all sand management systems will require the need to transport solids from one location to another. Most systems will require the solids to be transported from the point of separation to the point of post processing and then onto the point of discharge. The sand transportation process is as critical as the separation process but is often overlooked in favour of the latter. Slurry movement is not difficult (the mineral processing industry have being doing it successfully for decades) but it does require both the correct technology and the strict adherence to some basic process engineering principles. Get these wrong and the system will be the thorn in the side of any operations team.
 
Cyclotech’s philosophy on sand transportation is to transport sand at low concentrations to maximise system availability. Sand Management operations are rarely time critical procedures and thus it is prudent to trade some cycle time to limit slurry concentrations. Unexpected shutdowns during conventional jetting operations can lead to the need for manually rodding out the transfer pipework between the separator and the downstream jet water handling system due to uncontrolled high sand concentrations. A system which transports sand at low concentration will not block under the same shutdown scenario and can be easily recovered by the process itself.
 
Cyclotech offer two proprietary technologies to ensure robust and reliable sand transportation is achieved within our Sand Management systems.
 

Cyclotech SANDSCAPE® - Solids Fluidisation and Conveyance

The Cyclotech SANDSCAPE® is an in-house engineered eductor or jet pump designed to fluidise and pump a slurry without the requirement for a slurry pump. They have no moving parts and operate on the basis of Bernoulli’s Theorem which states the static pressure of a fluid is inversely proportional to its velocity.  High pressure motive fluid (water) is accelerated through the motive nozzle of the SANDSCAPE® and directed to a throat and a diffuser section, the diameter of which first narrows and then expands to the outlet. This causes the pressure of the motive flow to first drop at the throat and then increase again as the flow decelerates through the diffuser section. A suction nozzle positioned in the low pressure region of the throat will allow a high pressure motive stream to pump a low pressure suction stream (in this case a slurry to an intermediate pressure (as a combined stream).
 
The SANDSCAPE® performs the following functions:
  • In conjunction with a proprietary Cyclotech fluidisation nozzle, it can fluidise and pump a slurry;
  • It controls the “pumped” slurry concentration irrespective of the upstream sand volume;
  • It is highly effective at removing oil from sand through the forces of attrition promoted in the throat of the SANDSCAPE®. It is an integral component of our Sand Receiving, Cleaning and Disposal systems;
PLD SANDSCAPE Internals AH Triton SANDSCAPE
 

Cyclotech PLD Pressure Let Down device

Conventional methods for depressurizing sand from high pressure locations such as cyclone accumulators or production separators are :
  • Isolate and depressure the accumulator / separator and flush the solids in a low pressure environment. This requires extra equipment and often not practical for production separators;
  • Use high spec valving to handle the high wear rates associated with the dynamic depressurisation of a slurry.
Both methods above have some obvious limitations and the Cyclotech PLD (Pressure Let Down) device provides an alternative. The PLD is a proprietary in-pipe technology which offers the means to carry out on-line pressure reduction in high pressure slurries and removes the requirement for high spec valving. It consists of a number of carefully profiled ceramic cones in series set in a bespoke pipe spool. Locating a number of cones in series, the total pressure drop is taken down in a number of small steps which implies that the pressure drop across each element is low, thereby reducing velocities and minimising flow induced wear.
 
Our expertise lies in cyclonic devices but through our in house lab based research and in the field, we have found that an axial flow type PLD unit will outperform a cyclonic PLD device for the following reasons:
  • a cyclonic device will cause radial separation of the solids and fluid which will cause the solids to concentrate at the wall of the cyclonic device substantially increasing wear rates in this high velocity / high solids concentration environment;
  • to increase the capacity of a cyclonic based pressure letdown device will require either the increase in number of cyclones (which must therefore be manifolded in a vessel) or increase the diameter of the cyclone to maintain it at one unit. Either of these options will require a larger diameter pressure vessel. An axial device can be installed in a pipe and thus conform only to piping codes making the unit more compact, less complex and more cost effective to manufacture. This also allows the axial unit to be positioned anywhere in the pipework;
  • cyclonic devices are rarely installed in series which imply that a single unit is designed to take the full pressure drop rather than an axial unit which has cones in series with each cone taking a fraction of the total pressure drop. This implies that the erosion rates are substantially reduced.
The Cyclotech PLD is compact, flexible, reliable, erosion resistant and very cost effective solution to dynamic slurry depressurisation. It is modular in design and thus offers the significant benefit that these PLD pipe modules can be installed in different locations in the process pipework; they do not have to be installed as one long unit.
PLD Ekofisk 2/4M  AH Triton PLD
 

Mechanical Design

These sand transportation technologies incorporate a similar design methodology. The external pressure envelope is designed to standard piping codes and can be manufactured from a range materials including carbon steel through to most stainless steels, Duplex, 6Mo and other high end alloy steels. The internals are removable, and therefore easily replaceable and consist of a Reaction Bonded Silicon Carbide (RBSC) cone set inside a Stainless Steel cartridge housing which provides a sealing surface and mechanical protection. RBSC is an advanced ceramic material which provides ~6 times the wear life of Alumina ceramic.
 
All Cyclotech sand transportation technologies are tested in our in house proving flow loop to verify their designed pressure drop / flowrate characteristics prior to dispatch.
 
Please contact us if :
  • You have started to produced sand but have no topsides sand handling capability;
  • Suffer from slurry pipework blockages;
  • You have problems with your existing sand-jetting system.