Introduction
Sand Classifying Tanks have been refining both natural and manufactured sand for more than 60 years. They serve three main functions:
- To scalp water from the slurry feed for easier downstream processing
- To produce a uniform product by removing excess intermediate sand grain sizes
- To produce two controlled and one residual product from a single feed
As with any piece of processing equipment, maintaining your Sand Classifying Tank is imperative for optimizing its operation and reducing unexpected downtime.
Periodic inspections are key
Imagine you’re in the middle of your peak production period and everything is going great. You’re producing tons of sand and making good profits. Suddenly, all is not well. You notice your product isn’t meeting specifications and trace the problem back to the sand tank. A hole has worn in one of the elbows that connects the down-pipes to the collecting flume, contaminating classified spec sand. Now you have to stop production to replace the elbow so that you can get production back on track.
This scenario could have been avoided with simple routine maintenance inspections. Routine maintenance is key to avoiding unexpected downtime and costly repairs.
Since sand is very abrasive on equipment, it is doubly important to inspect your sand tank at manufacturer-recommended intervals to catch any damage or wear before it leads to downtime.
Components to inspect
- Valves and valve seats - Some of the most commonly replaced items on sand tanks are valves and valve seats. With some manufacturers, these components are often originally constructed of abrasion-resistant, hard cast iron alloys; however, replacing them with polyurethane ones can offer extended wear life.
- Elbows and down-pipes – Elbows that are connected to down-pipes keep sand discharging from the tank in the flume’s desired cell compartments. While these elbows and down-pipes have been made of hard iron and steel, they have been replaced with polyurethane elbows and thick-walled PVC pipes. These materials provide easier-to-handle, quicker-to-replace components without sacrificing performance.
- Flume liners – Flume liners protect the cell compartments from the abrasive sand as it discharges to the dewatering equipment. They can be made of abrasion-resistant steel, polyurethane and rubber. Although flume liners are optional, they help prolong the life of the flume. If you have flume liners in your sand tank, be sure to inspect and replace them as needed.
- Hydraulic power unit – The hydraulic power unit allows the opening and closing of the sand tank valves via lines connected to the hydraulic cylinders attached to each valve rod. The hydraulic fluid and filter should be replaced at intervals recommended in the manufacturer’s manual. If you shut down your sand tank seasonally, be sure to check the hydraulic reservoir for any water that may have accumulated from condensation caused by temperature variations. If water is present, drain it and fill the reservoir with the appropriate amount of hydraulic fluid as recommended by the manufacturer.
- Electrical systems, including wiring and hydraulic lines – Inspect these components for proper function and to ensure they won’t cause leakage or improper grounding that could potentially harm maintenance personnel. Electrical components such as programmable logic controllers and computers should be kept in a proper environment as recommended by the manufacturer.
- Torque motors, control enclosure housing the hydraulic cylinders, solenoid valves and any associated hydraulic lines and electrical wiring – Be sure these components are free of accumulated sand that could cause interference and component failure.
- Rising current recirculating pump system – Check the impeller for wear or damage and replace if needed. Check that the V-belt is properly tensioned in accordance with the manufacturer’s recommendations. Ensure the bearings are lubricated according to the manufacturer’s manual.
Periodically inspecting these components of your Sand Classifying Tank can help you avoid costly downtime.
Establish a maintenance schedule
Establishing a maintenance schedule that includes periodic inspections of critical wear parts is important to keeping your sand tank operating at its maximum efficiency, but sticking to and following that maintenance schedule is vital. Refer to your Sand Classifying Tank’s operation manual for recommended maintenance requirements.
First, create a list of maintenance tasks to be performed once per shift. These tasks should include the lubrication of applicable components and inspections of the bearings and motors.
Then, create a list of tasks that should be completed once per week, including inspecting all bolts for tightness.
Finally, create a list of tasks to be performed every three months, or every quarter. These should include things like inspecting the operating condition of the down-pipes and valves, and checking that the hydraulic power unit filter is clean.
You can also create tasks that should be performed every six months and every year. Depending on your application, more or less frequent inspections may be necessary. It’s up to you to establish a routine that is the most beneficial for your site, but use the following guide as the minimum when creating a schedule for your specific machine.
Before you perform any maintenance, repairs or adjustments to your sand tank, or any other piece of equipment, be sure to lockout/tagout/blockout all controls and applicable components to prevent movement of the machine. Be sure you wear the appropriate personal protective equipment at all times, and that you read and follow all safety tags, labels or signs. Replace any tags, labels or signs that are missing or worn to the point of illegibility. Also be sure to follow your site’s specific safety procedures when performing maintenance, repairs or adjustments on your sand tank.
A sample maintenance schedule may look like this:
Eight to 10 working hours
Once per shift:
- Lubricate all applicable components
- Inspect the feedbox to ensure it is free from debris and in good operating condition
- Verify that the motors are not running too hot
- Inspect all electrical cables and connections
- Inspect all hydraulic lines and connections
- Ensure that all V-belts have the right amount of tension and are aligned
- Verify that the bearings are not running too hot
140 working hours
Once per week:
- Inspect all motor bolts for tightness
- Inspect the area around the motor cooling fins and be sure it is clean and free from obstructions
1,800 working hours
Once every three months:
- Inspect all bolts and fasteners for tightness
- Inspect the discharge valves, valve seats, down-pipes and elbows
- Check that the hydraulic power unit filter is clean
- Inspect the pinch valves
If during any of these routine inspections you identify a problem or deficiency, perform the necessary repairs or adjustments immediately. After performing any maintenance, ensure all components are in proper working order before restarting the equipment. Also ensure that all personnel are clear of all moving parts and that all guards are in place, secured and functional before operating the sand tank.
Storage
If planning to store your Sand Classifying Tank:
- Be sure to run all the material out of the tank
- Drain the water from the tank and clean out any remaining material
- Drain the water lines
- Lock out the electrical controls
- Ensure the hydraulic power unit motor will stay clean and dry
- Fill the hydraulic power unit with oil
When bringing the Sand Classifying Tank out of storage, make sure you drain the old oil from the system and refill the hydraulic power unit with the proper amount of oil before operating your sand tank.
Lubrication
Lubrication plays another vital role in the operation of your sand tank. Using the wrong type of lubricant and/or not enough lubricant can cause the component to fail. Likewise, a contaminated lubricant can lead to component failure and a possible shutdown of the plant. Keeping your sand tank’s components properly lubricated will ensure they operate at their best.
Here are some best practices when it comes to lubricating your sand tank’s components:
- To prevent contamination from dust, dirt or moisture, be sure to seal all oil and grease storage containers
- Use a clean rag to wipe down hydraulic fittings before lubricating them to further prevent contamination
- Wipe off excess grease that has purged past the seals
- Take care not to over-grease the bearings, as over-greasing can lead to excessive bearing temperatures, bearing failure and premature lubricant breakdown
- Pump grease into the bearings slowly to prevent seal damage
Like routine maintenance schedules, establishing and following a set lubrication schedule will keep your sand tank running smoothly. Refer to your operator’s manual for additional lubrication instructions for certain components, such as motors, hydraulics, couplings and reducers. The type of lubricant you need for each component, along with the lubrication method, lubrication frequency, lubrication quantity, and frequency of maintenance can be found in your operator’s manual as well.
Top 5 ways to maintain your sand tank and keep your sand in spec
The best way to maintain your sand tank is to follow these five tips:
- Inspect the critical wear components and replace them if they are worn or damaged
- Sample the sand that discharges from the first three valve stations at regular intervals
- Adhere to the manufacturer’s recommendations for changing hydraulic fluid and filters
- Check all electrical and hydraulic components for wear or damage at intervals recommended by the manufacturer
- Make sure the service platforms are properly guarded and cleared at all times to ensure the safety of the maintenance personnel
Your operator’s manual will include additional information and can be used as a guide for getting the most out of your Sand Classifying Tank in regard to performance and yield.
