Do not let a pump run at zero flow
Do not let a pump operate for long periods of time at zero flow. In residential systems, the pressure switch shuts the pump down when the pressure is high which means there is low or no flow.
Do not let a pump run dry, use a check valve
Most pumps cannot run dry, ensure that the pump is always full of liquid. In residential systems, to ensure that the pump stays full of the liquid use a check valve (also called a foot valve) at the water source end of the suction line. Certain types of centrifugal pumps do not require a check valve as they can generate suction at the pump inlet to lift the fluid into the pump.
Suction valves
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Gate valves at the pump suction and discharge should be used as these offer no resistance to flow and can provide a tight shut-off. Butterfly valves are often used but they do provide some resistance and their presence in the flow stream can potentially be a source of hang-ups which would be critical at the suction. They do close faster than gate valves but are not as leak proof.
Eccentric reducer
Always use an eccentric reducer at the pump suction when a pipe size transition is required. Put the flat on top when the fluid is coming from below or straight (see next Figure) and the flat on the bottom when the fluid is coming from the top. This will avoid an air pocket at the pump suction and allow air to be evacuated.
Flow control
If you need to control the flow, use a valve on the discharge side of the pump, never use a valve on the suction side for this purpose.
Plan ahead for flow meters
For new systems that do not have a flow meter, install flanges that are designed for an orifice plate in a straight part of the pipe and do not install the orifice plate. In the future, whoever trouble-shoots the pump will have a way to measure flow without the owner having to incur major downtime or expense. Note: orifice plates are not suitable for slurries.
Avoid pockets and high points
Avoid pockets or high point where air can accumulate in the discharge piping. An ideal pipe run is one where the piping gradually slopes up from the pump to the outlet. This will ensure that any air in the discharge side of the pump can be evacuated to the outlet.
Location of control valves
Position control valves closer to the pump discharge outlet than the system outlet. This will ensure positive pressure at the valve inlet and therefore reduce the risk of cavitation.
When the valve must be located at the outlet such as the feed to a tank, bring the end of the pipe to the bottom of the tank and put the valve close to that point to provide some pressure on the discharge side of the valve making it easier to size the valve, extending it’s life and reducing the possibility of cavitation.
The right pipe size
The right pipe size is a compromise between cost (bigger pipes are more expensive) and excessive friction loss (small pipes cause high friction loss and will affect the pump performance).
Generally speaking, the discharge pipe size can be the same size as the pump discharge connection, you can see if this is reasonable by calculating the friction loss of the whole system. For the suction side, you can also use the same size pipe as the pump suction connection, often one size bigger is used A typical velocity range used for sizing pipes on the discharge side of the pump is 9-12 ft/s and for the suction side 3-6 ft/s.
Pressure at high point of system
Calculate the level of pressure of the high point in your system. The pressure may be low enough for the fluid to vaporize and create a vapor pocket which will be detrimental to the performance of the system. The pressure at this point can be increased by installing a valve at some point past the high point and by closing this valve you can adjust the pressure at the high point. Of course, you will need to take that into account in the total head calculations of the pump.
Pump pressure rating and series operation
For series pump installations make sure that the pressure rating of the pumps is adequate. This is particularly critical in the case where the system could become plugged due to an obstruction. All the pumps will reach their shut-of head and the pressure produced will be cumulative. The same applies for the pressure rating of the pipes and flanges.
Avoid running pump in reverse direction
Avoid running a pump in reverse direction, pump shafts have been broken this way especially if the pump is started while running backwards. The simplest solution is to install a check valve on the discharge line.
Tobee® What can you recommend to increase safe operation of my slurry pump?
Apart from the usual guarding of rotating components, it is important to get advice from the manufacturer or their dealer. This is especially true if buying a Slurry Pump secondhand — just because the manual says it was designed to pump 2,000 gpm, it may not pump anywhere close to that if the duty isn’t the same as the original. Each duty is very specific. Let’s say you installed the Slurry Pump and had the wrong size pipe, you could have a critical issue with material settling out, which may even cause the Pump to explode.
This phenomenon has been reported by the Mine Safety and Health Administration (2009 bulletin) as a major concern. If a condition occurs that blocks the inlet pipe and outlet pipe of the Slurry Pump, it is estimated that 40% of the energy from the motor will go to heating the contents of the wet end of the Slurry Pump. The heat rise can be rapid and steam pressure will build, and an explosion can occur. Confirming the correct flow rate to keep materials in suspension and maintaining the design percent solids and particle size can reduce this risk. Installing power and pressure monitoring sensors that are interlocked and/or alarmed are also advised. Tobee’s recently developed thermocouple device is another safety feature when fitted and alarmed.
Good process design, proper mechanical design of sumps and piping, and use of safety related add-ons are factors determining the safe operation of a Slurry Pump. The manufacturer is always the best place to start.
When I reduced the length of pipe line, why did the slurry pump trip out on overload?
Because the Slurry Pump is running at fixed speed and hasn’t been told that you removed a section of pipe, it will keep spinning away but now finds it is easier to slurry pump. If you look at your slurry pump curve, you will see that if you lower the head (resistance) that the Slurry Pump is pumping against, the new duty point will move to the right and the speed curve and head will intersect at a higher flowrate. The higher flowrate means more work is being done and thus power demand is greater. It would be the same if you reduced the height you are pumping to. The opposite occurs if you increase the head by adding pipe or vertical height to the discharge point. The danger with increasing the head without changing the speed is the lower flowrate that results, which may be below the critical setting velocity. Contact the slurry pump manufacturerslurry pump manufacturer if you are contemplating changes to any part of your slurry pumping system.
Can I use oil in my slurry pump bearings?
Tobee’s slurry pump bearing assemblies are designed around the use of grease lubrication - this means that the seals being used are not suitable for oil. It is more complicated to design for oil and any leakage is far more troublesome for both lack of lubrication and the spillage. Grease lubrication simplifies maintenance and is appropriate for the rpms typically seen in this type of equipment
I have an old slurry pump sump that my grandfather used in our old plant, can I use that for my new plant?
Rather than just say no, which would be the first reaction from any Slurry Pump manufacturer, let’s examine why you probably don’t want to consider this. From our perspective, 90% of problems are on the suction side of a Slurry Pump. Of those problems, 90% of those are associated with poor sump design, such as wrong wall angles (buildup in valley angles and corners), too shallow (vortexing), too big (settling and sloughing), too small (air entrainment, vortexing) and incorrect suction line (entrainment and NPSH issues). The science of sump design doesn’t start or finish with a cube or an old truck-mounted water tank — a correctly designed sump can save you many thousands of dollars in maintenance on your Slurry Pump, or even save a life.
My slurry pump bearings are running hot, what should I do?
How hot are they? Tobee’s slurry pump bearings are designed to run at a relatively high temperature — we set a maximum of 120 ℃ (248 ℉). Possible reasons for bearings running hot logically include slurry pump bearing failure; however, typically there will be other symptoms, such as unusual noise. Bearing failure can occur soon after gland failure if slurry has entered the seal at the wet end of the Slurry Pump.
It may simply be a faulty bearing. Were original equipment manufacturer bearings used during the last repair? It wouldn’t be the first time that price over value resulted in low-quality bearings being substituted.
Failure, or symptoms of failure, can also occur due to high belt tension (drive end) or air entrainment or cavitation (wet end), which will ultimately damage the bearings. Confirm the temperature rise (rises over time or almost immediate) and ultimate temperature. Look for other symptoms, such as noise. Ensuring personal safety, use a listening stick against the housing for signs that the bearings are not running smoothly. Consult the factory with the range of symptoms.
Fortunately, Tobee’s slurry pump bearing assemblies are simple to repair — purchase a bearing repair kit and follow the instructions. Be prepared with an oven for heating, but the assembly requires no preload settings — just locate the bearings in place, lubricate and put the end caps on, finish lubrication and you are done.
HEBEI TOBEE PUMP CO.,LIMITED
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Do not let a pump run at zero flow
Do not let a pump operate for long periods of time at zero flow. In residential systems, the pressure switch shuts the pump down when the pressure is high which means there is low or no flow.
Do not let a pump run dry, use a check valve
Most pumps cannot run dry, ensure that the pump is always full of liquid. In residential systems, to ensure that the pump stays full of the liquid use a check valve (also called a foot valve) at the water source end of the suction line. Certain types of centrifugal pumps do not require a check valve as they can generate suction at the pump inlet to lift the fluid into the pump.
Suction valves
Gate valves at the pump suction and discharge should be used as these offer no resistance to flow and can provide a tight shut-off. Butterfly valves are often used but they do provide some resistance and their presence in the flow stream can potentially be a source of hang-ups which would be critical at the suction. They do close faster than gate valves but are not as leak proof.
Eccentric reducer
Always use an eccentric reducer at the pump suction when a pipe size transition is required. Put the flat on top when the fluid is coming from below or straight (see next Figure) and the flat on the bottom when the fluid is coming from the top. This will avoid an air pocket at the pump suction and allow air to be evacuated.
Flow control
If you need to control the flow, use a valve on the discharge side of the pump, never use a valve on the suction side for this purpose.
Plan ahead for flow meters
For new systems that do not have a flow meter, install flanges that are designed for an orifice plate in a straight part of the pipe and do not install the orifice plate. In the future, whoever trouble-shoots the pump will have a way to measure flow without the owner having to incur major downtime or expense. Note: orifice plates are not suitable for slurries.
Avoid pockets and high points
Avoid pockets or high point where air can accumulate in the discharge piping. An ideal pipe run is one where the piping gradually slopes up from the pump to the outlet. This will ensure that any air in the discharge side of the pump can be evacuated to the outlet.
Location of control valves
Position control valves closer to the pump discharge outlet than the system outlet. This will ensure positive pressure at the valve inlet and therefore reduce the risk of cavitation.
When the valve must be located at the outlet such as the feed to a tank, bring the end of the pipe to the bottom of the tank and put the valve close to that point to provide some pressure on the discharge side of the valve making it easier to size the valve, extending it’s life and reducing the possibility of cavitation.
The right pipe size
The right pipe size is a compromise between cost (bigger pipes are more expensive) and excessive friction loss (small pipes cause high friction loss and will affect the pump performance).
Generally speaking, the discharge pipe size can be the same size as the pump discharge connection, you can see if this is reasonable by calculating the friction loss of the whole system. For the suction side, you can also use the same size pipe as the pump suction connection, often one size bigger is used A typical velocity range used for sizing pipes on the discharge side of the pump is 9-12 ft/s and for the suction side 3-6 ft/s.
Pressure at high point of system
Calculate the level of pressure of the high point in your system. The pressure may be low enough for the fluid to vaporize and create a vapor pocket which will be detrimental to the performance of the system. The pressure at this point can be increased by installing a valve at some point past the high point and by closing this valve you can adjust the pressure at the high point. Of course, you will need to take that into account in the total head calculations of the pump.
Pump pressure rating and series operation
For series pump installations make sure that the pressure rating of the pumps is adequate. This is particularly critical in the case where the system could become plugged due to an obstruction. All the pumps will reach their shut-of head and the pressure produced will be cumulative. The same applies for the pressure rating of the pipes and flanges.
Avoid running pump in reverse direction
Avoid running a pump in reverse direction, pump shafts have been broken this way especially if the pump is started while running backwards. The simplest solution is to install a check valve on the discharge line.