I have seen a few people mention that they have had problems with their ampmaster pumps. How was customer service? I have called and emailed with no answer. Is there a pump that I can replace this "piece" with that is as energy efficient? I've heard a little about the Sequence line, what do you guys think?
Leaking AmpMaster
- Thread starter Jime
- Start date
I'd say keep trying to contact their customer service. Sounds like all you need are new seals which aren't that expensive.
If you do decide to look at different pumps, the Sequence line is a good choice from the people I've talked to. In case you'd like to look over the different pumps available to the hobby, hit http://www.reefs.org/library/pumps
Shane
If you do decide to look at different pumps, the Sequence line is a good choice from the people I've talked to. In case you'd like to look over the different pumps available to the hobby, hit http://www.reefs.org/library/pumps
Shane
Greetings everyone,
Mechanical shaft seals for rotating equipment are indeed a tricky subject. I will, however, try to shed some light on this for those who are interested or curious.
A single mechanical seal consists of two faces, one which rotates and one which is stationary. There are also "secondary seals" that are typically, but not always o-rings. A typical component single seal can be seen in the following cutaway.
In this cutaway we see a rotating seal. This is a seal where the face that is spring loaded is rotating with the pump shaft. In this cutaway we have:
A Stationary face
B Rotating face
C Sleeve
D Gland
E Stuffing box
1. Stationary face
2. Dynamic Teflon® wedge
3. Sleeve gasket
4. Sealing interface
5. Gland gasket
Upon closer observation a few things are revealed about this component single seal. First off, the secondary seals are not all of the o-ring variety as there is a wedge sealing the shaft diameter. Second, it becomes crystal clear that the sealing interface is where the important sealing actually takes place. This is where the fluid that is being pumped enters the gap where the seal faces are running against one another, however slight.
Consider the following cutaway of a stationary seal and notice some fundamental differences. The loaded spring does not rotate with the pump shaft.
In this example of a stationary seal we have:
A Stationary face
B Rotating face
C Sleeve
D Gland
E Stuffing box
1. Dynamic O-ring
2. Static O-ring
4. Sealing interface
5. Gland gasket
In these drawings it is easy to place the mechanical seal rotating parts perpendicular, or square to the shaft, but in practice it is just about impossible to do so.
Please look at Figure #1 again:
We would like to have rotating face "B" perpendicular, or square to shaft "c", but that is impossible because rotating face "B" is being pushed against stationary face "A" that is positioned in gland "D", and gland "D" is not square to anything.
There are a few reasons why gland "D' is not square to the shaft:
You cannot tighten several gland bolts through a gasket and get any kind of squareness.
The gland is manufactured from a casting that is not perpendicular, or square to anything.
The face of the stuffing box is not manufactured square to the shaft. Most of the time it is a rough casting. Remember that the pump was designed for packing, there was no need to make this surface machined square to anything.
Assume the seal assembly was done with dial indicators to ensure squareness, the minute the pump comes up to temperature thermal growth will alter the careful setting you made.
There are some additional causes of this non-squareness to the shaft:
Plastic pump housing with poor tolerances or flexing
Misalignment between the pump and its driver.
Operating the pump off of its Best Efficiency Point (B.E.P.)
Thermal expansion at the wet end of the pump.
Pulley driven pump designs.
Dynamic unbalance of the rotating parts.
Bent shafts.
Pipe strain.
The cocking of the gland and stationary face means that the springs will be loaded unevenly and will have to move back and forth with shaft rotation.
The springs and rotating face "B" actually move back and forth twice per revolution of the shaft, and at 1750 rpm this would be 3500 times per minute, or just about 60 times per second (try and move one of your fingers back and forth 60 times per second to see how fast that really is). Needless to say any interference with this movement can lead to a premature seal failure:
The shaft tolerance and finish become critical because the Teflon® wedge has to slide back and forth with this movement.
Depending upon the amount of cocking, this sliding will lead to shaft fretting or damage in a short period of time.
Spring loaded Teflon® sometimes tends to stick to the shaft or sleeve if the sleeve outside diameter tolerance is on the high side, or if the shaft finish is not smooth enough.
The springs can break if they experience too much flexing. They will work harden and fatigue prematurely.
Centrifugal force can move the rotating face square to the shaft, opening the lapped faces. This happens at about 5000 fpm. surface speed or 25 m/second.
The seal faces can open if the springs fill with solids. There are multiple reasons why they would clog:
The pumped product can solidify with a change in temperature. This is not often a reversible process.
The product can crystallize with a change in temperature. This is normally a reversible process.
The product can become viscous with a change of temperature, or sometimes from agitation. Usually not reversible
Dirt or solids in the product can clog the springs.
Some fluids like hard water or hot petroleum can, and will build a hard film on the springs and sliding components.
Many of these solidification problems are experienced when the pump is shut down and subject to temperature changes in the stuffing box area. This can cause frequent seal failures when the pump is first started and lasting until the solidified product reverses back to its liquid state, which may be never.
The stationary version of the seal has none of these problems.
Look again at Figure #2. The rotating face is held square to the shaft by a clamped surface. This reference remains even if the pump experiences deflection from operating off the Best Efficiency Point (B.E.P.), pipe strain, or misalignment between the pump and its driver.
When the gland (D) is tightened to the face of the stuffing box it will kick for the same reasons that it did with the rotating version of the seal, but unlike the rotating version, the springs will not move back and forth twice per revolution of the shaft because they are not rotating with the shaft.
If the gland were severely cocked it would cause an uneven wear of the seal faces, but no back and forth movement that can be interfered with, causing the seal faces to open and leak.
This is the same type seal that is used in the pulley driven water pump of your automobile. And as you are well aware the radial thrusting caused by the pulley drive mechanism has little to no affect on the seal performance.
High speed pumps such as the Sundyne design use this type of seal to prevent the faces from opening as a result of the centrifugal forces generated at the high shaft speeds.
The main shaft seals of our atomic submarines use large size stationary seals to compensate for the terrible misalignment problems found in these applications.
Seal manufacturers can supply you with both stationary and rotary versions of the mechanical seal in solid, split and bellows designs. To ensure squareness to the rotating shaft they require positioning the rotating portion of the seal against a shaft shoulder or a clamped reference shoulder that has been installed on the shaft. This clamping arrangement accounts for the higher cost associated with stationary seals.
It's no contest, choose stationary every time.
With regards to the abrasive nature of our tank water and how that can cause mechanical seal failure, there are some important issues to consider. What is really between the faces while the pump is in operation? Quality mechanical seal faces are lapped as flat as mankind is capable of, which is 2 Helium light bands. With an optical flat and a helium light source, one can read the light bands across the mechanical seal faces and determine flatness. 2 Helium light bands is about 15 millionths of an inch.
So now we understand a few of the possible problems with the Ampmaster 3000 mechanical seal assemblies. They are as follows:
1. Is it a rotary seal? I dont know, I have never seen one but it certainly could be. If it is a rotary seal then it is quite possible that the seal is not perpendicular to the shaft. I do believe that the seal presses into a plastic housing and the tolerances could be loose. This would also explain why some people are having great luck with them and others are not. Those with seals that are perpendicular to the shaft are doing great while others are not.
2. Is the particulate matter that we are circulating in our tanks less than 15 millionths of an inch in diameter? If so, then this could be getting between the faces and damaging the carbon face, assuming that there is at least one carbon face. This would cause the face to go out of flatness, and after that all bets are off. It could also be possible that the seal faces were never flat to begin with due to poor manufacturing standards or quality control.
3. Other than modern non contacting "gas seals" there are NO mechanical seals that can run dry for any length of time. This generates friction and destroys the faces or at the very least brings them out of tolerance in terms of flatness.
The bottom line is that mechanical seals fail for only two reasons, and two reasons only. So if you remember nothing else from this post just remember that ANY mechanical seal that fails prematurely was either damaged or the faces opened. I consider a mechanical seal to have failed prematurely unless the carbon or other sacrificial face isnt completely worn away. If there is anyone that has a seal out of one of these pumps that has failed please feel free to send it to me for failure analysis. I can determine the mode of failure by looking at the seals in question. You can PM me here or feel free to email me at [email protected]
It is issues such as this that make the pumps that have no shaft seal appear to have an advantage!
Many thanks to Mr. McNally for his guidance over the last 12 years regarding mechanical seals.
Mechanical shaft seals for rotating equipment are indeed a tricky subject. I will, however, try to shed some light on this for those who are interested or curious.
A single mechanical seal consists of two faces, one which rotates and one which is stationary. There are also "secondary seals" that are typically, but not always o-rings. A typical component single seal can be seen in the following cutaway.
In this cutaway we see a rotating seal. This is a seal where the face that is spring loaded is rotating with the pump shaft. In this cutaway we have:
A Stationary face
B Rotating face
C Sleeve
D Gland
E Stuffing box
1. Stationary face
2. Dynamic Teflon® wedge
3. Sleeve gasket
4. Sealing interface
5. Gland gasket
Upon closer observation a few things are revealed about this component single seal. First off, the secondary seals are not all of the o-ring variety as there is a wedge sealing the shaft diameter. Second, it becomes crystal clear that the sealing interface is where the important sealing actually takes place. This is where the fluid that is being pumped enters the gap where the seal faces are running against one another, however slight.
Consider the following cutaway of a stationary seal and notice some fundamental differences. The loaded spring does not rotate with the pump shaft.
In this example of a stationary seal we have:
A Stationary face
B Rotating face
C Sleeve
D Gland
E Stuffing box
1. Dynamic O-ring
2. Static O-ring
4. Sealing interface
5. Gland gasket
In these drawings it is easy to place the mechanical seal rotating parts perpendicular, or square to the shaft, but in practice it is just about impossible to do so.
Please look at Figure #1 again:
We would like to have rotating face "B" perpendicular, or square to shaft "c", but that is impossible because rotating face "B" is being pushed against stationary face "A" that is positioned in gland "D", and gland "D" is not square to anything.
There are a few reasons why gland "D' is not square to the shaft:
You cannot tighten several gland bolts through a gasket and get any kind of squareness.
The gland is manufactured from a casting that is not perpendicular, or square to anything.
The face of the stuffing box is not manufactured square to the shaft. Most of the time it is a rough casting. Remember that the pump was designed for packing, there was no need to make this surface machined square to anything.
Assume the seal assembly was done with dial indicators to ensure squareness, the minute the pump comes up to temperature thermal growth will alter the careful setting you made.
There are some additional causes of this non-squareness to the shaft:
Plastic pump housing with poor tolerances or flexing
Misalignment between the pump and its driver.
Operating the pump off of its Best Efficiency Point (B.E.P.)
Thermal expansion at the wet end of the pump.
Pulley driven pump designs.
Dynamic unbalance of the rotating parts.
Bent shafts.
Pipe strain.
The cocking of the gland and stationary face means that the springs will be loaded unevenly and will have to move back and forth with shaft rotation.
The springs and rotating face "B" actually move back and forth twice per revolution of the shaft, and at 1750 rpm this would be 3500 times per minute, or just about 60 times per second (try and move one of your fingers back and forth 60 times per second to see how fast that really is). Needless to say any interference with this movement can lead to a premature seal failure:
The shaft tolerance and finish become critical because the Teflon® wedge has to slide back and forth with this movement.
Depending upon the amount of cocking, this sliding will lead to shaft fretting or damage in a short period of time.
Spring loaded Teflon® sometimes tends to stick to the shaft or sleeve if the sleeve outside diameter tolerance is on the high side, or if the shaft finish is not smooth enough.
The springs can break if they experience too much flexing. They will work harden and fatigue prematurely.
Centrifugal force can move the rotating face square to the shaft, opening the lapped faces. This happens at about 5000 fpm. surface speed or 25 m/second.
The seal faces can open if the springs fill with solids. There are multiple reasons why they would clog:
The pumped product can solidify with a change in temperature. This is not often a reversible process.
The product can crystallize with a change in temperature. This is normally a reversible process.
The product can become viscous with a change of temperature, or sometimes from agitation. Usually not reversible
Dirt or solids in the product can clog the springs.
Some fluids like hard water or hot petroleum can, and will build a hard film on the springs and sliding components.
Many of these solidification problems are experienced when the pump is shut down and subject to temperature changes in the stuffing box area. This can cause frequent seal failures when the pump is first started and lasting until the solidified product reverses back to its liquid state, which may be never.
The stationary version of the seal has none of these problems.
Look again at Figure #2. The rotating face is held square to the shaft by a clamped surface. This reference remains even if the pump experiences deflection from operating off the Best Efficiency Point (B.E.P.), pipe strain, or misalignment between the pump and its driver.
When the gland (D) is tightened to the face of the stuffing box it will kick for the same reasons that it did with the rotating version of the seal, but unlike the rotating version, the springs will not move back and forth twice per revolution of the shaft because they are not rotating with the shaft.
If the gland were severely cocked it would cause an uneven wear of the seal faces, but no back and forth movement that can be interfered with, causing the seal faces to open and leak.
This is the same type seal that is used in the pulley driven water pump of your automobile. And as you are well aware the radial thrusting caused by the pulley drive mechanism has little to no affect on the seal performance.
High speed pumps such as the Sundyne design use this type of seal to prevent the faces from opening as a result of the centrifugal forces generated at the high shaft speeds.
The main shaft seals of our atomic submarines use large size stationary seals to compensate for the terrible misalignment problems found in these applications.
Seal manufacturers can supply you with both stationary and rotary versions of the mechanical seal in solid, split and bellows designs. To ensure squareness to the rotating shaft they require positioning the rotating portion of the seal against a shaft shoulder or a clamped reference shoulder that has been installed on the shaft. This clamping arrangement accounts for the higher cost associated with stationary seals.
It's no contest, choose stationary every time.
With regards to the abrasive nature of our tank water and how that can cause mechanical seal failure, there are some important issues to consider. What is really between the faces while the pump is in operation? Quality mechanical seal faces are lapped as flat as mankind is capable of, which is 2 Helium light bands. With an optical flat and a helium light source, one can read the light bands across the mechanical seal faces and determine flatness. 2 Helium light bands is about 15 millionths of an inch.
So now we understand a few of the possible problems with the Ampmaster 3000 mechanical seal assemblies. They are as follows:
1. Is it a rotary seal? I dont know, I have never seen one but it certainly could be. If it is a rotary seal then it is quite possible that the seal is not perpendicular to the shaft. I do believe that the seal presses into a plastic housing and the tolerances could be loose. This would also explain why some people are having great luck with them and others are not. Those with seals that are perpendicular to the shaft are doing great while others are not.
2. Is the particulate matter that we are circulating in our tanks less than 15 millionths of an inch in diameter? If so, then this could be getting between the faces and damaging the carbon face, assuming that there is at least one carbon face. This would cause the face to go out of flatness, and after that all bets are off. It could also be possible that the seal faces were never flat to begin with due to poor manufacturing standards or quality control.
3. Other than modern non contacting "gas seals" there are NO mechanical seals that can run dry for any length of time. This generates friction and destroys the faces or at the very least brings them out of tolerance in terms of flatness.
The bottom line is that mechanical seals fail for only two reasons, and two reasons only. So if you remember nothing else from this post just remember that ANY mechanical seal that fails prematurely was either damaged or the faces opened. I consider a mechanical seal to have failed prematurely unless the carbon or other sacrificial face isnt completely worn away. If there is anyone that has a seal out of one of these pumps that has failed please feel free to send it to me for failure analysis. I can determine the mode of failure by looking at the seals in question. You can PM me here or feel free to email me at [email protected]
It is issues such as this that make the pumps that have no shaft seal appear to have an advantage!
Many thanks to Mr. McNally for his guidance over the last 12 years regarding mechanical seals.
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