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pump packing 1
- Thread starter fred9
- Start date
For services where a small amount of leakage is acceptable, this is common. The packing will leak a small amount continuously, even if it is well greased. If the leakage is unacceptable, it could be converted to a mechanical seal. However, depending on the particular pump design, there is often inadequate shaft seperation to allow the seal to be replaced without removing the motor driver. We have installed split mechanical seals in some similar installations. A split seal may leak a few drops per minuted, but it should leak much less than packing. In addition the seal will consume less power and will not result in wear to the shaft like packing.
PUMPDESIGNER
Mechanical
We have substituted what we call "Teflon Rope" packing for the standard packing. We got it at WW Grainger. Stuff is pure teflon and looks like teflon tape wound into a rope configuration. Works much better than standard rope, allows you to tighten the packing down a little more with less heating, lasts longer without frequent adjustment.
JJPellin is correct though. If you can go to a mechanical seal successfully you are better off.
PUMPDESIGNER
JJPellin is correct though. If you can go to a mechanical seal successfully you are better off.
PUMPDESIGNER
One company i represent has developed an aftermarket ' zero maintenance stuffing box" to replace the standard packing / shaft arrangement. It incorporates a separate sleeve that slips over the drive shaft, on which packing seals. The advantage is the sleeve is made to resist wear, and when eventually it needs replacement, the shaft does not require replacement, which involves lifting the pump.
This arrangement is beneficial where the water being pumped has particulates, such as in spring run-off. We also installed one where the shaft had been badly scored by over enthusiastic packing tightening, and the customer preferred to not lift the pump (difficult access for crane etc)
I believe that Peerless markets a similar arrangement as an option.
This arrangement is beneficial where the water being pumped has particulates, such as in spring run-off. We also installed one where the shaft had been badly scored by over enthusiastic packing tightening, and the customer preferred to not lift the pump (difficult access for crane etc)
I believe that Peerless markets a similar arrangement as an option.
The seal system you have is usually more than adequate for most aplications unless a small amount of leakage is a problem. For a "packed gland" as you have, the correct packing selection is important and you should request detail from a reliable source together with detail on proper maintenance proceedure.
I think has a packing handbook on their website which explains the right way to do this
Keep the wheels on the ground
Bob
showshine@aol.com
Keep the wheels on the ground
Bob
showshine@aol.com
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Fred9,
This type of packing configuration is very common in vertical turbine pump units. A few years ago I stumbled on a type of Graphite Packing that works exceptionally well. It is called Palmetto Pinnacle Packing made by Tweed & Co. 25 Engerman Ave Denton, MD. Phone-410-479-2244. This packing is the only packing I have on the shelf in our repair facility. Because it is made of 100% graphite it is a pure lubricant and will not burn when tightened to zero leakoff. It also has the lowest drag co-efficient of all the packings I have researched. Used in conjunction with ceramic coating at wear areas of sleeves and shafts,I have had pumps with over 4years use with zero or no wear at the packing area. Ceramic coating should be applied by a reputable vendor to an RMS finish not to exceed 15.
The only draw back with this packing is that it is soft. In systems with high concentrations of suspended solids, metal in particular, the abrasiveness tends to tear the packing apart. Unless a clean flush at the lantern ring placed in the bottom of the packing gland us used. This configuration will keep a clean water barrier between product and packing.
The Teflon rope packing Pumpdesigner mentions is fairly good, but. Teflon will burn if not lubricated properly or tightened too much. Once teflon burns it forms a hard abrasive crust at the point of burning. This will increase wear at either the sleeve area or shaft.
If a split mechanical seal is decided on insure you install a steady bearing on the shaft if your motor is of the hollow shaft design. If not, the vibration of the shafting between the coupling hub at the top of the motor and the mechanical seal will shorten the life of the mechanical seal. These steady bearings can be gotten from the motor manufacturer.
Poppeye
This type of packing configuration is very common in vertical turbine pump units. A few years ago I stumbled on a type of Graphite Packing that works exceptionally well. It is called Palmetto Pinnacle Packing made by Tweed & Co. 25 Engerman Ave Denton, MD. Phone-410-479-2244. This packing is the only packing I have on the shelf in our repair facility. Because it is made of 100% graphite it is a pure lubricant and will not burn when tightened to zero leakoff. It also has the lowest drag co-efficient of all the packings I have researched. Used in conjunction with ceramic coating at wear areas of sleeves and shafts,I have had pumps with over 4years use with zero or no wear at the packing area. Ceramic coating should be applied by a reputable vendor to an RMS finish not to exceed 15.
The only draw back with this packing is that it is soft. In systems with high concentrations of suspended solids, metal in particular, the abrasiveness tends to tear the packing apart. Unless a clean flush at the lantern ring placed in the bottom of the packing gland us used. This configuration will keep a clean water barrier between product and packing.
The Teflon rope packing Pumpdesigner mentions is fairly good, but. Teflon will burn if not lubricated properly or tightened too much. Once teflon burns it forms a hard abrasive crust at the point of burning. This will increase wear at either the sleeve area or shaft.
If a split mechanical seal is decided on insure you install a steady bearing on the shaft if your motor is of the hollow shaft design. If not, the vibration of the shafting between the coupling hub at the top of the motor and the mechanical seal will shorten the life of the mechanical seal. These steady bearings can be gotten from the motor manufacturer.
Poppeye
Poppeye,
I'm impressed and very well said. I agree with you 100% packing has always been a nitemare but compared to mechanical seals the cost savings is tremendous.
Split seals are OK but have speed restrictions and when the pump is being overhauled don't install the split faces buy the one-piece seals. Later should you have a failure of the mechanical seal (only) you can split the solid face seals and install the two-piece split ones. Solid faces are always better than split no matter what anyone tells you.
All you guys did a good job on this packing issue its one of my favorites I fight with in the field all the time.
wlovison@toyopumps.com
I'm impressed and very well said. I agree with you 100% packing has always been a nitemare but compared to mechanical seals the cost savings is tremendous.
Split seals are OK but have speed restrictions and when the pump is being overhauled don't install the split faces buy the one-piece seals. Later should you have a failure of the mechanical seal (only) you can split the solid face seals and install the two-piece split ones. Solid faces are always better than split no matter what anyone tells you.
All you guys did a good job on this packing issue its one of my favorites I fight with in the field all the time.
wlovison@toyopumps.com
Mechanical seals are good for pumps designed for them. Be careful if you wish to change from packing to sealed pump, though. Some of the old designs effectively use the packing as a sort of auxiliary bearing. An ill thought out change from packing to mech seal can lead to other forms of mechanical unreliability.
Also, bear in mind with vertical pumps, you can get a gas pocket under a seal which results in the faces running dry. This can lead you to needing an external lubrication or tandem seal.
There are traps for the unwary, and seal vendors sometimes don't have the full picture.
Also, bear in mind with vertical pumps, you can get a gas pocket under a seal which results in the faces running dry. This can lead you to needing an external lubrication or tandem seal.
There are traps for the unwary, and seal vendors sometimes don't have the full picture.
Fred9
Like Tonyh said in vertical turbine mechanical seal installations there can be an air or gas pocket under the seal chamber. Although this pocket normally will not last for long after start-up, just a couple minutes of run time can damage the seal faces from heat stress. Most single cartridge seals have a vent or flush port incorporated to provided seal flush or cooling at the seal faces. Normally the flow into this flush port is from clean product discharge into the flush port and then it enters the pump through the mechanical seal and the gland housing. On vertical turbine pumps the flow can sucesfully be piped to have trapped air or gas in the pump head to be vented through the seal with a small pipe or tube attached to the vent/flush port of the seal then have that discharge into the fluid sump through holes either drilled in the pumps base or on most units there are plugged holes for packing leakoff to be directed through the base from the gland housing. Or a separate seal flush can be piped into the vent/flush port, keeping in mind the seal flush pressure will have to be higher than the discharge pressure of the unit. This will ensure proper flow across the seal faces. Also keep in mind where the pump is located in relation to outside temperatures. Should the pump be exposed to freezing temps, this vent line can and will become blocked with ice thus making it useless. In this case, heat tracing is a must.
Like Tonyh said in vertical turbine mechanical seal installations there can be an air or gas pocket under the seal chamber. Although this pocket normally will not last for long after start-up, just a couple minutes of run time can damage the seal faces from heat stress. Most single cartridge seals have a vent or flush port incorporated to provided seal flush or cooling at the seal faces. Normally the flow into this flush port is from clean product discharge into the flush port and then it enters the pump through the mechanical seal and the gland housing. On vertical turbine pumps the flow can sucesfully be piped to have trapped air or gas in the pump head to be vented through the seal with a small pipe or tube attached to the vent/flush port of the seal then have that discharge into the fluid sump through holes either drilled in the pumps base or on most units there are plugged holes for packing leakoff to be directed through the base from the gland housing. Or a separate seal flush can be piped into the vent/flush port, keeping in mind the seal flush pressure will have to be higher than the discharge pressure of the unit. This will ensure proper flow across the seal faces. Also keep in mind where the pump is located in relation to outside temperatures. Should the pump be exposed to freezing temps, this vent line can and will become blocked with ice thus making it useless. In this case, heat tracing is a must.
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