LAsludge
Chemical
- Dec 27, 2005
- 28
I thought I’d start a new thread to get a little education into packing and stuffing boxes. I have very little experience in the use of packing. I’ve always used mechanical seals wherever possible but this is a reciprocating pump with no other option.
In our process we use a 3 cylinder pump to pressurize our fluid to 13,000 psi. The fluid is water with 5% solids, 100 cp viscosity, SG = 1.0, 130 degF, 8.5 PH. Not particularly abrasive. The flow is about 20 gpm.
Each cylinder has a 1.5 inch ceramic plunger The packing consists of 5 Teflon/kynar 5/16” braided packing rings with a plastic separator between each packing ring. There is no lantern ring or seal flush.
On the pressure side of the packing is a 1 3/4 inch loading spring and a metal washer. On the atmospheric side of the packing is another plastic separator and the brass packing gland.
We operate 24/7. We got over a month out of the first set of packing but have seen that interval shorten down to a week over the last 3 months. The pump manufacturer says it is a zero leak packing and if we see any fluid leakage then the packing has failed and needs replacing
I read another thread on a similar subject but at a lower pressure. It implied that a close tolerance metal follower ring should be placed between the last packing ring and the brass packing gland. This makes sense to me and will probably help as I’ve noticed that the packing glands have eroded some after the many packing failures. I’m having these rings made up and will try them soon. In the meantime I’d like to get a little more educated.
How do you choose a packing? I’ve looked at a bunch of sites that sell packing. All packing seems to be rated at a pressure but I’ve not seen any with a rating higher than 6000 PSI. Is this a cumulative thing? i.e 5 rings at 6000 pounds each for a total rating of 30,000 PSI?
How do you decide on the number of rings? What about loading? In my case there is a loading spring which I figure is about 75% compressed. Is that how the packing pressure is set?
Any comments would be appreciated.
In our process we use a 3 cylinder pump to pressurize our fluid to 13,000 psi. The fluid is water with 5% solids, 100 cp viscosity, SG = 1.0, 130 degF, 8.5 PH. Not particularly abrasive. The flow is about 20 gpm.
Each cylinder has a 1.5 inch ceramic plunger The packing consists of 5 Teflon/kynar 5/16” braided packing rings with a plastic separator between each packing ring. There is no lantern ring or seal flush.
On the pressure side of the packing is a 1 3/4 inch loading spring and a metal washer. On the atmospheric side of the packing is another plastic separator and the brass packing gland.
We operate 24/7. We got over a month out of the first set of packing but have seen that interval shorten down to a week over the last 3 months. The pump manufacturer says it is a zero leak packing and if we see any fluid leakage then the packing has failed and needs replacing
I read another thread on a similar subject but at a lower pressure. It implied that a close tolerance metal follower ring should be placed between the last packing ring and the brass packing gland. This makes sense to me and will probably help as I’ve noticed that the packing glands have eroded some after the many packing failures. I’m having these rings made up and will try them soon. In the meantime I’d like to get a little more educated.
How do you choose a packing? I’ve looked at a bunch of sites that sell packing. All packing seems to be rated at a pressure but I’ve not seen any with a rating higher than 6000 PSI. Is this a cumulative thing? i.e 5 rings at 6000 pounds each for a total rating of 30,000 PSI?
How do you decide on the number of rings? What about loading? In my case there is a loading spring which I figure is about 75% compressed. Is that how the packing pressure is set?
Any comments would be appreciated.