Pump Packing

Pump Packing

Tired of pump packing salesmen trying to sell you the latest and greatest packing when all you really need is something that seals your packing applications. Allow us to offer this simple pump packing guide as to what is needed in 90% of common braided pump packing applications. Ideally this guide will help you select the packing that will make it to your next preventive maintenance cycle.

We will break this down by water service packings, abrasive service packings, chemical service packings, high temperature service packings, mixer and agitator service packings, and food service packings. We also have a wide range of specialty service packings, which you will find a link to but, let's focus on that 90% segment first:

Water Service Packings: In truth this is the most fool proof section because short of a rolled up piece of paper, most pump packings will work, at least for a while. Because times are hard and companies are broke, lets start with the cheapest.

Flax : Flax as a packing is most commonly used in propeller shaft packings. In truth their are several grades of flax packing. But unless you are a boat manufacturer just looking for the cheapest thing for your lowest end boat, it's not worth the savings. Extend the life of your flax packing by getting a PTFE coated flax. It will protect the flax and prevent it burning up, or rotting. Flax is a grown plant, and as such is prone to degrade.

Non-asbestos pump packing: Very common in irrigation pumps or any plant that is pumping relatively clean water or condensate such a fresh water injection, or water companies, Non-asbestos pump packing holds up reasonably well and does the job for a while. There are differences in the quality of the non-asbestos pump packing (like any product). In general, if a packings yarn is dipped in the blocking agents and lubricants (that prevent it from being a screen door), before and after it is braided, it will be a better packing. The two basic coatings are 1) graphite (2) PTFE. Both work well but if you have any problems with contaminating your process, you better use PTFE.

Ameri-lon: Ameril-lon packing is an exceptional general service pump packing because it is made of two naturally lubricious products, graphite and PTFE. It is much more versatile than Non-asbestos packing since most chemicals will not attack it. The lubricants in it cannot wash out as in non-asbestos packings, so it lasts longer. It is also more resistant to abrasives. In fact it is the one pump packing we offer that is good for general service, chemical and abrasive service. If you have multiple pumps in different applications, this is the one pump packing that may just handle all your applications under 500 F.

GFO - GFO is Ameri-lon's name brand brother. GFO yarn was developed and originally produced by W.L. Gore. It's an exceptional product which solved a wide range of industrial pump applications. It's helped fill the void asbestos packings left when they were pulled from the market in the 1980's. GFO was developed by taking an existing product PTFE and adding graphite, which helped eliminate the cold flow and sleeve scaring issues PTFE alone has. American Seal & Packing does offer GFO if you prefer the W.L. Gore name brand. We keep it simple and call it GFO packing.

Abrasive resistant pump packings: This is the most common pump packing problem. Often when customers do not realize it. It's commonly said that "oh I'm just pumping water" but in truth the water is being pumped along with sand, silt, salt, and other abrasives that all eventually destroy the packing. The solution is to use an pump packing that resists abrasion. There are a number of packing yarns that fit this classification. Kevlar is the most common. It is an aramid fiber pump packing that is easily identifiable by it's yellow color. Often used on the corners of packings for it's strength, Kevar is 5 times the strength of steel by weight. It is effective for abrasive applications, but best in reciprocating applications. In centrifugal applications, abrasive material tends to get embedded into the fibers turning the packing into a grinding wheel Other abrasive service fibers include Novaloid, Nomex, and Kynol a phenolic material. These three materials each perform well and tend to be less abrasive to shafts than Kevlar so they are suited for centrifugal pump applications. In our experience, most of the time Ameri-lon is as effective and less expensive.

Chemical resistant pump packings: PTFE Packing - Because of Legal's preference that we do not use the well recognized trade name for this product, lets just say it's on your pans at home. Wikipedia gives a great explanation: "In chemistry, poly(tetrafluoroethylene) or poly(tetrafluoroethene) (PTFE) is a synthetic fluoropolymer which finds numerous applications. PTFE is most well known by the DuPont brand name Teflon". PTFE was the primary packing to fill the Asbestos void. Good for the same upper temperature (500 F), and for a wider range of chemicals PTFE was a god send. PTFE however has a couple drawbacks. First, it has a growth rate higher than metal. Which means if it's getting hot from the friction of a fast turning shaft, it will grow in size. Having nowhere to go because it's contained in the stuffing box, it does something surprising for a soft material, it cuts into the sleeves and shafts of pumps, leaving a groove. A pump sleeve with a groove in it is going to leak and must be repaired. The second issue with PTFE is "cold flow". Cold flow means the product will move, and in the case of pump packing this generally means extrusion. When pump packing extrudes, it creates a leak path and that means a leaking pump. Because of this PTFE must should selectively be used. FDA applications require it. Chemical applications that cannot have contamination require it. Slower turning shafts can get by using it with no or minimal damage. Since there is no or little movement in Valves it works well there. Pump packings that use PTFE as coating are not effected by cold flow or growth rates.

High temperature pump packings - Graphite, Carbon, & Flexible Graphite. Because PTFE, Kevlar, Nomex, Novaloid, Ameri-lon, Non-asbestos, and Kynol all stop at or near the - 500 F point, Any application above 500 F is what we consider "High Temperature". For this there really are not a lot of options. Let's start with our favorite, Ameri-graph pump packing. Ameri-graph is made of Flexible graphite. Flexible graphite is a soft and comfortable so it seals extremely well. It can be die formed to take on a the shape of a worn shaft, or can actually fill the pits of a shaft (within reason) and give itself a smooth surface to run against. This is due to the particle transfer characteristic. Because it is soft it is not great for abrasive service, but for high temperatures it is exceptional. How high a temperature it will handle depends on the application and its content of oxygen. The less the oxygen the greater the temperature. Up to 5400 F (non-oxydidzing). .. But starting at 850F (breathable air). This temperature range is a common characteristic of all carbon based packings, including Graphite, Carbon and Flexible Graphite. We offer several grades of flexible graphite. The most common and affordable, Ameri-graph is an industrial grade pump packing good for most applications. We also offer Genuine Grafoil flexible graphite in Industrial, and Nuclear grades as well as, with and without Inconel wire for high pressure applications. If you want the purist it's Grafoil® flexible Graphite. Carbon and graphite filaments yarns with and without graphite / PTFE coatings are generally used high temp applications like boiler feed applications or as end rings when used in combination with flexible graphite. In reciprocating high temperature applications carbon or graphitic yarns are used without flexible graphite. Flexible graphite pump packing is prone to particle transfer in reciprocating pumps which will coat the length of a pump rod removing flexable graphite from the seal area, and permit leakage. There is more to pump packing than you thought.