Pump cups, piston rings, and forming UHMWPE

[magneticanomaly]

I am overhauling an old FH Myers double-acting hand pump, 5" bore and slightly longer stroke, to pump used fryer oil from a receiving ("dirty") tank through a filter to a ready-to-use ("clean") tank. Not expecting clean enough to fry more taters, just to burn in Diesel engines.

Will be making a new stainless-steel piston-rod (13/16" diam with 14TPI on ends, to fit the tapped end of the cast rack, and nuts to hold piston on.. Will bore out and single-point 3/4-16 nuts to 13/16-14

The piston I removed looked like a piece of heavy conveyor belting between washers. Judging by the cast-iron washers and spacer, I guess originally it had a pair of leather cups.

Some years ago I rebuilt a piston-type motor-driven water pump with about a 3" bore, and found new urethane cups for it. I cannot now find a source...scores of Google hits, all for bicycle-pump-sized leather cups. Can anyone here recommend a source for wide variety of sizes of pump cups...leather OR synthetic?

Of course, a pump CUP usually acts as a check-valve as well as a seal. So for a DA pump, you either need two, or a bi-directional seal.
After soaking some leather and scratching around for something to make forming dies from, to make a pair of leather cups, I decided it would be no more work to make a solid UHMWPE piston, with a piston ring.

Rather than trepanning a ring out of the same 1 1/2" thick plate I will be making the piston out of, I cut a 1/2" wide strip out of some 1/2" plate, thinking to warm and bend it into a ring.

I first forced it cold, with some worry I might break it, into a little scrap of 8" ID pipe...of course the ends stayed straight, so I clamped them, and set the whole on the wood-stove to warm and take the set. My Harbor Freight temp gun said the pipe got to about 80 deg C. After a few hours I took it out and it was no longer straight, but neither did it have an 8" circular O.D.

So I forced it, still warm, into a 6" ID spool, again clamped the ends, and decided I needed more heat. I contemplated asking here, but did not want a jaunt into Computerland to eat another chunk of my day.

I set the 6" ring on the woodstove, and watched the temp with my temp gun. Saw litle if any change. "Fingernail hardness" did not seem to change at 130, 140 deg C. I saw 150..and..a tiny gleaming meniscus against the steel?

Snatched it off the heat....The ring is indeed now formed to 6" OD, with slightly variable radial thickness due to the melting. I will leave it and cut half-lap ends to fit the 5" bore..

But apparently UHMWPE, although it will creep even at room-temp, does not get noticeably soft before it melts...Or did I miss something?

Is there a commercial source for plastic piston rings? I found some from IGUS, but they only go up to 70mm, are radially very thin, and expensive!

Any recommendations for an adhesive to glue leather or rubber (what kind?) to the valves, for service in vegetable oil?

Photos of the pump will follow

 

[john.k]

The Graco paint pumps use the UMHWPE for pressures up to 7000psi ....but I think the seal stack also has teflon washers in it ,a hard white teflon.

 

[Joe Michaels]

Hello Magnetic:

Best wishes to you & your family for Thanksgiving. On the matter of piston cups: try your local "Parker Store". Or, contact The Frank Murken Company in Schenectady, NY. Murken is a dealer in packings and gaskets whom we used quite often when I worked at the NY Power Authority. On one occasion, we had some ca 1922 combined airbrake/jacking cylinders on a hydroelectric generator. These cylinders had about 6" bore and had original pump-type cup leathers on their pistons. These were so deteriorated/worn that they could not hold air to apply brakes, let alone higher pressure oil for jacking (to take the weight of the rotating assembly off the thrust bearing during periods of layup, or for repairs). I believe it was Murken who took the measurements we gave them and furnished us with new piston cups made from some soft synthetic material that was oil resisting. Parker has stores in most cities and localities, and they should also be able to provide some kind of synthetic cup type piston seals. Not sure about what diameters are furnished as stock sizes. You may wind up modifying the 'followers' that the piston rod runs thru and which clamp the cups in place to make up the piston.

 

[dana gear]

You can also try your local hydraulic supply, I have a 1938 windmill with a pump jack of some unknown manufacturer, I was able to find a piston cup that works great in the pump.

 

[john.k]

Leather bucket seals are used in the old Servex 30-200 ton presses.....they have the strange property of discharging water through the leather ,but retaining high pressure oil...up to 10,000psi..........Guy up the road had a lot of dozers,and he had big presses out in the weather where they would get rainwater in the tanks. As you pumped up the pressure ,water would run out the ram .....unusual.

 

[magneticanomaly]

Promised photos.
One shows almost all the pieces. Odd-shaped whitish flattish thing in back is my first attempt at UHMWPE piston ring, which almost melted
Other pic shows second piece of UHMWPE crammed in a 6" ring. Sticks force the ends to conform.
I am still pondering how much machining I want to do on the ring, and how i will hold it. Suggestions welcome. Machining the groove in the piston will be easy, so I plan to finish the ring forst anf make the groove to fit it.

 

[true temper]

Leather bucket seals are used in the old Servex 30-200 ton presses.....they have the strange property of discharging water through the leather ,but retaining high pressure oil...up to 10,000psi..........Guy up the road had a lot of dozers,and he had big presses out in the weather where they would get rainwater in the tanks. As you pumped up the pressure ,water would run out the ram .....unusual.

I can’t believe that leather cup seals will hold 10,000 psi. I looked them up McMaster Carr has them in smaller sizes and says they will….

 

[john.k]

Actually hold more ....a couple of sizes of Servex press go over the 10k ,to 13,000 in one size ....bores are up to 7" dia..........and in daily use in a truck workshop,the leather lasts 20+ years ,generally the steel and cast iron components fail............and did I mention ,the cylinder that holds 10k psi is cast iron?

 

[Joe Michaels]

Magneticanomaly:

I can appreciate your wanting to re-purpose the hand force pump for making 'veggie diesel' fuel. I do not claim to be any kind of maven as far as materials science. However, my gut instinct is telling me that handling heated vegetable oils is a bit of a special case. My instincts are telling me the heated vegetable oils may deteriorate or cause rapid deformation and failure of leather piston cups.

A though came to me which may be worth exploring. Namely, many years ago in the evolution of steam engines, before metal piston rings came into use, piston grooves were packed with 'tow' ( a jute fiber), or with other rope-like natural fibers. Using that as basis for my line of thinking, here is an idea:

1. Check the durability of various square braid packing materials as well as available sizes. There are some "Teflon" containing braided packings, which may
resist heated vegetable oils.

2. Make the piston with a groove (or grooves) to accomodate the square braided packing. I'd make a two-piece piston, such that once inside the cylinder, the piston
could be made up to expand the packing against the cylinder walls. A two-piece piston with a spigotted fit and an "O" ring to seal that fit is what I am
thinking of. A couple of socket head screws to draw the piston sections together would be used. The piston rod would pass thru the male spigotted half of the
piston and the spigot would pass thru the end face of the 'female' half of the piston. This lets the piston be made up tight on the rod, without involving the
packings.

3. Cut packing rings using an angled cut. Grooves should be approximately as wide as the packing and a little shallower than the packing 'depth'. Idea is to put the packing into the grooves with the piston halves loose. Once the piston and packing is in the cylinder, sock up on the capscrews to expand the packing so it
seals against the cylinder walls.

4. There is a packing material sold under such trade names as "Grafoil". It molds and forms a donut around valve stems and pump shafts. We used it on some
hydro turbine shafts and other valves. It is rated to some high temperatures and may be chemical resistant. Whether any fragments of the graphite or other fibers
used in making this packing would get loose in your vegetable oil (and mess up diesel engine injectors by being too fine for the fuel filters to catch) is my only
cause for concern in suggesting this type of packing.

5. As I wrote in my earlier post, before reinventing the wheel, I'd pay my local Parker Hydraulics store a visit. Parker has detailed catalogs of all sorts of seals,
including hydraulic piston seals with soft expander rings. They also have a listing for what seal materials resist what chemicals and operating temperatures for
those materials. I worked out of the Parker catalog a good bit when I was employed at the powerplant.

6. Another thought: could you simply make up a 'conventional' piston and use cast iron piston rings ? Plenty of piston pumps did use cast iron rings, as do
a number of larger hydraulic cylinders. When dealing with cast iron cylinders for pumps or engines running on saturated steam, I've turned worn pistons
down by about 0.100" on each side and built them back up with bronze brazing. I then remachined the outer diameter to fit whatever the cylinder finished up at
(by rebore and/or honing). The bronze overlay gives a nice wearing surface, and can be machined to a fairly close clearance in the cylinder. A little math on the
matter of thermal expansion and you may play it close enough to have this clearance really tighten up when the pump comes up to temperature. If your pump
is handling vegetable oil before conversion to "Veggie diesel", the vegetable oil may be viscous enough to allow the use of labyrinth sealing grooves on the piston.
No rings or seals needed. Not 100% 'positive displacement', but pretty close to it and follows the "K.I.S.S." rule of engineering.

 

[Joe in NH]

5" bore is a bit large, but one source I have used for pump leathers is Merrill Manufacturing.

Cup Leathers

No. 711 waterproof - Soft pliable waterproof leather precision formed - for easy installation ad proper seal - The top edge of cup beveled to ensure the seal of the cup in the cylinder at low pressure - for best operation in applications - For industrial and water system applications - Merrill...

www.merrillmfg.com

You can buy these through Amazon, or from retailers in Ebay, but the best pricing is from Merrill themselves.

Joe in NH

 

[john.k]

Seems that a simple centrifugal pump with a 1/2hp motor might be more suitable........since the OP has a hand pump,Im thinking any kind of seal that has high drag wont be suitable .

 

[Joe Michaels]

For handling oils at low flowrates, a simple gear pump is often the best choice. We used spur-gear pumps direct connected to NEMA frame 56 motors to transfer lube oils and for circulating oil from sump tanks on various powerplant equipment thru filters. Many years ago, when I was maybe 14 or so, I was in a doughnut shop with my parents. What caught my eye was a portable motor-driven gear pump on a hand truck. They had it for transferring oil from the various deep friers. I remember noting it was an Oberdorfer gear pump (made in Syracuse, NY). Simplest type of gear pump there is. On our ca 1921 hydro turbines, the lube oil pumps are original Brown & Sharpe gear pumps, as supplied by GE with the generators at time of manufacture. The generators have been thru at least two rewinds in the past 70 years, but the old B & S gear pumps just keep on without needing any servicing.

Magneticanomaly has said in his post that he intends to use the pump to move vegetable oil to be converted into bio diesel (aka 'Veggie Diesel'). There is no reason the hand piston pump could not work in his application if the rod packing, piston cups and valve discs were made from the right materials. I have a sneaking suspicion that heated vegetable oil may deteriorate leather pump piston cups. When I retired from the powerplant, I took my Parker manual with me. Now, all I have to do is an archaeological dig in multiple locations in my house and shop to find it. If I do, I will see what Parker recommends for synthetic materials for piston seals or cups. They list a bunch of liquids and gases in tabular form, with how well the different seal materials hold up to them.

 

[magneticanomaly]

Thanks, Joe NH for the suggestion of Merrill...a source I am very glad to now know about.
Thanks, Joe M for the excellent suggestion of using a ring of square braided packing as a piston ring. For a slow hand-operated pump it would probably work perfectly. Working back-and-forth in the groove of a fast or powered piston, maybe not.

The oil I will pump will be cold. I am not planning to go to the trouble of doing the transesterification process to make the waste oil into "biodiesel" I have been burning around 30% plain unfiltered but long-settled veg oil, mixed with #2 petroleum diesel, in my Yanmar tractor for two Summers now without any obvious problems. I have a 1-cyl China diesel genset from the scrapyard on which I intend to experiment burning straight veg oil. I have also heard of thinning veg oil with gasoline to lower the viscosity to match #2 diesel...may try that, too. Transesterification requires lye and methanol...does yield the possbly useful by-product of glycerine, but just seems overall more cost and trouble than it is worth.

Drifting from the subject, I can hear some protesting that adding gasoline will be dangerous. Here is why I think it will not be.

Many years ago i was a member of a volunteer fire company. They sent us to "fire school" One of many subjects covered was liquid fuels. Diesel oil has a low vapor pressure/high boiling point. So, since LIQUID does not burn, only vapor, since the liquid cannot mix with air, Diesel's low vapor pressure means that there will not be an ignitable mixture of fuel and air over a pool of spilled Diesel fuel
Heat the Diesel fuel up to a temp called the "flash point" (100-200 deg F) and the vapor pressure/evaporation rate is then enough that there will be. BUT, even then, unless the brief combustion of the vapor-mixed-with-air heats the bulk of the oil to the "fire point", there will nt be enough continuous evaporation of the fuel to MAINTAIN the inflammable mixture above the pool or container. YOu can easly demonstrate all this with a bottle-cap-full of diesel fuel, a candle to heat it, and a splinter to use to try to ignite vapors.

So, flash-point and fire-point refer to vapor pressure or evaporation rate. There is another important temperature, the "autoignition temperature". That is determined by the chemical stability of the fuel, the energy hump over which a mixture of fuel and air has to get over before the oxidation rate is rapid enough to produce enough heat to keep the reaction going. For Diesel, 350 - 625deg F.

Gasoline has a much higher vapor pressure, flash point 40 deg below zero F...but the autoignition temp is actually higher than for diesel fuel (495-833 F)

You want a low autoignition temp for diesel, so that the compression-heated air alone will reliably ignite it.as soon as it is injected But you want a high auoignition temp for gasoline, so that the compression-heated air does NOT ignite it, so that you can control the timing of ignition by the timing of the spark.

So inside a diesel cylinder, gasoline will not ignite any faster that diesel fuel. Fuel in a diesel is supposed to ignite immediately when injected. In fact, neglecting excessve wear of injectors due to poor lubricity of gasoline, a diesel will be harder to start on gasoline, because a higher compressed-air temp is required to ignite gasoline. Veg oil with gasoline added will surely give off vapor faster than without, but almost certainly slower than gasoline NOT dissolved in oil.

Of course this is all theoretical. I'd love to hear about any actual experience with veg oil with viscosity modified by addition of gasoline..


My biggest worry about the 5" hand pump is that it will not develop enough pressure to push the oil through my Cuno filter at a reasonable rate.

This is a very small-scale operation. I collect about 30 gallons of used veg oil a month. I dump it from jugs through a screened funnel into a 275 gallon tank...it is from that tank that i want to pump it through my cleanable Cuno filter, into another tank. That tank will have a standard 30 micron spin-on fuel filter on the outlet, before the hose. So I expect to do 15 minutes of pumping every couple of months

I got the new piston-rod mostly made yesterday. I bought a foot of 13/16" diam 304SS rod from McMaster..their looser-tolerance grade. It is eyeball-straight, but about .002" out-of-round. Just fine for this project.

Single-pointing the thread on my 10" SB, only problem is that a few thousandths of the tip of the formed threading tool (like the ones in this thread https://www.practicalmachinist.com/forum/threads/making-a-thread-forming-tool.218109/) keeps breaking off, so I have to regrind it in the middle of the job.

 

[kwfiggatt]

Mcmaster Carr lists a 5" piston cup seal made from Buna-N and cotton cloth, $18.25 each. They say its compatible with veg oil. mmc 9411k44

I burn waste engine oil in a heater for my house and use a 5:1 air operated Alemite Ram stub pump. The 5:1 means that the pump pressure is 5x greater than the air pressure. I've pumped 1000's of gallons of oil from drums and wouldn't think of using a hand pump. The air pump slows down quite a bit with cold engine oil and it is pushing ~500 psi through a 1/2" line in my application.

The ram pumps are expensive, but you can usually find them used on ebay for less money. (search stub pump). Here's a 5:1 for ~$100. ebay pump

 

[Joe Michaels]

Magneticanomaly:

To validate your thinking as to using 100% vegetable oil in the Chinese diesel engine: a neighbor has a one cylinder 'Listeroid' (Indian copy of a Lister diesel engine). He has it belted to a Chinese built AC generator. The fuel he uses is a combination of petroleum diesel and straight vegetable oil. The engine is started on petroleum diesel fuel (or number 2 home fuel oil) and then switched onto the vegetable oil. Other than straining the vegetable oil to get rid of particulate matter, I do not think any further treatment is done.

Some years ago, a co-worker asked me to help him with a similar project. He owned an older Mercedes-Benz diesel powered car. Not sure the model or whether the engine was turbocharged. This fellow wanted to run the car on vegetable oil, no chemical treatment. The plan was to start the car on petroleum diesel fuel and getthe engine warmed up. Once the engine was at operating temperature, coolant from its cooling system would be circulated thru a small heat exchanger to heat the vegetable oil. The heat exchanger design this fellow had seen was crude. It was two serpentine bent layers of copper tubing cast into a block of aluminum. Some of the heated coolant from the engine passed thru one serpentine layer of tubing, and the vegetable oil passed thru the other. The design approximated what a 'plate coil' type heat exchanger would do. The system required two fuel tanks, one smaller one for the petroleum diesel and one larger one for the vegetable oil. It also required some piping, 3-way cocks, and possibly a 12 volt transfer pump. I remember seeing some pie-in-the-sky magazine writeup from someone who was saving all kinds of money (and the environment) burning vegetable oil in his diesel car. We never went any further than sketching and rough design ideas.

Incidentally, my neighbor says the exhaust from his Listeroid smells like a fast-food joint as he gets used frier oil from some local eateries.

 

[44dwarf]

[email protected]
these guys and gals are great to deal with for odd ball and off-the-shelf seals and cups.

 

[Joe in NH]

Magneticanomaly:

To validate your thinking as to using 100% vegetable oil in the Chinese diesel engine: a neighbor has a one cylinder 'Listeroid' (Indian copy of a Lister diesel engine). He has it belted to a Chinese built AC generator. The fuel he uses is a combination of petroleum diesel and straight vegetable oil. The engine is started on petroleum diesel fuel (or number 2 home fuel oil) and then switched onto the vegetable oil. Other than straining the vegetable oil to get rid of particulate matter, I do not think any further treatment is done.

Some years ago, a co-worker asked me to help him with a similar project. He owned an older Mercedes-Benz diesel powered car. Not sure the model or whether the engine was turbocharged. This fellow wanted to run the car on vegetable oil, no chemical treatment. The plan was to start the car on petroleum diesel fuel and getthe engine warmed up. Once the engine was at operating temperature, coolant from its cooling system would be circulated thru a small heat exchanger to heat the vegetable oil. The heat exchanger design this fellow had seen was crude. It was two serpentine bent layers of copper tubing cast into a block of aluminum. Some of the heated coolant from the engine passed thru one serpentine layer of tubing, and the vegetable oil passed thru the other. The design approximated what a 'plate coil' type heat exchanger would do. The system required two fuel tanks, one smaller one for the petroleum diesel and one larger one for the vegetable oil. It also required some piping, 3-way cocks, and possibly a 12 volt transfer pump. I remember seeing some pie-in-the-sky magazine writeup from someone who was saving all kinds of money (and the environment) burning vegetable oil in his diesel car. We never went any further than sketching and rough design ideas.

Incidentally, my neighbor says the exhaust from his Listeroid smells like a fast-food joint as he gets used frier oil from some local eateries.

A neighbor and acquaintance did similar (notice I don't say "friend.") He had a Ford diesel pickup, was and is quite "woke," and had a lot of interest in "going green" through biodiesel - which he ultimately did.

His process involved Tran-esterification of the cooking oil as a way to purify it and remove the need for pre-heating. https://en.wikipedia.org/wiki/Transesterification#Methanolysis_and_biodiesel_production

The trans-esterification process for him involved dissolving lye (Sodium hydroxide) in methyl alcohol to make Sodium Methoxide - which is a singularly nasty chemical. It retains all the tissue destructive capability of sodium hydroxide with all the penetrating ability of methyl alcohol. A single drop on your hands leaves a NASTY burn which by days grows to about the size of a silver dollar. To say he was careful would be an understatement.

He worked it to the point where local fry-food joints all knew him - and some started charging him the same price that the oil recycler charged for oil removal. Free enterprise and demand (and market acumen) being what it is.

That is, he was doing this quite proudly and loudly until he dissolved out the interior of his Ford diesel engine nozzles - a full nozzle replacement was the better part of a grand. My comment then "You can buy a LOT of diesel fuel for a grand." But as I say by then I wasn't exactly a friend.

Our relationship soured after he "borrowed" my 2003 Golf TDI to make a video - he was that level of enthusiast - and paid to have the engine "steam cleaned" to make it pretty for the video. After he did that I had sporadic problems with the glow plugs and would re-occur every time it rained.

You don't mess with somebody's "baby."

Joe in NH