Oil Storage for Hydraulic Presses

[knots]

There has been a fair amount of interest in hydraulic forging presses here on the forum lately.  Having seen a variety of presses it seems like many of the presses featured have their hydraulic oil storage tanks below or immediately behind the forging dies.   Hoses are frequently unprotected and in close proximity to the work area and exposed to possible damage from a miss-move or mishap involving hot work pieces.  

 

Some of the more well developed presses have protective sleeves installed over the hoses or shields intended to keep the hot work and debris away from the tank and hoses and to protect the operator from high pressure hydraulic leaks.  I have been considering how the hydraulic components might be arranged to optimize safety.  One thought is that tubular press frame might become the oil resevouir.  This could reduce the amount of hydraulic hose and in general keep the oil supply close to the hydraulic cylinder, as well as make the machine more compact without increasing the exposure to the hot scale and swarf produced by the forging process.  I would like to hear your thoughts on this concept and in general other arrangements that might provide improvements to press lay out and function of these machines.to the general.

[DSW]

I have been considering how the hydraulic components might be arranged to optimize safety.  One thought is that tubular press frame might become the oil resevouir.  This could reduce the amount of hydraulic hose and in general keep the oil supply close to the hydraulic cylinder, as well as make the machine more compact without increasing the exposure to the hot scale and swarf produced by the forging process.  I would like to hear your thoughts on this concept and in general other arrangements that might provide improvements to press lay out and function of these machines.to the general.

 

 

 

If you are talking simple oil storage, there shouldn't be major issues with your hollow frame design. However getting leak tight welds with oil usually requires a fair amount of skill. Mig welds are notorious for cold starts and often will "weep" oil even if the welds will hold water.  Stick is often even worse if you aren't skilled. Tig is often the preferred method of getting leak tight welds on diesel tanks, or they go back over the mig welds and spot patch any issues with tig.

 

You mention trying to keep the oil supply close to the cylinder and reducing hoses. Do NOT use hollow sections in place of HP lines. If you are concerned about hose damage, use rigid hydraulic lines ( which you could route thru hollow sections). You need a great deal of skill to pull of pressure rated welds, and square tube is a poor choice at best for a pressure vessel. Even standard "pipe" is usually only rated to 250 PSI or so vs the 2K some hydraulic systems can be rated for.

 

Any good hydraulic shop can hook you up. There are all sorts of options available. They make braided steel and stainless lines that would take a small  to moderate amount of hot contact. They also sell steel spring like covers for lines that hav eto flex, but take abuse on equipment. They can also hook you up with the proper rigid tube and fittings for pressure applications. I usually deal with my local Parker Hydraulics shop, but the NAPA near me as well as all the heavy equipment dealers like CAT, JD , CASE etc will have what you need.

[Frosty]

Knots: I'm afraid you don't know enough about hydraulics to redesign them. To ease your concerns a little you are NOT going to burn a hole in hydraulic line unless you hold a piece of HOT steel against one for a while, a surprisingly long while. The hydraulic reservoir isn't under pressure and it's capped so it's no hazard.

 

You don't mention the one serious hazard regarding hydraulics in a hot shop. High pressure leaks. No you're NOT going to get sliced by one, not in a shop press, they're not high volume high pressure like the hydraulic system in an aircraft. The hazard is from a high pressure leak carburating the fluid making a flammable air fuel mixture. Still, a shop press isn't high enough volume flow to put enough in the air to make a decent air fuel explosion, hardly even a fire. You can prevent an air fuel explosion on a high volume system by sleaving the lines with old fire hose or even a sock to prevent it spraying a mist in the air.

 

If you have problems with an existing system have a hydraulics guy do the work. It's worth the money to have it safe and work correctly.

 

Frosty The Lucky.

[knots]

Leak tight welds ? With a tubular frame the concern about leakage would be limited to the end closures and low pressure intake and uptake ports. Weld joint leakage should be a manageable issue. Since the resevouir penetrations are only low pressure connections, pressure rated welds in the resevouir are a mute point. The few welds that might be subject to leaking would be pressure tested with compressed air to identify leaks for repair .

The way I would control hose damage exposure and length is to mount the hydraulic pump high on the frame, perhaps on top. This would reduce both the exposure and the length of hose needed. As indicated in my initial post well developed presses have hose protection. It is my intent to include this feature. You mention square tube as being a poor choice for a pressure vessel. I can't see that as being a problem since the oil resevouir is always at or near atmospheric pressure.



Frosty, Hydraulics I understand. What I do not understand is how you can presume that I am clueless and incompetent without careful consideration. The tone of your post and the fact that you obviously did not take care in reading and understand it is unfortunate and sad.

[petere76]

Knot,

In regard using the structural tubing for oil storage. Yes it will work. However, the units I have seen that use this design have issues with system contamination ( rust, debris and water from condensation). In industrial applications acid attack due to moisture contamination is a big issue. On ships we try to pickle all the hydraulic system components that have been repaired to help mitigate the rust and debris factor. We are always fighting the moisture because of the temp differential between the hot oil and the cooler surrounding metal structures, i.e. the surface condenser effect. Most home build hyd systems will suffer this same effect.

As to the leaking weld scenario, I would suggest a 6011 root pass to assure it is tight. That method works good for us.

Peter

[swedefiddle]

Good Morning,

 

I agree with KNOTS about putting the pump, reservoir and high pressure hoses on the top. In my mind it is obvious. The only problem is that the press is now top heavy. Paul Thorne brought his Press to CanIRON VI in Victoria, all the plumbing was on the top. He put two horizontal sections of rectangular tubing in the frame (+/- 6") so the forks of the forklift could pick it up at the balance point he designed into it. The forks would not twist in the rectangular tube sections so there was no fear of the frame rolling on the forks. K.I.S.S.

 

I have used sections of round pipe (6"+) for reservoirs. Round because I had it in stock, who cares what shape it is. Vent the top and pick-up from the bottom. If you are concerned about heat build-up in the tank, run the return through a copper automotive radiator with a fan. It works wonderful and simple.

 

Neil

[knots]

Thank you Peter.  Bringing`up condensation is a really good point that I had not considered.  OK, if you were to compare this scheme ot the normal application which is a seperate tank at the same location as the machine how would the two differ in terms of temperature differential exposure to the extent that internal condensation would be a problem ?    However, either way,couldn't the condensation problem be minimized by keeping the oil resevour topped up therefore limiting the area on which the condensation could form.

[knots]

Good Morning,

 

I agree with KNOTS about putting the pump, reservoir and high pressure hoses on the top. In my mind it is obvious. The only problem is that the press is now top heavy. Paul Thorne brought his Press to CanIRON VI in Victoria, all the plumbing was on the top. He put two horizontal sections of rectangular tubing in the frame (+/- 6") so the forks of the forklift could pick it up at the balance point he designed into it. The forks would not twist in the rectangular tube sections so there was no fear of the frame rolling on the forks. K.I.S.S.

 

I have used sections of round pipe (6"+) for reservoirs. Round because I had it in stock, who cares what shape it is. Vent the top and pick-up from the bottom. If you are concerned about heat build-up in the tank, run the return through a copper automotive radiator with a fan. It works wonderful and simple.

 

Neil

 

Top heavy ?  Yes, but now that you bring that up it would be easy enough to mount the motor an pump assembly on it's own base and plumb and wire the assembly to be easily disconnected, unbolted as a unit, and hoisted off of the machine for moving/shipping.

 

I have good sized screw press that I just recently moved.  Talk about top heavy, it got partially dissassembled .  Where there is will there is a way.  Thanks Good Point.

[petere76]

Knots,

In follow up. Hydraulics storage tanks are obviously vented. Outside air has moisture content. In systems without dedicated cooling loops the tank walls become the cooler surface. The heat generated is substantial and depending on the system op pressures and op cycle, things warm fairly quickly. Lacking a cooling loop you increase system capacity to accommodate the heat transfer rate. Also keep in mind the expansion factor, size the tank so that you have enough room for the added volume of hot vs cold medium. You don't want the rig warming up and dumping oil on you deck. Sounds like you are doing the right research, good luck with your build.

Peter

[knots]

Thanks Peter. One thing that I have going for me is that the service factor will be really low. On the other hand when using columns as the resivours the heated oil can only expand up. So I really need to run the numbers on expansion and see what to expect for the size columns being considered. Probably will design for oil volume/capacity plus 50-60 degrees of temperature expansion, then for my service just push the limits on overfill. A sight glass would be nice as well.

The other thing that I will do , for sure, is place a 1/4" tap and valve at the bottom of the columns, in addition to the drain plug/valve, to allow an easy way to check for free water in the system from time to time. I have installed one on a tractor that has condensation contamination problems. That addition has been a big help.

[yahoo2]

it is all going to depend on your setup. double acting rams and a variable displacement pump will run all day with a pressurised tank and no cooling loop. hoses to and from the spool valve would be the biggest concern not the pump and tank. You can buy stainless hose covers and heat wrap if you want but I cant recall ever burning a hole in double braid, I have chaffed through plenty. I am not a big fan of vertical tanks I think there needs to be a certain amount of surface area to let any fine air bubbles separate out of the oil , much prefer a horizontal tank built into a base and the pump mounted just above it.

 

cheers Yahoo

[Frosty]

Leak tight welds ? With a tubular frame the concern about leakage would be limited to the end closures and low pressure intake and uptake ports. Weld joint leakage should be a manageable issue. Since the resevouir penetrations are only low pressure connections, pressure rated welds in the resevouir are a mute point. The few welds that might be subject to leaking would be pressure tested with compressed air to identify leaks for repair .

The way I would control hose damage exposure and length is to mount the hydraulic pump high on the frame, perhaps on top. This would reduce both the exposure and the length of hose needed. As indicated in my initial post well developed presses have hose protection. It is my intent to include this feature. You mention square tube as being a poor choice for a pressure vessel. I can't see that as being a problem since the oil resevouir is always at or near atmospheric pressure.



Frosty, Hydraulics I understand. What I do not understand is how you can presume that I am clueless and incompetent without careful consideration. The tone of your post and the fact that you obviously did not take care in reading and understand it is unfortunate and sad.

 

Sorry I misunderstood your apparently very basic questions to indicate you don't know or understand hydraulics that well. I won't trouble you again.

 

Frosty The Lucky.

[knots]

Sorry I misunderstood your apparently very basic questions to indicate you don't know or understand hydraulics that well. I won't trouble you again.

 

Frosty The Lucky.

 

Frosty,

 

Thank you for your post.  I think there was likely a problem on both ends.  My guess is that we both had a bad day.  

 

Dan

[ptree]

OK team, here is the real, how to be safe with hydraulics and forging.

Reservoir goes on the other side of a fire proof barrier. The lines go INSIDE regular pipe. The pump and hoses NEVER go on top. If on top every little leak is a fire. The real hazard for a small shop press is much as noted by Frosty, a small leak through a orifice small enough to make an atomized mist that becomes a flame thrower when it reaches an ignition source. AND yes even a small power unit moves plenty to be a hazard, not just an aircraft system. Leaks through a small orifice can be injected into human tissue at about 2800PSI. Won't cut you in half, just injects dirty hydraulic fluid that kills the tissue and is a sure infection.

Hydraulic tanks should be a "Pickled and oiled" condition, and unless you do pickle and oil then square tube will fill your oil with pump killing trash. The trash that will kill a pump is way smaller than can be seen by eye. The tank also rejects heat, based on surface area. The tanks usually has a baffle that force the fluid to move all the way around a tank, giving time for cooling thru the walls and floor, allows foam to rise, and dirt to settle. The floor of the tank should not be flat, they have an angle and taper to the drain, so water can be pulled out. They are equipped with a breather, but most breathers are trash and allow dirt in.

Cylinders should also be considered as the most likely leak is from the rod seal, and whether above or below these will weep, but will also blow a spray occasionally.

I have designed presses to 50 tons, and have procured special presses made to my order to 1000tons. I have worked with high pressure hydraulic for over 30 years often working to 30,000 psi. I have also seen the fires, the lost portions of hands from a post oil injection infection, and cleaned up many many forge shop fires.

I do not currently have a press in my shop. I may yet build one, and when I do it will be based on what the forge industry does, and the things I know to NOT do.

[knots]

OK team, here is the real, how to be safe with hydraulics and forging.

Reservoir goes on the other side of a fire proof barrier. The lines go INSIDE regular pipe. The pump and hoses NEVER go on top. If on top every little leak is a fire. The real hazard for a small shop press is much as noted by Frosty, a small leak through a orifice small enough to make an atomized mist that becomes a flame thrower when it reaches an ignition source. AND yes even a small power unit moves plenty to be a hazard, not just an aircraft system. Leaks through a small orifice can be injected into human tissue at about 2800PSI. Won't cut you in half, just injects dirty hydraulic fluid that kills the tissue and is a sure infection.

Hydraulic tanks should be a "Pickled and oiled" condition, and unless you do pickle and oil then square tube will fill your oil with pump killing trash. The trash that will kill a pump is way smaller than can be seen by eye. The tank also rejects heat, based on surface area. The tanks usually has a baffle that force the fluid to move all the way around a tank, giving time for cooling thru the walls and floor, allows foam to rise, and dirt to settle. The floor of the tank should not be flat, they have an angle and taper to the drain, so water can be pulled out. They are equipped with a breather, but most breathers are trash and allow dirt in.

Cylinders should also be considered as the most likely leak is from the rod seal, and whether above or below these will weep, but will also blow a spray occasionally.

I have designed presses to 50 tons, and have procured special presses made to my order to 1000tons. I have worked with high pressure hydraulic for over 30 years often working to 30,000 psi. I have also seen the fires, the lost portions of hands from a post oil injection infection, and cleaned up many many forge shop fires.

I do not currently have a press in my shop. I may yet build one, and when I do it will be based on what the forge industry does, and the things I know to NOT do.

 

Holy Toledo !     This means that none of the forging presses, that I know of, being built by the Blacksmithing and knife-making community are not safe.  At least by the above stated standards, which I gather is the acceptable industrial standard.  

 

This thread started out as a inquiry into opinions regarding the use of the press frame as an oil reservoir.  What we have now is a much larger question:   What  is an acceptable compromise of the standard used for industrial forging presses for presses used in craft rather than industrial settings.  Good question.

[ptree]

In industry, where forging presses are regulated, and also highly regulated by the fire insurance companies there are many rules. Also, even with that said, many fire. If you do things right then you tend towards small fires. In industry we used "Less Flammable" or "Fire Resistant" fluids. NOTE that I did not say fire proof. There are to my knowledge NO fire proof fluids. Even water, if heated to steam and then heated hot enough disassociates into oxygen and hydrogen, remember the Japanese Nuke plant explosions? BUT at the temps we forge at water is very very very fire resistant:)

Water is the original hydraulic fluid, and was used for years in the forge industry on presses. The main thing is water is a truly lousy hydraulic fluid in every respect but the fire resistance. It freezes, has little lubricity, low vapor pressure, very low viscosity etc.

So then came high water content fluids, often a 5% oil addition to the water to try and overcome most of the water issues. BUT if you want to use water of HWCF then you have lots of design issues like seals and tank design.

The ethylene Glycol more fire resistant fluids are pretty good compromise. They do require some design consideration and maintenance of the fluid. Hot water/glycol fluids tend to evaporate of the water, and pure ethylene Glycol is a Flammable fluid, so you have to maintain the concentration, measuring with a refractometer.

Sooo... Design with the thought that it is not a question of if the system will leak, but rather where it will leak and how much. It will leak, I promise. I have never ever seen a leak free system. Sooner or later it leaks. So use proper hydraulic steel lines, with proper connections. Mount as much of the fluid bearing system on the far side of a fire resistant barrier as possible. Have a good, maintained extinguisher located so that when you have a fire and you bolt, the extinguisher is on the bugout path. Put an electrical kill switch on that bugout path. Use first quality hydraulic components. Maintain the system, and maintain the cleanliness of the machine and floor. I have seen more fire in oil dry that was at the base of a machine then from the leaks them selves. Lastly, if you are not a pro with hydraulics, find one and bend their ear.

Presses in forge shops do not have to be frightening, if proper care and preparation is taken.

Ask the follow questions if you have a press

Do I have a current, charged fire extinguisher on the path away from the machine?

Do I have a way to stop the machine from a distance?

Is there oil on the floor around the machine?

Do I have electrical conduit or wires on the floor that a hot forging can fry short and start a fire?

[ptree]

A bit more. I have seen many many cases of conduit run across a floor and a hot bar is dropped on the conduit. Within maybe 15 seconds the insulation has burnt off and the wires shorted.

Hydraulic hose has multi layer construction. There is an inner fluid conductor that is a smooth tube of flexible rubber, covered with braided metal (steel usually) to contain the pressure, and a rubber abrasion cover. The exterior cover will take some burn damage from a quick hot swipe and no leakage occur. But when you see the braid, replace before use. If you see little bubble in the outer cover, replace before use, that is fluid that has leaked past the inner, is in the braid and will soon push thru the outer cover. There are many varieties of hose, and they are not equal. There are excellent 5 layer hose, developed by CAT, that is tough and more abuse resistant but you pay for that.

In reality the most common leaks from hose is at the end fittings. Either they leak between the hose and the fitting, or the O-ring fails on swivel fittings. SOOO... put the swivel connection at the end furthest from the hot zone.

If you do not understand pressure rating in pipe, study the subject BEFORE you plumb. The bigger the pipe od the lower the pressure rating so a schedule 40 1/4" pipe will hold way more pressure than a schedule 40 2" pipe. Never use cast iron fitting on pipe carrying pressure. OK for a low pressure return, but never on pressure. I would flatly avoid cast iron fittings as they are filthy to hydraulic and will load the system with more dirt. If using tubing avoid JIC flared fittings, they are not a good choice in pulsating or hammering pressure systems like a press). The flares crack off. SAE O-ring fittings, properly installed are far better than pipe thread. Swaglok brand double ferrule fittings, installed to the makers spec are the best hands down of all the systems I used. Very pricey, but they work.

 

Consider that if you place the system remote from the press, say on the other side of a shop wall, the system will not be exposed to the ingression of all that scale dust, rust and grinder swarf. Every time that press cylinder strokes the tank will breath in and then out the volume difference between the blind side and the rod. Lots of breathing. That is where much of the water and dirt in the system comes from. Having the tank in a warm location will also greatly reduce the amount of water it ingests as well as make the system run uniformly when its -10F outside.

Have to run a hydraulic system in a cold unheated shop? consider ATF if you will use petroleum based oil. It has the lowest pour point, great viscosity index, great anti-wear and extreme pressure package and is cheap and easy to find anywhere. The red dye makes finding leaks alittle easier as well.

 

If the three posts above seem to be filled with jargon, or too hard to comply with you should strongly consider your choice to home build or start studying. Once I get home tonight I will probably post a few choice references for study.

[knots]

" If the three posts above seem to be filled with jargon, or too hard to comply with you should strongly consider your choice to home build or start studying. Once I get home tonight I will probably post a few choice references for study ".

I have no problem understanding what you have outlined here. I just question How some of this applies to a press that will be used for intermittent craft service rather than industrial production applications. Your position on the following question is still of interest to me. What is an acceptable compromise of the standard used for industrial forging presses for presses used in craft rather than industrial settings.

My experience with powered hydraulics has been limited to construction equipment. Tractors and accessories. I have experienced ruptured hydraulic lines and can appreciate what might result from injection of gallons of oil into the interior environment a shop in close proximity to a forge or forge furnace. However in an industrial environment where a forge press could be run eight or more hours each day where production is the norm how does the risk of that environment equate to a craft shop where the press might be run an average of an hour or two a day, or even an hour or two a month. If you view risk as a probability over time the less frequent the use the less the risk. I remember my mother telling me not to play with fire. I obviously have not followed that advice. Nothing that we do is risk free. Here the question where does the limit of acceptable risk lie?

The use of water ethylene glycol is new to me. If used as the hydraulic fluid I presume that placing the pump and tanks on the top of the machine would no longer be viewed as a hazard. However other details must come into play. For instance do the pump and tank need to be stainless steel ? What special provisions need to be incorporated into the equipment if used ? Does maintenance frequency increase ?

If the pump needs to be located outside the shop in my case that means it will be placed out doors. If that is the case I might as well use my tractor hydraulics as a source of power. The quick connectors would he outdoors as well.

Keep the ideas coming.

[ptree]

Knotts, Industrial VS craft. The probability of failure over time can looked at several ways. The simple truth is that hydraulics always use elastomeric seals. O-rings, gaskets, and hose. All of these age and have a fixed life. So from that standpoint, the risk is equal. From a probability of hot forging on a hose, then less because less exposure time. Risk of a fluid conductor failure due to poor maintenance? Higher in most cases because there is no maintenance dept, no Pm's, and often poorer design and choice of materials. ( we do tend to use what we can find/afford)

 

The fire issue from a rupture is less the gallons on the floor, as liquid oil burns pretty slowly, then sudden burst with a atomized spray cloud, is a no win situation. Before you realize what has happened the cloud burns instantly. If the pump can maintain pressure thru the orifice, then a flame thrower. Since you mention Tractor hydraulics, ever had a hose burst? Remember the cloud of hydraulic fluid? Now think fireball that big.

 

Other than inconvience of the power source being outside, a tractor on the other side of the wall takes much of the risk away from the operator location.

 

I have a really big cyclinder, and pump unit, 30GPM that I am considering building a press from. My current thoughts are to use an engine, outside the shop to run the pump. If I can find a small handy engine with electric start, I will put the starter controls next to the press and run metal conductors inside the shop.

 

Much of the risk in a hydraulic press in a forge shop can be minimized with good design, use of the proper materials  and planning for failure. If you have a thought out failure response, then you can respond, even if that plan is "Run away" and call 911.

 

Hydraulic system failures are so common that every industrial fire insurance company, especially FM have requirements for level switches and fire detecters usually required for every system over 200 gallons. That is because even with industrial water fire sprinklers the fire risk is too high. In our craft shop environment we do not have sprinklers, heck many don't even have a decent fire extinguisher.

 

Blacksmithing is inherently dangerous. I once was a skydiver and was an instructor/jumpmaster/jump pilot for about 8 years. In that arena we tried to think out every possible scenario of failure, and have a pre-planned countermeasure. Then we trained and retrained and retrained and practised. When I began to have children and other commitments that would have reduced me to occasional jumping I quit. I did not want to be at 1500', at 176 foot per second,in trouble and wondering what do I do now?

 

Same applies to almost any dangerous activity. Think through every scenario, plan a response and practice. Keep the equipment in first class condition.

 

Water-glycol hydraulic fluids are fairly common. Houghton and CITGO are both pretty large suppliers. The additive package on these will not require a SS tank, there is a vapor phase additive that stops rusting of the tank roof. Many hydraulic tanks are painted internally, and these fluids often cause paint failure that then clogs up everything. Many hydraulic components have urathane seals, especially cylinder rod seals and those are usually hydrologized and fail quickly. As for the tank and pump, in water and water based systems the vapor pressure is so low that pump inlet cavatation is a real problem. Bad inlet piping design that causes too high a negative inlet suction head pressure and your pump will sound like a gravel crusher as the cavation destroys the pump, and sheds metal into the system. Most water and high water content systems use a inlet supercharge system that keeps positive head pressure on the pressure pump inlet. This can be a centrafugal pump in the sump feeding the pressure pump or a tank raised above the pressure pump. Starting to get complicated isn't it :) There are rated pumps that have much better inlet design and seal rated that would be the choice.

 

Once in a previous century, as first an engineering co-op, then full time I worked in the engineering lab or a major manufacturer of hydraulic and pnuematic components. We searched for a non-petroleum based fluid and did thousands of hours of testing to try and qualify our hydraulic cylinders for HWCF. WE bought a test stand with pumps and so forth, and the pumps on the stand, designed for the fluid were more problem than the cylinders! AND I had the refractometer, the technical manuals from all the makers and full support. Much tougher service then petro based fluids.

 

Later at the Valve-fitting-boiler-and ice making machine shop we had a 1000 ton bull press, running on straight water. Had a 1920's vintage 7 cylinder Worthington pistion pump, modified with teflon seals. The cylinders were overhead, single acting and braided hemp packed. Water everywhere. Then we added teflon packing(lantern rings) and it only drizzled water:) We were hot forging plate into tank heads. Had a 1000 gallon accumulator. When a fluid conductor failed on that one it was exciting!

 

In the valve forge shop, we had 23 steam hammers and a number of presses. The presses were all mechanical. And we still had plenty of small fires as all were lubricated and total loss systems so oil on the floor, and in the pits.

 

The I moved to an upset forge shop, and there we had several old 4 post Erie hydraulic press. Systems totally over head as they originally were water. Those were scary as they had been converted to straight oil. and so every drip was a little flash of fire. and they dripped plenty.

 

We had hydraulic systems on nearly every forge machine there for tooling and auxillarys. many were converted for straight oil to the water gylcol, and they were failing and spraying pretty regulary. We averaged 13 fire extinguisher discharges a month there! I don't work there now. :)

[Frosty]

A couple thoughts to add. When we talk about heavy equipment the high pressure side seldom develops higher than 3,000psi and that's shock loading. Operating is rarely higher than 2,500psi. We had several different drill rigs, the foundations rigs were switched to CME 75s in the early/mid 80s. The centerline and airport rigs were, smallest to largest, CME 45, Mobile B-50s and CME-750s.  The foundation holes were generally a LOT deeper in the 100'-150'+ range, bridges have more foundations requirements than a road or airport.

 

The significant difference is in the airport rigs, they had to fold up enough to fit in a cargo plane, Boxcar typically so they had a lot more hydraulics of more vulnerable nature. that's hoses and flex fittings running up the towers to cylinders, locks and catches. The 750s were the most hydraulicly driven rigs we had and each had probably half a mile of lines and almost none were hard lines.

 

Every fitting under pressure seeped till everything warmed up, even if it was 80f out. There WAS one new guy on the airport crew who tightened up all the fittings against directions and in fact in the foundations rigs case express directions to NOT mess with the hydraulics. What it takes to stop hydraulic fittings seeping at -30f is get them REALLY tight and what happens when they warm up to the 200f operating temp? The male sides of the fittings expands significantly and tends to splits the female side. They don't SEEP though.

 

I' installed a preheat loop on our rigs, just a line that let oil flow from the high pressure side to the return side through the valve body. As part of the valve body group I'd installed a two position restricter so the oil was forced through a really narrow opening making it hot pretty quick and as it circulated around the lines it warmed everything up. We were on site and started warming the hydraulics up and happily in our case THAT was the fittings that split and blew so we got off easily, just one line to bypass and loosen every single XXXXXX fitting on the rig.

 

Dang, I can't seem to say anything without a story but it's hard to think of many things without dredging up memories and The new guy's bit of hubris was a kodak moment.

 

Foundations drilling was deep enough to require holding back on the drill string to keep from damaging the bits so we tended to watch the hydraulic pressure gauges like TV. Got to where we could tell a lot about what was going down the hole by hydraulic reaction. Blowing a hose on one of our rigs, even the main pressure line to the valve body was more a fast moving gusher than a dangerous spray. Still, it isn't much fun getting a shot of 200f hydraulic fluid in the face. Another story, but I'll spare you.

 

A carburating (misty) spray is not just a hire hazard it can be FAR worse. Think (FAE) Fuel Air Explosive. I don't know how many BTUs of energy a gallon of hydraulic oil has but it's heavier so it's got to be higher than fuel oil which runs a nominal 139,000 BTUs per gallon so for the purposes of discussion lets say common hydraulic oil is in the 150,000+ BTUs per gallon. Carburate it in air and when it reaches it's flammable air fuel ratio it can ignite. If you're LUCKY it only goes whoosh and singes your eyebrows, unlucky and it'll scatter the walls and roof of your shop over a considerable area. I had this fun loving buddy some years ago who liked carburating about 1/8 TSP of motor oil in an unlit 55gl burn barrel and toss a match in. The boom rattled windows for a couple blocks and tended to bulge the bottom of the barrels.

 

The HIGHER off the ground you emit a misty spray the unluckier you get as it has more time and distance to reach a flammable air fuel ratio before ignition. AND the larger the volume in the shop to expand with explosive power.

 

Frosty The Lucky.

[Ric Furrer]

Knots,

I like to have the press power pack on a wheeled cart and quick disconnects so to allow for moving it to other hydraulic tools...makes it more versatile for me.

If you are looking for a very compact design then maybe calculating your gpm need and cooling need for friction heating could give you a number for the amount of oil you need and you may be able to place the majority of the powerpack in a very discrete position with minimal exposed hoses.

If the coupling from the motor to the pump is off and you are running a 3600rpm motor you can get a vibration to the press ...assuming the pump/motor is bolted to the frame. With a completely sepearte powerpack this is eliminated and you can hardline on the press itself.

 

Ric

[knots]

Thank you all for your comments.   A recent move has created a space crisis in my shop.  My age has prompted the decision not to build another bigger shop.  I have been taking a hard look at my stable of equipment.  It looks like my faithfull old Waterbury Farrell screw press is a prime candidate for down sizing because of the large footprint required.  

 

This thread has helped me work through a piece of the solution to my space problem.   What ever I build will be a compact replacement for my big screw press.  Petree's Idea "power it from outside the shop" and Ricks input " a separate power unit"  will to be part of my space problem solution as well as safety issues discussed.   The current idea is that the Press will be located adjacent to an opening to my outside work area.  The pump unit will be wheeled out for use and inside when idle. The press will be built first and temporarily powered by my tractor hydraulics via quick connect couplers.   All hydraulics will be enclosed or jacketed so that even if there is a hydraulic line rupture the hydraulic fluid stream will be  localized and atomization minimized. 

 

Many thanks to all who have participated .  

[Frosty]

You have a tractor you can power your hydraulics from? this opens the possibility of making a low pressure high volume system. the volume requirements to raise a bucket at a reasonable rate is more than enough to drive a high sq in piston at a reasonable speed. A 40sq/in piston at 2,500psi = 50 tons and you have plenty of gpm to move it at a good clip.

 

2,500 psi will spray oil but more like paint than fuel out of a jet so explosion danger is reduced. It's also not necessary to STOP the spray, just attenuate it with something that will interrupt it. On the drill we'd just wrap the really problematical fittings with denim, it stopped the spray by soaking it up. At 2,500psi it was more a squirt than misty spray but it was still a PITA having the rig wet us down in oil.

 

Be nice to your own hydraulic drive though, build it a nice covered place to park on the other side of the wall. Before the accident when I still had bigger plans for my shop I was going to find a small diesel engine, VW maybe and set up a station engine hydraulic system and plumb the inside of the shop in steel lines and quick disconnects. Part of that plan was to use two radiators, one outside for summer cooling and one inside for winter shop heat.

 

Frosty The Lucky.

[ptree]

Frosty's heat system is also how one can sometimes find internal leaks. Start cold, and quickly start at the tank return and work upflow towards the pump. when you go from warm line to cold line the leak is inbetween.

 

Once upon a time in a lab far away and long long ago, I did research on pressure spikes. We made hydraulic cylinders, and a special type had bleed screws for air removal in the barrel. Worst possible location but it was a customer mandate. So we did a  hydraulic cycle to failure test. The cylinder was mounted verticall, rod down. weights were mounted to the rod, and the cylinder was set up with transducers in the head port, read by a high speed recording ocilligraph. I then started the cylinder cycling up and down and simple dialed the cushion screw in till I had the desired 5000 psi spike. We were operating at 3000 psi. The cushion was NOT anywhere near closed. Took about 30,000 cycles to crack the barrel radiating out from the bleed screw.

 

In a different lab long ago we were getting a customer complaint of our 2000 psi rated forged steel Tees cracking in the crotch. The crotch of a fitting is the inside angle of an Ell or the inside angle lead in to the branch connection in a Tee. Metalurgy sectioned and magna fluxed and so forth many from the same batch and zero faults. So I hooked up my handy dandy hydro pump and at 10,500 psi the Tee had swollen like a watermellon and finally cracked thru the crotch( the highest stress location). Asked about the service the fittings were in and got a " at the end of a row of molding presses, running on water, at 1000psi. I then asked for the description of how they were used, and got a  "Press, about 36" bore, 4' stroke, the press comes down and closes the mold solid and then sits for about 5 minutes and opens. Then I asked how fast does the press travel and got "Ohh it closes in about 15 seconds" and "These d@#% fittings are knocking the fuzz off our balls" "(Tennis ball maker) After I quit laughing, i did a little research and found that the pressure spike (water hammer) is a mathamatical fourmula that includes the mass density of the fluid, the speed of flow and the time spent closing the flow. As the time to stop flow approachs zero the pressure spike approaches infinity! Now we had a case where the velocity was huge, the stopping time was almost zero as that mold went solid. Soo,, I again set up my hydro system and pumped the fitting to 5000Psi and dropped. Did that about 3000 times and bingo, perfect crack in the crotch of the Tee just like they were getting. My pump it up was way gentler than their spike, that is why mine lasted so long compared to several cycles in their system. I suggested they put in a vertical pipe, and cap with a valve and let stay full of air. Worked as a water hammer stop. They did have to drain and refill with air every so often as the air would disolve into the water.

 

Now that long winded bit was to illustrate why a press, you know that is moving and hits cold metal on that last stroke and stops very fast... Pipe it well my friends.

 

Ohh and Frosty, want a really good FAE, Try ethylene oxide liquid, in a tank that ruptures and opens like flower petals, releasing say 1500# into vapor. Looks like a mini Nuke, that is what the Military uses for Fuel air Bombs. I have seen some high speed video, scary. In Nam they used 10,000# bladders of fuel oil dropped by parachute from a Herc, and at the right above the surface height a radar altimeter set off a bursting charge, followed a bit later by an igniting charge. Would blow do0wn several acres of rain forrest for a fire base.

 

Now we don't have that much fuel, but high pressure leaks can definatly atomize the oil, and we tend to have ignition sources in our hands.

[Ric Furrer]

Ptree,

Tried to send a PM on this, but it failed.

 

So the pressure spike is dependent upon several things...speed and cycle number among them.

At what point is one concerned about this effect and how can it be engineered out of the system when using hyd oil vs water?

 

My systems run at 1.5 inches per second and less at 3,000PSI max. Mostly hot work, but some cold pressing.

 

I have never had an issue that I am aware of, but tomorrow is another day.

If this failure can be engineered out of the system I'd like to do that.

 

Ric