These days we expect hydraulic pumps should be fully supported with detailed technical information ensuring that we use the pump in the correct application.
Often we have pages of stuff showing everything from displacement to recommended oil type.
I often find that the pressure duty is not well defined like what pressure can I safely generate without the pump falling apart. You will read descriptions like continuous, intermittent and peak.
Continuous speaks for itself but what about intermittent and peak, what does this description really mean.
Many years ago when I sold hydraulic components for a well known manufacturer the pumps had different ratings for industrial than mobile. For what I can only imagine were commercial reasons, the mobile pump pressures were much higher.
I have also used some pumps well outside their recommended pressure ranges (only for specific applications) and although not a practice I recommend I do wonder what technical basis manufacturers use to determine their pump pressure ratings.
I would like to see a graph with a direct correlation between pressure and life. I want to know that if I design a system that runs once a month for 15minutes at higher than normal pressure should I need to spend much more money on a more expensive pump.
Surely we should be able to get a better idea of pump life without always having to buy the highest spec pump or face the possibility of a bucket of scrap metal after just a few cycles.
Very best
Bob
Saturday 29 October 2011
Sunday 16 October 2011
Mystery Hydraulic Fault
Only a few days ago I had a call to look at a problem on a log handling system in a Saw Mills.
I was shown a fault on a log flipper. Flippers that can turn the log to any position to pass through the saw. Each pair of flipper rams are connected to a 3 position CETOP 5 solenoid valve mounted on a common manifold. An unloading valve is electrically sequenced to prevent the pump being continuously on load and creating heat.
So now for the problem, if a set of flippers were moved to say, half way and stopped and the other set of flippers were switched to move, the first set would continue moving. Now I hear you say, what ghost like things are going on in them there Hydraulics.
I got down close to the manifold and soon identified the valve responsible for the first set of flippers and removed the Electrical Hirschman plugs to see if I could repeat the problem with the electrics removed. Low and behold I could!
I would have bet a weeks pay that this was an electrical problem and be able to pass over to the Electrician. Now was the time to look very closely and find out what was going on as this was becoming a much more interesting fault.
“Ah! Found it,” I said.
The symbol on the valve showed that it was “Detented” making it not a 3 position valve but 2 position.
A detent will allow the solenoid to fire the spool across from one position to the other and hold the spool in that position even when the electrical signal is removed. So with our flipper when the ram is moved half way and the signal is removed and the dump valve diverts the flow to tank the ram will stop moving but only until the dump valve is re energised and allow the ram to complete its movement. So by operating the other flippers the first set will continue to move.
So how did a 2 position detent valve end up on this manifold block doing this job and causing this problem? Seems that no one knows except ghosties and things that go bump in the night.
Advice for you budding Hydraulic fault finders. Sometimes you will come across faults that will remain a mystery and no one will admit to touching.
More Hydraulics at www.hydraulicbrain.com
Cheers
Bob
I was shown a fault on a log flipper. Flippers that can turn the log to any position to pass through the saw. Each pair of flipper rams are connected to a 3 position CETOP 5 solenoid valve mounted on a common manifold. An unloading valve is electrically sequenced to prevent the pump being continuously on load and creating heat.
So now for the problem, if a set of flippers were moved to say, half way and stopped and the other set of flippers were switched to move, the first set would continue moving. Now I hear you say, what ghost like things are going on in them there Hydraulics.
I got down close to the manifold and soon identified the valve responsible for the first set of flippers and removed the Electrical Hirschman plugs to see if I could repeat the problem with the electrics removed. Low and behold I could!
I would have bet a weeks pay that this was an electrical problem and be able to pass over to the Electrician. Now was the time to look very closely and find out what was going on as this was becoming a much more interesting fault.
“Ah! Found it,” I said.
The symbol on the valve showed that it was “Detented” making it not a 3 position valve but 2 position.
A detent will allow the solenoid to fire the spool across from one position to the other and hold the spool in that position even when the electrical signal is removed. So with our flipper when the ram is moved half way and the signal is removed and the dump valve diverts the flow to tank the ram will stop moving but only until the dump valve is re energised and allow the ram to complete its movement. So by operating the other flippers the first set will continue to move.
So how did a 2 position detent valve end up on this manifold block doing this job and causing this problem? Seems that no one knows except ghosties and things that go bump in the night.
Advice for you budding Hydraulic fault finders. Sometimes you will come across faults that will remain a mystery and no one will admit to touching.
More Hydraulics at www.hydraulicbrain.com
Cheers
Bob
Saturday 8 October 2011
Engineering v IT
Having spent over 45 years in Engineering I now have ways of doing things that has become second nature and one of the basic rules Engineers work by is clarity.
Everything from drawings, instructions or systems must be unambiguous and crystal clear. The consequences of unclear instructions can be disastrous.
IT on the other hand comes from a very different world. Trying to follow instructions on how to set up a program or install some piece of equipment is rarely clear.
A typical example of my point happened a few days ago when I tried to install a new Broadband Router. No instruction except a brief letter giving me a user name, password and WEP Key code.
Need I say that I could not install the system? I contacted the helpline and they gave me a new User name and Password that differed from that sent to me in their letter. When I pointed out that the details did not match my letter I was told that there are about six user names and passwords for various parts of the system. The password I needed was in fact a Serial Number on the machine. In Engineering if it was gave something a Password it would remain so and not suddenly turn into a Serial Number. We have terminology that does not changed and names that are clear and unambiguous.
Until IT people get more discipline,consistency and accuracy in how they describe things and clearer instructions they give out we will continue to get it wrong, get frustrated and cost us all more time and money.
Cheers
Bob
Everything from drawings, instructions or systems must be unambiguous and crystal clear. The consequences of unclear instructions can be disastrous.
IT on the other hand comes from a very different world. Trying to follow instructions on how to set up a program or install some piece of equipment is rarely clear.
A typical example of my point happened a few days ago when I tried to install a new Broadband Router. No instruction except a brief letter giving me a user name, password and WEP Key code.
Need I say that I could not install the system? I contacted the helpline and they gave me a new User name and Password that differed from that sent to me in their letter. When I pointed out that the details did not match my letter I was told that there are about six user names and passwords for various parts of the system. The password I needed was in fact a Serial Number on the machine. In Engineering if it was gave something a Password it would remain so and not suddenly turn into a Serial Number. We have terminology that does not changed and names that are clear and unambiguous.
Until IT people get more discipline,consistency and accuracy in how they describe things and clearer instructions they give out we will continue to get it wrong, get frustrated and cost us all more time and money.
Cheers
Bob
The Benefits of Hydraulics
With rapid developments in Electric motor drives and the reduction in costs you might wonder if hydraulics is relegated to past technology.
There can be no doubt that electric drives have replaced some hydraulic applications, especially in the machine tool industry. Electric drives are cleaner, more efficient provide better control but hydraulics can still provide a better and often the only solution for many applications. Hydraulics provides better power to weight ratio. You can get a lot of power out of a very small package and where size and weight is important it will be the best choice. For small forces, the electric motor and worm drive can be a “no brainer” but if large forces are required for applications like Earth moving equipment, presses, jacks etc Hydraulics (at the moment) have no better alternatives.
Hydraulics provides other benefits that include:
1) Easy direction control
2) Easy speed control
3) Easy force control
4) Can take shock
5) Linear and rotary drives from the same system
6) No lubrication required
7) You can stall the drive without damage
8) Easy to keep cool
If you specialise in Hydraulic, pneumatic or electrical drive systems always try to use the best solution for the application and not just because you have a personal bias to a particular technology.
Very best Bob
www.hydraulicbrain.com
There can be no doubt that electric drives have replaced some hydraulic applications, especially in the machine tool industry. Electric drives are cleaner, more efficient provide better control but hydraulics can still provide a better and often the only solution for many applications. Hydraulics provides better power to weight ratio. You can get a lot of power out of a very small package and where size and weight is important it will be the best choice. For small forces, the electric motor and worm drive can be a “no brainer” but if large forces are required for applications like Earth moving equipment, presses, jacks etc Hydraulics (at the moment) have no better alternatives.
Hydraulics provides other benefits that include:
1) Easy direction control
2) Easy speed control
3) Easy force control
4) Can take shock
5) Linear and rotary drives from the same system
6) No lubrication required
7) You can stall the drive without damage
8) Easy to keep cool
If you specialise in Hydraulic, pneumatic or electrical drive systems always try to use the best solution for the application and not just because you have a personal bias to a particular technology.
Very best Bob
www.hydraulicbrain.com
Sunday 2 October 2011
Hydraulic Winches
Hydraulic Winches
My most common fear about Winches and Cranes is that they can both cause serious accidents if used or designed incorrectly.
Most of the winches I am involved with are on boats and range from small 1-2 tons pull to many tens of tons. The basic design is a drum with a coil of wire rope. This is driven by a hydraulic motor through a gearbox. The controls can just a very simple hand valve or much more complex with joystick and servo valve that can provide steady pull or payout speeds.
Read in full at www.hydraulicbrain.com
Bob Jackson
www.hydraulicbrain.com
Please revisit Hydraulic Brain and learn more about the fascinating subject of Hydraulics.
My most common fear about Winches and Cranes is that they can both cause serious accidents if used or designed incorrectly.
Most of the winches I am involved with are on boats and range from small 1-2 tons pull to many tens of tons. The basic design is a drum with a coil of wire rope. This is driven by a hydraulic motor through a gearbox. The controls can just a very simple hand valve or much more complex with joystick and servo valve that can provide steady pull or payout speeds.
Read in full at www.hydraulicbrain.com
Bob Jackson
www.hydraulicbrain.com
Please revisit Hydraulic Brain and learn more about the fascinating subject of Hydraulics.
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