I was asked to oversee the installation of a hydraulic winch system installed on a workboat and designed by (winch experts)
My client had used this company before and was very satisfied with their expertise and service. If my client was happy then so was I.
It came the day when I had to inspect the installation. There was a gear pump attached to a large diesel engine via a flexible coupling, the winch was fitted on deck and the control valve, counterbalance valve with manifold were supplied loose.
I studied the circuit and the first thing that caught my attention was the closed centre control valve. This prompted an immediate phone call to the designer, the last thing we wanted was a hot system. He assured me that the control valve supplied was in fact a Pressure to Tank configuration and that he had drawn the symbol incorrectly. I then asked him what speed had he designed the pump to run at, “1000rpm” he said.
Now under normal conditions whilst using the winch the engine speed would run at 1000rpm but when the boat steamed from one position to another the engine rpm can increase to 2100-2200rpm, more than twice the design speed and what is more important twice the design flow.
Now we have a problem!
The control valve and pipe-work was not large enough to handle this extra flow. The first suggestion by the designer was to increase the size of the control valve, an obvious solution you might think. The first problem was that it would need larger diameter hoses (difficult to get onto the valve) but more importantly the valve looses its sensitivity due to the flow gain of the larger valve. Being a proportional valve and using a joystick with electrical control the winch would not have the sensitivity and less easy to control at low speed.
The better option is to fit and unloading valve directly off the pump outlet. When unloaded half the flow could pass through the unloading valve and half through the control valve. When the engine speed is reduced to 1000rpm the unloading valve can be closed allowing the reduced flow to pass to the control valve and operate the winch at the correct speed.
When driving pumps using engines especially with fixed displacement pumps you should always consider the working and the maximum rpm of the pump. It might be necessary to adjust the specification to cater for the extra flow.
Attributed to: Omar Khayam, 13th century philosopher
He who knows not, and knows not that he knows not, is a fool. Shun him.
He who knows not, and knows that he knows not, is a child. Teach him.
He who knows, and knows not that he knows, is asleep. Wake him.
He who knows, and knows that he knows, is a leader. Follow him.
Very best
Bob Jackson (The Hydraulic man)
More hydraulics at www.hydraulicbrain.com
Saturday, 31 March 2012
Tuesday, 20 March 2012
What is the difference between airation and cavitation?
Often miss diagnosed and not surprising because the symptoms are similar but with very different causes.
Airation
Very simply this is the result of air getting into the hydraulic fluid and most likely through the suction pipe or if the oil level has been allowed to get too low, partially uncovering the inlet to the pump. The pump will sound noisy (lumpy), a very similar noise to cavitation and undesirable for the following reasons.
1) The system becomes spongy and movements become erratic with pressure fluctuations.
2) The lubrication of the sliding parts within the pump etc will be reduced and lead to failure.
3) Dieseling effect could cause ignition with very high temperature spots, damaging seals
The Cure: The suction pipe will be subject to vacuum so do not expect to see any oil leak so best check all fittings between the strainer and pump inlet. Another way is a little messy but try grease or oil around the joints and listen for pump tone change.
Cavitation There are many reasons for cavitation but they all result in restricting oil entering the pump.
Best to start with easy stuff first:
1) Tank breather blocked (remove and replace)
2) Suction valve not fully open
3) Oil cold or too thick (check viscosity)
4) Suction Strainer clogged (remove and replace)
5) Suction pipe too small
6) Suction pipe too long
7) Pump speed too high
Cavitation is very destructive and will damage the pump in a very short time. Minute explosions take place on the surface of the metal during the transition from vacuum to high pressure with temperatures reaching greater than that on the sun. Pitting and metal removal will quickly lead to failure.
Hope you find this interesting and helpful and you can find more valuable information if you sign up at www.hydraulicbrain.com
Keep safe
Bob Jackson (The Hydraulic man)
Airation
Very simply this is the result of air getting into the hydraulic fluid and most likely through the suction pipe or if the oil level has been allowed to get too low, partially uncovering the inlet to the pump. The pump will sound noisy (lumpy), a very similar noise to cavitation and undesirable for the following reasons.
1) The system becomes spongy and movements become erratic with pressure fluctuations.
2) The lubrication of the sliding parts within the pump etc will be reduced and lead to failure.
3) Dieseling effect could cause ignition with very high temperature spots, damaging seals
The Cure: The suction pipe will be subject to vacuum so do not expect to see any oil leak so best check all fittings between the strainer and pump inlet. Another way is a little messy but try grease or oil around the joints and listen for pump tone change.
Cavitation There are many reasons for cavitation but they all result in restricting oil entering the pump.
Best to start with easy stuff first:
1) Tank breather blocked (remove and replace)
2) Suction valve not fully open
3) Oil cold or too thick (check viscosity)
4) Suction Strainer clogged (remove and replace)
5) Suction pipe too small
6) Suction pipe too long
7) Pump speed too high
Cavitation is very destructive and will damage the pump in a very short time. Minute explosions take place on the surface of the metal during the transition from vacuum to high pressure with temperatures reaching greater than that on the sun. Pitting and metal removal will quickly lead to failure.
Hope you find this interesting and helpful and you can find more valuable information if you sign up at www.hydraulicbrain.com
Keep safe
Bob Jackson (The Hydraulic man)
Thursday, 15 March 2012
What is pressure compensation?
So what is pressure compensation?
For any flow of fluid through a pipe there must be a pressure drop with greater pressure at the source of flow (pump) and lessoning the further you go downstream. This is due to the frictional losses in pipe, fittings, valves, filters etc and we call this Pressure Drop or Delta P and often signified using the symbol (ΔP). If there is no difference in pressure then there will be no flow.
If the pressure difference (ΔP) is constant then the flow and hence the speed of the actuator will also be constant but if the flow or load changes there will also be a change in the pressure drop and consequently change in speed of the actuator.
With some applications, constant speed of a ram or motor can be very important, take an application like a hydraulic passenger lift. It is important that the speed with only one passenger is the same as when the lift is full of people. Without compensating for the pressure difference the speed would change. With more people in the lift the downward speed would increase and with just one person might be unacceptably slow.
So we need a valve that will automatically close down and reduce flow when the load is greater and open when the load is less or a pump that will increase flow or decrease flow to maintain a constant Delta P.
With a speed control valve make sure it is a pressure compensated type and sized correctly for the flow. To maintain Delta P with the pump use a load sensing option. Variable piston and vane pumps only have this option available. A load sensing pump will automatically adjust the flow to the required load and maintain the correct speed. Another benefit with this type of arrangement is power saving and less heat generation.
Bob Jackson (The Hydraulic man)
More interesting stuff at www.hydraulicbrain.com
For any flow of fluid through a pipe there must be a pressure drop with greater pressure at the source of flow (pump) and lessoning the further you go downstream. This is due to the frictional losses in pipe, fittings, valves, filters etc and we call this Pressure Drop or Delta P and often signified using the symbol (ΔP). If there is no difference in pressure then there will be no flow.
If the pressure difference (ΔP) is constant then the flow and hence the speed of the actuator will also be constant but if the flow or load changes there will also be a change in the pressure drop and consequently change in speed of the actuator.
With some applications, constant speed of a ram or motor can be very important, take an application like a hydraulic passenger lift. It is important that the speed with only one passenger is the same as when the lift is full of people. Without compensating for the pressure difference the speed would change. With more people in the lift the downward speed would increase and with just one person might be unacceptably slow.
So we need a valve that will automatically close down and reduce flow when the load is greater and open when the load is less or a pump that will increase flow or decrease flow to maintain a constant Delta P.
With a speed control valve make sure it is a pressure compensated type and sized correctly for the flow. To maintain Delta P with the pump use a load sensing option. Variable piston and vane pumps only have this option available. A load sensing pump will automatically adjust the flow to the required load and maintain the correct speed. Another benefit with this type of arrangement is power saving and less heat generation.
Bob Jackson (The Hydraulic man)
More interesting stuff at www.hydraulicbrain.com
Saturday, 3 March 2012
Eco Friendly Hydraulic Oil
The oil that flows through hydraulic systems can almost be compared with blood which flows through our bodies and like blood; any problems with the oil can affect components, performance or serious failure of the hydraulic system. Hydraulic oils can vary in their formulations using different additives to improve the system performance and protect components against wear and corrosion. In recent years new synthetic oils have become available and the ones most interesting to me are those that cause less damage to the environment if accidentally spilt on land, sea or rivers.
When we designed the recent hydraulic system for the open 60 racing Yacht “Acciona” our client stressed that the hydraulic system should present no risk of contamination to the sea. The amount of oil carried on this type of boat is very small compared to industrial applications but even one litre of mineral oil accidentally spilt into the sea is still far too much and not acceptable if we are serious about keeping our oceans free of pollution.
Rape seed oil has been available for many years for environmentally sensitive applications but do not offer the same protection to hydraulic components as mineral oils but synthetic based oils are a new generation of “Eco” oils that offer greater benefits for systems and environment.
We contacted Millers Oils who recommended Millmax 32HFD(u).
I wanted to know (in laymen terms) how effective the oil was in protecting the environment and hydraulic components and this is their reply:
Definitely would not recommend you drink it, would have a similar effect to drinking Castor Oil.
Would not kill fish as any escaped oil would lie on the surface oil while it was biodegrading away (being eaten by bacteria)
Synthetic esters which is made from are reaction products of fatty acids and alcohols, careful selection of the two components can radically change the end product.
They will provide better protection than mineral oils and also give better lubricity (more slippery) providing the oil stays at sensible temperature i.e. kept below 80˚C they will outlast a mineral oil
For us it is still early days to properly evaluate this oil but so far it has performed well. At the moment these oils can be five times the price of mineral oil but if it is as good as the manufacturer’s claim then I believe that we should be consider it for more applications especially where there is any risk to the environment.
Bob Jackson (The Hydraulicman)
For more hydraulics see www.hydraulicbrain.com
When we designed the recent hydraulic system for the open 60 racing Yacht “Acciona” our client stressed that the hydraulic system should present no risk of contamination to the sea. The amount of oil carried on this type of boat is very small compared to industrial applications but even one litre of mineral oil accidentally spilt into the sea is still far too much and not acceptable if we are serious about keeping our oceans free of pollution.
Rape seed oil has been available for many years for environmentally sensitive applications but do not offer the same protection to hydraulic components as mineral oils but synthetic based oils are a new generation of “Eco” oils that offer greater benefits for systems and environment.
We contacted Millers Oils who recommended Millmax 32HFD(u).
I wanted to know (in laymen terms) how effective the oil was in protecting the environment and hydraulic components and this is their reply:
Definitely would not recommend you drink it, would have a similar effect to drinking Castor Oil.
Would not kill fish as any escaped oil would lie on the surface oil while it was biodegrading away (being eaten by bacteria)
Synthetic esters which is made from are reaction products of fatty acids and alcohols, careful selection of the two components can radically change the end product.
They will provide better protection than mineral oils and also give better lubricity (more slippery) providing the oil stays at sensible temperature i.e. kept below 80˚C they will outlast a mineral oil
For us it is still early days to properly evaluate this oil but so far it has performed well. At the moment these oils can be five times the price of mineral oil but if it is as good as the manufacturer’s claim then I believe that we should be consider it for more applications especially where there is any risk to the environment.
Bob Jackson (The Hydraulicman)
For more hydraulics see www.hydraulicbrain.com
Saturday, 25 February 2012
All ports blocked control valve
Beware The All ports blocked Control valve
All hydraulic systems leak to some degree and any suspended load held on a ram will eventually creep down due to gravity. However there are occasions when a ram will creep out when the ram is mounted horizontally or even pointing upwards.
Whenever I am asked to investigate this fault I always look for the following:
1) Pressure is applied to the valve all the time (usually pressure compensated pump).
2) The control valve has a closed centre position (all ports blocked).
If we analyse this arrangement we must consider what is happening to the control valve. Pressure is being applied to the closed port (P). The A&B ports are situated either side of the pressure port (P) and the tank ports (T) are furthest away. When the valve is brand new the leakage is minimal but as time passes spool wear increases together with leakage from port P (pressure) to A&B. The same pressure applied to both sides of a ram will cause it to extend due to the difference In the area (full bore and annular).
There are two ways you can resolve this problem.
1) Replace the control valve with same.
2) Replace the valve with centre position P blocked with A&B to T and add a double PO check valve.
In this set up any leakage across P will flow directly to tank and should not create enough pressure to force the ram out. The PO check valves will lock the ram in position against external loads.
Hope you find this helpful
Bob Jackson (The Hydraulicman)
More of this can be found at www.hydraulicbrain.com
All hydraulic systems leak to some degree and any suspended load held on a ram will eventually creep down due to gravity. However there are occasions when a ram will creep out when the ram is mounted horizontally or even pointing upwards.
Whenever I am asked to investigate this fault I always look for the following:
1) Pressure is applied to the valve all the time (usually pressure compensated pump).
2) The control valve has a closed centre position (all ports blocked).
If we analyse this arrangement we must consider what is happening to the control valve. Pressure is being applied to the closed port (P). The A&B ports are situated either side of the pressure port (P) and the tank ports (T) are furthest away. When the valve is brand new the leakage is minimal but as time passes spool wear increases together with leakage from port P (pressure) to A&B. The same pressure applied to both sides of a ram will cause it to extend due to the difference In the area (full bore and annular).
There are two ways you can resolve this problem.
1) Replace the control valve with same.
2) Replace the valve with centre position P blocked with A&B to T and add a double PO check valve.
In this set up any leakage across P will flow directly to tank and should not create enough pressure to force the ram out. The PO check valves will lock the ram in position against external loads.
Hope you find this helpful
Bob Jackson (The Hydraulicman)
More of this can be found at www.hydraulicbrain.com
Sunday, 19 February 2012
Hydraulic design is like a day's fishing
When I was a small boy, nothing was more exciting than going for a day’s fishing. Not that I can remember catching much but it was the anticipation that it might just be the day when I would catch a whopper!
Many years later I now see how the experts do it and it is hardly surprising I caught very little. As a child I used the same method of fishing regardless of the conditions, location or the type of quarry I hoped to land. Top fishermen plan their task and select the right equipment to suit the conditions.
If they get it wrong, at best they will catch very little and at worse loose or break their equipment because the fish was too large for the tackle they selected for the task.
Now let us consider the Hydraulic designer, he must also consider the task. What are the loads and speeds required? Where will the equipment be used, (hot, cold, wet or dirty) and from a basket of pumps, valves, actuators and controls, select the right parts for the best result. Get the selection wrong, at best will not achieve the task and at worse cause significant damage to your customers equipment. Get it right and it’s as satisfying as catching the Whopper!
Good fishing.
Bob
More Hydraulics at www.hydraulicbrain.com
Many years later I now see how the experts do it and it is hardly surprising I caught very little. As a child I used the same method of fishing regardless of the conditions, location or the type of quarry I hoped to land. Top fishermen plan their task and select the right equipment to suit the conditions.
If they get it wrong, at best they will catch very little and at worse loose or break their equipment because the fish was too large for the tackle they selected for the task.
Now let us consider the Hydraulic designer, he must also consider the task. What are the loads and speeds required? Where will the equipment be used, (hot, cold, wet or dirty) and from a basket of pumps, valves, actuators and controls, select the right parts for the best result. Get the selection wrong, at best will not achieve the task and at worse cause significant damage to your customers equipment. Get it right and it’s as satisfying as catching the Whopper!
Good fishing.
Bob
More Hydraulics at www.hydraulicbrain.com
Saturday, 11 February 2012
Hydraulic pump suction strainers
I return to an old subject, should we fit pump suction strainers?
I posed this question to my Linked in forum (Hydraulic help) and the overwhelming opinion was to leave them off.
For those just starting out in hydraulics let me briefly recap on the purpose of suction strainers.
As its name implies this is not a typical filter but simply a piece of 125micron metal gauze rolled into a tube that fits to the end of the pump suction pipe. Particles over 125 micron will be blocked thus preventing them entering the pump possibly causing instant destruction. This sounds very admirable and because of their low cost one would see no reason for not installing them, however there is a downside.If the suction line is restricted Hydraulic Pumps will quickly deteriate due to cavitation.
Suction strainers can be difficult to change and most often end users are totally unaware that they even exist. Over time this will result in the gauze silting up and blocking the oil flow to the pump and may even collapse the strainer with catastrophic results.
Many engineers say that if the tank is very clean and free of all weld splatter, the strainer will serve little purpose. This strategy however is not risk free because you must be 100% sure that there is no way that any contaminant can drop into the tank, that the paint inside will not flake or peel and that hoses and pipework have been thoroughly cleaned prior to start up.
My opinion is, look at the application and risk assess the environment, housekeeping abilities and responsibilities of the user and the implications of serious pump failure with the consequence of serious contamination throughout the system and potential downtime to the plant. Also talk to your customer about these issues.
keep safe
Bob Jackson
More hydraulics on www.hydraulicbrain.com
I posed this question to my Linked in forum (Hydraulic help) and the overwhelming opinion was to leave them off.
For those just starting out in hydraulics let me briefly recap on the purpose of suction strainers.
As its name implies this is not a typical filter but simply a piece of 125micron metal gauze rolled into a tube that fits to the end of the pump suction pipe. Particles over 125 micron will be blocked thus preventing them entering the pump possibly causing instant destruction. This sounds very admirable and because of their low cost one would see no reason for not installing them, however there is a downside.If the suction line is restricted Hydraulic Pumps will quickly deteriate due to cavitation.
Suction strainers can be difficult to change and most often end users are totally unaware that they even exist. Over time this will result in the gauze silting up and blocking the oil flow to the pump and may even collapse the strainer with catastrophic results.
Many engineers say that if the tank is very clean and free of all weld splatter, the strainer will serve little purpose. This strategy however is not risk free because you must be 100% sure that there is no way that any contaminant can drop into the tank, that the paint inside will not flake or peel and that hoses and pipework have been thoroughly cleaned prior to start up.
My opinion is, look at the application and risk assess the environment, housekeeping abilities and responsibilities of the user and the implications of serious pump failure with the consequence of serious contamination throughout the system and potential downtime to the plant. Also talk to your customer about these issues.
keep safe
Bob Jackson
More hydraulics on www.hydraulicbrain.com
Sunday, 29 January 2012
Hydraulic Hose Burst Valves
Hydraulic Hose Burst Valves
I have talked many times about my dislike for Hose Burst valves (velocity fuse).
A cheap and nasty little valve that screws directly into the cylinder port and should close when the velocity across the valve exceeds the spring setting.
So why do I hate this valve so much?
Many unwitting users do not realise that these valves must be properly adjusted using feeler gauges if they have any chance of them working properly. The manufacturer should supply a chart with the valve showing a valve gap dimension based on flow. This is not the flow of the pump but the flow that will pass from the cylinder under normal conditions and is calculated using the displacement volume of the ram and its velocity.
The valve will not compensate for any change in temperature or load and can often close when operating under normal conditions, causing annoying stoppages. However the main purpose is that they must close should a pipe or hose burst. If the worst happens and the valve does not close, the result can be catastrophic and cause serious damage or injury.
If you are serious about protecting against hose burst then spend a little more money and do the job properly using a Pilot Operated Check valve. It will react instantly and must be built in as part of the cylinder with no pipe between the cylinder port and valve except for the pilot. This is a better quality valve and much more reliable.
Always keep in mind that there is NO complete failsafe way of hydraulically holding up any load with a ram except by using mechanical locking. Even if a new installation initially holds well, time and wear will eventually increase leakage and the load will creep down.
Be safe.
Bob Jackson (The Hydraulicman)
More stuff visit www.hydraulicbrain.com
I have talked many times about my dislike for Hose Burst valves (velocity fuse).
A cheap and nasty little valve that screws directly into the cylinder port and should close when the velocity across the valve exceeds the spring setting.
So why do I hate this valve so much?
Many unwitting users do not realise that these valves must be properly adjusted using feeler gauges if they have any chance of them working properly. The manufacturer should supply a chart with the valve showing a valve gap dimension based on flow. This is not the flow of the pump but the flow that will pass from the cylinder under normal conditions and is calculated using the displacement volume of the ram and its velocity.
The valve will not compensate for any change in temperature or load and can often close when operating under normal conditions, causing annoying stoppages. However the main purpose is that they must close should a pipe or hose burst. If the worst happens and the valve does not close, the result can be catastrophic and cause serious damage or injury.
If you are serious about protecting against hose burst then spend a little more money and do the job properly using a Pilot Operated Check valve. It will react instantly and must be built in as part of the cylinder with no pipe between the cylinder port and valve except for the pilot. This is a better quality valve and much more reliable.
Always keep in mind that there is NO complete failsafe way of hydraulically holding up any load with a ram except by using mechanical locking. Even if a new installation initially holds well, time and wear will eventually increase leakage and the load will creep down.
Be safe.
Bob Jackson (The Hydraulicman)
More stuff visit www.hydraulicbrain.com
Tuesday, 17 January 2012
Oil Viscosity
Viscosity of Hydraulic oil
Often in hydraulic systems the type of oil can be the last thing to consider in the overall design.
ISO 32 mineral oil is the most common Hydraulic oil and I often advise my clients to use this grade of oil because of its availability and compatibility with most pumps, valves and hydraulic components.
The viscosity can be extremely important and I will give a few examples of situations that I have encountered where the oil has been a key factor to resolving problems.
1) We designed a system for an animal park. Large sliding hydraulic doors enclosed Rhinoceros and it was our job to ensure that the doors closed quickly but with minimum force so not to injure the animal. Everything worked to plan but our client complained that on some occasions the electric motor would cut out. We discovered that the motor only cut out on cold days when the oil was at its thickest. The pack worked off 240v 30amp supply and we had no way of increasing the supply. The simple solution was to change the oil from iso 46 to 32. Our customer never had another failure and was very pleased with the simple remedy.
2) An aluminium casting machine uses hydraulic rams to tilt the machine and allow molten metal to fill the mould. When solidified the machine is tilted back to open the die and remove the casting. We had already increased the speed by using a Regen circuit but our customer wanted even more speed. We noticed that there was a difference in speed from morning to afternoon when things began to slow down. By monitoring the temperature we knew this was due to the change in oil viscosity. We recommended he replace the iSO32 for 46 and saved 8 seconds in the total cycle time.
3) In a saw mills proportional valves were used to set adjustable fence. The customer complained that the hydraulics needed to run for at least one hour before the system cut accurately. We changed the oil to thinner grade and immediately improved the accuracy without the need to waste time to bring the oil up to temperature.
The viscosity of hydraulic oil can be very important and often a great problem solver without having to modify expensive hardware.
Always best to check with pump manufacturer to be sure that the pump or motor will not be damaged by a change in oil viscosity.
A great problem solver to keep up your sleeve!
Very best
Bob Jackson
More hydraulic stuff at www.hydraulicbrain.com
Often in hydraulic systems the type of oil can be the last thing to consider in the overall design.
ISO 32 mineral oil is the most common Hydraulic oil and I often advise my clients to use this grade of oil because of its availability and compatibility with most pumps, valves and hydraulic components.
The viscosity can be extremely important and I will give a few examples of situations that I have encountered where the oil has been a key factor to resolving problems.
1) We designed a system for an animal park. Large sliding hydraulic doors enclosed Rhinoceros and it was our job to ensure that the doors closed quickly but with minimum force so not to injure the animal. Everything worked to plan but our client complained that on some occasions the electric motor would cut out. We discovered that the motor only cut out on cold days when the oil was at its thickest. The pack worked off 240v 30amp supply and we had no way of increasing the supply. The simple solution was to change the oil from iso 46 to 32. Our customer never had another failure and was very pleased with the simple remedy.
2) An aluminium casting machine uses hydraulic rams to tilt the machine and allow molten metal to fill the mould. When solidified the machine is tilted back to open the die and remove the casting. We had already increased the speed by using a Regen circuit but our customer wanted even more speed. We noticed that there was a difference in speed from morning to afternoon when things began to slow down. By monitoring the temperature we knew this was due to the change in oil viscosity. We recommended he replace the iSO32 for 46 and saved 8 seconds in the total cycle time.
3) In a saw mills proportional valves were used to set adjustable fence. The customer complained that the hydraulics needed to run for at least one hour before the system cut accurately. We changed the oil to thinner grade and immediately improved the accuracy without the need to waste time to bring the oil up to temperature.
The viscosity of hydraulic oil can be very important and often a great problem solver without having to modify expensive hardware.
Always best to check with pump manufacturer to be sure that the pump or motor will not be damaged by a change in oil viscosity.
A great problem solver to keep up your sleeve!
Very best
Bob Jackson
More hydraulic stuff at www.hydraulicbrain.com
Monday, 2 January 2012
My Top 7 Hydraulic Faults
I am often called out to Hydraulic breakdowns that take less than 1 minute to find and fix.
This can be an embarrassment for my customer and gives me no pleasure in having to give him a substantial bill for just 60 seconds of my time.
I have listed my 7 top simple faults that could save you a small fortune as well as the costly down time of your piece of machinery.
Check out my top 7 favourite faults before you start looking for more difficult reasons for your Hydraulic problem.
Register on my site www.hydraulicbrain.com for my 7 top faults.
Very best
Bob
This can be an embarrassment for my customer and gives me no pleasure in having to give him a substantial bill for just 60 seconds of my time.
I have listed my 7 top simple faults that could save you a small fortune as well as the costly down time of your piece of machinery.
Check out my top 7 favourite faults before you start looking for more difficult reasons for your Hydraulic problem.
Register on my site www.hydraulicbrain.com for my 7 top faults.
Very best
Bob
Tuesday, 27 December 2011
Sunday, 18 December 2011
Hydraulic Safety
Hydraulic Safety
Anyone involved with Hydraulic equipment can be subjected to considerable risk unless good working practice is always adopted. Hydraulic machines are often very powerful with large dynamic forces and high pressure fluid that can also sometimes be scalding hot.
When working on hydraulic equipment it is a good idea to do an assessment of risk (download example from www.hydraulicbrain.com)
Never work on systems until you are sure that the pump is switched off and all suspended loads are lowered so nothing can fall or move should you remove pipe-work.Accumulators are a source of large potential energy so ensure they are completely discharged.
Prevent equipment being started up by third parties. Maybe you can lock the system,remove the key,electricalfuses and put up signs to say that the system is being worked on and must not be used
There are many dangers for the Engineer and many things that you can do to make yourself safe.
For more stuff on Hydraulic Safety log on to www.hydraulicbrain.com
Very best
Bob
Anyone involved with Hydraulic equipment can be subjected to considerable risk unless good working practice is always adopted. Hydraulic machines are often very powerful with large dynamic forces and high pressure fluid that can also sometimes be scalding hot.
When working on hydraulic equipment it is a good idea to do an assessment of risk (download example from www.hydraulicbrain.com)
Never work on systems until you are sure that the pump is switched off and all suspended loads are lowered so nothing can fall or move should you remove pipe-work.Accumulators are a source of large potential energy so ensure they are completely discharged.
Prevent equipment being started up by third parties. Maybe you can lock the system,remove the key,electricalfuses and put up signs to say that the system is being worked on and must not be used
There are many dangers for the Engineer and many things that you can do to make yourself safe.
For more stuff on Hydraulic Safety log on to www.hydraulicbrain.com
Very best
Bob
Sunday, 6 November 2011
The Counterbalance valve
The counterbalance valve is used for load holding and prevents the load running away uncontrolled. The valve automatically throttles the outgoing flow using a pilot signal from the input flow leg to the ram or motor. The valve symbol is very similar to the Relief valve with a normally closed function and a check valve looped around the main valve.
To open the valve it will need a pilot pressure and for very large loads this should be as small as possible where lighter loads should be higher. The valve will be made with a designed pilot ratio, this is ratio of the pilot pressure against the induced load pressure to open the valve and can be typically 3:1 to 10:1
To establish the way to set up the Counterbalance valve you must know the Pilot Ratio. Pilot Pressure= Valve Setting Pressure – Pressure induced by load divided by the Pressure Ratio + the ratio of piston area divided by the annular ram . A hydraulic motor would be 1.
If we are using a hydraulic motor on a winch it will be important to ensure that there is enough pressure to release the brake. This might require a low Pressure Ratio to achieve enough pressure to release the brake.
If you do not set these valves up correctly the system can become unstable, the ram or motor may not move and in the case of winches the brake might not release.
For more about load holding become a member of www.hydraulicbrain.com
Very best wishes
Bob
To open the valve it will need a pilot pressure and for very large loads this should be as small as possible where lighter loads should be higher. The valve will be made with a designed pilot ratio, this is ratio of the pilot pressure against the induced load pressure to open the valve and can be typically 3:1 to 10:1
To establish the way to set up the Counterbalance valve you must know the Pilot Ratio. Pilot Pressure= Valve Setting Pressure – Pressure induced by load divided by the Pressure Ratio + the ratio of piston area divided by the annular ram . A hydraulic motor would be 1.
If we are using a hydraulic motor on a winch it will be important to ensure that there is enough pressure to release the brake. This might require a low Pressure Ratio to achieve enough pressure to release the brake.
If you do not set these valves up correctly the system can become unstable, the ram or motor may not move and in the case of winches the brake might not release.
For more about load holding become a member of www.hydraulicbrain.com
Very best wishes
Bob
Saturday, 29 October 2011
What is maximum pressure?
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
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
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.
Saturday, 24 September 2011
Dangerous Cranes
I think most will agree that hydraulic crane safety should be of paramount importance and I would like to mention just a few observations about the use of this potentially dangerous piece of machinery.
In my opinion the safest type of crane has been designed to prevent overloading. Not just on the main lift but more importantly where you pick up a load and then telescope out. As the telescope extends increasing its length the main lift cylinder pressure also increases in proportion.
Now some cranes have load sensing devices that will disengage the telescope so that overloading cannot occur and stop the telescope extending when the maximum load is exceeded.
Also the counterbalance valve can also relieve and lower the load in a controlled way.
However there are some cranes that I have come across where they have been fitted with a simple hand valve with all blocked centre ports. These cranes have often been salvaged and the hydraulics replaced by people not proficient in hydraulic systems or crane design. Unwittingly the users of these cranes are just waiting for disaster to strike, at best causing costly damage and at worst serious injury.
See more on www.hydraulicbrain.com
very best
Bob
In my opinion the safest type of crane has been designed to prevent overloading. Not just on the main lift but more importantly where you pick up a load and then telescope out. As the telescope extends increasing its length the main lift cylinder pressure also increases in proportion.
Now some cranes have load sensing devices that will disengage the telescope so that overloading cannot occur and stop the telescope extending when the maximum load is exceeded.
Also the counterbalance valve can also relieve and lower the load in a controlled way.
However there are some cranes that I have come across where they have been fitted with a simple hand valve with all blocked centre ports. These cranes have often been salvaged and the hydraulics replaced by people not proficient in hydraulic systems or crane design. Unwittingly the users of these cranes are just waiting for disaster to strike, at best causing costly damage and at worst serious injury.
See more on www.hydraulicbrain.com
very best
Bob
Sunday, 18 September 2011
My Trip to Breast
The use of hydraulics is often simply down to the ingenuity of the designer.
I have just returned from France after commissioning a hydraulic system on an Open 60 racing yacht, not the most likely place you would expect to find large hydraulic rams.
Designed and built by Target Fluid Services two 100mm bore rams are connected together in a push pull arrangement moving a 3ton keel from side to side. The canting keel ensures the boat is kept upright in an optimum position for maximum speed.
The most challenging part of the design is providing the lightest system possible but strong enough to take the large dynamic loads experienced in the worlds heaviest seas.
The boat has been sponsored by a Spanish company called Acciona who specialise in renewable energy. The boat is also eco friendly with many innovations to generate green power (as well as the sail). The boat is covered with solar cells and a Hydrogen cell system to generate electricity. This power is used to drive an electric motor for emergency use and for moving in and out of the harbour.
I apologise that we cannot show the hydraulic stuff inside the boat as the client is sensitive to showing this at present time but you can see the keel when a 90 degree test is being carried out and witnessed by IMOCA who are adjudicators for this class of boat.
Anyone who is keen on sailing I would suggest that you watch out for this boat when it starts on the racing circuit as I believe that it could be a very fast contender.
Very best
Bob
www.hydraulicbrain.com
Have you signed up yet for more information on Hydraulic Brain. It is great value and you get loads of hydraulic information. You can even advertise if you are looking for a job by sending us your details and we put it up on the site.
I have just returned from France after commissioning a hydraulic system on an Open 60 racing yacht, not the most likely place you would expect to find large hydraulic rams.
Designed and built by Target Fluid Services two 100mm bore rams are connected together in a push pull arrangement moving a 3ton keel from side to side. The canting keel ensures the boat is kept upright in an optimum position for maximum speed.
The most challenging part of the design is providing the lightest system possible but strong enough to take the large dynamic loads experienced in the worlds heaviest seas.
The boat has been sponsored by a Spanish company called Acciona who specialise in renewable energy. The boat is also eco friendly with many innovations to generate green power (as well as the sail). The boat is covered with solar cells and a Hydrogen cell system to generate electricity. This power is used to drive an electric motor for emergency use and for moving in and out of the harbour.
I apologise that we cannot show the hydraulic stuff inside the boat as the client is sensitive to showing this at present time but you can see the keel when a 90 degree test is being carried out and witnessed by IMOCA who are adjudicators for this class of boat.
Anyone who is keen on sailing I would suggest that you watch out for this boat when it starts on the racing circuit as I believe that it could be a very fast contender.
Very best
Bob
www.hydraulicbrain.com
Have you signed up yet for more information on Hydraulic Brain. It is great value and you get loads of hydraulic information. You can even advertise if you are looking for a job by sending us your details and we put it up on the site.
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