Get in touch today to discuss your requirements
Call: (+44) 01452 523352
Is it just about “three times flow rate”?
The widespread use of the “three times flow” rule of thumb serves well but current pressures on space, economics and environmental issues warrant a closer examination of this rule.
So what are the factors to be considered?
• Hold enough oil for system function
• Sufficient surface area to dissipate heat to the surroundings
• Large enough volume so turbulence is minimized allowing entrained air to escape and contaminations to settle
• Separating the suction from the return areas.
• Access for maintenance and cleaning
• Air space conditions, pressure, dryness and cleanliness
• “Real-estate” for fitting of main system components
Basic features of a traditional oil reservoir:-
There are a wide range of choices over an even wider range of budgets, but the right hydraulic oil will prolong your machine life and reduce your overall running costs.
Three initial questions must be answered:-
1) In what type of equipment will the hydraulic fluid be used?
2) How severe will the duty be?
3) What operating temperature and pressures will be experienced?
4) Environment food safe etc
Answers to these questions will lead to the primary choices of viscosity grade (VG) and hydraulic fluid types.
In what type of equipment will the hydraulic oils be used?
Selection of a hydraulic fluid with a viscosity that bests suits the system pump is a good place to start. Manufacturers will normally specify a range of oil viscosity. These will vary dependent upon the pump type. Vane pumps typically require 14-160 cSt, Piston pumps are more durable than a vane pump and require 10-160cSt. Gear pumps are the most tolerant to contamination and a conservative range would be 10-300cSt. Industrial machinery is typically designed to operate within a cleaner more stable environment, where outdoor and mobile applications will more likely have severe temperature variations, higher humidity and more demanding duty cycles.
How severe will the duty be?
Duty would normally be described by running time, environmental factors, likelihood of contamination ingress, maintenance arrangements etc.
Examples of Low/Medium/Heavy Duty would be:-
> 24 hours
Heavier duty demands will normally lead to the use of a mineral oil with a good additive package (such as a HVLP) to improve performance or the selection of a fully synthetic oil.
For hydraulic systems with high running times a fluid with a high viscosity index (VI>130) will avoid damage and breakdowns as it extends lifetime of hydraulic pumps and components.
What operating temperature and pressures will be experienced?
Where temperature extremes are large (below -5oC and above +60oC) and pressures above 250 bar the use of a fluid with a good mix of additives will be important. Mineral based oils (HM/HLP) will be sufficient in the most common applications as these often have anti-wear additives, oxidisation inhibitors and viscosity improvers. Fully synthetic oils will however out-perform mineral hydraulic oil ensuring that the viscosity and lubricity remains stable over a longer period.
Viscosity Grade (VG)
A hydraulic fluid has a low viscosity when it is thin and a high viscosity grade when it is thick. The viscosity reduces as the temperature rises and visa-versa. The hydraulic fluid must be thin enough to flow through the filter, inlet and return pipes without too much resistance. On the other hand, the hydraulic fluid must not be too thin, in order to avoid wear due to lack of lubrication and to keep internal leakage within limits. Viscosity grade is expressed at 40oC eg ISO46 which is an oil with a viscosity of 46 cSt measured at 40oC.
According to DINISO 2909 oil viscosity changes versus temperature, Viscosity Index (VI), is normally between 90-110. VI above 130 are largely insensitive to temperature change.
A viscosity range of 12-80sCt is recommended for a large range of commercially used hydraulic equipment.
Hydraulic oil specifications
Hydraulic power packs can be used with a wide range of hydraulic oil grades, commonly:-
· Hydraulic Oil (ISO11158-HM) – Mineral based – hydraulic oil grades widely used in light duty applications where temperature and pressures are moderate.
· Hydraulic Oil (DIN51524-2-HLP) – Mineral based with additives for oxidation, corrosion and wear protection. Used for general applications where temperature and viscosity conditions are observed.
· Hydraulic Oil (51524-3-HVLP) – Premium grade mineral based as per HLP but with improved viscosity temperature behaviour (VI>140).
· Biodegradable hydraulic oil – HETG, HEPG, HEES and HEPR – A developing technology and is yet to replace mineral oils in all applications. Storage and service life is limited, particularly at elevated temperatures.
· Fire Resistant Fluids (ISO12922 – HFA, HFB, HFC and HFD) – HFA,HFB and HFC contain water solutions and must only be used with specifically designed products. Not suitable for systems containing aluminium and some paint products. Seal compatibility must be checked.
For Hydraproducts powerpacks we recommend the following:-
HPU and HPR Micro powerpacks
HPM Mini packs
HPS Standard Hydraulic power units
Some sources of these oils would be:-
HM32 – Shell Hydrau HM32 – Castrol Hyspin VG32
HLP32 – Shell Tellus 32 – Castol Hyspin AWS32
HVLP32 – Shell Tellus S3V 32 – Castrol Hyspin HVI 32
Where environmentally sensitive fluids are required the use of Castrol Carelube HES32 can be employed in all our products, for light and medium duty ONLY.
Where a small level of fire resistance desirable then the use of a Castrol Anvol SWX FM HFDU fluid may be implemented in all of our products, for light and medium duty ONLY.
When connecting a DC hydraulic power pack to the battery it is important to get the cable sizing correct. The battery cable will carry high currents and they must be sized to minimise voltage drops. When a DC powerpack is running at full load currents up to 300 amps can be required.
Maximum current draw of your DC powerpack can be estimated as follows, but for exact current figures the dc motor performance curves must be referred to.
On many vehicles and trailers the battery can be mounted some distance from the power pack the length of the battery cables must be considered. This is because the voltage drop calculation is proportional to the resistance of the battery cables and therefore the amount of copper used.
These figures are based on the use of a Tri-rated cable (BS6231) as this a flexible and high temperature multi-stranded high current cable. Battery cable must be terminated with crimped ring ends, ensuring these are securely tightened onto battery and dc hydraulic power pack terminals.
Failure to adhere to these guidelines can cause excessive voltage drop in the cables at full load current. This can cause damage to the power pack and also result in dangerous overheating of the cables and connected equipment. The use of a suitably sized fuse is recommended.
It’s no secret that water can cause incredible damage to any hydraulic system.
If you’ve been a hydraulic system engineer for some time, you may have already seen a system that has cloudy oil in it. Cloudy oil is the result of having so much water in oil that it is above the saturation level. Most often the saturation level will be at 200 to 300 ppm at a temperature of 68°F or 20°C.
Going the other way on the scale, by reducing water in a system, you can increase the life of it by a significant amount. For example, by ensuring that it’s at a level that is lower than 100 ppm, the life of a bearing could be increased by 150%. (According to Timken Bearing Company in their Stauff Contamination Control Program).
If oil is cloudy, then it will have at least 200 ppm of water in it. Of course, the greater the level of water in the oil, the more issues you’ll have in terms of performance and reliability. We once had a look at a system for a client and it had more than 10,000 ppm of water which is more than 1%.
Here’s a checklist of why you don’t want water in your hydraulic fluid:
· It decreases the presence of some additives
· It reacts with some additives to make corrosive products that will attack metals
· Clogs filters
· Increases cavitation
· Increases air entrapment
· Reduces lubrication
Although if you do your own research, you may come across information that states that having 0.1% of water in your system is perfectly acceptable, according to the Timken Bearing Company report, it is far better to have as little as 0.01% of water in your hydraulic fluid as it will increase life expectancy of bearings in their case, but components etc. in ours.
If that isn’t enough information to convince you, then take note that 500 ppm of water and over can even create micro-biological contamination if you have the following elements also present:
· Food: i.e. nitrogen, carbon or phosphorous from the oil
· Oxygen: there is usually between 7 and 10% of air in hydraulic oil
· Temperature: bacterial growth can occur between 24°C and 49°C
· Low flow: the reservoir is a great place for breeding to take place
· Particles: these will help to transport and colonizing
Although you will need each of the above present to help keep bacterial growth going, water is what is behind the success of it. Therefore, keeping your oil dry is critical in stopping growth.
Offshore containers for Hydraulic Power Units (HPU)
Hydraulic equipment that is used and transported on and off ships is often housed within a container. Hydraulic power units are commonly required for Launch and Recovery Systems (LARS), Remotely Operated Vehicles (ROV) and Winches. This would be normally designed to meet Offshore or Maritime standards.
The offshore containers are designed for moving around supply ship decks and must withstand dynamic loads from “snatching” of installation cranes.
The portable offshore container has a maximum gross weight less than 25,000 kg for continuous transport of goods and equipment, and will be handled in open seas between fixed or floating platforms and decks. This differs from the containers used in the containerised transport of goods on a ship.
The offshore container will be designed and certified to meet the DNV Standard for Certification No 2.7-1 (April 2006) with effect from in 1989. This standard was introduced as the sea transport container standard (ISO 1496) was not intended offshore containers.
Basically the offshore container must be “tough” to support this DNV 2.7-1 focuses on strength and integrity in all stages of transport.
· shoreside (by fork lift truck)
· supply vessel
· craning on and off offshore platforms
Containers must have sufficient strength so not to suffer failure when subjected to extreme loads that may be encountered during offshore movements.
Containers designed according to DNV 2.7-2 will largely meet the design and certification needs to also satisfy CSC (Convention for Safe Container), IMDG (International Maritime Dangerous Goods Code) and the ISO1496 standards.
Whilst DNV 2.7-2 focus generally on the dimensions and weights another standard that runs alongside this is the European Standard EN12079. The bulk of this standard concentrates on the safety and recording documentation. Sections of EN12079 (Offshore containers and associated lifting sets) will shape the general design:-
● An offshore container should be designed to allow loading and unloading in wave heights to 6 m
● Must have an outer framework and pad eyes at or near the top
● Protrusions to be avoided
● Designed to withstand temperature of -20℃
● Must withstand 30˚ angle without tipping
The owners or representative are responsible for recording and maintaining certification of all containers. Periodic inspection including records of substantial repair, modification must ensure traceability.
Transit crash frames give essential protection for Offshore HPU’s. Hydraproducts can offer guidance on how to comply with the standards necessary when handling marine quality hydraulic power packs.
In this article we want to explain the ins and outs of hydraulic powerpacks. A vital piece of equipment that is used with so many machines we see every day.
In a nutshell, hydraulic powerpacks are self contained units that are used instead of a built in power supply for hydraulic machinery. Hydraulic power uses fluid to transmit power from one location to another in order to run a machine. It really is as simple as that.
So what do they look like?
In order to recognise and better understand hydraulic powerpacks, it is a good idea to get to know the key components. Hydraulic powerpacks come in many different shapes and sizes, some are very large and stationary whereas others are much smaller and more compact. In fact, some hydraulic powerpacks are so compact that they can easily be transported in a small van or even an estate car.
The only real way to identify hydraulic powerpacks is through its main components. No matter the size of the unit, all power packs will have the following; a hydraulic reservoir, regulators, a pump, motor, pressure supply lines and relief lines.
What do these components do?
It may be obvious to some but in this post we wanted to explain every component as simply as possible. So here goes.
First up is the hydraulic reservoir which quite simply holds the fluid. Reservoirs will come in different sizes.
Then we have the regulators. Regulators are vital as they control and maintain the amount of pressure that the hydraulic powerpack delivers.
Thirdly we have the pressure supply lines and relief lines. The supply line simply supplies fluid under pressure to the pump and the relief lines relieve pressure between the pump and the valves. The relief lines also control the direction of flow through the system.
Finally we have the pump and a motor. We will begin with the simpler component of the two, the motor. The motor is simply there to power the pump. Easy as that. Now the pump generally performs two actions. Firstly, it operates as a vacuum at the pump inlet and through atmospheric pressure forces fluid from the reservoir into the inlet line and then to the pump. It then delivers the fluid to the pump outlet and pumps it into the hydraulic system. We did warn you that the second part would be slightly more confusing.
So what is the function of hydraulic powerpacks?
Hydraulic powerpacks deliver power through a control valve which in turn runs the machine it is connected to. Hydraulic powerpacks come with a variety of valve connections. This means that you can power a variety of machines by using the appropriate valves.
Hydraulic powerpacks are relied upon by a range of different machines that use hydraulic power to do its work. If a machine is required to carry out heavy or systematic lifting then its likely it would need help from a hydraulic powerpack.
To make it easier for you to understand, we have included a list of trades that regularly rely on our powerpacks. On a building site you will see machines like bulldozers and excavators, which both need hydraulic powerpacks. But, it is not just on building sites that you will find these types of machines. Fishermen and mechanics both need hydraulic powerpacks too. If we did not have them then how would fishermen lift their nets or how would mechanics lift our cars?
When picking a hydraulic powerpack there are a variety of pumps and options to pick from and it is important to pick the right pack to meet your machines needs. It is also important to consider a pack that will help maximise productivity and minimise cost.
Many people will overlook the necessity of hydraulic powerpacks, but they really are vital to ensuring our society runs efficiently.
Do you need to maintain hydraulic powerpacks?
Yes you do and this is hugely important! Hydraulic powerpacks require regular maintenance to ensure they are working properly and safely and to help extend their life. Maintaining hydraulic powerpacks is relatively simple and includes checking the tubing, this can be for any noticeable problems such as dents or cracks. It is also vital to regularly change the hydraulic fluid and look at the reservoir to check for any corrosion or rust.
What hydraulic powerpacks do we provide?
Generally we provide four different types of hydraulic powerpacks. You can pick from a standard powerpack, a mini powerpack, a micro powerpack or a bespoke powerpack.
The standard hydraulic powerpack uses a standard range of modular components and is ideal for the most demanding industrial applications. The mini powerpack is ideal for applications requiring up to 5.5kW. The micro hydraulic powerpacks were originally produced for mobility applications, so are great for when space is limited. Finally, if none of these seem to fit your needs then we offer bespoke hydraulic powerpacks ensuring your application gets the hydraulic powerpack it requires.
Finally, who is the genius behind hydraulic powerpacks?
The man behind hydraulics was Laissez Pascal. A French mathematician, physicist and religious philosopher who lived in the mid seventeenth century. Pascal made observations about fluid and pressure which led to Pascal’s law. Pascal's law states that when there is an increase in pressure at any point in a confined fluid, there is an equal increase at every other point in the container. Hydraulic powerpacks have been designed based on Pascal's law of physics, drawing their power from ratios of area and pressure.
So, interested in our Power Packs? Come on over to the main website and see what we can do for your Hydraulic Power Pack Needs .
When designing hydraulic mobile equipment, it’s a necessity to position the reservoir in a suitable location. Unfortunately, this isn’t something that happens with every designer. They can be difficult to position in a compact area and can often be irregular in shape and then be situated in awkward and hard to reach locations.
Keep in mind that the mobile hydraulic equipment is usually operating under more extreme conditions than the static hydraulic machine. In addition to the limitations of needing to be smaller to retain the mobility, the limitations means that they are usually custom designed so that they can fit the exact space and requirements for optimal performance. It is possible to minimize size, cost and weight of the reservoir whilst ensuring that performance and efficiency do not suffer by taking time to consider what’s possible.
Quite often designers will use 3D modelling to produce the best designs for use and from a manufacturing point of view, designs that are complicated can be difficult and expensive to make. Here’s what is taken into consideration:
Balancing drawdown: the reservoir must provide enough fluid for the cylinder rods to operate effectively. There also needs to be enough time for the fluid to rest in the tank for contaminants to settle out and for air bubbles to coalesce. Here at HydraProducts we often use the rule of thumb to provide 1/3 of maximum pump output.
Thermal expansion: the reservoir needs to be large enough to be able to house fluid that has expanded from heat. This is why it’s important to not overfill the reservoir with cold fluid without considering what happens when that same fluid reaches maximum operating temperature.
Vented or pressurized: whether a reservoir is vented or pressurised depends on its location and what the inlet requirements of the pumps are. We usually recommend pressurisation otherwise there can be issues with cavitation which results in surface fatigue of metal.
Even humid air can get into the system if the oil level drops. Water can also get in by condensing on the interior walls when the ambient temperature drops. This condensate can lead to rust deposits and all manner of issues. Mobile reservoirs will usually be made of aluminium or stainless steel or steel to cut down on such issues.
Our mobile hydraulic solutions are designed carefully and to make the best of the limitations of size and weight. Call us today if you would like to discuss your requirements and we’ll see what we can do to help.
Hydraulic Power Pack
Connect with us
Connect with us on social media or eBay