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The majority of companies in the oil and gas extraction industry are not keen on using the term ‘environmentally friendly’ when it comes to lubricants such as hydraulic fluids. This is because there aren’t any established technical definitions or standards that specify a criteria to be met in order to be classified as ‘environmentally friendly’. Companies do however agree on the fact that fluids can effect both environment through their biodegradability, bioaccumulation and toxicity.
Strangely, the toxicity of a fluid is measured by how it will effect a rainbow trout. However, with the majority of the water supply of the world coming from oceans, it’s seems more appropriate to measure what a fluids’ effect is on salt water.
How toxic fluid is to a rainbow trout also limits the measurement of effect to how it effects just one species. There are other sensitive sea life that should be considered that are lower on the food chain and will be consumed by animals throughout the food chain.
Castrol responded to the needs of adhering to the ever increasing environmental legislation by producing their Greenfield range which are designed to be environmentally responsible and to help the offshore industry to reduce its impact on the environment.
The products that Castrol devised are now used on a variety of offshore machines such as drilling units, subsea production facilities, specialist support vehicles and supply boats including hydraulic machines. The product range includes hydraulic fluids, greases, lubricants, subsea control fluids.
With such products, the marine environment is at less risk of being polluted. These products were developed using the most stringent of environmental legislation but do not compromise performance whilst keeping ahead of the legislative trends that companies in the marine industry need to consider even for use in sensitive areas such as the Artic.
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.
Performance and reliability don’t have to be sacrificed in order to use green and clean hydraulic fluids.
Industrial equipment needs continuous lubrication to keep it operating reliably, efficiently and for long periods of time. The offshore industry relies on hydraulic fluids with high performance, more so because some equipment can be located over 100 miles from shore. Replacement parts and spare components can be days away, so all machinery being fully functional is integral to full operations.
Sourcing hydraulic fluids that are more compatible with the environment is something that many operators are struggling with. The current environmental climate demands that companies deliver a maximum output of oil whilst not crossing any boundaries of the increasing legislation that is environment related and adding to the complexity of oil and gas extraction in areas such as the North Sea. This is a trend that we predict to continue and spread to other parts of the oil-producing world.
Marine environments are protected by a number of international bodies and therefore offshore production is particularly challenging. Fluids that are less likely to impact delicate eco systems are catching the attention of offshore operators.
Fluids that could spill or leak into the sea need to be selected with the consideration of what effect they could have on the environment. There needs to be a balance between choosing a fluid that might be considered better for the environment, but that offers less in terms of performance results than one that provides improved performance. This is because the lesser fluid may need to be more frequently replenished and that carries a risk of spillage in itself. There could also be an associated increase in packaging, shipping, storage and of course disposal. All affecting the environment in a negative way.
Hydraulics is an area that can greatly impact the environment due to high pressures, flexible hoses and high flow rates. They can all make it possible for there to be a significant spill.
When selecting your fluid, stay sensitive to the environment and recognise what impact it could have from all angles including bioaccumulation, toxicity and biodegradation.
Watch this space for further information about what’s possible with environmentally responsible hydraulic fluids.
How to read hydraulic circuits
Hydraulics symbols are an essential component of hydraulic circuit diagrams. Knowing some of the basic principles will help understand a wider range of symbols. Explaining the common ISO1219 symbols enables a complete hydraulic system to be followed:
1. Hydraulic Pump
Hydraulic pump produces flow. Oil is pumped from the hydraulic reservoir into the system. The basic symbol for a pump:
A fixed displacement pump is the simplest type and has a fixed output for each revolution of the input shaft. Modifications to this symbol describe the variable displacement pump. The types of control circuits show how the output is varied.
Filters clean oil entering the system, and are used in various places within a system. They protect hydraulic valves and pumps. Suction filters are placed at pump inlets to ensure only clean oil enters the system. Pressure filters can be placed throughout system. Return filters are common and filter oil returning to the reservoir.
3. Pressure Relief Valve
Pressure in a hydraulic system should be limited to control the force any motive devices produce and to ensure the safe/design limits are not exceeded. A pressure relief valve symbol is normally shown as:
A pressure relief valve or PRV passes fluid from an area of higher pressure to a lower pressure (typically the tank). Hydraulic pressure shown by the dotted line acts as a pilot to actuate the PRV by moving the arrow across the box. This happens when the pilot pressure produces an internal force equal to the spring load the valve begins to open and pass flow.
4. Check Valve
This valve is a one way valve that prevents flow in one direction. The addition of a spring ensures the valve will only open when this pressure is exceeded. Dotted pilot lines can be added so that pilot operating pressures can be used to open the valve and allow flow in the reverse direction. Commonly used to hold pressure in a hydraulic cylinder.
5. Hydraulic Reservoir (tank)
Hydraulic systems all have a means of storing hydraulic fluid. This is referred to as the hydraulic reservoir. Hydraulic reservoirs are shown as:
Vented hydraulic reservoirs are common place, but sealed systems can be found ion aerospace and marine applications. The return lines shown indicate the position above or below the oil level.
6. Directional Control Valve
Hydraulic fluid flow is controlled by a directional control valve. Commonly consists of four parts, valve body, spool, actuator, and springs. The spool is moved with respect to the valve body, this opens and closes internal flow galleries to control fluid flow. Various types of actuators provide power to shift the spool and springs are normally used to return the spool when the actuator is de-energised.
Look at the typical three position four way valve:
How to read directional control valve symbols:
a. Each box in the valve symbol represents a possible valve condition. In the three position valve above there are 3 possible conditions controlled by the actuators.
b. Number of ways tells you how many hydraulic connections could be connected to the valve.
c. Actuators always push and never pull the spool.
d. The box furthest away from the actuator is the normal or de-energized position, and is the position where the circuit connections are drawn. In the above valve this is the middle position.
7. Hydraulic Cylinder
Hydraulic cylinder or actuator uses hydraulic power to generate mechanical force. A hydraulic cylinder is shown as:
A double acting cylinder (above) has two ports and is therefore powered in and out. Single acting cylinders have one port and would typically be used for lifting applications.
We hope this gives you a useful introduction to hydraulic circuits. For a full list of hydraulic symbols can be found in ISO1219, or contact www.hydraproducts.co.uk for more help.
Hydraulic power units are used for a broad range of applications from operating control valves in the outback of Australia to raising parking barriers in Siberia. To match this range of applications there are an equally large range of hydraulic systems and products.
Whether you are designing, specifying, manufacturing or purchasing a hydraulic power pack there are several pointers that will narrow down this range.
Firstly an assessment of the power that will be required. This does often require the use of appropriate hydraulic and mechanical design tools. Some useful tools can be found here http://www.hydraproducts.co.uk/hydraulic-calculators.aspx. When the power (kW) level is known this leads to second stage of deciding upon what power source might be available.
Power sources are typically electrical, combustion engines or mechanical drive. Electrical sources will divide into AC and DC, this will depend greatly on the application and location. Where electrical sources are not possible, such as trailers, petrol, diesel or gas combustion engines can form the centre of a hydraulic power pack. Common for vehicle based hydraulic systems a DC, or battery will give the motive power source.
Each of the power sources will have their practical and economic limits.
Typically DC Power available on the majority of vehicles is a maximum of 3kW. A small commercial vehicle or van would be 12VDC and a maximum battery power of 2kW. Whereas a larger heavy goods vehicle could have a 4kW 24VDC system. Forklifts and other goods handling equipment will often be 48 or 72VDC.
AC electrical power can generally be spilt into two camps, 1 phase and 3 phase. For domestic/office applications 220-240V 1phase will be available up to a limit of 2.2kW. Site work will often be operated at 110V 1 phase and this will be limited to 1.5kW. 3 phase power covers a much larger range from 0.09kW to over 100kW, and this will be common in all industrial applications.
Combustion engines cover a wide range, with small single cylinder petrol engines starting at 4HP and diesel engines starting slightly higher than this at 6HP up to over 100HP.
This chart summarises the maximum power source ranges:-
AC 1 PHASE
AC 3 PHASE
This chart is based on products that can be built economically, and not what is physically possible.
The next question to ask yourself might be what is the operating duty of the powerpack will have to work within. This is important when selecting which type of powerpack as for example it may not be possible to specific features such as tank size or motor type that will ensure they can run continuously. If we simply divide these into S1 (running 100% of a day) and S2 (running for a short operating time).
This chart will allow some division of our product range based on operating duty:-
Eco-friendly hydraulic fluids are in demand for use on environmentally sensitive projects, such as work on nature reserves, as well as sub-sea applications. The requirement for a biodegradable fluid is often specified by the landowner or project owner, as they cannot risk a fluid leak contaminating the land and getting into the water systems in the area. There are biodegradable hydraulic fluids available on the market, and these typically use canola, sunflower or soybean oil as the base rather than the more traditional mineral oil. Under certain conditions these bio-based fluids achieve a similar performance to mineral oil based fluids, but these have not been tested extensively and for this reason it is recommended that the equipment be run at a 20% deficit compared to the usual pressure (so, at 80% of the maximum permissible operating load).
As the use of biodegradable hydraulic fluids is usually determined by the project owners as a condition of the work being undertaken, there is no room for compromise here. Instead, the compromises must be made with the machinery and how it is set up. If time constraints are an issue as well as the eco-friendly credentials of the materials used, it is wise to select bigger and faster versions of the machinery that was intended to be used, as even running at 80% the job will get done in the same amount of time, as the intended equipment would at full capacity.
There are also costs associated with the draining and flushing of unsuitable hydraulic fluid; some clients may insist on testing the fluid in the machinery to ensure it passes their tests for biodegradability. The oil itself is more expensive than the cheaper mineral oil based fluids, so the whole job becomes more expensive immediately biodegradable oils are used. Often, when a job has been priced without these considerations it becomes unprofitable unless the client is accommodating of over-runs due to the changes required in the machinery or the rental of bigger equipment.
With time and the growing popularity of renewable energy and the general shift towards the use of more sustainable materials there will be developments in the production and testing of biodegradable hydraulic fluids. The costs associated with the purchase and use of bio-based fluids will come down, and the concerns around the maximum performance pressure will be assuaged, meaning that biodegradable hydraulic fluids will be able to compete at the same level as traditional mineral oil based ones.
Some companies run a lot of different hydraulic equipment. Firefighters are one example of a workplace that uses a range of hydraulic equipment, each with its own specification of the type of hydraulic fluid that is indicated for use. Construction, healthcare and agriculture also use a range of different hydraulically powered equipment, from hospital beds to hay balers and everything in between. Being in charge of maintaining all this equipment is a large undertaking, and a common theme for those tasked with keeping everything running is staying on top of the sheer number of different types of hydraulic fluids that are stored and used routinely.
There may be very good reasons why a piece of equipment uses a certain type of hydraulic fluid, but sometimes the choice is determined by the past – “we've always used that type of oil so we will continue to do so” – is a common reason behind why different types of oil are used. That, coupled with the fact that some engineers have their own favourite types, can mean that after a few years the stock of hydraulic fluids is running into tens of bottles, all half empty (or full, depending on how you look at things) and taking up valuable storage space. There are some ways you can reduce the number of containers and types of oil you use.
Firstly, identify which bottle correlates to which piece of equipment. There may be more than one for very complex equipment. Mark the bottles so you know what hydraulic fluid goes with what. Anything that is unmarked can be discarded, as it is probably not in use anymore. Any bottles that are old or have been open for a long time may have degraded past the point at which they are still useable – the more contact there is between a hydraulic fluid and the air the more degradation will have occurred, so to avoid accidentally using hydraulic fluids that have gone off it is a good idea to regularly discard old containers.
The next stage is to identify where the same, or very similar fluids are being used on more than one type of hydraulic equipment. All hydraulic fluids have a viscosity rating, but these are a guideline of the viscosity under normal operating conditions. There is a 10 per cent variation on the viscosity grade, so where there are fluids of, say, 38, 40 and 42 grade then one grade should fulfil the requirements of the three varying grades. Consolidating the same types of fluid into one viscosity grade for all pieces of hydraulic equipment could reduce the number of bottles considerably, and make it much easier for anyone replacing or topping up the fluid levels.
It is important when consolidating fluid choices in this way that one refers to the specification of each piece of machinery, to ensure that there are no special reasons why a particular grade of hydraulic fluid is used. Pieces of machinery that experience a lot of fluctuation in operating temperature may require a certain type of hydraulic oil to ensure premium performance throughout operation.
When choosing new hydraulic equipment, it is worth considering whether the fluid types indicated by the manufacturer matches what you already have, and whether you are able to use one of the hydraulic fluids you already own if they are a close enough match. By keeping things very simple and reducing the number of hydraulic fluids kept on site you can save money, time and avoid unnecessary cross contamination of fluids within the machinery.
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