Hydraulic Cylinders, Jacks, or Rams. The names vary but whatever you choose to call them the definition is the same → a device that harnesses the pressure generated in a hydraulic system to move a load.
Due to the wide variety of cylinder options to choose from, you will need to consider your needs carefully when selecting a cylinder for your job. Answering the following questions will help you to choose the right hydraulic cylinder for your lifting and pulling projects.
How will the cylinder be used?
Cylinders are versatile products. Not only are they used for lifting and jacking, but also for pulling, pressing, holding, lowering, and clamping. Knowing the application you need a cylinder to perform is your first important step towards making the right decision.
How much space is needed?
The question of how much room you have for your cylinder is an important one. For an available space of only 145 mm, you wouldn’t choose a cylinder that has a collapsed height of 176 mm. There are purpose-designed cylinders made for jobs in confined spaces. These go by the name of (Low Height) Hydraulic Cylinders or (Flat) Hydraulic Cylinders.
What stroke is required?
Related to the maximum collapsed height, is the stroke length required. Stroke is defined as the difference between the fully extended height and the fully collapsed height of the cylinder. It’s the distance between the top of the plunger piston and the bottom of the stop ring. For jobs that need extra stroke, there are (Telescopic) Hydraulic Cylinders available. The stroke determines how far the cylinder will lift, push, pull, or move your load. When considering the stroke of a cylinder, you should keep within 80% of the maximum stroke. This helps ensure better stability and damage from side-load.
How heavy is the load?
Each hydraulic cylinder is built to lift a certain capacity. There are general purpose designs, which are your “basic” options, and also high tonnage cylinders that have a capacity of up to 1,000 tons. Like cylinder stroke, the 80% rule also applies to tonnage also. Manufacturers always list their maximum weight capacity as a safe limit. However, good practice with cylinders encourages users to only go to 80% of the manufacturer’s limit.
Does the application require mounting?
Some jobs need extra stability or precise cylinder positioning. If your job falls under that category you will need a hydraulic cylinder with either mounting holes or collar threads. Mounting holes are located on the bottom of the cylinder’s base and can even be attached to a base plate.
What hydraulic pressure do you need?
Ok so you’ve answered the questions above and probably should have a cylinder in mind. Good job! But before making your final selection, don’t forget to check whether the hydraulic pressure from your pump will be sufficient or not. If you need an upgrade there’s many great pumps to choose from. For example, electric, hand operated, foot operated, gasoline, air over hydraulic, cordless and lightweight models for working at heights.
Where will the cylinder be used?
Hydraulic cylinders are used for countless applications. Many job sites involve harsh conditions, whether that being extreme heat, or the rough conditions of a construction site. Knowing the conditions of the place where the cylinder is going to be used is important.
How much accuracy and control is needed?
Hydraulic cylinders are available in single acting and double-acting configurations. A single acting hydraulic cylinder uses hydraulic pressure to extend the plunger and a return spring to bring it back to the original position. A double acting hydraulic cylinder uses hydraulic force to both lift and lower the plunger which provides much more control and precision.
Is load holding needed?
If your load needs holding in place while you perform your job, a cylinder with load holding is a safe choice. Cylinders that hold your load, eliminate the time-consuming process of cribbing. (Lock Nut) Hydraulic Cylinders are the perfect fit for such load holding applications.
Steel or Aluminium Cylinders?
If you’re looking for a cylinder for regular use, you will need one that’s built to last. Steel cylinders are inherently stronger than their aluminium counterparts. However, if weight is an issue, aluminium cylinders are also robust and much easier for a person to lift, transport, and reposition.
How many lifting points are required?
For many larger lifts, you may need more than one cylinder. If that is the case, you will need to select a pump with the appropriate oil capacity, multiple hoses & couplers depending on the number and type of hydraulic cylinders to be used and also manifolds.
How level will the contact point be with the saddle?
In many lifting projects, sometimes it is difficult to achieve sufficient contact between the saddle and the load. When this happens there is the risk of damage to the cylinder from side loading – often with the user completely unaware it is happening. A greater contact area can be achieved using Tilt Saddles. These are an option that can be specified to help extend the life of the hydraulic cylinders.
Do you need it to pull as well as push?
A (Hollow Plunger) Hydraulic Cylinder design allows for both pull and push forces. This is achieved thanks to a threaded collar for attaching suitable fixing rods.
Single Acting or Double Acting?
When comparing single acting vs double acting hydraulic cylinders, the most visible difference is the number of couplers or connection ports. A single acting hydraulic cylinder includes just one port. This is where the hydraulic fluid enters and forces the plunger out in one direction. A double acting cylinder includes two ports. One for the hydraulic fluid to enter and extend the plunger, and the other for retracting the cylinder.
Single Acting Hydraulic Cylinders
- The single acting cylinder is simpler than its double acting counterpart.
- With fewer components, there is much less to go wrong, which is good news when it comes to maintenance.
- The plunger in a single acting hydraulic cylinder extends when hydraulic fluid under high pressure is pumped into the cylinder. When it is time to retract the cylinder, depending upon the cylinder design, the plunger can be retracted using a return spring, by the load, or simply by gravity.
- Single acting cylinders are ideal for straightforward jobs – especially when fast or controlled retraction isn’t essential.
- Springs can wear out faster with time.
Double Acting Hydraulic Cylinders
- Double acting hydraulic cylinders have the ability to pump hydraulic fluid to both sides of the plunger. Connection ports positioned near both ends allow the piston rod to move both forwards and backwards. The extra port also allows more control of the plunger during retraction and ensures it always returns back to its starting point.
- In a double acting hydraulic cylinder, the plunger retracts when hydraulic fluid is pumped under high pressure into the top port, forcing the plunger back to its original position. This can be done quickly, if required, or very gradually with precise control.
- The faster and predictable retraction of double acting cylinders makes them the better choice for projects needing repeatable accuracy.
- Are costlier than their single acting counterparts.
Keep these things in mind when looking for a hydraulic cylinder and you will come away with the best option for your application. If you have any more questions about how to choose the right hydraulic cylinder, do contact us.