Safety Handbook for Hydraulic Cylinders
The cylinder (or ram) operates much the same as the jack, except that it is more versatile. Since the pump is separate, the cylinder can be used in several positions. By adding extensions and attachments to the cylinder, you can create a wide variety of hydraulic tools. The extensions and attachments are covered in the Maintenance Set section of this handbook on pages 29-30.
The saddle in the plunger serves two important purposes. It protects the plunger threads from damage and it keeps the end of the plunger from becoming deformed. Keep the saddle in place at all times. Do not thread attachments into the plunger and rely on the plunger threads
support. The load must be transferred to the face of the plunger. The threads in the plunger may be stripped if loaded.
As with the bottle jack, the cylinder is a load lifting device and should never be used as a load holding device, especially when a person will be going underneath the supported load.
Keep the following in mind when using a cylinder:
• The base of the cylinder should be fully supported. Where applicable, use a cylinder base plate for added stability. Do not weld or otherwise modify the cylinder to attach a base or other support.
• The saddle on the end of the plunger should make full contact with the load. Try to move the load on the centerline of force to prevent side loading. Be especially careful about side loading long-stroke cylinders.
• Do not try to lift a load more than the rated stroke. If you need to lift the load further, block the load, raise the level of the cylinder with a sturdy support, and continue the lift.
REMEMBER: Do not go under a load supported by a cylinder. After the load has been raised, it should be blocked.
Setup Considerations: The 80% Rule
When you make hydraulic setups, you should always examine the setup before using it. You want to look for ways to protect yourself and others, and ways to protect your equipment and other property.
Try to create the ideal setup. Since few things in life are ideal, following the 80% rule will result in more stable setups and prolong the life of your equipment. The 80% rule applies to cylinder stroke and cylinder capacity.
The illustration at right shows two benefits of applying the 80% rule to cylinder stroke. The first is that leaving distance between the stop ring and the bearing reduces side loading force resulting in a more stable cylinder. The second is that you avoid damaging the stop ring by running the plunger all the way up and hitting the stop ring with the bearing.
The reason for applying the 80% rule to cylinder capacity (tonnage) is that most loads are not lifted on their true center. This results in side loading of the cylinder. Allowing for a safety factor is the simplest way to compensate for the off-center characteristics of a one-point lift.
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