What is in this article?:
- Fluid power safety in the workplace, part 3
- A common occurrence?
This is part 3 in a series on the importance of following good safety protocol in fluid power system maintenance and design. It highlights real-life examples of the dangers and injuries that can occur and provides advice on preventing them. Find part 1 here; part 2 here; part 4 here; part 5 here; and part 6 here.
A common occurrence?
Unfortunately, the results of an industry-wide survey of heavy-duty mechanics yielded discouraging results —over 90% of the heavy-duty mechanics we spoke to have either used compressed air to extricate a rod/gland assembly or know someone who has.
This shows that not only is this a common practice, but also one that is regarded as acceptable. Even companies with the most rigorous safety programs may overlook this critical safety issue. Many of the people with whom we spoke about this practice, responded anecdotally about having blasted a cylinder rod assembly through a door or a wall.
How this accident could have been prevented
Training —there is no tool that is more effective at reducing or eliminating work-related accidents than training. Training empowers people to make safety-based decisions. This accident would not have occurred had the victims received proper training on how to disassemble a hydraulic cylinder.
This is a simple, straightforward procedure for a properly trained person. Oftentimes, it is assumed that mechanics can figure out disassembly and assembly procedures. These are times when written instructions are vital.
All hydraulic accidents must be investigated —Hydraulic accidents occur on a daily basis in plants and factories around the world. Unfortunately, in most cases, only those in which a person is injured or killed are investigated.
For example, a hydraulic hose-end failure is an accident. However, less than 1% of the hose-end failures that occur are ever investigated to determine the root-cause of the failure.
Follow service and repair instructions —Component and machinery manufacturers must provide clear, safety-based, accurate information that is user-friendly. The information must apply to their machinery. For example, a manufacturer might use a particular brand of pump in a machine. The information about the pump is usually a photocopy of the pump manufacturer’s generic information. However, the information might not apply directly to that entire machine.
A manufacturer must state very clearly if specialized tools are needed for a particular task, and make those tools available. If specialized skills are needed to do the job, they must be stated.
Competent technical assistance —Component and machinery manufacturers must have properly trained personnel to cater to customers╒needs. The advice people are given must be safety-based and accurate.
Proper tools — There are certain tools that are needed for almost any job. A hydraulic technician should have flow meters, pressure gages, temperature gages, and any other special tools required to service and repair hydraulics.
How to safely remove a stubborn rod or gland
1. Wear safety glasses.
2. Place the cylinder on a suitable table and secure it with the ports in the vertical position.
3. Remove the locking device from the rod/gland assembly (refer to cylinder manufacturer’s information for guidance).
4. Pull the rod out (if possible) all the way, until it stops against the end of the cylinder.
5. Place a suitable support under the rod to prevent it from falling and causing possible injuries. The support will also prevent the rod from getting damaged, when it comes out.
6. Place a suitable receptacle under the cylinder (rod/gland area) to catch the oil when the rod/gland comes out.
7. Pluse the ort in the rod end of the cylidner with a suitable plug that has the proper pressure rating.
8. Tilt the closed-end of the cylinder upwards slightly and place suitable spacer (approximately 1 in.) under it.
9. Fill the cylinder (through the closed-end port) with hydraulic oil.
10. Connect a 300-psi mechanical hand-pump with pressure gauge to the closed-end port.
11. Gradually pump the hand pump while observing the pressure gauge. The rod/gland assembly should begin to move. Keep on pumping until the rod/gland is pushed completely out of the cylinder tube.
12. If the rod/gland assembly does not move the time the pressure reaches the maximum pressure rating of the cylinder, suspend pumping and release the pressure.
13. Call the cylinder manufacturer for guidance.
Warning - do not continue gland removal using trial-and-error methods.
Note: this procedure is recommended for occasional cylinder service and repair only. For high-volume cylinder service and repair, we recommend that you consider acquiring a proper cylinder-service repair bench.
Caution: Rory McLaren and the Fluid Power Training Institute do everything possible to ensure that the information and drawings contained in these reports are accurate and that the suggested procedures are deemed safe and reliable. However, these are general recommendations only and might not be applicable to all situations. You must have your engineering and service departments read these recommendations and make the necessary changes for your specific conditions.
The Fluid Power Training Institute is not responsible for actions taken by untrained or unauthorized persons. All hydraulic system service, repair, and troubleshooting should be conducted only by trained, authorized personnel.