FLUID POWER SAFETY ALERT
Misleading troubleshooting procedures that could cause severe injury, death, or severe property damage.
What they recommend:
We are concerned with the recommendations a manufacturer of coil tubing machines makes with respect to troubleshooting their machine's hydraulic system. After analysing their recommendations we find the following procedures to present some serious safety hazards:
The first item that concerns us is regarding the procedures they recommend to determine if the problem is the "Pump or Relief Valve," quote:
"Further testing must be done to determine whether the pump is worn out or if the relief valve is malfunctioning."
"Discharge from the relief valve tank port must be observed. If possible, disconnect the tank return line for the relief valve at point C (shows an ANSI hydraulic schematic with line indicating relief valve return line). Attach a short length of hose to the relief valve outlet. Hold the open end of the hose over the tank filler opening where the flow rate can be observed. Start the pump and run the relief adjustment up and down while observing the relief valve discharge flow. If the pump is bad, a full stream of oil may possibly be observed when the relief valve is backed off but this stream will greatly diminish or stop as the relief valve setting is increased. If a flowmeter is available, the flow rate can be measured and compared with the catalog flow rating of the pump."
"If a flowmeter is not available the flow can be estimated by discharging the stream into a clean container over a measured time interval. However, even without any measurement of the flow volume, a bad pump is indicated if discharge flow varies widely as the relief valve adjustment is run up and down. The discharge flow should be fairly constant at all pressure levels, dropping off slightly at higher pressures."
In the next paragraph, they recommend,
"If the relief valve discharge line cannot be disconnected, a person can place his hand near the discharge opening inside the tank and can detect a large change in the flow volume as the pressure is varied.
If the flow decreases as the relief valve setting is raised, and only a moderate but not full pressure can be developed, this may also indicate pump trouble. Proceed to step 4."
"During this test if gauge pressure does not rise above a low value, 100 to 200 PSI, and if the discharge flow remains constant as the relief valve adjustment is tightened, the relief valve may be at fault and should be cleaned or replaced as instructed in step 5."
Why are this manufacturer's recommendations, in our opinion, potentially hazardous?:
Anytime you allow hydraulic oil to exhaust to atmosphere, you create a multitude of potentially hazardous situations:
1) Hot oil can cause severe burn injuries, and/or death.
2) Skin penetration can occur causing severe injury, and/or death.
3) Hot oil escaping to atmosphere can ignite if it comes into contact with an ignition source. This can lead to severe property damage.
Lets explore these situations individually so you can see how and why they might lead to an accident:
Burn injuries -
Whenever hot hydraulic oil is permitted to exhaust to atmosphere, it can come into contact with the skin. In most cases the volume is unknown, and the velocity can be extremely high, leaving the outcome unpredictable.
Hydraulic systems generally operate at temperatures ranging from 130º F to 180ºF under normal operating conditions. These temperatures can easily exceed 250ºF if there is excessive wear in a system.
Petroleum-based hydraulic fluids become hot during operations. A heated petroleum-based hydraulic fluid presents a considerable fire hazard, particularly in those processes where ignition sources are usually present.
A typical petroleum-based hydraulic fluid has a flash point that ranges from 300ºF to 600ºF, and an auto ignition temperature of 500ºF to 750º F. When hydraulic fluid is purposely or accidentally discharged under high pressure an easily ignitable fine oil mist is sprayed into the surrounding area. If the mist reaches an ignition source the result can be a torch-like ball of fire, or if the mist is confined, it can result in and cause a violent explosion.
Case history -
According to a report from the Workers Compensation Board of British Columbia, a 61-year-old bulldozer operator was sprayed with hot hydraulic oil when a hydraulic hose unexpectedly ruptured. He later died from his burn injuries. This proves that hydraulic oil, at normal operating temperature, can kill you.
At what temperature will you burn?:
According to information we received from a very helpful individual at the Intermountain Burn Center in Utah, a persons skin will scald at 120ºF. It will take approximately 2 to 3 minutes to receive a 2nd degree burn at this temperature if the heat is sustained.
If the temperature is increased to 140ºF, the average operating temperature of a hydraulic system, it takes 1/2 to 1 second of sustained heat for a 2nd degree burn. Oil is inclined to adhere to ones skin, consequently, the longer the contact, the deeper the burn.
Burn injuries are the worst type of injury from a rehabilitation and cost point of view. The rule of thumb is; one day in a hospital for each 1% of burnt body area.
The costs associated with the treatment of burn injuries are astronomical: a burn that covers 30% of total body area can cost as much as $200,000.00 in initial hospitalization costs and physicians fees. For extensive burns, there are additional significant costs, which include costs for repeat admission for reconstruction and for rehabilitation.
Exhausting high pressure oil to atmosphere can cause skin penetration injuries -
In addition to the risk of suffering burn injuries one must consider the consequences of high-pressure oil penetrating the skin.
According to the "Occupational Injuries Handbook," oil can penetrate the skin at pressures as low as 100 PSI -
"The force of injection, which can range from 100 to 1000 pounds per square inch, causes the fluid to track along the planes of the tissue and flexor tendon sheath. In this way, it can travel from the fingertip throughout the hand and even proximally into the forearm."
|Pressure/velocity related injury to the index finger
estimated at between 100-1,000 lbs/sq.in.
Bibliography: "Occupational Injuries" - Thomas N. Herrington & Linda H. Morse
|Radical debridement following high pressure/velocity
related injury to index finger
Bibliography: "Occupational Injuries" - Thomas N. Herrington & Linda H. Morse
Exhausting high pressure oil to atmosphere can cause severe property damage -
When hydraulic fluid is purposely or accidentally discharged under high pressure an extremely volatile fine oil mist is sprayed into the surrounding area. If the mist reaches an ignition source the result can be a torch-like ball of fire, or if the mist is confined, it can result in and cause a violent explosion.
Our analysis of this manufacturers troubleshooting recommendations:
|Case history -
A maintenance technician, using the standard industry-wide "test" to check for seal by-bass leakage in a cylinder, removed a hose from the cylinder to "look" for leakage - the seal, in this case had failed.
The damaged seal allowed oil to spray out of the open port at high velocity. The "atomized" oil ignited into a fireball when it came into contact with the gas heater that was mounted above the machine.
Although there were no injuries, the fire caused $3.5 million in damages - a flowmeter costs approximately $200.00 (two hundred dollars) and a school to learn how to troubleshoot hydraulics cost approximately $1,000.00 (one thousand dollars) - you do the math!
1. Testing the Relief Valve
Disconnecting the exhaust port of a relief valve and holding the open end over the tank filler port to "see" the flow rate while the machine is operating is extraordinarily unsafe for the following reasons:
a) The temperature of the oil might be in excess of 200ºF, and the volume of oil that exhausts from the open hose is totally unpredictable. The dynamics of the high volume exhausting from the open end of the hose could cause it to whip out of your hand and spray you with oil.
b) If the hose inadvertently moves away from the narrow filler opening, the oil could deflect off the tank and spray onto your body and into your face.
c) If the relief valve is the type that allows the entire adjustment assembly to screw out of the housing when it is backed off completely, you have to contend with the parts of the relief valve, in addition to the hot oil "blowing" out of the valve.
d) Even if you were successful with this "test," the manufacturer fails to warn you that this procedure can ONLY be executed with this specific machine. Bear in mind that the vast majority of people who work on and around hydraulic systems have NEVER been trained. Consequently, when you make these types of recommendations you have to be very careful not to generalize.
e) Even though the purpose of our Safety Advisories is not to edit the technical content of manufacturers service, repair, and troubleshooting recommendations, this "test" for a relief valve is not only dangerous, but also ineffective.
2. Placing your hand into the oil reservoir
This recommendation is hardly deserving of comment - it is nothing less than outrageous!
Only the fluid power industry, in the year 2001, can continue to provide such fallacious recommendations, and get away with it!
Again, because there are so many untrained people in the industry, DO NOT, under any circumstances put your hand in a hydraulic reservoir while the machine is operating to "feel" the condition of a relief valve, or any other valve for that matter - it is extraordinarily hazardous!
3. Testing the pump into a container
This manufacturer's recommendation for "testing" a pump is consistent with the standard industry practice of discharging the pump flow into a container.
Once again, exhausting flow to atmosphere, regardless of what type of component you are "testing," leaves you vulnerable to burn injuries, or skin penetration injuries.
In addition, "testing" hydraulic components at nominal load (pressure) makes the test futile.
With respect to this Safety Alert, we make the following recommendations (guidelines only):
1. Never "test" any hydraulic component to atmosphere regardless of who makes the recommendation - it is extremely dangerous, and is usually ineffective.
2. Always follow your companys prescribed lockout and tagout rules before working on any hydraulic system or machine.
3. Always wear safety glasses when working on or around a hydraulic system.
4. If you have not been trained to service, repair, or troubleshoot a hydraulic system you are at risk of an accident. Ask your supervisor to send you to a training course.
5. Ask your supervisor to provide proper test equipment so you can do your job safely and efficiently.
6. All manufacturers have a moral responsibility to provide you with SAFE, PROVEN, service, repair, and troubleshooting recommendations. This includes the proper and safe use of diagnostic instrumentation.
7. If ever you install a new or rebuilt component or transmission line on a machine, and it fails unexpectedly, even if you dont get hurt, you DID suffer an accident. Tell your safety department to write it up. You need to determine the root-cause of EVERY failure. Remember, the next time it occurs it could hurt or kill you.
8. If, while following a manufacturers service, repair, and/or troubleshooting procedure, you get bathed with oil, burnt, or injured, even if the injury does not qualify as "lost time," contact an attorney. You have grounds for a lawsuit.
Once again, it is a manufacturer's responsibility to provide you with safe and accurate service, repair, and troubleshooting procedures - never forget this!
9. If a manufacturer tells you to "relieve the pressure" before removing a transmission line, and you have no way of doing so safely, which is usually the case, contact their service personnel, and ask for assistance. If they tell you to "carefully" crack a connector to remove the stored energy, ask them to send one of their own people to do it. Dont sacrifice your safety because of poor safety design.
We strongly advise machinery and equipment manufacturers to review their written service, repair, and troubleshooting procedures and recommendations. Make sure any and all recommendations are safety-based.
Hydraulic component manufacturers, and mobile and industrial machinery manufacturers, routinely recommend "testing" hydraulic components to atmosphere. It is clearly unsafe, and should therefore never be done!
There is overwhelming evidence that the outcome of "testing" to atmosphere is inherently unpredictable, and can lead to severe injury, death, and/or substantial property damage.
Our advice to hydraulic component and machinery manufacturers; train your service personnel on how to safely and effectively test hydraulic components. Train your technical writing group on how to write safety-based hydraulic troubleshooting procedures.
Bear in mind that the majority of the people who work on and around your machines are untrained, or not properly trained. If they have more than three days of training in hydraulics they are lucky!
Be absolutely emphatic about the use of proper test equipment - absolutely no substitutions!
Our final word on "testing" to atmosphere, dont do it, regardless of the source - it could severely injure or kill you!