Why lockout and tagout doesn`t guarantee hydraulic system safety
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1. Mine Safety and Health Administration MSHA American Society of Safety Engineers ASSE e National Fluid Power Association NFPA Federal Aviation Administration FAA When it comes to hydraulic safety it s a NO win situation No Federal or State oversight e No emphasis on safe design from the fluid power industry No safe design training for engineers No safe design standards No safety training required for people that work on and around hydraulic systems Over 80 of the people working on and around hydraulic systems have never received any training in hydraulics at all Less than 1 of hydraulic systems have the means to after they are locked out in accordance with OSHA s lockout guidelines Safely and reliably determine if the system is energized Safely and reliably de energize the system a Misconceptions about hydraulic systems and stored energy 1 Ifa hydraulic pump is shut off there is no pressure in the system 1 Ifa hydraulic pump is shut off there is no pressure in the system 2 When a hydraulic pump is shut off the stored energy immediately dissipates throughout the system FALSE If a hydraulic pump is shut off there is no pressure in the system When a hydraulic pump is shut off the stored energy immediately dissipates throughout the system If you activate a manual directional control valve with the hydraulic pump shut off the system will bleed off2. FALSE FALSE If a hydraulic pump is shut off there is no pressure in the system When a hydraulic pump is shut off the stored energy immediately dissipates throughout the system If you activate a manual directional control valve with the hydraulic pump shut off the system will bleed off Activating the override pushpin on a solenoid operated directional control valve with the hydraulic pump shut off will de energize the system FALSE FALSE FALSE Misconceptions about hydraulic systems and stored energy 1 2 If a hydraulic pump is shut off there is no pressure in the system When a hydraulic pump is shut off the stored energy immediately dissipates throughout the system If you activate a manual directional control valve with the hydraulic pump shut off the system will bleed off Activating the override pushpin on a solenoid operated directional control valve with the hydraulic pump shut off will de energize the system A hydraulic system cannot be safely de energized by cracking loosening a connector and allowing the stored energy to vent to atmosphere FALSE FALSE FALSE FALSE Misconceptions ab C Out hydraulic systems and stored energy 1 2 If a hydraulic pump is shut off there is no pressure in the system When a hydraulic pump is shut off the stored energy immediately dissipates throughout the system If you activate a manual direction
3. directional control valve with the hydraulic pump shut off will de energize the system A hydraulic system cannot be safely de energized by cracking loosening a connector and allowing the stored energy to vent to atmosphere When a hydraulic system is equipped with an accumulator the accumulator will automatically de energize when the pump is shut off Sound is a reliable means of knowing when an accumulator is de energized Air bleeding a hydraulic cylinder can be safely accomplished by cracking a connector and cycling the cylinder FALSE FALSE FALSE FALSE TRUE FALSE FALSE FALSE What workers do after a hydraulic system is safely locked and presumably safe to work on after performing a lockout and tagout procedure as set forth by OSHA e Loosen a connector and allow stored energy to dissipate to atmosphere Open a valve e g ball valve and drain stored energy to the reservoir typically with no means of verifying Most workers rely on noise to determine if and when stored energy is internally released A time triggered valve releases stored energy with typically no means to verify the process of de energizing occurred e Remove a cartridge valve slowly and release the stored energy to atmosphere This reckless suggestion generally applies to load holding valves e g counterbalance and pilot operated check Here are examples of questionable lockouts currently employed in
4. ITUTE Copyright 2013
5. Misconceptions ab Out hydraulic systems and stored energy 1 2 If a hydraulic pump is shut off there is no pressure in the system When a hydraulic pump is shut off the stored energy immediately dissipates throughout the system If you activate a manual directional control valve with the hydraulic pump shut off the system will bleed off Activating the override pushpin on a solenoid operated directional control valve with the hydraulic pump shut off will de energize the system A hydraulic system cannot be safely de energized by cracking loosening a connector and allowing the stored energy to vent to atmosphere When a hydraulic system is equipped with an accumulator the accumulator will automatically de energize when the pump is shut off Sound is a reliable means of knowing when an accumulator is de energized Air bleeding a hydraulic cylinder can be safely accomplished by cracking a connector and cycling the cylinder FALSE FALSE FALSE FALSE TRUE FALSE FALSE Misconceptions ab Out hydraulic systems and stored energy 1 2 If a hydraulic pump is shut off there is no pressure in the system When a hydraulic pump is shut off the stored energy immediately dissipates throughout the system If you activate a manual directional control valve with the hydraulic pump shut off the system will bleed off Activating the override pushpin on a solenoid operated
6. WHY LOCKOUT AND TAGOUT DOESN T GUARANTEE HYDRAULIC SYSTEM SAFETY Presented by Rory S McLaren fluiziower TRAINING INSTITUTE www fpti org ALL FORMS ENERGY HAVE TO BE BROUGHT TOA ZERO MECHANICAL STATE Critical steps you must take to safely lockout a hydraulic system A Lockout tagout electric motor circuit B Lockout tagout DCV circuit C Depressurize and verify hydraulic circuit D Install mechanical locks Electric Motor LOCKOUT TAGOUT PROCEDURES The OSHA established procedures cover the following six steps These steps should be performed in sequence 6 STEP SHUTDOWN PROCEDURE 1 Before Shutdown The authorized employee must know the type and magnitude of the energy the hazards of the energy to be controlled and the method or means to control the energy The authorized employee must notify all affected employees of the lockout 2 Shutdown The authorized employee shuts down the machine or equipment by use of the normal stopping procedure pressing the stop button moving the switch to the OFF position etc 3 Isolation The main power switches circuit or other sources of energy are moved to the OFF position or otherwise rendered inoperative 4 Lockout Locks are placed on switches or other energy sources in the safe or OFF position During a groups lockout all members of the group must add their own locks to the lockout Warning tags should be placed with each lock After e
7. al control valve with the hydraulic pump shut off the system will bleed off Activating the override pushpin on a solenoid operated directional control valve with the hydraulic pump shut off will de energize the system A hydraulic system cannot be safely de energized by cracking loosening a connector and allowing the stored energy to vent to atmosphere When a hydraulic system is equipped with an accumulator the accumulator will automatically de energize when the pump is shut off FALSE FALSE FALSE FALSE TRUE Misconceptions ab C Out hydraulic systems and stored energy 1 2 If a hydraulic pump is shut off there is no pressure in the system When a hydraulic pump is shut off the stored energy immediately dissipates throughout the system If you activate a manual directional control valve with the hydraulic pump shut off the system will bleed off Activating the override pushpin on a solenoid operated directional control valve with the hydraulic pump shut off will de energize the system A hydraulic system cannot be safely de energized by cracking loosening a connector and allowing the stored energy to vent to atmosphere When a hydraulic system is equipped with an accumulator the accumulator will automatically de energize when the pump is shut off Sound is a reliable means of knowing when an accumulator is de energized FALSE FALSE FALSE FALSE TRUE FALSE
8. ating for example a directional control valve does not always release stored energy e Pilot operated and two stage directional control valves typically dont function when the pump is shut off Load holding valves like counterbalance pilot operated check and velocity fuses don t function when the pump is shut off There two ways to make this possible 1 Install small bleed valves at every actuator port with micro bore lines terminating to nearby return lines The bleed valves must be able to facilitate a pressure gauge for energy status verification 2 Install Safe T Bleed valves at each actuator port Safe T Bleed s Energy Control Module is used to connect under pressure to the valve and check for stored energy If stored energy is detected it can be safely removed by connecting a special conduit from the Energy Control Module to a Safe T Bleed connector in a return line T 23 The only way to insure a hydraulic system is safe to work on after the prime mover has been locked out is for a worker to have the ability to verify if there 15 stored energy and remove the stored energy if necessary at the point of work This will only be possible if the hydraulic system is specifically designed and built to facilitate point of work verification and de energization WHY LOCKOUT AND TAGOUT DOESN T GUARANTEE HYDRAULIC SYSTEM SAFETY http www foti org fluiziower TRAINING INST
9. hydraulic systems Typical isolation for a multiple pump parallel circuit operating two or more machines Machine 3 Machine 2 Machine 1 enabled enabled enabled Copyright FPTI CPU Central Power Unit Copyright Problem A ball valve is not a fail safe device no redundant safety Incorrect procedure Multiple machine lockout Here is an extremely hazardous hydraulic lockout technique The designers of this type of lockout believe total isolation is the safest solution Problem is if the seat of the ball valve on the pressure line leaks it will pressure up the system Without a drain the pressure will cause double acting single rod cylinders to extend unexpectedly 20 Here is an example of a Machine 3 Machine 2 Machine 1 OC ko t curren t enabled enabled enabled employed in hydraulic systems Typical isolation for a multiple pump parallel circuit operating two or more machines Correct procedure 0101 1010 21 10 Central Power Unit Copyright FPTI 21 Hydraulic systems present unique challenges with regard to insuring they are safe to work on Hydraulic systems have the inherent capability of storing energy when the pump is shut off A single hydraulic system can store multiple pockets or zones of stored energy Activ
10. nsuring that no personnel are exposed and as a check on having disconnected the energy sources the authorized employee operates the push button or other normal operating controls to make certain the equipment will not operate Return operating control s to NEUTRAL or OFF position after the test The equipment is now locked out Exhausting oil to atmosphere can cause severe injury death or substantial property damage Apparently its a well recognized problem John Deere 643G and 843G Feller Buncher Operation and Test Manual Safety Information section reference 9000 01 1 under the sub heading Avoid High Pressure Fluids Caterpillar PM 565 Cold Planer Service Manual Troubleshooting section Sauer Sundstrand Series 90 Axial Piston Pumps and Motors Service Manual Introduction section paragraph 1 2 Safety Precautions The problem is serious enough that NIOSH published an article in which they asked for assistance in preventing the death or injury of workers exposed to the unexpected or uncontrolled release of hazardous energy including hydraulic energy The problem is not easy to fix because hydraulics is apparently the ugly stepsister of an industry that no state federal or private safety organization seems to want to have anything to do with from the point of view of safety at least none of the following organizations e Occupational Health and Safety Administration OSHA
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