OSHA Hazard Information Bulletins
March 23, 1993
| MEMORANDUM FOR: |
REGIONAL ADMINISTRATORS |
| THROUGH: |
LEO CAREY
Director
Office of Field Programs |
| FROM: |
PATRICIA K. CLARK
Director
Directorate of Technical Support |
| SUBJECT: |
Hazard Information Bulletin - Misuse and Improper
Maintenance of Double Acting Hydraulic Cylinders |
The Directorate of Technical Support issues Hazard Information Bulletins
(HIBs) in accordance with OSHA Instruction CPL 2.65 to provide relevant
information regarding unrecognized or misunderstood health hazards,
inadequacies of materials, devices, techniques, and safety engineering
controls. HIBs are initiated based on information provided by the field
staff, studies, reports and concerns expressed by safety and health
professionals, employers, and the public. Information is compiled based on a
thorough evaluation of available facts, literature and in coordination with
appropriate parties.
The Eau Claire District Office investigated a fatality involving a double
acting hydraulic cylinder which was improperly set up for use.
The double acting cylinder involved in the incident was a hydraulic jack
that extended or retracted using hydraulic pressure and was used to squeeze
materials into proper position for welding. Such cylinders require that two
hydraulic hoses be connected, one below and one above the piston in the
cylinder. It is a routine matter to connect and disconnect the hoses using
quick disconnect couplings. The cylinder manufacturer's literature clearly
warns against attaching only one of the two hoses to a double acting
hydraulic cylinder. The construction, inspection, testing, maintenance, and
operation of these cylinders should comply with the American National
Standards Institute (ANSI) Safety Standards for Jacks, ANSI B30.1.
Investigation of the incident revealed that only one of the two hydraulic
hoses was properly attached between the hydraulic pump and the cylinder. When
pressure was applied to the cylinder by a hydraulic pump, the shutoff ball of
the top quick disconnect coupling attached to the cylinder was forcefully
expelled and fatally injured a worker.
The hydraulic cylinder was equipped with a pressure relief valve in the ram.
Accordingly to the manufacturer of the cylinder, the relief valve was set at
approximately 12,000 psi (82,700 kPa). The relief valve, if it was properly
functioning, should have prevented damage to the ram when the top hose was
inadvertently left disconnected or improperly connected. However, the relief
valve did not open at 12,000 psi (82,700 kPa).
Following the incident, the manufacturer of the cylinder tested identical
couplings to failure. The shutoff balls were found to fail at pressures over
27,000 psi (186,000 kPa). In view of its test report, the manufacturer
believed that the relief valve of the cylinder involved in the incident had
been improperly tampered with, and therefore did not function at the preset
pressure.
Based on the information available, it appears that the accident occurred
because the top hose was not properly connected as required by the
manufacturer. Additionally, the relief valve may have been inappropriately
adjusted and did not function at the preset pressure.
Compliance and consultation personnel should be aware that improper
maintenance, replacement or adjustment of relief valves on double acting
cylinders could create the potential for overpressurizing the cylinder system
which could result in equipment failure and harm to employees. ANSI B30.1 and
the manufacturer's literature should be used to determine compliance with the
proper procedure for maintenance and use of double acting hydraulic
cylinders.
Please distribute this bulletin to all Area Offices, State Plan States,
Consultation Projects and appropriate local labor and industry associations.
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