Inspection and Preventive Maintenance--Don't Forget the Nuts and Bolts
Hazard [Health Devices Mar 1998;27(3):116-7]
ECRI has received several reports of a wide variety of medical equipment
failures related to loose or missing fasteners (e.g., screws, bolts). In almost all these
instances, proper inspection and preventive maintenance (IPM) of the equipment could have
prevented the failures. Examples of these reports are as follows:
- Assembly hardware came loose on a number of bed frames:
— On several beds, the
shoulder bolts supporting the four corners were found to be very loose. On
two occasions, the bolts fell out, making the beds uneven and
unstable and presenting a hazard to both patients and staff.
— A shoulder screw on the
intermediate frame of a birthing bed from a different manufacturer came out
of place while a patient was being prepared for childbirth. This failure
caused the foot of the bed to drop and the head of the bed to rise
- An x-ray unit's collimator fell off the tube
because a screw from the collar that holds the collimator in place was
missing. No one was reported to have been hurt, but the failure could easily
have led to patient or staff injury.
- Set screws came loose in two aerosol treatment enclosure
units—devices that are used to isolate patients and protect bystanders
from contamination by infectious aerosols or toxic drugs during pulmonary
treatments (e.g., for patients infected with tuberculosis or HIV).
Reportedly, in each unit, a set screw designed to keep one of the blower
assembly pulleys in place came loose, allowing the center of the pulley to
grind against the blower shaft. As a result, metal shavings were created;
these shavings exited the rear of the unit and then were sucked back into
the front of the unit where the patient was receiving treatment.
As these examples illustrate, loose or missing fasteners on medical
equipment can present hazards to both patients and staff. Therefore, we remind readers
that it is important to check all fasteners on all medical devices during both incoming
inspections and routine preventive maintenance.
Each procedure in ECRI's Health Devices IPM System specifies that
the device's chassis/housing be checked; this is listed as the first qualitative test that
should be performed. As part of the procedure, we typically recommend that the person
performing the test ensure that all assembly hardware (e.g., screws, fasteners) is present
and tight. This can be done by jiggling the device and then moving any movable parts
through their normal range of motion. If any unexpected movements or noises occur, all
fasteners in the affected area should be checked and tightened or replaced as appropriate.
For some devices, threadlocking products (e.g., Loctite, Permalok) or lock
washers can be used to keep screws and bolts tight. However, it is important to verify
with the manufacturer (e.g., by checking the service manual) that a specific threadlocking
compound is appropriate for a given situation. Some threadlocking compounds are permanent,
while others can be broken if necessary. Also, some compounds cannot be used with plastic
components because they degrade the plastic.
To avoid the types of problems described in this report, we recommend that
all staff be instructed to report the presence of loose fasteners on medical equipment to
the clinical engineering department (or to other personnel responsible for maintaining the
equipment). We also encourage readers to continue reporting such problems to ECRI.
- Beds, Birthing [15-732]
- Beds, Electric [10-347]
- Collimators, Radiographic [16-389]
- Enclosures, Aerosol Treatment [18-048]
Cause of Device-Related Incident
Device factor: Improper maintenance, testing, repair, or lack or
failure of incoming inspection
Support system failure:
Error in hospital policy
Mechanism of Injury