Log in Article Discussion Edit History Go to the site toolbox

HTM ComDoc 2

From HTMcommunityDB.org

Important definitions


(This document was last revised on 9-7-18)


AEHF (average exposure to hidden failures)
...is the average fraction (or percentage) of the interval between Safety Verification (SV) tests during which the patient could be exposed to hidden failures. It is equal to 0.5 times the ratio of the SV testing interval to the Mean Time Between Failures (MTBF) of the device's hidden failure(s) and is a reasonable measure of patient safety with respect to those hidden failure(s). Smaller is better.
AEM (Alternate Equipment Management) Program
...is an option provided in the current CMS regulations whereby devices that do not meet the CMS definition of being "critical equipment" items can be maintained in a manner other than that recommended by the device manufacturer.
APM (automatic protection mechanism)
... is a mechanism that is designed to prevent or mitigate the consequence or consequences of either a hidden failure or an evident failure.
Availability (RCM term)
...is the complement of device downtime when expressed as a percentage. For example; a device that experienced 2% downtime during a certain period would be said to have experienced 98% availability during that same period.
Calibration
... is the periodic adjustment of components affecting the functional performance of the device so that it is functioning properly and meeting the device's original performance specifications.
Cause coding
...is the process of separating a device’s reported failures into a number of categories such as the three primary categories described in Section 1.3 of HTM ComDoc 1, titled What causes equipment systems to fail? It is particularly helpful to separate the total failure count into at least the three primary categories; process failures, inherent reliability-related failures, and maintenance-preventable failures.
Corrective maintenance or, as it is more commonly called, device repair
...is the restoration of the device to its original level of functional performance and safety after it has malfunctioned or sustained damage. Repairs may or may not include “cosmetic restoration” (which is the restoration, partial restoration, or replacement of any components of the device that do not have a direct effect on the functional performance or safety of the device). It should also include the correction of any hidden failures that may not have completely disabled the primary function(s) of the device.
Cosmetic restoration
... is the restoration, partial restoration, or replacement of those components of the device that do not have a direct effect on the functional performance or safety of the device. While cosmetic repairs are generally considered to be a lower priority because the device is still functioning within the manufacturer’s functional specifications, it may be damaged in such a way that it is hazardous. For example, a damaged cover may be presenting a sharp edge that could be hazardous to either the patient or to a user.
Condition monitoring
...is the use of some kind of non-destructive technique (physical, chemical or some other) to determine how close a device or a part of a device is to failing. Among the techniques sometimes used are vibration analysis, eddy current analysis, ultrasonic analysis, and infrared imaging. Other methods include detecting pressure changes (e.g. pressure differences across a filter); temperature effects (e.g. from the frictional heating associated with a mechanically worn bearing); or chemical effects (e.g. the presence of trace quantities of metal in lubricants). Condition monitoring techniques are used to track changes in the performance of equipment and components over time to identify an “early warning” point, well before the point at which the component reaches the wear out zone of its life cycle. While use of the unaided human senses are is not considered to be a very sensitive or reliable technique for predicting failures in this way, the use of visual inspections is quite common in the context of medical equipment maintenance.
Critical equipment
...is the term used by the CMS to describe "biomedical equipment for which there is a risk of serious injury or death to a patient or staff person should the equipment fail.

Note: However, there is a practical problem with using this term because, to the best of our knowledge, there is still no real consensus on which types of devices the CMS intends to be considered as "critical equipment". This is also the case for the similar term used by The Joint Commission (TJC) - which is “high-risk medical equipment”. The only examples of “critical equipment” provided in the CMS regulation are ventilators, defibrillators, and robotic surgery devices.

Understanding what equipment CMS intends to cover when they use this term is important because the intent in the "clarification memo" is to disqualify such items from immediate inclusion in an AEM Program (unless the facility can provide specific justification for including them). The regulation requires the facility to conduct a formal risk analysis to identify (and label as “critical equipment”) those devices whose failure could result in such a serious risk. The CMS surveyors are also instructed in the same memo to pay particular attention to any items that the facility has labeled “critical equipment” but that are being maintained other than as recommended by the manufacturer. This implies that when such items are found the facility will be asked to explain why this has not reduced the overall level of patient safety.

In an attempt to make a best guess at what CMS intends, the Maintenance Practices Task Force (MPTF) considered the following:

There are many different causes for medical equipment failures but they can be grouped into three general categories (see Section 1.8 of HTM ComDoc 1):

  • Failures attributable to the device’s inherent reliability, including the random failure of its components, as well as poor design or poor construction of the device itself
  • Process-related failures, attributable to causes such as use errors, physical damage, environmental stress, accessory problems, tampering, and connected network issues
  • Maintenance-related failures, attributable to causes such as non-durable parts that were inadequately restored during the device's last PM or hidden failures that have occurred since the device's last PM, as well failures resulting from intrusive maintenance, and those resulting from poor initial set-up of the device itself

And there are only four ways in which such failures can become hazardous.

  1. When a device on which a patient’s continued well-being is completely dependent (such as a critical care ventilator) fails unexpectedly.
  2. When a device on which a patient’s continued well-being is dependent develops a failure that reduces its performance or safety to an unacceptable level, and the failure is not likely to be obvious to the device user (often called a “hidden” failure)
  3. When the device is used improperly.
  4. When the device is damaged in such a way that it presents some kind of direct physical threat to the safety of patients or staff. For example, if the damage leaves an exposed sharp edge.

However, the CMS "clarification memo" is focused exclusively on equipment planned maintenance (PM) and, of these four ways of becoming hazardous, only two subsets of the four are PM-preventable:

  • Unexpected failures that are caused by the premature deterioration of a critical part that is usually restored during a periodic PM
  • “Hidden” failures that reduce the device’s performance or safety below a critical level, and which would be detected by performance and/or safety verification testing recommended by the manufacturer to be performed during periodic PMs.

Keep in mind also that not all of these failures will necessarily result in outcomes that could result in serious injury or death. See entry for Level of Severity (LOS) below.

Since the objective of the AEM Program option is to allow the facility to use more efficient maintenance practices than are otherwise mandated (following the manufacturer’s PM recommendations for every single piece of medical equipment) - provided that this will not increase the risk to patients or the attending staff, a logical place to start would be to determine which devices could result in some kind of serious, life-threatening outcome if they should fail - from any cause, not just a PM-preventable cause. But this interpretation could be overly inclusive and there is considerable uncertainty about the extent to which CMS intended items that:

(a) demonstrate a relatively high level of inherent unreliability (devices that could be called reliability-critical?), or that
(b) are relatively easy to use improperly in a way that makes them hazardous (devices that could be called human factors-critical?), or that
(c) are unusually vulnerable to becoming damaged in a way that could be dangerous (devices that could be called fragility-critical?),

... be classified as “critical equipment” - and thus excluded from possible inclusion in an AEM program.

The Task Force has taken the position that this ambiguity in the definition was not intended by CMS and such items should therefore not be considered to be “critical equipment”. To make this interpretation absolutely clear the Task Force has chosen to use a more specific term than "critical equipment", such as PM-critical device" or potentially high PM risk device" to label devices with critical, life-threatening ways of failing (failure modes) that can be prevented by competent and timely planned maintenance. See "A rational, evidence-based approach to designing a safe and effective equipment maintenance program. Part 1: A very simple, basic AEM program" (HTM ComRef 35.) for more on the Task Force's PM-focused risk analysis. The tentative result of this analysis (documented in Part 1 of the paper - HTM ComRef 35.) is that there are only 20 specific device types should be considered potentially high PM risk devices.


Critical failure mode
...is a way in which the device could theoretically fail, and which has the potential to create some kind of adverse patient outcome with potentially the highest level of severity.
Critical PM-preventable failure mode
...is a way in which the device could theoretically fail if it is not subjected to appropriate periodic PM, and which has the potential to create some kind of adverse patient outcome with potentially the highest level of severity.
Damaged
...is the descriptor for a device that has incurred some kind of physical harm that has impaired the device’s function, integrity or value. It is a term applied to a piece of equipment that may be completely functional but in need of cosmetic repair/ restoration. A damaged device may, or may not present a hazard. For example, a broken part of the device’s case could be sharp enough to cause an injury to either the patient or a member of the facility’s staff. Note that a device can be both damaged and in a failed state.
Device restoration
... is the periodic restoration or replacement of any non-durable (consumable) components of the device that have a direct effect on the functional performance or safety of the device but are not intended to last for the anticipated useful lifetime of the device.
Device restoration-critical
... is a descriptor for a device that has a component that the manufacturer has stated needs to be periodically restored in some way to proper working order, and which has the potential to cause harm when it stops working completely while it is in use.
Device restoration-related failure mode
... is a device failure that is attributable to inadequate restoration of the device's non-durable parts.
Device unavailability
...is the RCM term corresponding to average exposure to hidden failures {AEHF}
DR-related failure mode
... See Device restoration-related failure mode.
Downtime
... is a measure of the time that a piece of equipment is completely unusable or in an only partially unusable condition. The most logical measure of equipment downtime is the total time that elapses from the moment the equipment is considered to be in need of attention, to the time that it is available to be put back into clinical service. However, in the practical world, if the device is covered under a business contract, this logical definition is modified to take account of only the business hours (time periods when the device is required to be available for use) for which the device is covered by the maintenance contract. In some situations this could be around the clock, seven days a week, but is more likely to be 8 am to 5 pm, Monday through Friday.
It is also customary for contracts to include a provision to reduce the calculated downtime if the equipment is only partially disabled and can still be used for some patient procedures. The designated “percentage down” factors may be 100% (hard down) and 50% (partially down), or some other agreed-to values. In such situations the percentage downtime calculation will have as its numerator the aggregate number of covered hours that the device was out of service for a certain time period, such as three months, as reduced by the agreed "percentage down" factor; and the denominator will be the total number of covered hours during that same time period. This fraction is conventionally expressed as a percentage.
Economic risk
... is something that puts a business or organization at risk of incurring an additional expense or a reduction in revenues.
Equipment availability
...see Availability
Evident failure
... is a device failure that is obvious to the device user. Also called an overt failure or a total failure.
Experience base
... is a measure (usually expressed in device-years) of the cumulative amount of time that the device or devices being observed were examined in order to develop some parameter such as the number of times that a device failed in a certain way. It is equal to the product of the number of devices observed multiplied by the cumulative length of time that the devices were under observation.
Failure effect
... is what happens when a failure mode occurs (RCM term).
Failure mode
... is a single event that causes a functional failure (RCM term).
Failure modes and effects analysis
... see Failure mode and effects analysis
Fennigkoh-Smith method
... The original method for prioritizing the different types of medical devices according to which would benefit most from periodic PM was described in a publication by Larry Fennigkoh and Brigid Smith who were then at St Luke’s Medical Center in Milwaukee (HTM ComRef 6). The Fennigkoh-Smith method used a simple prioritization metric that the authors called the EM (equipment management) number, which is derived by quantifying and compounding together four other descriptors (equipment function, clinical application, maintenance requirements and equipment incident history). The EM number is then used as an indicator for which types of device would benefit from some kind of planned maintenance. Items with a higher EM number were considered to benefit more than those with lower numbers and device types with an EM number above a certain value were required to be included in a documented "equipment management program" where they were subjected to certain control measures such as being maintained according to manufacturer's recommendations.
Fixed interval preventive maintenance
... is the term that has traditionally been used to describe the restoration of a device's non-durable parts at a fixed interval that usually shorter than the useful life of the part or parts.
FMEA or failure mode and effects analysis 
... is a systematic step-by-step method for identifying system vulnerabilities i.e. ways in which things could go wrong in any kind of process, and prioritizing those vulnerabilities with respect to the likelihood that those things will happen, and the seriousness of the consequences of those process failures. It is the core methodology on which the RCM or Reliability-centered Maintenance approach is based.
An FMEA analysis invariably identifies a number of possible causes of system failure that cannot be addressed by strategies that we conventionally think of as maintenance. It is for this reason that most texts suggest that the team performing FMEAs on equipment systems should be made up of representatives from multiple disciplines, not just equipment specialists.
Hazardous
... means unsafe; a condition that puts someone or something at non-neglible risk of injury or some other form of adverse consequence.
Hidden failure (RCM term)
... is a failure mode that will not be evident (obvious) to the user under normal circumstances if it occurs on its own. (It is an RCM term). Usually, only total failures of the equipment are obvious (evident) to the user.
Hidden failures are more likely to occur in the more complex devices, such as patient monitoring systems with multiple electronic modules, where one module failing may degrade the overall performance of the device in a way that is perhaps unlikely to be noticed by the user. For example, a heart rate alarm that has malfunctioned so that it does not go off at the set limit will be a hidden failure because the failure will not be evident until the alarm function is checked. Depending on the nature and extent of the consequences, hidden failures may or may not be important. For example, a hidden failure that has a significant effect on the output of a therapeutic device, such as a defibrillator or an electrosurgical unit, could have a serious patient safety consequence. On the other hand, a hidden failure that affects the output of a device such as a patient warming blanket that has a much lower potential to harm the patient, may not be subject to a periodic performance check and may well go unnoticed for some time.
Hidden failure-critical device (RCM term)
... is a device or type of device that has a significant probability of developing a defect that either reduces the performance of the device to much less than the manufacturer's specification calls for, or reduces the safety of the device to much less than the manufacturer's specification calls for, and does so in a way that will not be obvious to the user(s).
High-risk medical device
... see High-risk medical equipment (below)
High-risk medical equipment
... is the descriptor used by The Joint Commission for a type of device "for which there is a risk of serious injury or death to a patient or staff member should the equipment fail". They also note that ... "High-risk medical equipment includes life-support equipment.
  • See Note under "Critical equipment" (above)
Installation
... is the setting of a device, or a hardware or software component of a device, into its proper position and making it ready for use according to the manufacturer’s specifications
IRF or inherent reliability-related failure 
... a device failure that can be attributed to; a random failure of one of the device’s components, poor fabrication or assembly of the device itself, or poor design of the device’s hardware or of the processes required to operate the device
Inherent failure rate
... is determined by the frequency with which a device fails because of random failures attributable to the poor quality of one of the device's components, poor fabrication or assembly of the device itself, or poor design of the device’s hardware.
Inherent reliability
... is that part of a device's overall reliability that is attributable to random failures resulting from the poor quality of one of the device's components, poor fabrication or assembly of the device itself, or poor design of the device’s hardware.
Inherently safe
... is a term used to describe a device that has no known critical (hazardous) failure modes.
Inspections
... is the term used by ECRI Institute and others for what the Task Force prefers to call safety verification tasks.
Interval exploration
... is a technique that involves comparing the relative effectiveness of planned maintenance performed at different intervals by using some kind of PM effectiveness metric.
"Just-in-time"
... in the RCM context this phrase refers to the use of some kind of wear detector to signal the need to restore the wearing component before it wears to the point that the device would fail. It is a key part of the concept known as "predictive maintenance".
Level of Severity (LOS)
... is the projected severity of the adverse outcome of a device failure. It is defined at three levels. LOS 3 represents a potentially life-threatening situation; LOS 2 represents the possibility of a non life-threatening patient injury; and LOS 1 represents a possible disruption of patient care such as a significant delay in obtaining diagnostic information, a significant delay in treating the patient, or increasing the patient's length of stay in some other way.
Life support device
... is a device that has the potential to cause a serious, life-threatening injury to the patient, or others, if it suddenly stops working while it is in use.
  • Return to [[Main Page]
Light maintenance
... is a maintenance strategy in which no planned maintenance is performed and the device is allowed to run until it fails. Also known as Run-To-Failure or RTF.
Low risk
... is a term used to describe both inherently safe devices and devices with critical (hazardous) failure modes but high reliability (with respect to life-support-critical devices) or with a very low failure rate (with respect to hidden failure-critical devices).
Maintenance
... is the process used to keep equipment in good condition, in proper working order and completely safe to use. The RCM definition for this is “keeping the equipment available for use”. Traditionally maintenance consists of three basic components; corrective maintenance, cosmetic repair, and preventive maintenance. It is the "maintenance" part of the ubiquitous phrase "maintenance and repair". In the context of medical equipment maintenance the third component, preventive maintenance, is replaced with the term "planned maintenance".
MPF or maintenance-preventable failure
... is a device failure that can be prevented by some kind of maintenance activity. Maintenance-preventable failures include failures resulting from; progressive wear or deterioration of one of the device’s non-durable parts, a poor quality repair, failures resulting from disturbing the device during intrusive maintenance, and poor or incomplete initial installation of the device.
Maintenance procedure
... is a description of a particular method of performing maintenance on something. In the context of medical device maintenance it frequently consists of a collection of specific maintenance tasks, and sometimes a specification of when and how often the tasks should be performed.
Maintenance-related failure
... is a device failure that can be attributed to; progressive wear or deterioration of one of the device’s non-durable parts, a poor quality repair, earlier intrusive maintenance, and poor or incomplete initial installation of the device. MRFs are sometimes called maintenance-preventable failures because they can usually be prevented by some kind of maintenance activity addressing these causes, just listed above, being incorporated into the facility’s maintenance program.
Maintenance strategy
... is a plan to use certain maintenance procedures, methods or techniques, such as time interval PMs, or light maintenance (run-to-failure). One of the remedial options in the classical FMEA analysis used in the RCM approach is to redesign the equipment system and, somewhat confusingly, some RCM texts characterize this system redesign option as a “maintenance strategy”. However, this appears to be just a semantic peculiarity since this option should, more logically, be classified as a failure management strategy.
MTBF or mean time between failures 
... is the inverse of the device’s failure rate. For example; a device that failed twice in nine years has an MTBF of 4.5 years. Can also be expressed as the number of device-years of of device experience divided by the number of device failures occurring during the period represented by the device experience. The greater the number of devices in the sample and the longer the period of the observations, the closer the estimated reliability will be to the device's true reliability.
Mission-critical
... a descriptor for a device that is capable of harming the organization’s reputation for competency if it demonstrates poor reliability.
Non-critical device
... is a type of device that is theoretically incapable of causing any kind of patient injury or any other form of harm if it fails.
Non-durable part (NDP)
... is a part that either the device manufacturer or common industry knowledge identifies as not intended to, or not capable of continuing to perform properly for the anticipated working lifetime of the device without some kind of attention. Such parts are sometimes described as "consumables". Examples include batteries, filters, cables, bearings, gaskets, drive belts and flexible tubing.
On-condition task (RCM term)
... A scheduled task used to provide an indication of whether or not a potential failure has actually occurred or is about to occur.
Operating crew (RCM term)
... is a term applied to anyone who has occasion to observe the equipment, or what the equipment is doing, at any time during the course of their normal daily activities, and who can be reasonably relied upon to report that it has failed. In the case of medical devices the operating crew would normally be the clinician or clinical technologist using the equipment.
Overt failure
... see evident failure
Performance verification
... is the periodic testing conducted to verify that the device is still functioning properly and meeting the device's original performance specifications.
Periodic safety verification
... is a maintenance method or strategy that uses one or more safety verification (SV) tasks performed periodically to determine whether or not the the device is still meeting all of its critical performance and/or safety specifications or whether it has developed one or more imperceptible ("hidden") failures.
Physical risk
... is something that puts someone or something at risk of injury or physical harm.
Planned maintenance
... consists of one or both of two basic maintenance activities: device restoration and safety verification.
PM
... see planned maintenance
PM-critical device
... is a device that is either device-restoration-critical or safety testing-critical, or both.
PM-preventable failure
... is a device failure that could have been prevented by the competent and timely execution of a maintenance procedure that would have restored the device to proper working order.
PM Priority 1 device
... is a device that could create a risk of serious injury or death to a patient or staff person should it fail, from a PM-preventable cause.
PM-related failure
... a PM-related failure is
PM-related reliability
... a device's PM-related reliability is the lesser of (the one representing the lower level of reliability) of the following two MTBFs:
  • The MTBF based on the total of 1) any overt MR1 failures caused by inadequate device restoration (from the repair cause coding) and 2) any PM Code 9 findings (which are immediate precursors of the overt MR1 failures caused by inadequate restoration).
  • The MTBF based on the total of any hidden performance and safety degradations detected by the safety verification tasks (PM Code F findings)
PM-related risk
... is a measure of the extent to which a patient or device user is exposed to possible injury if the device with which they are being treated is not provided with adequate periodic restoration.
Potentially high PM risk device 
... is a device that is either potentially device-restoration-critical or potentially safety testing-critical, or both.
Potentially PM-critical device or, more simply, potentially-critical device
... is a device that is either potentially device-restoration-critical or potentially safety testing-critical, or both.
Potentially PM Priority 1 device
... is a device that potentially presents the highest level of potential risk of injuring a patient if it is not given the highest priority for attention and timely PM. If the device exhibits a PM-related reliability of more than one failure every 75 years (for devices with a failure severity of LOS 3), the it becomes a PM Priority 1 device.
Predictive maintenance (RCM term)
... is a term used for tasks that restore, refurbish or replace a device’s non-durable part at a time that is determined by some kind of condition monitoring.
Preventive maintenance 
... in the term that has traditionally been used to describe the periodic restoration of a device's non-durable parts.
Process-related failure
...is a device failure that can be attributed to: incorrect set-up or operation of the device by the user; subjecting the device to physical stress outside of its design tolerances; exposing the device to environmental stress outside of its design tolerances; using a wrong or defective accessory; or human interference with the device.
RCM
... see Reliability-centered Maintenance (below).
Recondition
... to make something like-new again. Most often used for making entire devices (rather than non-durable parts) like-new again.
Rejuvenation
... to make a non-durable part like-new again. Sometimes used as an alternative to the blanket term "restoration"
Restoration
... is often used as a blanket term covering cleaning, making like-new again (reconditioning or rejuvenating) or replacing a device's non-durable parts.
Reliability-centered Maintenance (RCM)
... is a maintenance approach or philosophy that resulted from work started in the 1960s in the civil aviation industry which brought into question the effectiveness and value of the traditional approach to machine maintenance that was at the time heavily biased towards regularly scheduled “preventive maintenance". Without the economies achieved by adopting RCM it would have been economically impossible to introduce the jumbo jet into commercial aviation. Remarkably, the analysis of failure data collected by all of the major airlines, but particularly by United Airlines, made it possible to not only achieve very significant economies by utilizing less of the intrusive and manpower-intensive traditional PM but this change also produced a totally unexpected bonus in that it also dramatically increased aircraft reliability. Since its discovery and subsequent development in the latter part of the last century RCM has been widely adopted by NASA, the US military and virtually every other high reliability industry – except healthcare.
The RCM approach uses the term "preventive maintenance" to encompass what it calls “scheduled restoration tasks” in which the vulnerable part is restored or refurbished rather than being totally replaced, and “scheduled discard tasks” in which the vulnerable part is totally replaced. However, RCM also introduces a third element to the PM component that it calls predictive maintenance. In predictive maintenance the deteriorating part is replaced or restored at a time that is determined by directly monitoring the condition of the part, utilizing what RCM calls an “on-condition task”. In this case the deteriorating part is replaced or refurbished on a “just in time” basis, i.e. at a time that is determined by directly monitoring the actual condition of the part in order to detect the impending failure at the beginning of the wear-out phase of its life cycle, before it reaches a level that would result in total failure of the component.
Repair, also known as corrective maintenance
... is the restoration of the device to its original level of functional performance and safety after it has malfunctioned or sustained damage. Repairs may or may not include “cosmetic restoration” (which is the restoration, partial restoration, or replacement of any components of the device that do not have a direct effect on the functional performance or safety of the device).
Risk
... See economic risk and physical risk
Run-to-failure maintenance (or RTF)
... is a maintenance management strategy that permits a specific failure mode to occur without making any attempt to prevent it. Also called "light maintenance".
Safe
... means free from danger. Not hazardous.
Safety verification
... is the second constituent element of the planned maintenance component. This second element consists of tasks that are conducted periodically to verify that the device is still functioning properly and safely and meeting the device manufacturer’s original performance and safety specifications. In the RCM approach these safety-related failures are called hidden failures. These actions are preventive in the sense that, if done in time, detecting and repairing these hidden failures will prevent a possible patient injury. This second element has been given the name “inspections” by ECRI Institute and others but the Task Force considers this term to be less confusing.
Safety verification-critical
... is a descriptor for a device that has a (hidden) failure that can be revealed by testing the functional performance or safety of the device (using tests specified by the device manufacturer) and that has the potential to cause harm if not corrected before the device is put to use.
Safety verification failure mode or SV-related failure mode is a failure mode that can be attributed to a hidden performance or safety deterioration that was not discovered and repaired during the device's last PM.
Scheduled maintenance
... A term that has been proposed as an alternate to the term “preventive maintenance” but this characterization is not such a good fit because it implies that the rejuvenation action is always performed according to some kind of clock; either by conventional timing (e.g. every 6 or 12 months) or by a time-of-use clock (e.g. every 1000 hours of use). However, there is a more modern practice in which the deteriorating part is restored on a more efficient "just-in-time" basis by measuring or monitoring the actual condition of the part. In some cases the monitoring is performed by some kind of sensor but more commonly in the medical equipment sector it is simply done by conducting periodic visual inspections. In the RCM approach this just-in-time rejuvenation technique is called predictive maintenance.
Scheduled discard task (RCM term)
... is a task that entails discarding and replacing a non-durable part at or before a specified age limit, regardless of its condition at the time.
Scheduled restoration task (RCM term)
... is a task that restores the initial capability of a non-durable part at or before a specified age limit, regardless of its condition at the time.
System failure
In RCM terminology an equipment system is considered to have failed when it no longer performs the function or functions that the user wants it to perform, or it performs as specified – but in an unsafe manner. The system failure may be a total failure (i.e. one in which the system no longer delivers the primary output or function that the user wants, and is expecting) or it may be a hidden failure (i.e. one in which the system delivers an output or function that is significantly out of specification but similar enough to the output the user wants that the failure is not immediately obvious to the user}. When this more subtle type of failure introduces a significant performance or safety degradation that is not obvious to the “operating crew” until it is revealed by some kind of performance verification or safety test, it can constitute a serious safety threat.
Total failure
...is a term that is used when a device completely fails to perform its primary function.
TPM or traditional preventive maintenance
... consists of periodic rejuvenation (refurbishment or replacement) tasks that restore to like-new condition any parts of the device that are subject to wear or some other kind of deterioration during the time frame that the manufacturer considers to be the normal working lifetime of the complete device.
Components of the device that fall into this category can be identified by virtue of being identified in a manufacturer-specified PM procedure as needing either periodic replacement, or some other kind of periodic attention, on either a time-based or use-based schedule.
These components are also referred to as non-durable parts (NDPs) or "consumables". Examples include batteries, filters, cables, bearings, gaskets, drive belts and flexible tubing. These actions constituting TPM are preventive in the sense that they prevent the device from failing prematurely because of the substandard performance of the deteriorating part.
TWA or time weighted average
... is
Updating
– is the completion of any changes recommended or required by the device manufacturer since the device, or hardware or software components of the device, was originally sold.
Uptime
... is the complement of downtime. Uptime is equal to the time that the equipment is required to be available for use (i.e. normal staffed hours) minus the equipment’s calculated downtime.
As we have already noted, it is customary, when a certain level of uptime is guaranteed as a part of a contractual arrangement, for only the hours that are covered under the contract – say, Monday-Friday 8 am to 5 pm – to be considered as the time that the facility needs the equipment to be available for use. Equipment uptime is clearly greatest when:
(a) the equipment failure rate is as low as possible, and
(b) the average time to restore the failed equipment to proper working order is as short as possible.


  • Back to Main Page, HTM ComDoc 1 "PM Basics, key concepts and terminology", or on to HTM ComDoc 3 "Risk assessment: Determining which medical devices can be made safer (but only a little safer) by PM", (old page archived at HTM ComDoc 2.)

Site Toolbox:

Personal tools
This page was last modified 18:59, 10 December 2018. - This page has been accessed 176 times. - Disclaimers - About HTMcommunityDB.org