PR S 40004 Flashcards
Failures
what are the two types of maintenance failures and give a brief description
Functional failure- the failure of an item to perform it’s normal/characteristic function within specified limits.
Conditional failure- the failure of an item to meet desirable quantifiable performance criteria.
what needs to be reported when replacing items such as vital signalling relays, track transmitters or receivers.
The unique serial number of the part being replaced and the replacement part.
What needs to happen if the cause of a failure is unidentifiable or the piece of equipment that has failed has now come good
The equipment failure analysis must follow a No cause found failure form and must provide all relevant information required by the form for the specific equipment.
PR S 40004 FM01
what are the 5 failure catagories
no cause found,
vandalism
seldom used
working personnel
component defects
What two network rules/procedures followed during the process of investigation
NWT312 and NPR 704 using IBA
Who needs to be advised once a failure is rectified
the signaller and ICON
What is a crucial piece of telemetry and how is it verified and by who
A signalling log. It is verified against real time by creating an event and then compared by the signal engineer when investigating an irregularity.
What is an Irregularity
The failure of vital signalling equipment that is contrary to system design, is not fail safe and which in combination with other failures or circumstances can cause a less restrictive/unsafe condition.
what are the two types of signalling irregularities and what is the difference
Wrong side and not wrong side failures. The difference is the protection afforded by the system or whether there are elements of a safe condition.
what are 3 examples of common failures not considered irregularities
signal lamp or led failure
a trainstop in the lowered position due to a mechanical failure
level crossing having some lights out or one failed bell or siren,
Is it considered an irregularity if a DPU picks up under the presence of a train
No as it will not provide early release of the conditions.
however it must be treated as an irregularity if longer than 7 seconds.
examples of wrong side failures
the unsafe release of points when they should be locked,
detection made with the switch open
a higher aspect of a signal is displayed incorrectly
a trainstop falsely indicates a normal position
if rail vehicle detection fails to detect the presence of a train
level crossing fails to activate for an approaching train
incorrect release of mechanical interlocking
ETCS fails to provide appropriate train brake intervention
ASDO releases doors off a platform
examples of not wrong side failures
signal displays incorrect combination of lights, clearly seen as an invalid aspect,
failure of a trainstop which is proved in the track stick circuit,
level crossing booms/gates are proved in the XNR circuit and when not detetcted in the normal position keeping protecting signals at stop for approaching trains.
Relay falsely energised but is required to be proved in the de-energised state.
when does the signal engineer need to be involved in the investigation
Deemed an Irregularity
when the evidence cannot support a right side failure analysis
when no cause is found
what do you do for equipment suspected of causing an irregularity
book out on paper on and book out and disconnect immediate signals in the rear
can you make the signalling system operable before the investigation is complete
no only a signal engineer con fulfill such a request
Is a witness required for simple case irregularities
no.
What is a simple case irregularity and give an example
when the cause is obvious to the licensed signalling personnel conducting the investigation and does not required the signalling engineer to attend site.
a signal which displays an irregular combination of lights, which is discovered to have the back of the lamp case open and light shining through illuminates all the lenses.
can a signal electrician certify a simple case irregularity
no, only the signal engineer can make the judgement to certify the simple case irregularity
responsibilities of signal electrician during investigation
arrange protection of the site and suspected signalling equipment
assist with the investigation and act upon instructions from the investigating signal engineer
events and conditions can be noted by the signal electrician prior to the arrive of the engineer.
be careful not to destroy any evidence or disturbing any equipment
advise the engineer of all investigations carried out
what is a right side failure
a failure which is failsafe.
protection of failed points
protecting signals to be booked out of use unless permitted by the signaller of release and use of the ESML/EOL facilites.
however if locking is ineffective, protecting signals are required to be booked out and points to be clipped and SL locked.
when can signals be left operation on failed points
not disarranged or disconnected
locking is still effective
detection is still in working order
point switches in correct position
panel indication is correct
protection of broken rail
protecting signal and trackcircuit to be booked out of use and disconnected.
handsignaller and civil rep to be arranged
once the rail is certified fit for traffic by civil, a temporary bond can be placed around the brake and signals booked into use.
