Tripcock Testers

[DWS]

What are the locations of Tripcock Testers on the Bakerloo Line ?

[Dstock7080]

Baker Street - both
Queens Park - approaching DOWN platform 4
Harrow & Wealdstone - UP platform

[Tom]

Previously also at Kilburn Park both as a temporary measure in 2009. There was a plan in 2005/6 to install additional permanent testers at Kilburn Park and Charing Cross on both roads, probably eliminating the Baker Street ones as they're on a curve and were a reliability concern.

[chepstow]

I always assumed that a tripcock tester gave you some assurance that the tripcock was going to do its job. After an incident in the early 90s (I can't remember exactly when) we had an incident during a signal failure when trains had to trip past signals at danger, but on one train the Westinghouse didn't apply. It turned out the tripcock hose had been fitted twisted, so regardless of the trip arm the Train Line pressure was never lost. The driver's defence was that the previous Tripcock Tester had cleared - which was true - but the problem was that a Tripcock Tester is misnamed, it is only a trip arm detector. It does not prove the tripcock operation. You could weld a piece of angle iron onto a train to pass a TT. The only defence against such an error is for Fleet staff to actually do their tripcock test and bash the trip arm with a paddle on prep. But they didn't in this case. Or indeed on the 12 previous days on which they allegedly performed prep since the tripcock was changed. For context, I was in the Fleet organisation and we banged some heads.

[Dstock7080]

I remember being a Guard on a relatively new westbound D Stock, the Driver called to say we’d need to “Apply the Rule” at two defective home signals at St. James’s Park. While staying on the cab-to-cab we went past the first signal and didn’t get tripped; the driver thought it must’ve cleared as the train went over.
Getting ready for the second signal we thought it very odd that the train wasn’t tripped again!

Detrained and ran empty, with me in the front cab.
Picked up the Area Manager at South Kensington.
Tripcock tester at Earl’s Court pfm.3 passed!

Trying to think how to test the tripcock, the Area Manager gave authority to enter Ravenscourt Park station at speed as the automatic starting signal had a timing relay for non-stopping trains (station was closed on Sunday).
All three of us were amazed when the red signal zoomed past without the train being tripped!
An incorrectly fitted air valve was the cause and required a fleet wide inspection. (D Stock had pressure-switch tripcocks).

[blootop]

Mar 20, 2023 23:07:01 GMT chepstow said:

I always assumed that a tripcock tester gave you some assurance that the tripcock was going to do its job. After an incident in the early 90s (I can't remember exactly when) we had an incident during a signal failure when trains had to trip past signals at danger, but on one train the Westinghouse didn't apply. It turned out the tripcock hose had been fitted twisted, so regardless of the trip arm the Train Line pressure was never lost. The driver's defence was that the previous Tripcock Tester had cleared - which was true - but the problem was that a Tripcock Tester is misnamed, it is only a trip arm detector. It does not prove the tripcock operation. You could weld a piece of angle iron onto a train to pass a TT. The only defence against such an error is for Fleet staff to actually do their tripcock test and bash the trip arm with a paddle on prep. But they didn't in this case. Or indeed on the 12 previous days on which they allegedly performed prep since the tripcock was changed. For context, I was in the Fleet organisation and we banged some heads.

It’s not the only misnomer. The “brake test” doesn’t test the brakes at all. As long as the Trainline air pipe proves to be continuous, you could have no brake shoes fitted and you’d still pass the brake test.

[towerman]

Mar 21, 2023 7:14:19 GMT Dstock7080 said:

I remember being a Guard on a relatively new westbound D Stock, the Driver called to say we’d need to “Apply the Rule” at two defective home signals at St. James’s Park. While staying on the cab-to-cab we went past the first signal and didn’t get tripped; the driver thought it must’ve cleared as the train went over.
Getting ready for the second signal we thought it very odd that the train wasn’t tripped again!

Detrained and ran empty, with me in the front cab.
Picked up the Area Manager at South Kensington.
Tripcock tester at Earl’s Court pfm.3 passed!

Trying to think how to test the tripcock, the Area Manager gave authority to enter Ravenscourt Park station at speed as the automatic starting signal had a timing relay for non-stopping trains (station was closed on Sunday).
All three of us were amazed when the red signal zoomed past without the train being tripped!
An incorrectly fitted air valve was the cause and required a fleet wide inspection. (D Stock had pressure-switch tripcocks).

Had the same thing happen on the Central back in the day,train failed to trip applying the rule,the chamber at the top of the tripcock had worked loose.Chap that signed it off as tested demoted to cleaner for two years.

[jimbo]

Aug 29, 2023 15:21:55 GMT blootop said:

Mar 20, 2023 23:07:01 GMT chepstow said:

It’s not the only misnomer. The “brake test” doesn’t test the brakes at all. As long as the Trainline air pipe proves to be continuous, you could have no brake shoes fitted and you’d still pass the brake test.

I think that once happened to a train coming into service from Ealing Depot at Acton Town! A long time back!

[towerman]

In the early days of the Victoria Line guy was adjusting brake shoes,someone else was doing something on the train that applied the brakes and he kept winding them off,when the train entered service for the evening peak nothing happened when T/Op applied the brakes.

[roythebus]

"the Brake Test" is a misnomer, it's a brake line continuity test to check that any isolating cocks are in the open position. The "running brake test" is actually for testing the operation of the brake.

[spsmiler]

Aug 29, 2023 21:30:58 GMT towerman said:

In the early days of the Victoria Line guy was adjusting brake shoes,someone else was doing something on the train that applied the brakes and he kept winding them off,when the train entered service for the evening peak nothing happened when T/Op applied the brakes.

was this in the days when the back of a departing train and front of an arriving train were alongside the platform (in a way that was visible to all passengers) at the same time?

[towerman]

The home stick cleared when the rear of the train in the platform passed the starter.

[towerman]

Back in the 70s was talking to the signal lineman at Seven Sisters,said when he was based at Wembley Pk one of the Met locos spadded a signal on the fast road,triparm went round in a full circle and reset itself.

[philthetube]

Aug 29, 2023 22:17:50 GMT roythebus said:

"the Brake Test" is a misnomer, it's a brake line continuity test to check that any isolating cocks are in the open position. The "running brake test" is actually for testing the operation of the brake.

Running brake tests are no done on the underground when entering service.

95 stock, (when new), also had at least one incident of a train being tripped and the trip resetting itself.

[towerman]

Used to be the rule if more than 50% of brake blocks were changed on examination the train had to be shunted round the depot to ensure brakes were working.

[t697]

Aug 29, 2023 17:04:19 GMT towerman said:

Had the same thing happen on the Central back in the day,train failed to trip applying the rule,the chamber at the top of the tripcock had worked loose.Chap that signed it off as tested demoted to cleaner for two years.

I don't know how often that failure mode happened but I recall doing the engineering investigation for what could well have been this same incident.  Units had just been reformed with a middle cab becoming an end cab.  Middle tripcocks are isolated from the Train Line (Brake Pipe) and should be latched up so they don't keep striking trainstops that rise as the front of the train drops the next track circuit.  It appeared this hadn't been done or the latch was defective and the continued battering caused the bolts holding the valve to the top of the main body to stretch so the cam inside wouldn't open the valve.

This led to a requirement to use better grade bolts. Suspicion was a well meaning bean counter had changed spec and supplier!  However as already mentioned above, the reform test should have tested the tripcock and it seems that wasn't done, which would have revealed the fault and stopped the train entering service.

Overall one less hazard on fleets without middle cabs.

I suppose we must thank the signal failure for revealing the fault before the tripcock was called on to provide real protection...