Having obtained our replacements we have held back from the second phase of testing until we were close to completing the refurbishment of the auxiliary room and its roof section which is where most of the tanks are situated. This also includes the overhaul of the various auxiliary machines that occupy this compartment as some of the air tanks are positioned under these machines. So with the end of these tasks in sight it was time to carry out the pressure test.

We had 13 tanks to test, two of which are ‘dual’ chambered giving us 15 tests to undertake in all. In addition it was also decided to test one of the new tanks simply to bring its test date more into line with all the others. So physically we had in one large tank to test A2 (the "torpedo" - for those of you familiar with 47s this sits under the compressors), three medium tanks to test and ten small tanks.

The testing itself is straightforward enough but time consuming so in order to speed up the process some of the tanks can be coupled together and tested as one. Generally the working air pressure system on a Class 47 is 140psi which means for testing purposes you must test upto 1.5 times ie. 210psi. However to complicate matters a few of the tanks work at different pressures to others so you have to be careful on ‘doubling up’. With that in mind valuable brain power was expended putting together a running order of tests taking into account the couplings available – male/female threads, size ¾  bsp, ½ bsp etc, etc. Quite simply you then fill up each tank with water and the inspector pumps this up to the required pressure and then makes sure this holds over the next 10 to 15 minutes.

Come the big day we got off to a flyer and by lunch time seven tests had been completed, which included the dual chambered air tanks one each of which sits under the driver’s seat – these are peculiar to the ‘Generators’. Apart from a slight ‘weep’ from a reducer all went well and while this testing was going on the ‘torpedo’ was moved onto a forklift truck and placed in position. Our first minor hiccup came with tank A4 which I’d hoped to double up. Having filled up its partner and connected the two up it was then realised that A4 contained not only a filter but also a further reducer meaning it would take ages to fill up even though it was only a small tank. With its ‘mate’ ready they were split off and A4 was eventually tested solo.

Just after lunch the threatened rains set in and we had to move undercover. Rain is not very helpful when you are checking for potential leaks. We had three small tanks left to do and then the bigger items, which to save time we had already begun to fill up. Filling up an approximately 280 litre vessel through a small ½ connection is not a quick job. However we soon arrived at our nemesis A2 the ‘torpedo’. Pressure was applied but unfortunately at about 100psi the blanking plates started to leak rather badly with little fountains of water appearing. So whilst the blanking plates were taken off and tried again the remaining medium sized tanks were tested.

After two further attempts with the ‘torpedo’ a combination of PTFE Tape, Boss White and Horse Hair finally cured one leak and brought the other under sufficient control to allow the test to be carried out at the designated pressure and that was it, no leaks, success.

All we had to do now was pack up and empty out all the water. By now the rain had stopped and the sun came out to shine on a successful day. Our thanks to Martyn, John, Paul and Richard for giving up their time.

Over the next few weeks the air tanks will be repainted and then put back in their rightful place. D1516 will internally start to look a complete loco again.