CCN 1 Practical Exam. Can't find an answer i need in books.

[Mike28]

I was asked on this exam "why do we test natural gas at 20 mb.
I gave the answers i'd read in my books, but i was told that wasn't the answer he wanted. i tried to find the answer afterwards, but i still can't find it. Re-doing exam this week. Help!!!!!!
All answers would be appreciated. Mike28

 

[kirkgas]

not really sure of the question TBH, it isnt a question I have ever asked anyone who was taking their assessment, I have asked them why we do let by at 10mb and TT at 20mb, but not why we test at 20mb, (not really sure I know the answer either, other than we want to TT at pressure less thsn lock up pressure, to me it is the test pressure and that has always been good enogh for me)

 

[kevplumb]

i was always told the timing for the test is worked out for 20 mb

if your over the gov locks up

under you might get a false result

this is what ive been told

not a definitive answer

 

[ChrisR]

I think they'd want that it's because at 20mbar, the regulator shouldn't be locked up.
If you did the test at the standing pressure ( ie whatever you got after you'd shut the ECV, which could easily be say 25mbar) there's a good chance the reg would be locked up, so you wouldn't be testing the plummin between the ECV and the regulator while you were doing the tightness test.

Tthere IS a bit more to it, but I reckon that'll do.

 

[Boilerman2]

Spot on ChrisR!!!

 

[expertgasman]

[quote="Boilerman2";p="1785545"]Spot on ChrisR!!! [/quote]

Oddly, I was trying to post exact same response,

20mb avoids lockout.

 

[picasso]

It used to be 19mb, when was it changed to 20 ?

 

[onlyfitidealboilers]

just say "because it is the highest pressure you can test at without the guvnor locking up"

 

[scatmanjohn]

20mb avoids lockout.

Ya mean "lock UP" , Lockout is something completely different.

 

[scatmanjohn]

I think its 19 mBar on medium pressure.

Only ever done it in the acs centre.

 

[kevplumb]

ditto

long time no post scat

 

[scatmanjohn]

ditto

long time no post scat

Got myself a life recently kev