COMPEX EXd

[vivas]

hey people,

EXd equipment, with flange joints as flame paths, am i right in thinking ur meant to add grease to the flanges, other than on gas detectors, and if so do u have to add the grease on every occasion or is it optional

 

[Knobhead]

Under no circumstances should oil or grease be applied to the flange faces.

The flange faces serve two purposes in the event of an internal explosion:
1/ it provides a pressure relief path.
2/ as the pressure is relived the gasses are cooled by the surfaces.

The flange should have a maximum gap of 6/1000”.

 

[vivas]

then why does the check sheet ask if the flange joints and threads,(also flame paths) have approved grease applied, and on exd kit wherethe flame path is a thread, ie a rosemount pressure transmitter,grease is applied to thethreads

 

[Knobhead]

I’m just going on what I was taught at “The Safety in Mines Research Centre” 35 years ago.

 

[Engineer54]

Not too sure about Ex rules as i deal more with the American standards in this area. But agree with Tony on flange joints, they act as a pressure relief path in the case of internal explosions...

 

[vivas]

well im not disagreeing or anything but can i quote from the official compex book, under weatherproofng of exd kit//

ingress of moisure and water through joints and gaps may be minimise by the use of suitabe grease or tape. Gaps can be protected through the use of a non hardening grease to flange faces...

And on a heli pad recently we were made to grease the flange faces of the exd heli pad lights

 

[Knobhead]

If the manufactures recommend it then yes, I’d not argue. But for EX flange joints I would for the reasons I gave.

I’m a member of a mining board I’ll have a word with the lads there.
I recall the demonstrations given at BASEFA’s Buxton test station regarding flame paths were fun. With the correct length and gap the explosion was contained. Get it wrong and bang. We were treated to lots of bangs while there, but it hammered it home.

 

[bomjac]

Simple answer is you follow the requirements of the certification system you are working to. The issue in mines I would imagine would be the danger of coal dust sticking to the grease and affecting the contact of the flange faces every tme you opened up a box.

Greasing of flange faces is allowed under ATEX so far as Eexd kit goes - but that is not to say that the absence of grease is wrong either. The stipulation is as above in that it is a light smear of non setting grease.

 

[listener]

bomjac is right. A light smear of non setting grease is allowed. Older EEMUA books used to say PBC grease but not any more. I think the confusion here is silicon grease is not to be used on gas detector heads. I dont have the EEMUA book to hand but if you would like I will look it up and tell you what is says.