Compex Exia and ip washers

[Chilli]

Hi there

i am looking for a question answered regarding Ip washers on Exia equipment, the equipment is rated at Exia iic T6 ip rating of Ip68 intrinsically safe in zone 2 with an Exde Hawke cable gland on the cable Ip rated at Ip66/67, does this still require an Ip washer as the minimum Ip rating for offshore is Ip 56 ?, thanks :banghead:

 

[Sandman34]

Hi chilli if the enclosure you are glanding into has a threaded entry hole with wall thickness of 6mm or greater then not adding a IP washer will give you a IP54 rating of that gland entering the enclosure. If you add a IP washer then this will increase the IP rating if this gland entering the enclosure. If the hole is a clearance hole IP washer has to be fitted for minimum standard on clearance holes then you will achieve IP54. Minimum standard in hazardous areas is IP54. If the hole is threaded but less than 6mm wall thickness then to achieve minimum standard you have to add a IP washer which will give you IP54. Hope this helps.

Kind regards

 

[LeeH]

More the 6mm of thread then no, but check in your literature as its not a field you want to be getting answers for from the Internet.

 

[timbobelfast]

IS ip is IP20. You could use a coke can! Although IS circuits within say and ex e jb then you gave to maintain minimum IP54. Can be site specific to IP66. Is this an IS instrument?

 

[mache]

As has been pointed out the IS IP requirement is less than that required by the site minimum IP requirement. If its offshore then fit an IP washer if thin wall junction box, if its a threaded entry then you could use IP washer or a thread sealing compound if permitted by the platform installation standards.

 

[Chilli]

Instrument is an IS pressure switch rated at IP68, minimum site standard is IP54, it has more than 6 threads into the instrument from the Exde rated Hawke glande rated at IP66 in Zone2 so not much chance of Gas, surely there's no need to install an IP washer ?

 

[timbobelfast]

Instrument is an IS pressure switch rated at IP68, minimum site standard is IP54, it has more than 6 threads into the instrument from the Exde rated Hawke glande rated at IP66 in Zone2 so not much chance of Gas, surely there's no need to install an IP washer ?

This will be site specific.
As I.S is a Concept, there is no need to fit a certified gland, unless the barrier is in a Ex d panel say Ex d [ia], then a suitable certified gland will be required.

IP washers are normally fitted as standard in most applications.

Sounds like this has been snagged by the commisioning team?

Any pressure switch I have came across have been Ex d!

I presume that you are Compex qualified?

 

[Chilli]

Hi timbobelfast
this came up whilst working offshore recently, a discussion took place regarding a failed Ex inspection of a pressure transmitter due to a missing IP washer, the equipment in question was a rosemount pressure transmitter fed with an IS circuit, the instrument was rated Exia 11c T6 IP 66/67 and was in Zone 2, the gland was an Hawke Exd/e rated C20 IP66/67 gland with more than 6 threads into the instrument, I am aware this doesn't require a certified gland however I was of the opinion it also didn't require the IP washer and therefore would not fail an Ex inspection, as you know lots of these discussions take place offshore and I found myself questioning myself, just looking for some clarity as my heads spinning now, cheers in advance

 

[mache]

From what I can see the failed inspection is not infact an EX failure but is an IP failure. The instrument manufacturer will have all necessary seals etc in place on their housing part to ensure the IP rating they declare is achieved. However when it comes to the cable entry all the manufacturer can do is ensure that the thread is compliant to the thread standard required and that it is capable of achieving the required IP when used with appropriate glands and installation methods. When a gland manufacturer declares a IP67/68 gland, then they are talking about the integrity of the gland to the cable that is installed in it via the internal sealing arrangement.
For M20 threads if the gland or housing does not have an integral seal on the mounting thread then an additional seal will need to be fitted when fitted outdoors. This is because on parallel threads such as the Metric form there is always clearance between the crest and roots of the thread and will let moisture and gas pass through. Even changes in atmospheric pressure will breath through these clearances.
The following statement is made in Hawke Gland installation and assembly instructions under schedule of limitations 'A seal must be formed between the equipment and the cable gland to maintain the appropriate degree of protection against ingress of dust,solid objects and water.' That seal could be via a sealing washer or via a liquid sealant.
Tapered thread forms such as NPT would not require a sealing washer.