Electric Actuator in Oxygen Service 2

[fpnut]

Hi,

I am in the process of designing some pipelines for gaseous oxygen, and is in need of an actuated shut off ball valve. Typically I would use a pneumatic actuator for this service. However, for this application there are no compressed air or nitrogen available for actuating the ball valve.

So I'm thinking of using an motorized/electric actuator instead, but I have concerns over the safety, due to my inexperience with electric actuators:
1. Do electric actuators use grease/oil in its mechanism?
2. If they use grease/oil, any chance of it leaking out? Or can gas enter the mechanism?
3. Anybody else have a similar experience?

If push comes to shove, is it perhaps possible to run a pneumatic actuator using oxygen gas? It'll be dry and the actuator perhaps will need to be oil free as well is what I'm thinking.

 

[Danlap]

Hi,

Suggest whenever possible to avoid using electric motor. Unless multi department assessment can confirm that the electric insulation will never be damage/mitigated and electric spark will never reach ignitable material.
1. Do electric actuators use grease/oil in its mechanism? Most of them yes, some say risk can be minimized if we use BAM certified grease.
2. If they use grease/oil, any chance of it leaking out? Or can gas enter the mechanism? As no one can warrant this, so yes it is possible for both scenario.
3. Anybody else have a similar experience? My place of work (refinery) have pure oxygen application from bio-treater (5 bar, ambient temperature) up to gasifier (380 degC, 83 bar) and we don’t use electric actuator. Always pneumatic or hand operated.

There are in-depth course about how to analyze Oxygen hazard for example by WHA International, etc. and there are many standards in the industries as well. Therefore please do not simplified my summary below:
Common Ignition Mechanisms are: electrical arc, Particle impact, compression heating, flow induced heating, mechanical impact, galling and friction, static discharge, promoted ignition / kindling chain and some others.
It is not common, but indeed relatively easy to ignite pure gaseous oxygen (its even easier with liquid oxygen) especially when it is high velocity, non-exempted material and some grease or lubrication involved (read: fuel). Stories such as welding tank ignited upon oxygen released by welder, scuba diver tank ignited, oxygen hyperbaric incidents, etc. are some of the stories you will hear if you enroll the course.

Suggest to read EIGA document ‘Oxygen Pipeline and Piping Systems’ IGC Doc 13/12/E. You will find materials considered as exempted, some parameters such as thickness, pressure and temperature for materials possible to be ignited.
You need to assess your own risk in terms of: material used within the Oxygen regime, pressure and temperature, are you using oxygen approved gasket (without or with minimum fossil based impurities), etc.
The concept is relatively simple, if sparks or any other ignition mechanism are confined and not in contact with Oxygen and its potential fuel, then it should be ALARP.
Assuming you can install pneumatic actuated valve, but the pneumatic line is not entirely oil free and might contaminate the spindle (just for the sake of dramatization) and valve do not use BAM certified gland packing.
Then the next question would be: in the event of valve gland packing burst and impact against the ‘oiled’ spindle, is the pressure/temperature/velocity sufficient to ignite the burst packing or ‘oil’ on the spindle. And is it possible for kindling effect to follow e.g. spindle caught on fire as well. If the answer is No, then you should be ok.

I suggest to use Monel material (exempted material), BAM approved packing, assembling/testing and preservation to be done as per Oxygen recommended practice (ASTM G93).

PS: better to contact some of the institution I’ve mentioned above for more professional assessment.

Regards,
MR

https://nosuchvalve.com

All valves will last for years, except the ones that were poorly manufactured; are still wrongly operated and or were wrongly selected

http://www.eng-tips.com/faqs.cfm?&rat1=2&fid=376

 

[fpnut]

Hi MR,

Thanks for the detailed explanation. Looking at those documents and the risks involved, I think I'll have to change the design to avoid using electric actuators. I am aware of those documents, but have not consulted them.
In regards to the oil/grease, assuming pneumatic actuation is possible, it would be possible to use grease which are oxygen safe. But then again this is not available onsite.
I guess I'll have to discuss with the project owner about this.

Thanks again for your detailed explanation, I appreciate it.

 

[gerhardl]

Hi fpnut,

As for all applications a selection of actuator type is depending on a lot of local details. For your case for instance placement indoors, outdoors, forced ventilation, used for emergency shutdown or repeated actuations on/off, shutdown time required, number of operations over time, actual required certifications and safety factors in general, required signals, etc. etc.

This might well lead to Danlaps recommendations as the best solution, but you could also, as an option, have a look at ex. proof actuators, often used within petrochemical and chemical plants.

Electrical actuators are more commonly selected and better constructed than for twenty years ago, especially where extensive automated and external controlled systems are planned.

Below up to date EX Approvals of an electric actuator range, AUMAs as an example, data from homepage. (ROTORK would be a typical competitor, among others)

Europe - ATEX
Ex de IIC/IIB T4 or T3
Ex d IIC/IIB T4 or T3
International level/Australia - IEC
Ex de IIC/IIB T4 or T3
Ex d IIC/IIB T4 or T3
USA - FM
FM CLASS I DIV 1 GROUPS (B), C, D T4 (T3C)
FM CLASS II DIV 1 GROUPS E, F, G T4 (T3C)
FM CLASS III DIV 1 T4 (T3)
Russia - ROSTECHNADSOR/EAC (TR-CU)
1ExdeIICT4/T3
1ExdIICT4/T3

You would probably get the best answers for your problem by asking for a preliminary offer from one or more of the best brands, presenting all the detailed application requirements.

Good luck!

 

[Danlap]

Thanks gerhardl for your constructive input, as always.
I fully agree with you. Some of the main reason my Plant don't want to use electric actuator indeed is not our comfort zone, so many risks assessment to be done and to be approved by several disciplines and extra works required for routine maintenance.
But yes, risk should be ALARP if:
- the electric components are EX certified
- there are routine check and maintenance over electric components during on the run and/or TurnAround e.g. checking cable glands, replace whenever required, operator routine check with oxygen sniffer over leakage path, etc.
- well ventilated or good air flow
- if grease/lubrication present it is ideal shall can be insulated from the potential ignition source e.g. spark. And not in direct contact with potential Oxygen flow path (shall leaking)
- P, v and T of Oxygen (shall leaking) are below the suggested threshold when about to reach the potential ignition source and fuel
- as per gerhardl suggestion to provide robust logic emergency function shall required.

In Oxygen it takes three to tango (Oxygen, fuel and ignition source). We had several Oxygen gland leakage in the past, but since there is substantial distance between gland and 'not so clean after years in operation' gearbox, therefore the Oxygen already disperse in terms of concentration and flow. And it is unlikely to be ignited.

Regards,
MR

https://nosuchvalve.com

All valves will last for years, except the ones that were poorly manufactured; are still wrongly operated and or were wrongly selected

http://www.eng-tips.com/faqs.cfm?&rat1=2&fid=376

 

[ScottyUK]

Rotork ATEX-certified actuators definitely leak lubricant in small quantities. Maybe they shouldn't, but they do.

Rotork and similar actuators typically use the flameproof protection concept, that is to say that it is possible for flammable material to enter the enclosure and if that happens then it is plausible that an explosion will occur within the actuator housing, but the internal explosion won't give rise to danger outside the actuator housing. I don't think this protection concept is a good match for oxygen service.

 

[gerhardl]

It would be interesting to know if anyone know about actual use or has any knowledge about practical experience for electric actuators in oxygen service. Has it been used at all?

 

[fpnut]

I've scoured over the internet looking for information on this, and there seems to be little to no information on the track record of such usage.
I did find one company with a picture of what looks like an electric actuator on a copper piping line that is implied to be oxygen. The company didn't respond though.

Like Danlap's suggestion, if the actuator is situated outdoors, logic dictates that it would have been sufficiently dispersed, and thus not have any significant effect.

As for my application, I've played it safe and changed to a pneumatic valve instead, which seems much more common in practice.