Max pressure for electronics (deepwater, downhole)? - Page 1
Forum section: electronics / projects

author: sicco
author_rank: Regular Contributor
timestamp: August 13, 2022, 07:02:58 pm
content: I’m designing downhole electronics with Hall and other sensors such as ST MEMS accelerometers, magnetometers like ISM303DAC, LIS2MDL, Infineon TLE4968, TLE5012B. These automotive sensor chips in their LGA12, SOT23, SOIC-8 or PG-SSO-3-2 packages have the temperature spec that works for me (150 C ish). But the application will expose the packages, likely submerged in oil, to pressures into the 100rds of Bars (5000, 10000, maybe 15000 psi).Not one single datasheet that i could find says anything on max outside pressure before such sensors in their epoxy housings stop working, or lose spec, recoverable or irrecoverable.Anyone any experience on how much pressure before this stuff breaks?I fear that approaching ST, Infineon, NXP or TI, ADI field application engineers / sales channels will not get me anywhere, so asking it here now.

author: voltsandjolts
author_rank: Unknown
timestamp: August 13, 2022, 07:39:11 pm
content: The electronics must not be exposed to pressure, that would quickly destroy your circuits.Pressure is your mechanical engineer's problemFor wires that need to enter the pressure housing you need to use pressure feedthroughs (Kemlon,Greene Tweedetc.)

author: mag_therm
author_rank: Frequent Contributor
timestamp: August 13, 2022, 07:55:43 pm
content: This is another case I have seen before on eevblog of designers reluctant to contact vendor applications engineers with queries on products they intend to use.Why is that?In my day and up to retirement recently they were #1 contactThere are lots of electronic systems down boreholes and undersea, and of course it has to be done with the right parts and methods.

author: sicco
author_rank: Regular Contributor
timestamp: August 13, 2022, 09:48:07 pm
content: Quote from: voltsandjolts on August 13, 2022, 07:39:11 pmWhat i have is a spinning shaft driven by a BLDC motor. The motor with Hall sensors is a Maxon catalog item, and claimed to survive the targeted high P high T when oil immersed. All drive electronics is in a pressure isolated atmospheric chamber, with the high pressure feedthroughs that you mention. The motor shaft and thus the motor is directly exposed to fluid, at high pressure, because it must interact with that fluid. I need a few more Hall position and orientation sensors, plus some magnetic sensor coils with sensor chips. Those sense something in the fluid. And those will be directly exposed to the high pressure.The 3 Hall sensors inside the Maxon BLDC oil&gas, geothermal well ‘catalog’ assembly somehow can survive high pressure exposures. So what i want to learn now is what to do with mass market automotive style Hall and MEMS etc sensors to make them also survive downhole. Embed into glass maybe? Or just use the naked epoxy package and keep fingers crossed? Pot into another layer of epoxy?

author: sicco
author_rank: Regular Contributor
timestamp: August 13, 2022, 09:49:28 pm
content: Quote from: mag_therm on August 13, 2022, 07:55:43 pmWhen did you retire then?

author: mag_therm
author_rank: Frequent Contributor
timestamp: August 13, 2022, 09:59:50 pm
content: Closed my business 8 months ago.What did your comment about fearing contact with your vendors mean?

author: TC
author_rank: Contributor
timestamp: August 13, 2022, 10:31:49 pm
content: Probably the best search term to use is "pressure tolerant electronics". You won't find much. I'll reccommend starting with an article here ...https://uutech.com/ptepaper/That provides a good starting point. You aren't going to find vendors qualifying components for high pressure. You have to test to demonstrate that the components and assembly are pressure tolerant.Generally, any component that has an internal cavity is out.There is a dated paper from the Navy (I think) that I found as a useful reference. I'm talking 1960's... maybe 1970's. It gives some insights on test methods, etc. This is the sort of stuff that is tested in specially designed chambers behind 3 foot concrete blast walls.

author: tunk
author_rank: Super Contributor
timestamp: August 13, 2022, 10:33:22 pm
content: Quote from: sicco on August 13, 2022, 09:48:07 pmI guess what voltsandjolts said above is that you have to design an enclosure that can withstand the pressure.

author: voltsandjolts
author_rank: Unknown
timestamp: August 14, 2022, 08:25:03 am
content: Quote from: sicco on August 13, 2022, 09:48:07 pmI think you have misunderstood theMaxonspecification. Their motors may be used submerged in oil, but they don't rate their motors to operate directly in oilat 15kpsi. They operate in high temperature and high pressure environments but within a sealed pressure housing which isolates them from the wellbore pressure. Design, test, manufacture and full qualification of a dowhole electro-hydraulic power unit is an expensive business, but it has been done of course. A pressure balanced HPU design needs to isolate the motor from the wellbore pressure.

author: sicco
author_rank: Regular Contributor
timestamp: August 14, 2022, 09:30:29 am
content: Quote from: mag_therm on August 13, 2022, 09:59:50 pmThe sensor ic’s I’d like to use are targeted at automotive, the sales and support by their vendors is willing to help if you aim at 10k plus volumes. Not up to 100 annually. As stated byQuote from: TC on August 13, 2022, 10:31:49 pmBut hey, if any proud committed ST, Infineon, NXP, TI, ADI or Toshiba FAE reads this and has experience or knowledge about successful application of their modern LGA12, SOIC8, SOT23 epoxy packaged sensor products under 100+ Bars (1500+ PSI) immersed in oil then please let them comment to this forum thread! My guess was (now confirmed already in the middle of the weekend!) that EEVBlog forum would get me more meaningful guidance.

author: sicco
author_rank: Regular Contributor
timestamp: August 24, 2022, 02:55:23 pm
content: Quote from: voltsandjolts on August 14, 2022, 08:25:03 amDouble checked with Maxon. They say "We do have customers who use these motors over years at 150°C and pressures up to 20’000 PSI at the same time."So that's what their motors operate at (immersed in clean hydraulic oil, oil that also gets pressured up to downhole wellbore pressures of the same magnitude - pressurised via a seal that communicates P).

author: sicco
author_rank: Regular Contributor
timestamp: August 24, 2022, 02:58:56 pm
content: Plus an encouraging note from MPS: "The MAQ473 would be a better choice. About the pressure, according to some experimental data we have: at 100 bar there’s no effect on sensor behaviour, while at 1000 bar the sensor can still operate, but there may be a drift on the output in the range of 1°."That's the best response I got so far! So I ordered some samples...

author: tszaboo
author_rank: Super Contributor
timestamp: August 24, 2022, 03:00:38 pm
content: Quote from: mag_therm on August 13, 2022, 07:55:43 pmBecause they often times are not getting replies to their questions.Because industrial systems are made in the quantity of hundreds, maybe thousands and not millions (like consumer), we are second class engineers when it comes to support.I heard TI closing down my support, telling me "to just ask it on their E2E forum". Or not getting back a reply when I asked for a quote.And the world would literally fall apart if it wasn't for us. This is downhole drilling. Imagine not getting your parts and support, and running out of oil.

author: mag_therm
author_rank: Frequent Contributor
timestamp: August 24, 2022, 06:06:44 pm
content: Quote from: tszaboo on August 24, 2022, 03:00:38 pmYes, I was in high power electronics. While the control electronics were usually no problem with ordinary industrial grade, the power side was specialised often with vendors providing custom made semiconductors, capacitors etc.I would recommend that the design engineers in such positions should properly archive all vendor correspondence, and understand vendors legal terms and limitations of use of their parts.(sometimes at back of data sheets), or pass on to corporate legal.Taking advice on a public forum probably won't be regarded as diligent practice in workplace engineering although times are changing.

author: voltsandjolts
author_rank: Unknown
timestamp: August 24, 2022, 07:37:18 pm
content: Quote from: sicco on August 24, 2022, 02:55:23 pmSLB ESP's use motors operating in clean oil which ispressure balancedwith the wellbore, to several thousand psi, but they are custom motor designs with mucho horsepower. You might want search some ESP patents from SLB / WFT and others if interested. Also some info on youtube e.g.Code:https://youtu.be/8sTQx5kJq5M?t=153Hmm, I'm still skeptical of Maxon off-the-shelf motors being using within high pressure clean oil and would recommend you triple check in case of some language barrier or such like before committing money. And do some early qualification tests. I am happy to be wrongThey are certainly used downhole within pressure housings, likeGlobealso. You mentioned using hall sensors in a brushless maxon motor, but no way hall sensors are gonna survive anything like 20kpsi, so the rep must have been talking about a different motor type, if indeed they do operate at 20kpsi.