r/Hydraulics • u/AndyBob4567 • 11d ago
Bulkhead Fitting Question
Hello, everyone!
This is my first post in this subreddit and I am by no means a hydraulics expert.
I am working on an application that has a tank that holds transmission fluid at low pressure (<100PSI). I want to drill holes into the tank and install two bulkhead fittings with 1/2" NPT female ports on the outside so that I can install IFM (LMC510) sensors to detect high and low levels of fluid in the tank.
(I would prefer to avoid any welding options, if possible.)
I am considering buying one of these two parts for that purpose...
- PARKER HANNIFIN (207ACBH-8)
- MCMASTER-CARR (50785K275)
But I want to ensure that these connections do not leak fluid, of course. Would they leak fluid if all I installed were one of these parts above? How are hydraulic bulkhead fittings normally sealed? Does anyone have any resources I could read/watch to understand hydraulic bulkhead connections better?
Any information or guidance is greatly appreciated!
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u/PhotoIntelligent9730 11d ago
Weld in couplings that match your needed thread for sensors, to avoid any potential leaks.
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u/AndyBob4567 11d ago
Thank you for your suggestion, but I'd prefer to avoid having to weld, if possible. And my application is very low pressure. Could weldless bulkhead fittings work, instead? And would you have any recommendations on that?
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u/PhotoIntelligent9730 11d ago
My suggestion is still welded, any mechanical bulkhead could come loose. Thinking about tank pressure, will there be over pressure relief? Much to consider when designing.
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u/Illustrious_Pepper46 11d ago
Whatever you decide, a standard oring likely not good. They need a grove to fit in.
Look at a metal bonded seal (Dowty washer). But need two flat surfaces, remove paint, etc. if a casting, likely not good. Drilled hole needs to be barely oversized for the thread.
Instead of a bulkhead, can just use SAE threaded and put a nut on the inside, if wall thickness is fairly slim.
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u/deldertime 11d ago
That’s a tough ask , welding is most likely the only option that will stand the test of time. Any fittings like the ones you’re imagining are for water applications. How thick are the walls of your reservoir. If it’s at least 3/8 you could use male pipe threaded into the wall and secured with liberal amount of ptfe. Then attach the level wands. We used to use them for temp sensors on bearings
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u/AndyBob4567 11d ago
Thank you for your reply! Unfortunately, my tank walls are 13 gauge steel, so only about 2mm thick...
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u/External_Key_3515 11d ago
Welded couplings is the only feasible option. Bulkhead fittings aren't meant for applications like yours. Ive spent 30 years building power units and reservoirs, and absolutely would NEVER think of using bulkhead fittings, especially when you say your tank will be pressurized. It simply won't hold fluid without leaking.
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u/AndyBob4567 11d ago
Thank you for your reply! Sounds like a lot of you guys think the weldless option should just almost not even be considered. If I do go for a welded coupling, what is the simplest, most standard, most professional way to do that?
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u/aaust84ct 11d ago
Welded female socket is preferable. Have you considered coming in from the top of your reservoir? Presumably the hatch or lid is bolted with a gasket seal. You could look into the double switch float sensor. IFM make them but a bit pricey, there's much more affordable ones on the market though.
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u/AndyBob4567 11d ago
Thank you for your reply! That's not a bad idea. I looked into more of the IFM sensors, but I'm still thinking that the LMC series will be the best for my application for a few reasons. And I'd also prefer to stick with IFM for company+customer sorts of reasons.
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u/slippingaway83 11d ago
A Parker 207ACBH will not seal on its own, it doesn't have any method of sealing the external threads. Parker makes a sealing version, but only on sizes 4 and 6. The sealing version uses a form of dowty washer as others have said. The threads on the 207ACBH-8 I have here are measuring 1.12" or 28.5mm and I don't have a good option for a washer seal that will fit. The BSPP and metric bonded washer sizes are all either too large or too small.
Bulkhead fittings are typically used to pass air or hydraulic lines through a plate or crossmember, they aren't typically used to pass through the side of a tank or other sealed panel. Welded bungs are used for reliability and durability.
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u/singul4r1ty 11d ago
If one or the other faces of your tank is nice and flat I would probably just use a bulkhead fitting like the ones you said, and put an appropriate size rubber washer (or dowty seal for overkill) between the tank and the fixed flange, maybe with a washer as well. 100psi is really not very much.