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Manway Spring Assists 1

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michigander

michigander

Mechanical
Joined
Apr 10, 2006
Messages
46
Location
US
I have a client that insists on having top head manways mounted with spring assisted covers as opposed to davit arms. Frankly, I don't know how you can safely spring assist an 800 lb 24" 300# blind flange to open vertically. What happens if the spring fails and a body part happens to be in the way? If anyone has any advice on companies that may offer a spring cartridge, that offer higher pressure spring assisted manways, or ideas to dissuade said client from this selection, please advise.

Thanks,
Michigander
 
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You might check if they have existing manways built like this. Are they trying to match existing facilities or dreaming up something new?
 
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Young MBA clients can cause many, many problems with their brand new "out-of-the-box" ideas ....

Be aware that, at some point in the future, the client will hotly deny that he ever asked you to waste time and investigate this.

My thoughts:

- Be aware that a spring for a horizontal manway only helps to lift the manway off of the face of the adjoining vessel flange. A davit is still required to move the cover plate horizontally. Usually the "breaking" of the seal is handled by tightening an eye bolt that is part of a well designed davit. The cover plate is also convinced to move by pipefitters with pinch bars.

- The only kind of spring that is suitable for this service would be a spring sold as part of a pipe support. Corrosion for any outdoor application is also a concern.

- Layout (even a hand drawn sketch) of the platform and davit is important. The cover and davit must swing horizontally. Is the platform big enough for two fitters, tools and a cover swung horizontally ?

- Consider XYLAN coated bolts, nuts and hardware for the manway. New 21st century PTFE coatings can make things easier for everyone

- A reasonable diameter for the manway is important.... Many fat clients want 30" diameter, 24" is more reasonable

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Can you share with us either an outline drawing of the proposed vessel or perhaps some pictures of the situation ?

We need more information .....

MJCronin
Sr. Process Engineer
 
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Take off your davit, replace it with a hinge, and put a torsion spring on the hinge to assist in the lift.
 
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Well apart from telling him or her they are off their head, the issue if this is a bolted pressure containing flange is that a device like that need a hinge.

If the hinge is even a few mm out, the flange won't sit nice and evenly and seal. Hence it will leak. The only hinged covers have very flexible and deep seals to allow for any slight mismatch of the cover.

Also how many times are you going to do this? Once every five years?? Are they going to sign off on a 500% increase in cost of a davit for this??

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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Hinges work well. We use them all the time. Alignment is not an issue. I don't want to absorb the cost of going to a quick acting closure like a tube turns due to cost and the spring seems impossible for this weight. The preload on the torsion spring alone strikes me as implausible.
 
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Hinges do work well, but not normally on 400 kg blind flanges.

A photo or two would help here.

A hydrualic arm and pivot, like you get on a car bonnet might work?

Like this
or this



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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I doubt that hydraulic springs would work at an 800 lb lift. This is a pressure vessel. 400 psi at 600 degrees. MJCronin published a picture. Its a manway with a hinge in lieu of a davit.

The client is obstinate. I need to
1) Provide it and only it....a torsion spring with a hinge I dont have a picture.
2) Convince him it is unsafe or some other compelling reason to not use #1

I do not have the options to offer alternatives at this time. I really am just looking for help on either specific question so we can explore options if they accept #2.

So again, briefly, I have to give him what he wants or have a valid argument as to why he should not want what he wants.
 
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Spring. No. Counterweight. Yes.

The problem with sloppy work is that the supply FAR EXCEEDS the demand
 
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A hydraulic jack can easily lift your wheel off the floor - I think a blind won't be any problem,

but in answer to your questions

1) Simply state that you've spent xx hours researching this and talking to vendors ( even if you haven't) and can't find any suppliers or track records of this typre of device for this weight of flange. Of course if he or she has any leads (expect a bit of silence here) you would be very happy to follow them. Also you've consulted with your peers and they've never heard of anything so brainless before and hence no one does it this way.

2) See 1) Springs can break / corrode or seize when exposed to the elements. There is a risk in any device which is not a fail safe device or positive mechanical connection that it can fail and kill or injure people who are reliant on it working. Also the spring can either be under powered so you have the risk of injury as some worker tries to lift the flange expecting a level of assistance which isn't there, or over powered in which case the flange could "spring up" and hit them and then take a lot of force to get it closed again (the fat guy approach). Hence considering all these factors, the fact that you only need to open it once every (insert figure here) months / years (delete as required), you would recommend the conventional approach of a simple davit seen and used in all other similar locations and facilities. And they are very cheap.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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The only hinges that I have seen on tanks/vessels have been on very lightweight steel covers OR on plastic/FRP tanks

You may want to also consider:

The website
VEFV1117 – Vessel Vertical Manway Davits
VEFV1118 – Vessel Horizontal Manway Davits
VEFV1119 – Vessel Column Davits (2 Pages)

or the old standard "Pressure Vessel Handbook" 15th ed ....

BTW: ...I have always strongly supported and endorsed drug-testing for all unreasonable clients ...

MJCronin
Sr. Process Engineer
 
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Does anyone here know any reference that shows the required dimension for domed manways?? PIP only has 3 types of connections :(
 
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