Testing Davits for pressure vessels

[johnthebest]

Hello everyone

As per our project specification:
"Davits shall be tested to a safe working load 25% greater than the weight to be lifted. The safe working load shall be stamped on the davit following the test."

The contractor claims that this clause is only applicable to the top davit that is used to lift and lower the pressure vessel internals

However, for man way davits, this clause is not applicable because it is used only to lift the cover flange.

What are your thoughts and what are the common practices?

 

[MJCronin]

It has been my experience that the design of manway davits is not unique for each manway ...

Manways typically utilize a "Standard Design Davit " that is tried and true.

This standard is typically robust and may be supplied by the customer or the fabrication shop.

I do not see the testing and stamping of a maximum load on the manway davit as a big deal ....

..... But aside from the manway cover, I also do not understand what else you would be lifting with the davit !!



But all this does not apply to the top manway davit, which is used to remove the top manway cover AND insert and remove column internals. This top davit should be designed and tested to 125% of rated load

MJCronin
Sr. Process Engineer

 

[r6155]

See PIP “Process Industry Practices” drawing VEFV1119 COLUMN DAVIT.
The load test should be done once the davit is installed, Shell stresses must be considered.

@ MJCronin
Please read again (OP)

Regards

 

[Geoff13]

I would agree with the Contractor that the 125% load test is only applicable to the top lifting davit.

A 125% load test is pretty normal for lifting equipment to provide proof that everyday overloads are within the capacity of the equipment.
[ul]
[li]What if the load is a bit heavier than listed in the paperwork?[/li]
[li]What if the operator jerks the load when starting or stopping the lift?[/li]
[/ul]

None of this is applicable to a simple manway davit. I've never heard of a manway davit being load tested after installation.

 

[DriveMeNuts]

I'm not familiar with the wording of your spec. The safe working load (SWL) or working load limit (WLL) is the weight to be lifted during the general operation of the davit. In my experience, the SWL is stamped on the equipment and the load test should be some percentage greater than this SWL value. Stamping the load test weight on the equipment is frowned upon, because if a dodgy risk-taker has a load heavier than SWL and is aware of the test weight then the temptation of "giving it a go" is greater.

I think the design margin of the davit plays a role in deciding if a load test should be conducted.
If the design margin is less than 200% of SWL, then I think a 125% load test would be wise for all davits.
If the design margin is over 200% of SWL, then perhaps testing could be waived for a davit that will only ever lift the same manway with negligible dynamic loading.

The lifting davits mounted to workshop walls that I have worked with have a test load of 150% of SWL with a calculated design margin of 200% to cater for dynamic loading or accidental overloading. They typically have an SWL of less than 1500kg.

 

[r6155]

PIP VEFV1119 says “STAMP LOAD CAPACITY”
As I said in 12 JUN 20 The load test should be done once the davit is installed.
During load test of column davit, all individual basis on shell shall be inspected..
Platforms shall be designed for that loads.

Regards

 

[DriveMeNuts]

What is the definition of 'load capacity'?
Working load capacity?
Test load capacity?
Design load capacity?

 

[SnTMan]

johnthebest, as you said it is your spec. Either you interpret it for the contractor, or the contractor interprets it for you.

Regards,

Mike[pre][/pre]

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[r6155]

@ DriveMeNuts
Which one is valid for you?

Regards

 

[johnthebest]

@SnTMan
I just wanna know what is the common practice and if the Man way davit has to be tested or it just follow the design standards.

 

[DriveMeNuts]

r6155,
A davit that has "load capacity" stamped on it with a value next to it is completely useless.
The user needs to know what "load capacity" means.
Surely you understand this?

 

[r6155]

DriveMeNuts.
PIP is very clear

Marking 1t or 1T are correct, no more words.

Also you can see:
LOLER Lifting Operations and Lifting Equipment Regulations
OSHA 1926.251
ASME B30.20

Regards

 

[SnTMan]

johnthebest, what you need to do is talk to the party or parties who wrote your spec and determine the intent. Makes no difference what common practice is.

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[MJCronin]

OSHA has something to say about this issue:

1910.179(a)(50) Rated load means the maximum load for which a crane or individual hoist is designed and built by the manufacturer and shown on the equipment nameplate(s)

OSHA uses the term "RATED LOAD" and requires the crane or lifting device to be marked with this term. OSHA requires a nameplate to be affixed to the device

More about additional crane load marking here:

https://www.osha.gov/laws-regs/standardinterpretations/1998-02-25

MJCronin
Sr. Process Engineer

 

[r6155]

MJCronin
Nameplate means paint , adhesive attachment, etc.
Think that size of letter may be 300 mm or more for cranes.

Regards