Load Handling Question

The question (via E-mail):
We are considering structures above 9m which have components (i.e. valves or other items sitting on them) over 90kg (198.4lbs) to have a davit installed on them. But what if a valve weighs 80kg (176.4lbs)? It’s still heavy!

My answer:
A great deal of “Good” engineering and Design is Judgment. It would depend on the probable frequency of the need and any other extenuating circumstances. This weight is too much for one person to handle alone. If it were me I would put in the Davit.

Load Handling Devices:
Load handling devices should be considered for all heavy objects in elevated locations that require periodic removal and replacement. This does not always mean that a permanent fixed device is required. It may be that the frequency of “Need” is such that a rented Mobile Truck Crane is the best consideration. There is more than one answer to question of the kind of load handling device.
There are:
– Chain Hoists
– Davits
– Davit Crane
– Mono-rails
– Gantry Cranes
– Cherry Picker Cranes
– Medium Sized Mobile Truck Cranes
– Large size Cranes

Chain Hoist – Chain Hoists are available in various lifting capacities. Their use in a maintenance environment is common. They can be hung from a permanent overhead structure or rigged from a portable Rolling “A”-Frame. The advantage of a Chain Hoist is that it can be put anywhere you have a fixed or portable structure to hang them from.
http://www.electrical-res.com/EX/10-19- … _hoist.jpg

Davit – Normally provided on vertical vessel for handling items such as internals and relief valves and other objects exceeding a height of 30 feet (9m) above the high point of the finished surface, and on vessels not accessible by mobile crane. Orient davits to allow the lowering of appurtenances into the access area. Provide a clear access area at grade for vessels with removable internals or for vessels requiring loading and unloading of catalyst or packing. The lifting capacity of any Davit in based on the lift (weight) requirement, the strength of the mounting vessel and the design of the Davit itself.
http://www.bartswatersports.com/images/ … age506.jpg

Davit Crane – A Davit Crane is a cross between a “Davit” and a “Crane”. It is mounted on a fixed platform or base and can swing around like a Davit but some Davit Cranes can also raise and lower the lifting beam.
http://images.google.com/images?hl=en&c … i=&start=0

Mono-Rail – These are normally installed where you have repeat removal and installation of large heavy objects. They can be manually (chain) operated for both lift and travel or power operated for both. The drawback to a Mono-Rail is that it has limited flexibility as far as side reach. All lifts are located in a single straight line.
http://imghost1.indiamart.com/data2/TJ/ … 50×250.jpg

Gantry Crane – These are also installed where you have repeat removal and installation of large heavy objects. They can be manually (chain) operated for both lift and travel or power operated for both. The advantage to a Gantry Crane is that it has broader flexibility limited only to the design of the main longitudinal and transverse travel.
http://images.google.com/images?hl=en&c … i=&start=0

Cherry Picker – These are normally used to lift a person and a limited amount of tools and parts. They come in various sizes (reach and lifted weight) and different methods of transport. The advantage of the Cherry Picker is its flexibility. It can be moved and used almost anywhere.
http://images.google.com/images?hl=en&c … x3&start=0

Medium Size Mobile Truck Cranes – These have a lot of flexibility as far as use, lift capacity and reach. Most are rented on an as-need-only basis so there is no capital equipment cost involved.
http://www.nescosales.com/cranes-truck- … nAodujGVzg

Large Crawler Cranes – These have a lot of flexibility as far as initial plant construction is concerned. They are not normally considered a piece of Maintenance equipment. The really large Crawler Cranes have tremendous lift capacity and reach. These are normally rented on an as-need-only basis by the General Contractor so there is no capital equipment cost involved.
http://images.google.com/images?client= … CB0QsAQwAA