This preview shows page 1. Sign up to view the full content.
Unformatted text preview: al and environment for employer.
Some of these topics will dominate the design concept and in general the concept
is a compromise, however it is a must to analyse the major criteria that will be
used in the assessment of a design
- Cost/performance ratio
After defining one or some typical operational situations (load cycle, one-day
operation, representative load-pattern, etc.), the concept can be analysed on its
cost/performance ratio which requires estimating capacity for maintenance cost,
operating cost, energy consumption, availability etc. The determination of the
future performance under operating conditions is quite difficult and requires the 4 support form the operational staff and data about operational disturbances which
will decrease the designed technical capacity.
Although it could be considered as a separate design topic the selection of load
handling devices is an important topic for the overall equipment performance.
Examples of such load handling devices are: clamshell (grab), container spreader,
pallet hook, magnet, paper roll clamps. - The requirements for such handling devices are:
* proper positioning onto/over the load
* quick release from the load
* easily adaptable to various dimensions of the load
* quickly exchangeable (in case of break-downs; for various types of loads)
* a low mass (saves energy in every load cycle)
* shock-absorbing; shock resistant
* capabilities to function in automatic mode.
In many cases the characteristics of a load handling device may influence the
operational capacity with ± 25%.
Equipment size (required capacity/performance)
Terminals, transportation companies etc. are faced with the question: many
smaller units or only one or a few large units.
Although large handling (transportation) units can benefit from economies of
scale (lower cost per unit handled), there are some more aspects to decide on the
optimal size of equipment:
* the allowed loads on quay wall, site surface
* clearance dimensions on the site
* ratio between peak demands and average capacity
* utilisation rate of the equipment
* restrictions in various operating conditions (vessel sizes, transportation track
* (future) requirements for automation.
When it comes to handling and storage there is a tendency to install larger (and
thus less) equipment to benefit from the economies of scale (lower life cycle cost
per unit handed). In automated processes the application of smaller equipment is
sometimes preferred due to a better redundancy and maintainability (MTBF,
MTTR). Optimisation of the concept is a real itirative process and requires a broad knowledge
of all interfering aspects in the design of equipment. 3. Purchase specifications
Especially the procurement of large, expensive equipment asks for a proper
description of the equipment to be purchased, and such specifications are normally
presented by the purchaser (the end user or its representative e.q. an engineering
consultant). The specifications form the basis for the purchasing (negotiating) process,
however the specifications presented by the purchaser should never release the
manufacturer from his responsibility to provide a safe and properly...
View Full Document
This note was uploaded on 06/06/2010 for the course FF wb3094 taught by Professor Loderwy during the Spring '10 term at Renmin University of China.
- Spring '10