Measures For Achieving Safe Working Periods S.w.p; General; Calculating The Actual Duration Of Service S - DEMAG DC-Com 1 Operating Instructions Manual

8.3.3

Measures for achieving safe working periods S.W.P.

8.3.3.1

General

The safety and health provisions of the EC Machine Directive make it a legal requirement to eliminate special hazards
which may be caused, for example, by fatigue and ageing.
This requirement is also reflected in the third supplement to German accident prevention regulations UVV/BGV D8
(VBG 8) of 1.4.1996.
This requirement obliges the owner of serial hoist units to determine the actual duration of service of the chain hoist
on the basis of the operating hours, load spectra and/or recording factors. This is based on FEM 9.755/06.1993
Measures for achieving safe working periods for powered serial hoist units (S.W.P.).
The objective of this rule is to determine measures for achieving safe working periods over the entire duration of
service, although, according to the state-of-the-art, the hoist units are designed for specific periods of operation.
Premature failure cannot, however, be ruled out.
The following items have been taken from FEM rule 9.755 with reference to the electric chain hoist:
1. The actual duration of service determined on the basis of operating time and load must be documented at least
once per year.
2. The operating time T
3. The load k
4. The value determined for operating time T
recording factor f = 1,1.
5. The value determined for the estimated operating hours and load spectrum must be multiplied by the type of
recording factor f = 1,2.
6. The actual duration of service S is calculated as: S = k
7. A general overhaul must be carried out when the theoretical duration of service is reached.
8. All checks and inspections and the general overhaul must be arranged by the owner of the hoist unit.
A general overhaul is defined as:
Inspection of the machinery for the purpose of detecting all defective components and/or components and parts
close to failure and the replacement of all such components and parts. Following a general overhaul, the machinery
is in a condition similar to that of the same machinery in new condition as far as the principle of operation and
performance values are concerned.
For electric chain hoists classified according to FEM 9.511, the following theoretical durations of service apply (con‐
verted into full load hours):
Group of mechanisms
Duration of service / full load hours
[h]
Tab. 44
The actual duration of service is considerably increased if the chain hoist is only operated with partial load. For a
chain hoist operated on average with half load, for example, this results in an 8-fold increase in the actual duration
of service, with operation at one quarter of the full load, a 64-fold increase.
8.3.3.2

Calculating the actual duration of service S

The actual duration of service S of the electric chain hoist can be determined as follows:
S = k • T • f
mi i
k : Actual load spectrum factor
mi
T : Number of operating hours
i
f : Factor depending on the type of recording
(number of operating hours) can be estimated or read on an elapsed time indicator.
i
(load spectrum) must be estimated.
mi
1Cm
200
using an elapsed time indicator must be multiplied by the type of
i
• T • f
mi i
1Bm 1Am 2m
400 800 1600
2m+ 3m 4m
1900 3200 6300
71