A-How to apply the OCRA Checklist_02.04.09

THE OCRA CHECKLIST

For a quick evaluation of the exposure of the upper limbs to ripetitive movements

INTRODUCTION

This chapter is devoted to a description of the contents and the criteria for setting up a concise procedure, useful to identify the presence of upper limb bio-mechanical overload risk by means of the OCRA checklist. The use of the checklist does not substitute the exposure evaluation calculated with the OCRA index, which is more accurate, but it is still essential during the first phase of risk evaluation to produce the first " map of risk ".

The OCRA checklist describes a work-place and estimates its intrinsic risk, as if the work-place were used for the whole of the shift by one worker. This procedure makes it possible to find out which work-places in the company are at risk because of their intrinsic structural characteristics, the risk being classified as "absent", "borderline", "present high".

In other words, at the first stage, the OCRA checklist supplies an early estimate of the intrinsic risk of each work-place, but not the exposure indexes for the operators, because that part of the assessment must be completed later.

The analysis system suggested with the checklist begins with the establishment of pre-assigned scores (higher with the higher risk), for each of the 4 main risk factors (lack of recovery periods, frequency, force, awkward postures and movements), and for the additional factors.The sum total of the partial values obtained in this way (weighted for the net duration of the repetitive task in a shift) produces a figure (a score) which then enables the estimation of the actual risk level.

1^st STEP

EVALUATION OF THE NET DURATION OF THE REPETITIVE TASK AND THE NET DURATION OF THE CYCLE TIME

The sheet 1 ( ANNEX CHECKLIST MODEL) of the Ocra checklist includes a short description of the work-place and of the kind of work done there. It is advisable to find out how many shifts (e.g.: unic shift of 8 hours or 2-3 shfts of 8 hours or 2-3 shifts of 6 hours) a day are present, how many work-places are identical to the one described, and how many, although not identical, are very similar.In large companies, it is always useful to carry out analyses based on similarities, because in this way it is possible to obtain more information in a shorter time.

Before starting with the risk analysis a scheme proposes the evaluation of the net duration of the repetitive task (TAB.1). This is possible subtracting by the total duration of the shift, all the periods spent in recovery periods (lunch, breaks official or not) or doing not repetitive activities (clean, supply).

DESCRIPTION		MINUTES
SHIFT DURATION	official
	real
OFFICIAL PAUSES	contractual
REAL PAUSES	real
LUNCH BREAK	official
	real
NON REPETITIVE TASKS (eg: cleaning, supplies, etc)	official
	real
NET DURATION OF REPETITIVE TASK/S
No. Of UNITS (or cycles	planned
	real
NET CYCLE TIME (secs.)
OBSERVED CYCLE TIME

TABLE 1

DESCRIZIONE		MINUTI
SHIFT DURATION	official= 480	460
	real=460
OFFICIAL PAUSES	2 breaks of 10 min. each	30
REAL PAUSES	2 breaks of 15 minutis each
LUNCH BREAK	official=30	45
	real=45
NON REPETITIVE TASKS (eg: cleaning, supplies, etc)	official=30	30
	real
NET DURATION OF REPETITIVE TASK/S		355
No. Of UNITS (or cycles	planned	354
	real
No. Of UNITS (or cycles		60
OBSERVED CYCLE TIME		59
4%= difference % between cycle net duration and observed cycle duration

Exemple

Example A1: Net Duration

Write the numbers of the real produced Units

Proceed with calculation of the net duration of the cycle time (no. of pieces or cycles/ net duration of the repetitive task):

(1)

Now the suggestion is to compare the observed cycle time with the net cycle time: if they are similar it is possible to start the risk analysis, otherwise explain the difference before continuing. Difference not exceeding 5% can still be acceptable. if they are more of 5% it is necessary to reassess the duration of the different organizational component of the shift and/or the actual number of unit produced.

2^nd STEP

EVALUATION OF THE NET DURATION MULTIPLIER

If the repetitive task lasts less than 8 hours within one shift, it is possible to correct the value obtained, according to actual net duration, multiplying the final score for the duration multipliers corresponding with the net duration of the repetitive task as shows below (TAB. 2):

duration (min.)	multipliers
60-120	0.5
121-180	0.65
181-240	0.75
241-300	0.85
301-360	0.925
361-420	0.95
421-480	1
> 480	1.5

TABLE 2

The resulting number must be written in the proper box (duration factor ).

Exemple A1: Net Duration Factor

3^rd STEP

EVALUATION OF THE LACK OF RECOVERY SCORE

A recovery period ( ANNEX RECOVERY ) is a period during which one or more muscle-tendon groups are basically at rest. The following can be considered as recovery periods:

Breaks (official or non official) including the lunch break

Visual control tasks

Periods within the cycle that leave muscle groups totally at rest consecutively for at least 10 seconds almost

every few minutes.

For repetitive task the reference condition is represented by the presence, for each hour of repetitive task, of work breaks of at least 8-10 minutes consecutively or, for working periods lasting less than one hour, in a ratio of 5:1 between work time and recovery time . In relation to these reference criteria it is possible to consider how many hours, during the work shift, do not have an adequate recovery period. It requires the observation, one by one, of the single hours that make up a working shift: for each hour, a check must be made if there are repetitive tasks and if there are adequate recovery periods. For the hour preceding the lunch break (if present), and for the hour before the end of the shift, the recovery period is represented by these two events.On the basis of the presence or absence of adequate recovery periods within every hour of repetitive work, the number of hours with "no recovery" is counted.

To simplify the evaluation of the lack of recovery peiods the OCRA CHECKLIST presents six different scenarios (TAB. 3) whereby the interruptions of the tasks and/or pauses are distributed during the working shift: a score corresponds to each scenario. The scenario to choose is the one most similar to the one which is usually (and realistically) used by the workers at that work-place. Intermediate scores may be used with respect to the suggested ones, if they give a better picture of the real situation. Using this table do not count the breaks in the hour before lunch or in the last hour of the shift as recovery. Draw the breaks distribution in the shift.

0	there is an interruption of at least 8/10 minutes every hour in the repetitive work (also count the lunch break) or the recovery period in included in the cycle.
2	there are 2 interruptions in the morning and 2 in the afternoon (plus the lunch break), lasting at least 8-10 minutes on the 7-8 hour shift, or at least 4 interruptions per shift (plus the lunch break), or four 8/10 minute interruptions in the 6-hour shift.
3	there are 2 pauses, lasting at least 8-10 minutes each in the 6-hour shift (without lunch break); or, 3 pauses, plus the lunch break, in a 7-8-hour shift.
4	there are 2 pauses, plus the lunch break, lasting at least 8?10 minutes each over a 7-8 hour shift (or 3 pauses without the lunch break), or 1 pause of at least 8-10 minutes over a 6-hour shift;
6	there is a single pause, lasting at least 10 minutes, in a 7-hour shift without lunch break; or, in an 8-hour shift there only is a lunch break (the lunch break is not counted among the working hours).
10	there are no real pauses except for a few minutes (less than 5) in a 7 to 8-hour shift..

TABLE 3

The resulting number must be written in the proper box (recovery)

Exemple A1: Recovery Factor

4^th STEP

EVALUATION OF FREQUENCY OF TECHNICAL ACTIONS SCORE

Here too, nine scenarios are offered ( TAB. 4), each characterized by a score from 0 to 10. ( ANNEX FREQUENCY). Each item describes the type of upper limbs technical actions in time (slow, quite fast, fast, very fast), relating it to the possibility, or impossibility, of having short breaks (constant, or inconstant). ?Action frequencies per minute? are also indicated as reference points, to help in the choice of the most representative scenario for the task under examination at that moment.

It is advisable to estimate the action frequency of the limb which is more involved in the task, by using a stop-watch video or by observing the operator, counting the technical actions directly and asking the operators what he is doing (he can help easily in find the technical actions).
It is also possible to choose intermediate scores with respect to those indicated, if they better reflect the actual situation. In using intermediate scores, if there is the possibility or not of having short breaks, respectively reduce or add 1 point score at the presented scenarios. It is possible to describe ?dynamic and static? actions:?as most representative of the task choose the one with the highest risk value.

	DYNAMIC TECHNICAL ACTIONS
0	arm movements are slow. frequent short interruptions are possible (20 actions per minute).
1	arm movements are not too fast. short interruptions are possible (30 actions per minute).
3	arm movements are quite fast (about 40) but short interruptions are possible
4	arm movements are quite fast. only occasional and irregular short pauses are possible (about 40 actions per minute).
6	arm movements are fast. only occasional and irregular short pauses are possible (about 50 actions per minute).
8	arm movements are very fast. the lack of interruptions makes it difficult to keep the pace, which is about 60 actions per minute
10	very high frequencies: 70 actions per minute, or more. absolutely no interruptions are possible
	STATIC TECHNICAL ACTIONS
2.5	an object is held for at least 5 consecutive seconds, incurring one or more static actions for 2/3 of the cycle (or observation ) time
4	4,5 - an object is held for at least 5 consecutive seconds secs., incurring one or more static actions for 3/3 of the cycle (or observation ) time .

TABLE 4

Choose one answer for each upper limb. It is possible to use intermediate scores. If both static and dynamic actions are present:

. CONSIDER both static and dynamic actions

. As most representative of the task CHOOSE the one with the highest risk value.

he score obtained must be written in the proper box (frequency).

Exemple A1:Frequency Factor

5^th STEP

EVALUATION OF FORCE SCORE

The exertion of force ( ANNEX FORCE) is significant for the upper limb disorders under analysis here, and must be reported when it occurs periodically at least every few cycles. The question concerns the presence of the need of force necessary to carry out different operations. As indicated above: the greater the presence in the cycle, the higher the value of the numerical indicator. Here, too, intermediate values can be chosen. The group of questions (TAB. 5) include the description of some among the most common working activities ( LEVEL AND DURATION), which require the exertion of quite maximum force (score of 8 or more on the Borg CR-10 scale) or high force (scores 5-6-7 on the Borg scale) or moderate degree of force (score 3-4 on the Borg scale) respectively. The activities which must be described for the three different levels of force are: to pull or push a lever, push buttons, close or open, press or handle components, use tools. It is also possible to add other items, which may be needed to represent other actions where the use of force is required. Here, too, it is possible to choose intermediate scores. The total score which is representative of force exerted is obtained by adding the scores indicated in one or more of the three boxes (FORCE). To describe an activity that requires use of force, it is advisable, as for the OCRA index, to interview the operator/s directly and to try.

PRESENCE OF WORKING ACTIVITIES INVOLVING THE REPEATED USE OF FORCE IN THE HANDS-ARMS (AT LEAST ONCE EVERY FEW CYCLES DURING ALL THE TASK ANALYSED)
THE WORKING ACTIVITY REQUIRES THE USE OF ALMOST MAXIMUM FORCE FOR: (score 8 or more on the Borg scale)
c pulling or pushing levers	2 seconds every 10 min	6
c pushing buttons	1 % of the time	12
c closing or opening	5 % of the time	24
c pressing or handling	*over 10% of the time ()**	32
c using tools
Lifting or handling objects
THE WORKING ACTIVITY REQUIRES THE USE OF STRONG FORCE FOR: (score 5-6-7 on the Borg scale)
c pulling or pushing levers	2 seconds every 10 min	4
c pushing buttons	1 % of the time	8
c closing or opening	5 % of the time	16
c pressing or handling	*over 10% of the time ()**	24
c using tools
Lifting or handling objects
THE WORKING ACTIVITY REQUIRES THE USE OF MODERATE FORCE FOR:(score 3-4 on the Borg scale)
c pulling or pushing levers	2 seconds every 10 min	2
c pushing buttons	1 % of the time	4
c closing or opening	5 % of the time	6
c pressing or handling	*over 10% of the time ()**	8
c using tools
Lifting or handling objects

TABLE 5

The score obtained must be written in the proper box (force).

Exemple A1: Force Factor

6^th STEP

EVALUATION OF AWKWARD POSTURE AND MOVEMENTS AND LACK OF VARIATION (OR STREREOTYPY) SCORES

Five blocks (TAB. 6) of questions are foreseen for the description of awkward postures

The groups of questions marked with the letters A, B, C, D each describe a separate joint segment, while the last group describes the presence of stereotypy, which means the presence of identical gestures (technical actions), repeated for at least 2/3 of cycle time ( score 1,5) or all the time (score 3). If cycle time is between 9-15 seconds, stereotypy must still be considered as present (score 1,5); if cycle time is equal or less or than 8 the score will be 3. Out of the scores for each of the separate joint segments (A, B, C, D), only the highest must be taken, and it can be added to that of stereotypy, if present (E): the total sum will be the general score for posture (POSTURE). The questions which are used to describe posture for each of the joint segments are very simple. For the arms, they describe how long the arms are kept at shoulder height, roughly; for the wrist, whether extreme postures are required; for the elbow, whether sudden movements, or hitting movements or extreme postures, are required ;for the hand, if the type of grip is a PINCH, a palmar grip, or a hook grip.

TABLE 6

The score obtained must be written in the proper box (posture).

Exemple A1:Posture Factor

7^th STEP

EVALUATION OF ADDITIONAL FACTORS SCORE

The presence of additional factors( ANNEX ADDITIONAL FACTORS) for a relevant part of cycle time must be described (e.g., inadequate gloves, vibrations, compression on the skin, etc.) using the showed scenarios (TAB. 7). The description must also include specifications as to whether the working pace is either partially or totally imposed by the machine. For each block, or group of questions, a single answer is allowed: the sum total of the partial scores thereby obtained gives the additional factor score .

2	gloves inadequate( which interfere with the handling ability required by the task) are used for over half the time
2	the working gestures required, imply a countershock ( such as e.g., hammering, or hitting with a pick over hard surfaces, etc.) with frequency of 2 time per minute or more
2	the working gestures required, imply a countershock using the hand as a tool, etc.) with frequency of 10 time per hour or more
2	exposure to cold or refrigeration (less than 0 degree) for over half the time
2	vibrating tools are used for 1/3 of the time o more.For tools with high level of vibrations use score 4.
2	the tools employed cause compressions of the skin (reddering, callosities, blisters, etc.)
2	precision tasks are carried out for over half the time (tasks over areas smaller than 2-3 mm)
2	more than one additional factor is present at the same time and , overall, the occupy over half the time
3	more than one additional factor is present at the same time and , overall, the occupy the whole of the time
1	WORKING PACE SET BY THE MACHINE, BUT THERE ARE ?BREATHING SPACES? (BUFFERS) IN WHICH THE WORKING RHYTHM CAN EITHER BE SLOWED DOWN OR ACCELERATED.
2	WORKING PACE COMPLETELY DETERMINED BY THE MACHINERY

TABLE 7

The score obtained must be written in the proper box for frequency (additional factors).

Example A1:Additional Factors

8^th STEP

CALCULATION OF THE RISK INDEX EXPRESSED BY THE CHECKLIST ACCORDING TO THE WOKPLACE STATION

The sum of the partial values obtained in this way (weighted for the net duration of the repetitive task in a shift) produces a figure (a score) which then enables the estimation of the actual risk level.

RISK FACTORS

By the OCRA checklist final score

( ANNEX OCRA INDEX) it becomes possible to identify the different risk areas (green, yellow and red) in accordance with "Critical" OCRA index values and to indicate the consequent preventive actions as reported in the following table (TABLE 8). Tramite il punteggio finale di checklist OCRA (vedi ALLEGATO Indice OCRA) è possibile classificare il lavoro come appartenente a diverse aree di rischio (verde, giallo e rosso), in in accordo con le zone 'critiche' dll'indice OCRA, allo scopo di indicare i valori e le conseguenti azioni preventive, come riportato nella tabella seguente (TAB. 8).

TABLE 8

The score obtained must be written in the proper box for frequency (force).

Example A1:FINAL CHECKLIST OCRA SCORE

9^th STEP

CALCULATION OF THE RISK INDEX EXPRESSED BY THE CHECKLIST ACCORDING TO OPERATORS EXPOSURE LEVELS: INTRODUCTION OF JOB ROTATION CONCEPT

If it is necessary to estimate the exposure of the workers, the following procedures should be adopted:

a) if the operator/s works exclusively at the work-place described in the analysis, then the OCRA checklist score given to the work-place is the same as that given to the operators;

b) if the operator/s works in two or more workplaces implying repetitive tasks (multiple task), to obtain the specific exposure index of that operator it is necessary to distinguish two different scenarios:

B1) Rotation among repetitive tasks has a frequency of almost once every hour.

In this case the "weighted by time" approach should be used , employing the following formula:

Checklist final score = [(score A x %PA) + (score B x %PB) +...+(score N x %PN)] x ( Dumtot )

Where:

score A = RECOVERY (shift)+FREQUENCY(task A)+FORCE(task A)+POSTURE(task A)+ADDITIONAL(task A)

score B = RECOVERY (shift)+FREQUENCY(task B)+FORCE(task B)+POSTURE(task B)+ADDITIONAL(task B)

score N = RECOVERY (shift)+FREQUENCY(task N )+FORCE(task N )+POSTURE(task N) +ADDITIONAL(task N)

%PA , %PB, %PN = percentage duration of single repetitive tasks (A, B and N) with respect to the total duration of repetitive tasks

Dumtot (duration multiplier)= multiplier given by the total net duration of all repetitive tasks (A+B+..+N) in the shift

RISK MAP SOFTWARE

B2) Rotation among repetitive tasks has a frequency of less of once every hour. In this case the "worst condition" approach should be used , employing the following formula

Where:

1,2,3,...,N = repetitive tasks ordered by their exposure levels (1= highest) considering respective duration multipliers (Dum_i)

Dum_i = duration multiplier for task_i real duration

Dum_tot = duration multiplier for total duration of all repetitive tasks

NB: the formula could be difficult TO CALCULATE MANUALLY, but using the software for the map of risk, it is possible to obtain automatically both, the index for the worker exposition for ONE HOUR ROTATION and for MORE THAN ONE HOUR ROTATION

NB: In order to build up "a map of risk" for the repetitive tasks in a company, a software was prepared for collecting the results of each (workplace/task) OCRA checklist. It allows to draw not only the map of risk of individual worplaces but also the one that refers to exposure of workers considering the job rotation. Go to the HELP of this software	RISK MAP SOFTWARE
NB: for learning how to count the technical action and how to evaluate the awkward postures and movements, see the specific chapter	ANNEX: RECOGNITION AND COUNTING TECHNICAL ACTIONS