PROCESS CHARTS

Process charts provide diagrammatic means for recording the sequence of activities in an existing method under study. In this way it is possible to have a visual aid to the overall conception of the method and a sound basis on which to effect improvements. Process charts of all types are constructed by using five different symbols linked together to represent the sequence of individual events or activities in the total operation under study. The total operation must be clearly defined before the study commences, as must be the points where it commences and where it finishes. The ASME symbols were derived by a committee of the American Society of Mechanical Engineers from those originally used by Gilbreth and are now shown.

Ο Operation (i.e. doing something, e.g. laying a brick, knocking in a nail)

→ Transport (i.e. moving something—plant, labour or material, e.g. pushing a barrow, hoisting by crane)

 Storage (permanent) i.e. material kept and protected until wanted for use e.g.cement in silo, brick stacks)

D Delay or temporary storage (i.e. when next operation cannot take place e.g. hoist waiting to be loaded, operatives awaiting material, an excavator awaiting a lorry to load)

□ Inspection (i.e. examining for quality and/or quantity, e.g. measuring opening, checking the weight of ballast at the concrete mixer, checking the vertical height of courses in brickwork)

◘ Combined activity (i.e. two activities performed at the same time or by same operator, e.g. loading aggregate into weigh batcher)

Process charts can be very useful in assisting with the establishment of an economic layout for workshops and yards where a repetitive process is to be undertaken. For example, the layout of a concrete precasting yard, an area in which steel reinforcement will be stored, cut, and bent, or the layout of a stores compound, which is often provided for some of the more valuable building materials. The charts can be drawn at varying levels of detail depending on the scope of the process to be recorded.

Time study is a work measurement technique for recording the times and rates of

working for the elements of a specified job carried under specified condition and for

analyzing the data so as to obtain the time necessary for the carrying out of the job at a

defined level of performance.

This can be carried out quite often by the use of an ordinary wristwatch or stopwatch and

is possibly the most useful form of work measurement used in the building industry; it can be

used on both single operatives or gangs, as required. Stages in time study are:

1. Timing

2. Rating

3. Normalizing

4. Allowances

Timing : is the actual taking of the time to complete an operation. The degree of accuracy in

Timing will depend upon the task being recorded.

Rating: This is the allocating to a worker a relationship to a standard. The Standard Rating

of 100 in BS 3138 is equivalent to the ‘average rate at which qualified workers will naturally

work at a job, provided they know and adhere to the specified method and provided they are

motivated to apply themselves to their work’. An employee adjudged to be at a slower pace,

He may be rated at, say, 80. The skilled, efficient worker can achieve over 100.

Normalizing: This is the time that, in the judgement of the work-study man, an element

should be performed. Normalized time is referred to as basic time and is obtained by a simple

formula: Observed Time Observed Rating

Standard Time: The time in which an average worker can work continuously under

standard conditions without adversely affecting his health.

Allowances: Can be divided into two groups:

1. Process allowances

2. Rest allowances

PROCESS ALLOWANCE

A process or unavoidable delay allowance is given so that the worker will not lose earnings

due to an enforced delay over which he has no control, e.g., the cleaning of tools or plant.

REST ALLOWANCE

Rest (or relaxation or fatigue) allowance is the time that an operator is allowed for

his personal needs and for fatigue. Varies with every performance and condition of work,

and are added so that a worker can keep physically and psychologically fit to perform an

operation for an allotted time.

Contingency allowance: This is a special allowance applied to various tasks that have to be

carried out by the worker who will not be doing a productive job, e.g. a joiner sharpening saw

or chisels, consultation with supervisors, obtaining special materials/tools from stores. These

allowances should not exceed 5% and should only be applied to justifiable cases.