Specification Writing and Management

Max Mcrobb

• Publisher: CRC Press
• Year: 2020
• eBook ISBN: 9781000147391
• Topic: Technology & Engineering
• Subtopic: Civil Engineering
• Index: Technology & Engineering

This book deals with the fundamentals of specification writing and management. It is useful for anyone concerned with the preparation of standards in a world that is shrinking due to improvement in communication and where many specifications have to hold clarity when translated into other languages.

1

A Brief Historical Review

The following quotation regarding Solomon’s temple is from Kings 1:6:

In the inner sanctuary he made two cherubim of olive wood, each ten cubits high.

Five cubits was the length of one wing of the cherub, and five cubits was the length of the other wing of the cherub.

It was ten cubits from the tip on one wing to the tip of the other. The other cherub also measured ten cubits.

Both cherubim had the same measurements and the same form.

The height of one cherub was ten cubits and so was the height of the other cherub.

That specification is one of the earliest known. In addition to its historical interest, something else about it is of note: It has faults. It does not provide any manufacturing tolerances and it is repetitious. It could be said to be a construction industry specification—an industry not noted for high-quality specifications, although the situation is said to be improving. The problem caused by lack of tolerances in this specification is highlighted by the fact that the cubit varied between 18 and 22 inches according to the country and the period. Could that lead to interchangeability problems?

There is at least one other specification of note in the Old Testament, which could be said to belong to the food industry. From Leviticus 11:3:

Whatever parts the hoof and is cloven footed and chews the cud, among the animals, ye may eat

That is a very clear statement of requirements. Unfortunately, however, the clarity of that statement is blurred by the following qualification:

Nevertheless, amongst those, ye shall not eat these:

The camel which parts the hoof and is cloven footed and chews the cud, is unclean to you

And the rock badger . . . is unclean to you;

and the hare . . . is unclean to you;

and the swine . . . is unclean to you.

This qualification to the original requirement introduces confusion. For example, the hare does not part the hoof. I am not an authority on animals, nor could I get any help from the Children’s Britannica, but certainly one of those unclean animals does not conform to the stipulated exclusion requirements. The message from this example is, clearly: Do not qualify otherwise clear statements. There may also be a translation problem. That is dealt with in later chapters. It is clear that specification problems are not new.

One can find other early examples of processes that can be presumed to have had specifications, although it is more than likely that in the earliest times at least, most of them were oral. Very few people could read or write. One will never know for certain how long it took to develop those earliest processes and to determine the most suitable specifications. But it surely must have taken a long time before those early workers could be sure that their processes were consistent and reliable.

One example is brickmaking. About 1500 B.C., in Egypt, bricks were made by mixing mud and straw and then letting them dry in the sun. As time went on the Egyptians discovered that if they baked their bricks in a kiln, the results were much superior. They were more damp resistant and much harder. But it would have been necessary to determine the maximum and minimum times and temperatures for firing in the kilns. Without this determination the bricks would either be burned or be soft and porous.

Another example from Egypt is that of glassmaking. Originally, it had been found that sand and ash heated together produced glass. Then it was discovered that the ash had to have a high potash content. For many centuries there was little change until, comparatively recently, limestone was used as one of the constituents. In addition, for thousands of years all glass was made by hand, and some still is. It is only within the last hundred or so years that glass has come to be made by machine, with close process control and precise specifications.

Some of Leonardo da Vinci’s pigments have been lost to us because of the apparent absence of written specifications. At Ham-mershus on the Danish island of Bornholm, in the middle of the Baltic Sea, there are 1000 year-old castle ruins. In these ruins the bricks have been eroded by time, but the mortar has not. Today, no one knows what the specification was for this extremely hard wearing mortar. Hydraulic cement was used by the Romans, but the process was lost with the decline of the Roman Empire. It was rediscovered in the mid-eighteenth century when Smeaton built the Eddystone lighthouse. Then, about 1824, Aspdin discovered the process for producing portland cement. It has remained virtually unchanged ever since.

Originally, all these specifications must have been oral and were handed down through the generations. Oral communication of this type is neither safe nor satisfactory. It is not surprising, therefore, that many valuable processes were lost and have not been rediscovered. A game that was popular at family parties during my childhood illustrates very well the problems that can be caused by the oral transfer of information from one person to another, especially when it is between people of different generations. Even with written specifications this can be a problem when, as is so often the case, the users choose to rely on their memories instead of referring to the written text.

In that childhood game the players sat on the floor in a ring. One player would make up a short sentence and whisper it into the ear of the next person. This person passed it on again, and so on, until “a” message came back to the originator. No repetitions were permitted, and each person had to pass on what he or she thought had been said. Invariably, the message that came back to the originator bore little or no resemblance to the original message. The game always provided a lot of fun. Memory applied in a similar fashion to a specification does not provide fun. It costs money.

LOST COSTS.

In comparatively recent times, during the reign of Charles I in England, there were written specifications laid down by the Master General of the Ordnance (MGO) for the ammunition supplied for the use of the forces of the king. Some of these specifications have been on view at the old headquarters of the Royal Engineers at the Woolwich Arsenal. (Incidentally, the post of MGO is still in existence, and the Prince of Wales served part of his army career on its staff).

In the early days of industrial history, there was not much direct measurement. For one thing, there was no precise standard of length and no accurate means of measurement. In medieval Germany the foot was equal to the average length of the feet of 12 men emerging, successively, from church on Sunday. The foot was also an ancient measure for black tin, a metallic ore, and equaled 2 gallons. That measure is now nominal and about 60 pounds in weight. The Celtic, or natural foot was equal to 9.9 inches. Three barleycorns equalled 1 thumb; 3 thumbs equalled 1 palm; 3 palms equalled 1 Celtic foot. The yard was equal to 12 palms or ½ fathom or 16 nails. The mile was equal to 1408 ells. It is perhaps no wonder that measurement was neither easy nor accurate.

Much more recently there was developed an international inch, which was derived from the international meter. It is equal to precisely 25.4 millimeters. But there was also a British “standard” inch and an American “standard” inch. All three were different from each other, although not by much—just a few millionths of an inch. This did not cause any problems in ordinary day-to-day measurement but was a cause of difficulty in international work. Resolution of the problem was achieved in 1959. In that year the United Kingdom, the United States, and the countries that used the international inch reached agreement, that the international inch would be used by all countries and would become truly international. Not only in medieval times were measurements difficult to standardize.

In the not too distant past it was common for goods to be sold on the basis of a bargain struck between the seller and the buyer. However, the meaning of words, even then, was subject to considerable change, and the law recognized that fact. This was made crystal clear by the concept of caveat emptor: let the buyer beware. It was up to the buyers to satisfy themselves of the quality of a bargain before it was sealed. That is a maxim that still holds, as many people have found to their cost.

A good present-day example of caveat emptor is that of the street trader whose goods are openly displayed for all to see. A seller may have on display boxes of fruit of excellent quality and good size. A purchaser who buys a quantity of that fruit is liable to have the purchase made up from stock taken from boxes not on display and of lesser quality. It is up to the purchaser to insist on being served from the boxes of high quality fruit being displayed. If the customer does so, the seller cannot, by law, refuse, as the fruit is openly displayed for sale.

Quite early on, it was customary for sellers and buyers to strike a bargain on the basis of agreed samples that would be offered by the seller. The samples would be examined by the buyer and accepted if the buyer was satisfied. This practice is also frequently used today. One well-known industrial example was the British Admiralty pattern. With the use of samples it was easy for the buyer, especially if in possession of an approved copy, to ensure that the goods supplied conformed to the specification (the sample) that had been agreed upon. Three very common examples in general use today are cloth, wallpaper, and paint, the first two usually for appearance, pattern, texture, and color, and the last for color only. For none of these does there appear to be a simple alternative, so their use is likely to continue for a long time to come.

In many kinds of industrial products, which are built up from individual parts, interchangeability was a problem. Perhaps it would be more correct to say that interchangeability was not a problem, as it was not recognized. There was no guarantee that parts made later would fit an earlier product or even that these parts could be used as replacement parts for a current product. Chronometers are an excellent case in point. A damaged one would be returned to the makers for repair and replacement parts would be specially made to fit.

However, the principle of interchangeability could not come into its own until a means of precision measurement became available. Otherwise, it would not be possible to measure parts with sufficient accuracy to ensure interchangeability. It was probably not until the latter part of the nineteenth century, when the micrometer was developed, that it became possible to make measurements of sufficient accuracy for the purpose. Then interchangeable manufacture became a reality.

Early in the twentieth century Johansson blocks, or slip gauges, were developed. In the United Kingdom in about 1914, the Eden “Millionth” Comparator was developed at the National Physical Laboratory. This instrument was still in use as recently as the 1960s.

Despite these developments there is still selective assembly, even actual fitting. As demand grew, so did growth in the size of the manufacturing organization necessary to deal with it. With growth came the inevitable separation of the various functions within the organization: design, sales, purchasing, engineering, manufacturing, inspection/quality activities. They all became separate and recognizable parts of the whole. All this, of course, helped to speed the increase in the number of specifications in use.

Their use became highly desirable not only for manufacturing purposes but also for buyer protection. Buyers were becoming increasingly less knowledgeable about the details of the products they bought. Reliance on the specifications grew steadily until we find at present that there are many different kinds of specifications used for different purposes. This reliance applies to industrial buyers as well as to private buyers, alth...

Table of contents

• Cover
• Half Title
• Series
• Title Page
• Copyright Page
• About the Series
• Foreword
• Preface
• Contents
• 1 A Brief Historical Review
• 2 Current Specification Types and Their Purpose
• 3 Basic Specification Problems
• 4 Specification Faults: Group 1—Words
• 5 Specification Faults: Group 2—Ideas
• 6 Specification Faults: Group 3—Presentation
• 7 Case Study 1: Customer Specification Problem
• 8 Case Study 1: Customer Specification Problems—A Solution
• 9 Case Study 2: Manufacturing Specification Problem
• 10 Case Study 2: Manufacturing Specification Problems—A Solution
• 11 Case Study 3: In-House Acceptance Specification Problems
• 12 Case Study 3: In-House Acceptance Specification Problems—A Solution
• 13 Case Study 4: Control Procedure for Procurement Specifications
• 14 Case Study 5: Control Procedure for Incoming Piece-Part Acceptance Specifications
• 15 Case Study 6: Pointing to Specification Management
• 16 The Concept of Specification Management
• 17 Introducing Specification Management
• 18 Case Study 7: A Recent Practical Exercise
• 19 Word Processors and Document Preparation
• 20 Conclusions
• Index