Drawing control made easy

Oct. 18, 2006
Ensuring that your drawings are accurate and up-to-date is easier than you might expect.

Have you ever tried to construct a model plane when the instructions are missing? Has anyone ever asked you for directions when you yourself were lost? These questions are synonymous with out-of-date or inaccurate drawings in the work place.

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Recently someone asked me to help them develop a five-year plan for managing a work area. I asked if they had an up-to-date set of drawings for this particular area. The answer was all too familiar in industry: "No, we don't have up-to-date drawings but we still need a plan."

How can anyone provide valid guidance or make reasoned recommendations without an accurate picture for that plant area? Yet, this the type of problem that management usually faces. The answer to the question affects the safety, productivity, and financial performance of any plant or company. This article deals with the issue of integrating drawings in accordance with the Process Safety Management process, OSHA 1910.119.

Some type of procedural system — better known as document control — is the key to a successful program for accurate drawings. Today, most document control systems are electronic. There are many types of computer aided design packages from which to choose. Each makes implementing and maintaining document control easy.

However, it is important to standardize on a CAD system and software package throughout the plant or corporation. If more than one CAD system is in use, then there must be software compatibility among systems or you must have software to translate CAD files.

Once the CAD software is implemented on a network, access to the drawing files must be controlled. The personnel that needs access to the drawings includes plant maintenance personnel, plant engineers, and others. Maintenance needs the drawings for troubleshooting process equipment. Engineers need access to drawings for plant expansions and renovations.

A good document control system provides access using any of several methods. The first is controlled access through a supervisor's office where the system can be monitored and kept under lock and key if necessary. This may be the least complicated and least expensive approach but it is not the preferred method. The second approach is through password-limited "read only" access to files for the majority of the employees in a plant. Only the engineers and designers have "read/write" access to the files.

The conduit of change for any drawing should be a formal procedure that requires several signatures to ensure adequate checks and balances. After updating drawings, conduct a formal review that includes the design engineer, the safety representative, relevant plant personnel, and any management representatives for the area affected by the change. If the plant is under the jurisdiction of OSHA 1910.119, then a management-of-change document must be filed and the proper signatures for this change must be documented.

Once parties agree and the change is documented, the next step in the Process Safety Management process is to complete the hazard and operability review. There are several other steps to integrate the Process Safety Management process into this change but these are beyond the scope of this article.

Drawing numbering system

Over a period of years many numbering systems for drawings have been tried. The following technique for assigning drawing numbers is the result of carefully reviewing these systems.

The drawing number itself should encode the building or area represented by the drawing, the discipline represented by the drawing content, and the equipment the drawing depicts.

Consider drawing number 114-E-105, for example. The first three numbers represent the building number--in this example, building number 114. The letter represents the discipline addressed by the drawing as in the following coding scheme:

  • E for electrical,
  • I for instrumentation,
  • A for architectural,
  • C for civil,
  • M for mechanical,
  • P for process or piping (P&ID), and
  • S for structural.

The three numbers following the letter represent the process area or equipment number. For instance, 105 may represent Furnace Number 1 or Chiller Number 3. This number should also be used in a database when filing information related to that particular equipment number. This database should contain information such as spare parts data and vendor cut-sheets on pumps, valves, and agitators, and so forth. The encoded information should also be used when purchasing equipment, troubleshooting or maintaining it, and recording information regarding equipment capacity.

Some drawing numbering systems depend upon key words in the drawing title to find the drawing in an electronic file or database. These systems are inefficient and usually require extensive effort to locate the proper drawing. Search time equates to dollars lost for those doing the searching. Most systems using this method have drawing numbers that convey absolutely nothing about the drawing itself.

For example, if the title of the drawing is "Waste Treatment Facility MCC", then the electronic file or database should contain the keyword MCC and not M.C.C. or Motor Control Center. If you cannot determine the keyword, you are shooting in the dark. As you can see, lacking some standardization, you need to search on several key words.

In cases like this, reengineering is necessary and the cost can be staggering. On the other hand, there are certain numbering systems that can be efficient. These systems require that certain numbers be blocked out for certain disciplines. An example is using 95800-96800 represents electrical drawings.

Drawing verification

One of the problems that plague most engineers is confirming that the most current revision the drawing is in use. If there is a formal document control system in place, then this issue is of minimal concern. Once the document control system is proven to be accurate, conduct an audit using parties outside the controlled area. Keeping the drawings on electronic media and creative batch file writing significantly reduces the opportunities for using incorrect revisions.

The design engineer and production personnel should verify completed drawings using a formal walk down in the field. After completing the field verification, the person or persons associated with the field verification process should formally sign-off on the drawing. This formal verification becomes an essential part of the conformance to the 14 elements of the Process Safety Management process.  Documentation in the Process Safety Management process must be an accurate reflection of the physical system in the plant. This is needed to perform an accurate hazard and operability study. This applies to Piping & Instrument Diagrams more than any other drawing in the process. For example, assume a fuel train drawing shows a check valve in the fuel supply line to a burner management system. If the check valve was never installed, a hazard and operability meeting would have caught the error. The check valve shows up as an action item in the hazop report and thereby prevents the potential for reverse flow of gas. Long downtimes for repair are the result of not detecting errors like this early enough.

Advantages of an accurate drawing

There are many advantages to having accurate drawings. A partial list includes:

  • safety of personnel,
  • conformance by law to OSHA 1910.119, and
  • saving dollars on engineering maintenance and lost production cost.

These are just a few good reasons how and why your drawings should be kept up-to-date

If a drawing is accurate, it can be used as another reliable tool in the lock-out-tag-out procedure for verifying proper voltage sources. If a plant is covered under the Process Safety Management law, the drawings depicting the process must be accurate according to the Process Safety Information Element of the law. This element requires that employers must develop and maintain written safety information that covers the hazards of the chemicals used in the process, the technology of the process, and the equipment used in the process.

Should a plant not be covered by the Process Safety Management law, the process of updating drawings and the procedures that require this process to be successful should be an active part of the operating plant. No matter how large or small the plant, documentation control is the very lifeline of your plant environment. This saves money in the long run and, more importantly, could save someone's life.

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