Case study - Better maintenance starts with better documentation

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Courtesy of Anguil Environmental Systems, Inc.

OXIDIZER SERVICE SERIES: PART 1

Your oxidizer system is both a significant investment in - and a long term commitment to - environmental compliance. Part of properly servicing your oxidizer system is maintaining the design documentation associated with that system. In the oxidizer design world, National Fire Protection Association (NFPA) standards are often viewed as good practice. However, not everyone realizes that those same standards include requirements for ongoing oxidizer maintenance and system documentation.

The following is a list of critical design documentation that oxidizer users should have on hand as the first step in implementing an overall system reliability plan. This is the same set of documents that Anguil seeks to build and maintain to offer value-added service on anyone's oxidizer system, regardless of original manufacturer.

1. Process and Instrumentation Diagram (P&ID): The P&ID is the command drawing that summarizes system instrumentation, safety devices, operational limits, and control loops. The P&ID typically provides the tag numbers for oxidizer components as well as the number and type of process exhaust pickups for the system. Often times, the system utility requirements and performance parameters are listed as well.

2. Electrical Schematics: The Electrical Schematics provide the detailed connectivity of the entire system. Almost all system troubleshooting is performed with the electrical schematics in hand. It is critical that the Electric Schematics are not only kept readily available, but also revised to keep up with system changes.

3. Sequence of Operation / List of Set Points & Alarm Conditions: The Sequence of Operation is a step-by-step description of how the oxidizer is designed to operate: how it starts, how it brings process exhausts online, how it maintains airflow and temperature control, and how it safely shuts down. It typically contains a list of the set points and alarm conditions for the system. One of the key codes in oxidizer design is the National Fire Protection Association's NFPA 86: 'Wiring diagrams and sequence of operations for all safety controls shall be provided' (From NFPA 86: Standard for Ovens and Furnaces 2011 Edition - Section 4.1.1.2)

4. Programmable Logic Controller (PLC) Program:   If your system includes a PLC, we recommend you keep a fully documented copy of your PLC program on file. Some oxidizer suppliers may be reluctant to release this information to system end users as PLC Programs can include proprietary control schemes. However, with a signed confidentiality agreement in place, end users should be able to obtain this code. If your oxidizer manufacturer is no longer in business, it is often possible to upload the program directly from the PLC. However, uploaded code will likely be undocumented and you may have to hire an oxidizer service provider to re-enter the code documentation. Information on Anguil's PLC programming capabilities can be found here.

5. Human Machine Interface (HMI) Program:   The HMI (aka Operator Interface, Operator Touch Screen) is the operator's window into the workings of the oxidizer's PLC. The HMI Program goes hand-in-hand with the PLC Program to control your oxidizer system by determining which data points from the PLC are displayed for the operator and which set points and tuning parameters the operator will be allowed to adjust from the HMI. The HMI also provides system status messages and/or alarm messages based on the PLC's outputs.  A failed display can leave you essentially blind when it comes to safely operating your oxidizer system. If this happens at an inopportune moment, you want to be prepared to download your HMI Program to a replacement display from your spare parts inventory.

6. Expected Pressure-Temperature Profile: This is one of the more obscure documents to obtain. However, it is pivotal in the development of a reliability plan for your system. This can be as simple as a small table on the P&ID Diagram giving the expected temperature and pressure values at various points throughout the oxidizer. It is critical to know what those values are to set up a regular inspection protocol for your maintenance personnel. Ideally, you should have a table showing expected pressure and temperature data at the common process exhaust airflow amounts your production requires. If this is unknown, ask your system provider to provide data for two conditions: at full oxidizer airflow capacity and at half oxidizer airflow capacity. You will then be able to approximate the points in between when establishing your customized inspection checklists.

7. Bill of Materials / Recommended Spare Parts Lists: Finally, a complete bill of materials for your oxidizer system will allow you to obtain the parts you need to maintain system operation. Ideally, the parts listed in the Bill of Materials would be further categorized as 'Critical Spare Parts,' 'Recommended Spare Parts,' 'Consumable Spare Parts,' 'Convenience Items,' 'Long Lead Time Components,' etc. This allows operators to make an informed decision on the type and quantity of spare parts to stock based on specific production and compliance requirements. Some air permits actually require that critical spare parts be kept on hand. More detailed information on these categories can be found on the Spare Parts section of our website.

Note: This list was specifically generated with oxidizer system maintenance in mind. One area not covered is permit compliance documentation. Compliance documentation requirements vary greatly across local, state and federal agencies, making it difficult to provide generalized recommendations appropriate for all operation scenarios. At a minimum, Anguil highly recommends that you summarize permit compliance documentation requirements in a single concise document that will keep all parties aware of the key compliance parameters to monitor and record with respect to your oxidizer system.  

ADDITIONAL INFORMATION

Here are some additional highlights regarding system documentation from the current edition of NFPA 86 Standard for Ovens and Furnaces 2011 Edition:

4.1.1.1 Plans shall be drawn that show all essential details with regard to construction, ventilation, piping, and electrical safety equipment. A list of all combustion, control, and safety equipment providing the manufacturer and type number shall be included.

4.1.1.2 Wiring diagrams and sequence of operations for all safety controls shall be included.

7.3.2 Operating instructions that include all of the following shall be provided…

(1) Schematic piping and wiring diagrams

(2) Startup procedures

(3) Shutdown procedures

(4) Emergency procedures

(5) Maintenance procedures

7.3.3 When the original equipment manufacturer no longer exists, the user shall develop inspection, testing, and maintenance procedures.

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