How the Process Safety Should Influence Maintenance Strategies

Abstract: <>

Almost all chemical companies has Process Safety as major (sometimes the only) source of information to define how the Maintenance Strategies should be designed. One can say that this influence can be an excuse for too many preventive activities of maintenance; some studies show that too much maintenance could lead the equipment to premature failure. The purpose of this work is to show how Monsanto do Brasil – São José dos Campos use Process Safety as part of criteria well defined in order to avoid subjective analysis as well as what premises are used for Maintenance Strategies.

The Maintenance Strategies became more important that due date.

ABC Classification is defined as:

·         “A” – to apply maintenance techniques to assure the highest reliability of the equipment to avoid equipment failures.  

·         “B” – to apply maintenance techniques to assure the highest availability of the equipment to offer a reliable operation, and an acceptable cost for the businesses.

·         “C” – to apply maintenance methods that minimize maintenance costs in the long run.

Classification “A”

µ  Maintenance activities shall be established so that defects do not occur, or they are detected beforehand, in a way that the equipment does not lose its function.

µ  Preventive and/or predictive maintenance activities are required, and the use of advanced techniques is indicated. Information from the manufacturer shall be considered;

µ  Periodic tests and inspections are required, depending on the failure mode, in order to assure the equipment highest reliability.  Preventive replacements can be used.

µ  Detected defects shall be repaired as fast as possible. It is not recommended to monitor defect trends that can lead to the equipment loss of function. Exceptions shall be carefully analyzed by the Maintenance Engineer;

µ  Inventory of the spare parts in the warehouse shall be evaluated, on the basis of the information from the manufacturer. It is for the Maintenance Engineer to define the list of spare parts that shall be kept in stock;

µ  A quality assurance program for receiving spare parts is required;

µ  Deviations in maintenance activities will be managed by the Incident Registration system – IR;

µ  Failure or loss of function shall be analyzed technically, identifying the root causes.

µ   RCM and/or FMEA studies can be indicated for the increase of reliability and failure reduction.

      Classification “B”

µ  Maintenance activities shall be established so that defects are detected beforehand, and repair occurs rapidly in order to keep the equipment function available as long as possible.  

µ  Preventive and/or predictive maintenance activities are required. Information from the manufacturer shall be considered;

µ  Detected defects can be monitored to optimize the use of the equipment, or to make the repair suitable for the maintenance planning;

µ  Assembly instructions, special tools, training can be used in order to reduce repair time;

µ  Inventory of spare parts in the warehouse shall be evaluated in the basis of the information from the manufacturer and delivery time. The Maintenance Engineer is responsible for defining the list of spare parts that shall be kept in stock;

µ  The preventive/predictive maintenance program shall be accomplished according to the availability of the areas.

µ  Maintenance activities demanded by internal (guidelines) or external (legal and regulatory requirements) requirements SHALL be accomplished within the due date; Deviations in this activities will be managed by the  Incident Registration system – IR

µ  Studies for reducing maintenance costs are indicated for this classification;

Classification “C”

µ  Maintenance activities shall be established aiming at the best relation cost benefit between the conservation of equipment and repair cost. For this classification the loss of function does not impact significantly on the production volume, quality, or ESH;

µ  Preventive and/or predictive maintenance activities are optional, and can be created or canceled at the discretion of the Maintenance Engineer; proper register shall be assured;

µ  To consider the use of spare parts directly from the supplier whenever possible;

µ  Events related to equipment with that classification that entail in impacts on production, ESH, or quality shall be analyzed critically in order to revise the classification.

Method of Classification

The items to be assessed for the equipment criticality classification are: production, ESH (environment, safety, and health), quality, and maintenance cost.

PRODUCTION

Effects of Failure	Criticality Index
Complete plant downtime – total interruption of production a.     Vital and unique equipment, without redundancy, that participates directly or indirectly in the productive process, whose downtime interrupts the productive process with total loss of function of the system, and significant impact on sales to customers.	1
Partial plant downtime – reduced capacity of production a.     Vital and unique equipment, without redundancy, that participates directly or indirectly in the productive process, whose downtime interrupts the productive process with total loss of function of the system, without significant impact on sales to customers. (possible recovery of production); b.     Vital equipment and with duplicates (sometimes redundant), that participates directly or indirectly in the productive process, whose downtime may reduce the capacity of the project, but it does not interrupt the productive process, without the total loss of the system function resulting in losses of production.	2
There is no downtime of the plant or impact on the production a.     Non-vital equipment or that does not participate in the productive process, whose downtime does not interrupt production, and does not damage production significantly.	3

ESH (ENVIRONMENT, SAFETY, AND HEALTH)

Significance	Criticality Index
High significance b.     Interlocks classes 1 and 2; c.     NFPA85 protection interlocks; d.     Safety Systems (Emergency showers, fire detection and firefighting systems, gas detectors, emergency communication systems); e.     Non-redundant instruments that control or monitor critical variables to the process; f.      Instruments / Equipment linked directly to the plant operation permit; g.     Equipment linked to the Mechanical Integrity classified in NR13 as CAT I, II, or Boilers; h.     Pressure and/or vacuum relieve devices; i.       Hoses classified as Group I in compliance with SJC-TSD-MAN-IT-007; j.      Equipment for protection against load and/or persons fall or lifting; k.     Uninterruptible power systems (UPS) for electric power of systems of control and Interlocks; l.       Control System DCS (Delta V)	1
Medium significance a.     Interlocks class 3 b.     Redundant instruments that control or monitor critical variables to the process; c.     Equipment related to the Mechanical Integrity Program classified in NR-13 (III, IV, and V), and those linked to Program 2 (P#2); d.     Containment dam and SUMPs; e.     Systems related to SPDA, ground, PPE (personal/collective protective equipment)	2
Low significance a.     Interlocks class 4 and U b.     Others	3

 QualiTY

Effects of Failure	Criticality Index
-      Equipment that affects or causes impacts directly on the quality and/or specification of the product.	1
-      It causes variations, but it does not compromise the specification.	2
-      Without impact on the product specification.	3

Maintenance COST

Annual Maintenance1;2 Cost	Criticality Index
-      Average annual maintenance cost > KR$50	1
-      Average annual maintenance cost between KR$10 and KR$50.	2
-      Average annual maintenance cost less than KR$10	3

1-   The maintenance cost is constituted by the sum of all the costs pointed in service order during a period of at least 2 years. An average is calculated to determine the annual value.

2-   If the cost is not available for a certain area, the value 3 for the criticality index shall be adopted.

The value of the General Criticality is determined by the result of the product of the individual criticality indexes in production volume, quality, ESH, and cost.

 

GeNEral CriticALITY = ProduCtion x ESH x QualiTY X COST

For equipment where the individual criticality is 1 in ESH or Quality, the value of the General Criticality will be 1 regardless of the value of the product. It will be, therefore, characterized as Class A equipment.

After the determination of the General Criticality, the equipment will be classified according to its framework in the criteria defined³ below:

Class A Equipment: Criticality <= 4 (Critical to the Integrate Management System)

Class B Equipment: 4 < Criticality <= 36

Class C Equipment: Criticality > 36

As overall results, there is no redundancy of analysis and the criterion has no subjectivity. The strategies are in line with the business but respecting all Process Safety tools already implemented at Monsanto do Brasil – São José dos Campos