Tackle the tough first

Maintenance was my favorite job from childhood. And I am still enjoying my career as a maintenance engineer. It provides challenges and brainteasers. Crisis management under resource and manpower constraints stretch your thinking on ways to circumvent the problem. While I was working on an oil processing platform as maintenance superintendent, there was not even a single day I was free and every day I confront a basket of problems with varied difficulties and importance. One of the important lesson I learnt was categorizing the problems and attack the problem which seems to be very difficult and time consuming.

At an Off shore platform, normally the day begins at 0700 am. The first thing I do in the morning is to take stock of the previous days’ performance and list unfinished jobs. To this fresh complaints are added and the total task is prioritized on the basis of urgency. Since fresh in the morning, I used to attempt the most difficult job first. This used to assure the availability of time and have an unbiased look at the problem. Many a times some other jobs may veer off your attention or even force you to suspend the job at hand due to urgency. Even while attending same, one can think of the ways to trouble shoot the problem which you have kept in abeyance temporarily.

ATS Starting Problem

At one of our onshore plants, there are two 100 HP motor driven effluent pumps. These are started with ATS (Auto Transformer Starter) with 60%,75%,90% tappings. During starting session the motor is connected through these tappings successively and the final contactor is closed. In one occasion the auto transformer in one of the starter burnt out. On inspection,it was found the timer for cutting out one of the tappings was defective and the auto transformer remained in the circuit causing over heating and subsequent failure. To avoid such mishaps, one indicator is provided in the starters which will glow when the main contactor connects the motor to the main. Operators are advised to watch this indication and asked to stop the unit if it does not glow within 8 seconds, the normal time taken for the main contactor to close. Also in one of the starters only the 60% tapping is used on experimental basis which can reduce the probability of failure.

In another occasion, it is found that the motor is tripping even before the completion of the starting session. There is a latching contactor in the starter which remains energized till the motor is stopped. This contactor is found releasing immediately after closing and the start fails. The circuit was checked thoroughly but found all components are healthy. Interestingly, this is happening in both starters. Finally the problem was traced to the gas fuel regulators of the gen-set catering power to the motors. The regulators could not supply the required fuel gas at the starting and the gen-set becomes sluggish and its voltage drops below the minimum voltage required by the coil of the contactor to hold the moving contacts and breaks the control circuit and the motor stops. The regulators were repaired/replaced and the problem is rectified.

My Bizarre Experiences

Experience – 1

7 o’ Clock Shut down Syndrome

This happened while I was working at an Off Shore Oil Processing platform. There are three gas turbine driven generating units, for powering the platform, with two of them are running in parallel and the third one in stand by. Suddenly the platform started experiencing a power shut down at 7 O’ Clock in the morning even though there was no process upset or starting or stopping of any equipment. It was observed that this was happening only when the third unit is running in parallel with one of the other units. The control system of the unit is checked thoroughly for any fault but nothing abnormal is noticed. On close observation, it is found that the third unit is tripping due to fuel system malfunction and through the full load on the other unit, causing the second unit also to trip causing total black out. The load shedding unit could not get enough time to limit the load and avoid total shut down.

All the process were closely monitored and operators were advised to avoid starting/stopping of any load from 6 am to 8 am. Still it is found that the unit is tripping at 7 am. The platform is the central location from where personals are transported by helicopter to well head platforms for operation and maintenance in the morning and brought back in the evening. The operation starts at 7 am and the communication system is switched on at that time.

Operators in the power control room are advised to be vigil while the communication system is switched on. The reported there is a fluctuation in the fuel supply-demand indicator while the communication unit is switched on and the unit trips there after. On inspection it is found that the communication unit and the third GT genset control unit are connected to a common battery bank. The other two units are supplied from another battery bank. While the communication unit is switched on, the radio signal travels to the GT control unit also through the DC Power cable and caused disturbances in fuel control system and subsequent shut down.

The GT control and communication power supplies were, then, isolated and the signal path is interrupted so that the signal cannot reach the GT control through the power cable. Also earthing of all equipments in the control panel is redone. The problem never recurred after that!

Equipment Maintenance Log Book

Equipment Maintenance Log Book or simply Log Book is an essential record which must be kept up to date. The log book should contain the following minimum details on its front page:

1. Equipment Model

2.Serial No

3. Date of Commissioning

4.Recommended Lube Oil (LO) to be used

5. Ratings (like Power, Temperature,Pressure or any other applicable parameters)

6.Duty Cycle

7.Safety Precautions etc.

Every time any maintenance is carried out, the service personnel should clearly record the date, nature of maintenance done, spares replaced, no. of hrs the machine operated before taking out for maintenance, any unanticipated defect noticed/rectified etc.

This log book should accompany the machines like gas turbines when they are send for major overhaul at manufacturer's facility. The scope of work is ascertained on the basis of the log book information.

Many a times some of the good parts are removed and defective one are fitted before the machine is sent for overhaul (OH). This is a bad practice as the information available in the log book may differ from the physical condition of the engine parts and manufacturer may wrongly recommend replacement of additional parts which may not be warranted and incur additional expense. It is always advisable to order new parts for replacement rather than removing and keeping them from engines sent for OH.

Log book provides a system approach for carrying out the maintenance. Service personals may come and go, the log book provides a basis for carrying out routine maintenance as well as major OH.

One last word about the book: The log book is normally filled immediately after the completion of the job. The hands of technicians may be dirty while filling. This fact should be kept in mind while selecting the paper and cover for the book. It is advisable to have cloth covering and good quality paper for the books.

It is the responsibility of the Maintenance In charge (MI) to ensure that the log books are filled and kept up to date.

Qualities & Qualifications of A Maintenance Incharge

Total Plant Maintenance (TPM) concept is a well suited policy for large manufacturing or processing plants. Instead of spreading maintenance to a number of departments, it is better to have a single point responsibility with a Maintenance In charge supervising all activities. This can help better pooling of resources and deployment of manpower. The inter departmental rivalry can be reduced and multitasking ability can be cultivated under this concept.

Being a team leader, Maintenance In charge (MI) should posses certain qualifications and qualities. He should have the over all view of the electrical,mechanical,instrumentation maintenance requirement of all the equipments under his supervision. Some of the most vital qualities we should look forward to are:

Engineering Maintenance Skill: The MI should have hands on experience in mechanical, electrical, instrumentation maintenance. These three are the basic maintenance requirement of any large plant. He should be able to judge the time requirement for carrying out the maintenance jobs and deploy enough manpower for carrying out the same.

IT Skill: Now-a-days tendering, procurement etc are being done online. The MI should have knowledge in the preparation of purchase request, purchase order etc using software packages like SAP. On line recording of consumption of store & spares help in the auto generation of purchase request. Timely availability of spares can considerably reduce the shut down time and production loss.

General Knowledge in NDT: Some of the jobs can not be done departmentally and required to be out sourced. Non Destructive Testing (NDT) of materials,welding etc is usually done through external agencies who posses qualifications and experience in their field. A general knowledge of these methods is desirable for MI, to make sure that appropriate testing has been conducted.

Human Resource Management: By Human Resource Management (HRM), I do not mean recruitment of people. Being a leader of a team, MI should be able to resolve ego clashes of subordinates and make them understand the value of their contributions in the maintenance jobs. In isolated places like Off shore Oil & Gas Processing complexes, some times he has to act as a counsellor for the employees and help them to reduce the mental stress due to work overload and prolonged isolation from their dear and near.

Companies while recruiting MIs should give importance to the above requirements and a person possessing above qualities shall be appointed for the post.

Total Plant Maintenance

Total Plant Maintenance

All equipments during their life cycle require timely and proper maintenance for smooth operation. The words “timely” and “proper” require careful attention. Any maintenance which is not carried out on time may require extra efforts to bring the machine back to normal. If the maintenance is not proper or adequate, it can cause premature breakdown or may reduce the useful life. These will entail additional expenses and may affect the reputation and profitability of companies.

Where there are only a few machines are installed, the maintenance can be easily planned. In large process complexes like petro-chemical plants, fertilizer plants etc, a large number of machines are working and their maintenance requires a careful planning. A shut down in these plants may require a lot of time to normalize and may cause considerable production loss. Here, if the breakdown of a machine is not attended on time may lead to secondary breakdown of a series of down stream equipments. Recovery from such a disaster may require a lot of efforts, wastage of resources, loss of production etc.

Total Plant Maintenance (TPM) envisages proper planning and execution of the maintenance in a plant. It starts with the study of the role and criticality of process equipments, ABC analysis of breakdowns etc. Procurement of spares and their timely availability and imparting training to engineers and technicians are also part of TPM.