Condition monitoring can be an insurance policy for oil & gas processors

London – In the downstream oil & gas sector, ’lost’ production time can equate to hundreds of thousands of pounds per day, so operating operating companies must ensure that production machinery and other critical plant equipment must be adequately insured against the cost of unforeseen breakdowns.

Although the cost of a machine component such as a bearing, pump or electric motor is very small compared to the total cost of the machinery, the cost of production downtime and any consequential losses as a result of the bearing failure, are often significant, warns Kate Hartigan, managing director of Schaeffler (UK) Ltd..

For example, take a petrochemical processing plant. The typical cost of production downtime can be anything from £100,000 to £500,000 per day. Total maintenance costs for a typical oil and gas processing plant are around 10 to 15% of total costs.

Of course, every processing plant has a maintenance department to deal with problems like these, but often, because of time and resource constraints, the maintenance team becomes reactive, fire fighting problems around the plant as they occur, with no predictive maintenance systems, little preventive maintenance and often with no maintenance strategy at all.

Using the latest condition monitoring and predictive maintenance systems, including bearing vibration monitoring, acoustic emissions monitoring and thermography to protect plant and machines, is what the more enlightened plants are doing. But many more companies need to pay heed.

“Plant managers and maintenance managers need to justify any expenditure on condition monitoring systems and services, to their finance director or MD,” noted Hartigan, who recommends using a risk management approach fwhen making these proposals.

“Ask the question of your finance director: ’What will it cost the company in lost production if I lose that critical pump or motor for five hours?’ Or ’What would you be prepared to pay as an insurance premium, to secure the running of the plant and to protect it against unforeseen breakdowns?’ You may get some very positive responses.”

One of the finance director’s responsibilities is to ensure that the company’s assets are protected. Risk assessments should be carried out regularly to see what effect breakdowns would have on critical machinery and equipment.

The severity and likelihood of breakdowns on particular machinery are assessed and given a corresponding risk value. Those with the highest risk scores are given priority by the maintenance team and should certainly be protected with some sort of condition monitoring device.

Of course, companies can protect their plant without using condition monitoring or predictive maintenance systems, for example, by holding more stock of a particular component such as a gearbox, bearing, pump, coupling or shaft. This means when a breakdown occurs in the plant, the component that caused the breakdown is available to hand, ready for the maintenance team to fix the problem.

However, Hartigan pointed out: “As well as the obvious increase in stock holding costs, the company also runs the risk of the stock deteriorating or becoming obsolete over time. We would recommend that customers reduce the risk of unexpected failures, by implementing suitable condition monitoring systems on rotating plant and machinery. Don’t think of this as capital outlay, but as insurance against the risk of possible lost production.”

According to Hartigan, by installing a predictive maintenance system, the customer picks up any problems early. During the next convenient downtime period, the maintenance team can then remove and replace a bearing with minimum disruption costs and also avoid the risk of breakdown damage to the equipment.

Condition monitoring also prevents maintenance teams replacing components unnecessarily and introducing possible new and unrelated problems. Manufacturing maintenance staff should be using CM systems to predict when failures are likely to occur and plan replacement during production shutdowns.

“In too many companies, parts are changed on a time basis rather than on a condition basis because the maintenance team considers this to be the safest option. However, this introduces a further risk, because whenever there’s human intervention, problems can occur,” explains Hartigan.

“Most companies work in a breakdown culture which is reactive rather than proactive,” she continues. “Rather than boasting about how rapidly they can repair or replace components and get machinery or pumps back into production, maintenance teams need to be asking themselves ’How can we prevent the problems occurring in the first place?’ CM is the most effective solution.”

Project at Pequiven

Hartigan went on to highlight the application of Schaeffler’s condition monitoring technology along with its corrosion-resistant coatings for bearings and automatic lubrication systems at Pequiven, a Venezuelan government-owned producer of petrochemical products. The company specialises in the production of fertilisers and chemical products, as well as olefins and other synthetic resins.

At its phosphoric acid plant, which has a production capacity of around 250 tonnes of P2O5 per day, Pequiven wanted to improve the running time of a critical conveyor system that separates the solids from the phosphoric acid mixture.

The bearings on the conveyor system were regularly failing after just 15 days. As the plant was planning to increase its production capacity, it needed a bearing supplier that was able to provide an integral solution to the bearing problem, including maintenance advice and guidance.

Schaeffler Venezuela recommended that Pequiven use a coating material for the bearings, to improve the quality of the housing material. Also, Schaeffler engineers noticed that manual grease lubrication of the bearings was not always being carried out correctly at the plant. Therefore, along with new coating materials for the bearings,

The engineers recommended that the plant use automatic lubrication systems to ensure that relubrication of the bearings is controlled and that sufficient quantities of fresh grease is constantly supplied to the contact points inside the rolling bearings.

Schaeffler replaced the existing bearings with its RASE40-N-FA125 housed bearing units, with the housings coated with Corrotect®. Corrotect® is a relatively low cost, 0.5 to 5µm thick zinc alloy coating with cathodic protection, which is effective against condensation, rainwater, contaminated water and weak alkaline and weak acidic cleaning agents. Under load, the coating is compacted into the surface roughness profile and is partly worn away. The chromate coating and the passivation increase anti-corrosion protection and contribute to the optical appearance of the component.

Corrotect® is ideal for small bearings and bearing mating parts that need to have a greater resistance to corrosion, for example drawn cup needle roller bearings with open ends and thin-walled components in large numbers.

Schaeffler also supplied its ’FAG Motion Guard Champion’ automatic lubrication system – electromechanically driven unit that operates on replaceable batteries. The device is electronically controlled and has a back-geared motor that enables the unit to discharge lubricant at adjustable intervals of one, three, six or 12 months.

A lubricant canister is screwed to the drive unit, holding 60, 120 or 250cm3 of lubricating grease. Automatic pressure control at 5 bar is provided and the unit operates in temperatures from -10°C up to 50°C. The device is also protected against dust and splash water and is immune to electromagnetic interference from surrounding equipment.

By using Motion Guard Select Manager software, the user can select the discharge interval for the application, determine replenishment quantities and select preferred lubricating greases.

After supplying the Corrotect® coated bearings and automatic lubricators, the running time of the conveyor system was improved as the bearings were now lasting more than twice the time of the original bearings - but this still wasn’t long enough for Pequiven.

Because of the very harsh corrosive environment in which the bearings had to operate, Schaeffler then recommended using stainless steel bearings and a thermoplastic housing.

After installing the new bearings, Pequiven is now satisfied with the running times of the conveyor system and maintenance cost has been reduced significantly. Schaeffler now takes full responsibility of bearing maintenance and has helped the customer develop a special maintenance programme.