While equipment repair is a constant concern for processing plant operators, current business realities have underscored the importance of preventing equipment failures before they happen; before falling to the mercy of industry supply chains to deliver the parts and services you need to keep your plant running.

This is a particular concern for mission-critical equipment, which for many food manufacturers means their processing vessels and mixers.

Even setting aside delays, the cost of vessel equipment failure can be significant. The ability to prevent expensive repair or downtime is why over 40% of companies in process industries view their plant maintenance as a source of higher profits to their operations.¹

Fortunately, food processing companies with a well-designed vessel maintenance program can virtually eliminate unexpected breakdowns and their corresponding financial losses. And starting such a program is within reach for most food processing operations.

Preventive Inspection and Scheduled Replacement:  Your Two Critical Maintenance Objectives

To best manage your critical production vessel assets, divide your service planning into two categories:  1) Preventive Inspection and 2) Scheduled Replacement.  With proper attention to both, you can keep small problems from becoming major vessel repairs that can shut down production for hours, days or even weeks.

1. Preventive Vessel Inspections: What to Check

Regular vessel inspections, performed throughout the year, keep your kettles, tanks and agitators operating without interruption.

Here are the key components of production vessels, how to inspect them, and common signs of component failure requiring immediate service:

• Jacket integrity: Jacket leaks are sometimes obvious in production vessels, and sometimes not, depending on whether the vessel has an exposed jacket. Conduct a visual inspection for obvious leaks, but if a problem is suspected, a pressure test should be performed to identify and assess jacket leaks. If leaks are discovered, they must be repaired and certified by a qualified boiler technician.
• Agitator shaft alignment: Examine your agitator shaft for unusual or excessive vibration or noises during product mixing, which can indicate a bent or misaligned agitator shaft.  Not only can misalignment impair mixing performance, it can also impact other parts in the driveline. In extreme cases, misalignment can lead to a broken agitator shaft, a custom part that can take several weeks to replace.
• Driveline, gearbox, and motor bearings: Unusual grinding noises can also be a sign of worn bearings or bushings, either in the gearbox or the electric drive motor. Check for wear (e.g., roundness) and replace as needed.
• Gearbox: Inspect gears for chipped or missing teeth or other signs of excess wear and replace as needed. Worn gear teeth can cause gear slippage and further gear damage during operation. While inspecting the gearbox, also check associated gearbox bushings, seals, and drive bearings for noisy operation, wear, excessive play or leakage.
• Vessel safety features: Periodically check for proper operation of vessel cutoff safety switches, lid lifting hinges and hydraulic lift operation.

2. Scheduled Replacement: What to Replace on a Pre-Emptive Basis

While your maintenance team should inspect your plant's production vessels throughout the year, food processors that experience the least unscheduled downtime pro-actively inspect and replace critical vessel parts during their planned plant shutdowns.

Pre-emptive replacement is particularly recommended for key wear parts, such as vessel agitator drive bearings and seals, which can fail suddenly and cause major problems (e.g., bent agitator shaft or product contamination from oil leakage). Replacement can be based on pre-determined criteria, such as the number of hours of each vessel's running time, or the number of months since the part was last replaced.

Here are the parts in vessel drive assemblies that are most often pre-emptively replaced on vessel drive assemblies during seasonal maintenance shutdowns:

• Seals: Replace seals in driveline, gearbox and agitator shaft assemblies to prevent leakage and contamination.
• Shafts: Agitator and gearbox shafts should be inspected for excessive bearing or seal wear and replaced as needed.
• Scraper blades: Replace agitator scraper blades before they chip or break. 
• Bearings: Replace gearbox and agitator drive bearings and -- less frequently -- electric motor bearings.
• Bushings: Replace gearbox and agitator shaft bushings.
• Ball valves: Replace o-rings and seals on sanitary ball valves to prevent leakage and assure correct operation.

Preventive Inspection and Scheduled Replacement are important elements of an effective vessel maintenance program for food processors.  These days, such a program may be more essential than ever.

For more on this topic, download Better Production Through Improved Vessel Service and Maintenance.

1. 2014 Plant Engineering Survey