Determining the correct maintenance strategy for industrial production assets poses a problem for many plant asset managers and reliability and maintenance engineers.

Although the use of transmitters in pressure measurement is growing, mechanical pressure gauges are still used on most systems as local pressure display to back up electrical readings. The selection and installation of these gauges can be difficult in certain locations. Harsh conditions that can require special consideration include vibration, pressure pulsation, overpressure, corrosive media and extreme process and ambient temperatures. This article is designed to address harsh conditions with best practice recommendations to extend gauge life and provide for the safest installation possible.

Last month we reviewed the pump selection criteria for a closed loop circulation system (Vp-Vf). This month we will take a look at a similar application that adds some elevation to the equation.

If pump cavitation is not detected and quickly eliminated, significant damage can occur to the impeller and other internal components. Since cavitation (the formation and collapse of vapor bubbles in the pumped fluid as it passes through the pump impeller) is often temporary or even induced by the process, timely knowledge of the condition is extremely important so operators can act to alleviate the problem and prevent damage.

One of the major contributors to unbalance in rotating machinery is eccentricity. When we disassemble parts, we must also reassemble them. Even if the reassembly requires heating to shrink-fit the elements back together, we probably balanced them in a balancing machine where tolerances due to fit-up on mandrels or roundness of journals may possibly far exceed the heavy spot tolerances that the target standard of balance allows.

PWM inverters introduce motor shaft voltages and bearing currents. The bearing damage in inverter-driven motors is mainly caused by the shaft voltage and bearing currents created by the common-mode voltage and its sharp edges [1]. All inverters generate common-mode voltages relative to the power source ground that cause coupling currents through the parasitic capacitances inside the motor. The main source of bearing currents is the capacitance-coupling currents that return via the motor bearings back to the ground.

Even when a redundant pumping system is in place, it can be advisable to monitor the condition of the operating units in critical applications where maintaining production depends on motor-pump reliability.

Mechanical pressure gauges, which require no external power, provide an affordable and reliable source of accurate pressure measurement. Using the criteria below can help maximize gauge life.

What Are Your Vibration Monitoring Goals?

Identifying goals before starting is key to designing a process tailored to specific needs. What are you hoping to accomplish by monitoring vibration? How would you like to acquire data? What are you going to do with the data? These important questions should be addressed before moving forward.

Many items must be considered when designing pump station control systems with power requirements, level control method and control panel location often among the most important.

Joseph Gallo Farms in Atwater, Calif., uses captured methane gas from its 5,000 dairy cows to run up to 50 percent of the electricity for its cheese factory.

Of the technologies available for condition monitoring of rotating equipment, the quickest return on investment is from vibration analysis. For the novice, vibration data seems complex and is generally difficult to assess compared to other techniques. Once trained, however, the novice can recognize the patterns and diagnose a machine problem.

Potential to Failure (P-F) curves graphically display the failure time cycle and measurement techniques that can be used to detect asset failures prior to reaching the asset incurring functional failure. Proactive strategies should focus on managing assets high on the P-F curve, or early (P1 to P5) in the failure cycle (Figure 1). The ability to detect failures early in development allows top quartile performers to proactively manage their maintenance programs by understanding the health of their assets. Many companies, however, find it difficult to operate proactively and continually react to assets that reach functional failure with little or no warning.

How a monitoring alarm system with control and shutdown capabilities prevented costly pump damage and environmental hazards and made the job of the pump operator safer and easier.

Cavitation is a destructive condition that can destroy the inside of a pump before you even realize it is occurring. Early detection can minimize damage, reduce downtime, and save money. Cavitation involves the creation of bubbles formed when the fluid being pumped vaporizes due to a decrease in pressure as the fluid enters the pump. These bubbles are then acted on by the pump impeller, causing them to implode.

With the wide use of variable frequency drives in the pump industry and increasing unit size, it is becoming more difficult to design mechanical systems free from natural frequencies within operating speed range. If such an occurrence is allowed in the field, a resulting resonance condition threatens to significantly impact performance and longevity of the equipment.

Pumps are sent to rebuilding and remanufacturing companies because buying new can be expensive and require long lead times. For instance, a 39 in diameter, 1,000 lb bronze impeller may cost $28,000 and take many weeks to deliver. In these cases, the impellers involved in an overhaul are often built back up to the required specifications and rebalanced.

Back in the old days, level control had little or nothing to do with saving energy. In fact, it was often a necessary evil. Today, that is no longer true - the VFD offers the potential for power savings in lift station applications that range from a few hundred gallons per minute to those that have to move thousands of gallons each minute.

A dangerous misconception exists regarding the "Arc Rating" of infrared (IR) windows or viewing panes. Many reliability and maintenance professionals are under the impression that an IR window will protect them in the event of an arc blast. Others believe that installing IR windows will turn non-arc-rated switchgear or electrical equipment into "arc-rated" cabinets. Neither is true. Both misconceptions need to be corrected because they present safety concerns.

For controller-to-controller coordination, wireless Bluetooth is an excellent alternative to Class 3 radios.