## PID Controls

PID control stands for proportional, integral, and derivative control. This type of process management is used to maintain set parameters, and works well for temperature or motion. All three portions of this control setup manage whatever parameter you desire in different manners.

Proportional control controls how far the measured parameter is from the set parameter. In terms of temperature it will tell you how far off from ideal the process is running; i.e. +1.85 °F or -.07°F. Managing the process with proportional controls alone will work, but the systems will swing between over- and under- correcting.

Integral controls are added onto proportional controls to factor in timing into the setup. By measuring the time between measurements of the parameter the system can determine the speed at which the motion or temperature are changing; i.e. -.1 °F/second. By knowing this measurement the system can then account for this with more precision, cutting down the amount of over-correcting. Still this combination will need one final layer to appropriately maintain the parameter dynamically.

Derivative control measures the acceleration of the parameter, in effect the speed at which the speed is changing. With this level of control, the parameter changes can be dampened and returned to the set point reliably. In terms of motion parameters, with a properly installed PID control system a ball bearing can be kept from rolling off a glass plate even when pushed by people.

## Water Corrosion Protection

In steam producing boilers high temperatures and pressures increase the likelihood for corrosion and failure from said damage. The main culprit in this situation comes during the shutdown process, as pressure drops air enters the boiler and oxygen within the air reacts with the metal boiler causing weaknesses and pits in the metal. These small weaknesses can turn into leaks quickly requiring immediate shutdown.

To solve the problem of oxygen entering the system a nitrogen blanket can be installed. This is a system which fills the boiler system with nitrogen before dumping the pressure to eliminate air ingress, nitrogen is non-reactive in the system avoiding further pitting or corrosion. Supplying nitrogen for a blanket can come from bottled sources, liquid supplies, or through pressure swing adsorbtion.

## How to Calibrate a Flow Meter

Flow meters are used in many industries to measure and control the movement of gases or liquids. Accuracy is crucial in order to ensure that the manufacturing process is going smoothly. Precise measurements are key to many kinds of manufacturing, processing and transfer processes. For this reason, manufacturers look for the highest quality flow meters available on the market.

## Why Regular Calibration Is a Must

However, even the most durable and sensitive meter can become imprecise and lose accuracy after prolonged use. Some common causes are regular wear and tear, exposure to moisture or corrosion due to chemicals. Flow meter function can also become disrupted due to accumulation of dirt, impact or faults in the installation process. Regular inspection and calibration of your flow meter is necessary in order to ensure consistently precise readings. To ensure that your calibration of your flow meter achieves the results you want, it is smart to follow the following best practices.

## Use Accurate Testing Equipment

First of all, make sure that your testing equipment is up to standard. This means that before you can start using your standard to test your flow meter’s measurements, you must take care to test your standard against another recognized standard and document the results. This will help you maintain a high degree of accuracy when checking the precision of your flow meter’s measurements.

In addition to comparing your standard’s accuracy to that of an already known standard, make sure that its measurements are sufficiently accurate. When you are using a standard to calibrate your flow meter, your standard typically needs to be four times as accurate as the meter you are testing. In some cases, the accuracy requirement can be different based on the specific type of calibration.

## Ensure Typical Environment

Now that you have checked your testing equipment, you need to make sure that the testing environment is conducive to precise results. If you want to know how your flow meter is operating on a daily basis, you should test it under conditions that are as similar as possible to its typical environment. The type of substance whose movement is measured by the meter can affect operation, so be sure to test using the same substance. Factors such as heat, density and rate of movement can also affect operation; thus, for optimal testing accuracy, these should also be similar to the regular operating environment.

## Consistent Flow

When testing, it is important to keep the flow rate steady. In a typical testing scenario, you will be making a real-time comparison between the flow rate of your meter and your testing standard. Thus, variations in system flow can lead to imprecise results and suboptimal calibration.

## Eliminate Variations in Heat and Volume

For best calibrating results, your testing unit will need to measure everything your flow meter regularly measures, simultaneously. This means that it is important that there not be any variations in temperature or volume during the testing process. Before beginning the calibration, check the system for leaks or other irregularities that could compromise test results.

If you find that you are unable to calibrate your flow meter successfully, it may be time for a repair or an upgrade. Flow meters can lose function when they are being used in applications where a particular type or model is not optimal. Improper installation can also lead to damage that may not be easily fixed by recalibrating.  Consult your manufacturer as to the best type of flow meter for your purposes.

## Signs of a Poorly Constructed Valve System

• Bolts that are too long: If engineers are wasting money on excessively large bolts, they must be cutting corners somewhere.
• Non-isolated control valves: Maintenance is always required, if there is no way to easily remove a valve then maintenance is not being done on the valve.
• Lack of pressure gauges and connections: At some point it will be necessary to monitor the pressure at the valve. Build with future needs in mind.
• No air vent caps: Valves that reduce pressure will buildup air pockets during operation, if this air is not vented you can bet a costly repair will be needed soon.

## Hydraulic Valves Preventative Maintenance

Hydraulic systems are dependent on every part within the system, any small leak or failure from one piece will bring the system to a grinding halt. The fluids used in particular systems can even harm personnel nearby or the environment in the occurrence of failure. Valves are critical to hydraulic systems as they control the flow of hydraulic fluid through the system to perform work. A preventative maintenance program should focus on valves more thoroughly than any other component.

Reactive maintenance expects to run components to failure, often valves fail first, and then enact repairs while productivity is zero and then make up for lost production time later. This process is costly and usually fraught with high tensions. A preventative maintenance schedule uses time or specific conditions to “schedule” repairs and replacements. This scheduling process can be in terms of time; i.e. replacing seals and gaskets every 2 years, or it may be based on operations; i.e. after every 5,000 cycles, or both depending on which “schedule” comes first.

Industry data shows that performing maintenance on a scheduled basis is three to five times less expensive than the same repair being made on a reactive basis.

## Hot Bolting Dangers

Hot bolting, or tightening bolts on flanges and other pipeline connectors while in operation, brings dangerous liabilities into fluid control operations. One example of the dangers occurred in 1992 where a hot bolted heat exchanger exploding killing 17 when a gasket-retaining ring slipped upon tightening. One common flaw in operators during maintenance practices is to believe they are more experienced and knowledgeable than is true, the Dunning-Kruger effect.

Bolts are only capable of shifting so far under stress, and during thermal loads the bolt materials may have reduced limits. Hot bolting adds stress to the material and combined with the lower limits these stresses may exceed resulting in ruptures or explosions of hot fluids. To reduce the risks of failure from thermal expansion springs may be added to bolted connections allowing more travel yet providing the needed sealing forces.

## Flow Control Through Smart Components

Hydraulic-power units in Colorado’s Carter Lake are being fit with smart systems to optimize the flow rate of water through the dam. Through the use of PID controllers, position feedback devices, and backup manual valves installed in parallel Carter Lake Hydroelectric maintains the flow of water through its wicket gates in turn regulating the generation of electricity from the flowing water.

The entire hydaulic system is designed for long term use with little maintenance. Redundant oil filters maintain internal hydraulic components, fluid check valves prevent counter-flow from harming sensitive pressure sensors and flow meters.

## Flow Metering in Street Locations

In the situation of flow control under streets there are two common practices, and one new method to maintain standard regulations; on-site metering, off-site metering, and near-site metering.

On-site metering locates the flow meter in the same manhole as the pipe(s) to be measured. If the manhole installation is classified as a confined space, calibration and maintenance may pose a problem. In this situation multiple operators, a hoist, and gas detection equipment may be mandatory and pose increased costs for maintenance. Some of the difficulties may be avoided by installing remote reading equipment, but to calibrate the flow meter the operator must enter the manhole.

To avoid traffic congestion due to maintenance off-site metering utilizes a manhole placed outside of traffic flow for reading, measuring, and calibrating the flow meter. Concerns with the off-site metering methodology is lag-time between visual observation of the flow rate and calibration of the flow meter. As distance between the measurement location and the remote calibration location increases the possibility and degree of error increases as well.

A compromise of both methodologies above is the near-site metering practice. In this situation a short manhole is located directly next to the metering manhole, yet outside of traffic. In this shorter manhole the flow meter and remote  reading equipment is placed, preferably on a telescoping stand. By sealing both manholes from each other, even if the operator must enter the new manhole it is not calssified as a confined space therefore avoiding additional operators and equipment.

## Aircraft Maintenance With Flying Colors

Whether you are handling a commercial jet or a passenger plane, caring for an aircraft is an important task that should be handled with caution. Successful aircraft maintenance is dependent upon the tools and resources you need to complete the job, however, so getting access to the best resources is imperative. What exactly is needed to complete aircraft maintenance to the highest standards possible? What does the process of aircraft maintenance involve? Well, a flow meter can be commonly used to measure and test air conditions in the aircraft, gauge fuel consumption and evaluate overall performance. These are important metrics for any aircraft, so if you want to pass aircraft maintenance with flying colors, you should invest in a capable flow meter to help.

How a Flow Meter Can Improve Maintenance Routines

The typical maintenance routine for an aircraft includes four different stages. They are commonly referred to as A, B, C and D checks, and each of them examines an aircraft at a different level of scrutiny. The parts of aircraft maintenance include:

• The D check: The most extensive of these is completed only every 6 years. In this examination, the aircraft is nearly disassembled in order to inspect all parts.
• The C check: This inspection occurs more frequently at every 20-24 months, on average, unless a minimum number of flight hours has been reached first. It is a substantial inspection that may take up to two weeks to complete.
• The B check: Every 6-8 months, an aircraft is due for a B check, which entails slightly more in-depth inspection than the A check.
• The A check: The frequency of this check varies based on the manufacturer’s recommendation, the number of flight hours logged and the type of aircraft.

A flow meter can help automate many of the processes entailed in each of these checks.

Measurement Solutions for Aircrafts

When you need to perform essential maintenance, a big part of the process is the measurement of certain substances and emissions. Some of these include:

• Fuel
• Lubrication
• Hydraulic fluid
• Coolant
• Engine emissions
• Leaks

Each of these requires a different approach to effective and accurate measurement. A high quality flow meter, however, will likely be able to measure all of these components and gather detailed readings of the data that is most necessary to measuring the performance of an aircraft. The latter of these items, leaks, are particularly important to detect early. A flow meter can do so by sensing any abnormalities or continual decreases in pressure.

Finding the Right Flow Meter for Aircraft Maintenance

It’s clear that a flow meter offers solutions to many of the steps in an aircraft maintenance routine, but how can you tell which will best meet your needs? You want one, of course, that will minimize additional effort and perform the required steps easily. You should consider these factors when selecting one:

• Inclusion of features such as pickups and signal conditioners
• Size of turbine
• Measurement rates
• Ability to process chemicals

There are many other items that you should check for, too, according to the needs of your aircraft maintenance needs.