Data Acquisition for Plating and Environmental Applications

Ed. Note: This paper, written by Larry Farnsworth of A-Brite Company for AESF 2000, addresses the benefits of automating data collecting for plating shops. Part I will discuss the various aspects of the plating process and the pros and cons of collecting data manually vs. automatically. Part II will discuss how automation can save your plating shop money and time.

By Larry Farnsworth, A-Brite Company

INTRODUCTION

The demand for information in a plating shop has never been greater. All types of manufacturing, including plating, are rapidly moving into the information age. Complying with the rules of ISO 9000 or ISO 14000 is more about quality and uniformity through information and documentation than any thing else. Information is equally important as plating customers establish rigid quality control requirements.

This paper will discuss the various sources of information available in a plating shop. The paper will also discuss the difficulties and weaknesses of manually collecting information. You will see that automating the process of gathering information may help solve plating problems and help solve them faster. With more accurate information the plater can save time, reduce cost, rejects, etc.

The paper will discuss various types of equipment that can supply the plater information and how to check your existing equipment to determine if it has the ability to supply information.

MONITORING THE PLATING SHOP

Almost every tank or process in a plating shop has specifications that require some type of monitoring. Some tanks may require several factors to be monitored, -- these include temperature, level, and concentration control. Monitoring on other processes may be as simple as checking to see if a blower motor is providing agitation to a tank or a heater providing temperature control in a plating solution. If you have been around a plating shop very long, you know there are more things to monitor than there are employees to monitor them. Most of the variables listed below are important and any or all of these can have an impact on the performance of the plating process. Automating your shop will allow you to collect data from any of these variables:

CHEMISTRY-concentration, pH, ORP, metals,TDS, conductivity.

LIQUIDS- pressure, flow, temp, level.

ENERGY - current, resistance, amps.

AIR - pressure, flow.

ENVIRONMENT-temperature, humidity, air quality.

CRITICAL INFORMATION

In most plating shops experience and common sense dictate which process are critical and requires monitoring every hour. While the number of available employees and, more importantly, the available time may determine the processes that are not monitored. Installing even the most basic automated system will help in monitoring critical things that may be temporarily over looked:

• Loss of plating solution from an overfilled tank or open valve.

• Excessive use of chemicals in plating line or in waste treatment.

• Discharge Water containing contaminates or out of pH range.

Some variables that may not be monitored regularly only get checked when plating problems arise. The investigation of these problems usually exposes equipment malfunctions, chemistry problems or even something as simple as dirty rinse water. These problems may be harder to uncover because they are not as obvious as overfilling a plating tank. An example of some of these important processes include:

• Temperature of process tanks either too hot or too cool.

• Cleaning tanks or acid tanks out of specification (needing additions).

• Rectifiers functioning correctly.

• Rinse tanks with increased TDS or dirty pH and ORP probes needing cleaned or replaced.

You may already have a temperature controller or a gauge on your rectifier, but if you don't have someone checking these variables on a regular basis it is impossible to know how they were functioning several hours ago when the rack of bad parts went through the line.

Automating the process of collecting that information or data will give you a "snap shot in time" of all the above variables. This snap shot will eliminate all of the known values of equipment and chemicals and hopefully expedite solving the real problem with that particular lot of parts.

There is also a level of comfort in knowing that in a single glance at your computer your can check all the above variables and see they are working correctly.

Other variables or factors that may not be monitored on regular basis and may be overlooked when plating problem occur include:

• Pumps, Blowers, Chillers, and other electrical equipment.

• Boiler Pressure or Compressor pressure adequate for production work.

• Heaters working correctly.

• Mixers and other environmental equipment functioning properly.

This type of equipment is also easily monitored by a glance on a computer terminal by the plating manager. Automation also gives you the ability to notify employees when the equipment is not working correctly, by installing lights or alarms.

MANUALLY COLLECTING INFORMATION

The main issue is selecting a responsible employee that will religiously monitor the processes in the plating shop. The employee assigned must understand the process, and their schedule must allow time to monitor the process. Depending on the size, a small plating shop may only have one person responsible for everything in the plant, while larger shops with multiple plating lines may have an employee assigned to each line.

Some shops may require the employee to document some of the information while other shops under the rules of ISO 9000 or ISO 14000 may require the employee to document everything. Procedures established for the employee normally determine the frequency and the information they must monitor. Some vital functions may be so important that they are monitored once an hour while other factors may be monitored once a shift or even once a week.

The information is normally recorded in a logbook, clip board or spiral notebook where the information is entered and stored for reference. The plating supervisor reviews these books, usually when plating problems exist.

PROBLEMS WITH MANUAL FORMS OF DATA COLLECTION

Manual forms of collecting data have many inherent problems that are common in plating shops. Some events may not be observed if the operator is distracted with other duties or responsibilities. Other times the operator may not be quite as observant as you would like (especially in critical areas) because of distractions while solving unexpected equipment problems.

Some events may go undetected while your employee is busy solving difficult problems. Other times events go unnoticed because an employee from a different area is filling in while the normal operator is at lunch, on break, off sick or on vacation. In these instances the temporary employee may be overwhelmed with the additional duties and does not realize or have time to monitor and recorded critical or important information.

The example in graph 1 documents an event that occurred on third shift. The third shift supervisor, responsible for checking the waste treatment system every two hours, was distracted by an unusually difficult plating problem. The level in the caustic tank was allowed to fall below the pickup tubes for the chemical feed pumps and the pH fell below the normal working range.

Monitoring some processes may require five to 10 minutes of undivided time from the operator. This process may require obtaining a sample of the plating solution and going to a lab or other work area to perform chemical test, checking for concentration or other variables. When your operator is under pressure to get work out the door or dealing with equipment malfunctions, testing the plating solution may become a low priority. Larger shops usually have the luxury of a lab technician responsible for testing and maintaining the bath concentrations.

However, if you don't have a lab technician, and the test must be performed you may want to train several employees to perform the chemical analysis, but be aware that the test results may vary from employee to employee. Regular training will help minimize this variance.

Another problem associated with manual forms of collecting information is the accuracy of the information. Sometimes the operator must make a decision on what information he is going to record in the log. An example of this is as follows:

The operator may check the discharge water at 9:00 am and the reading is a pH of 9.3. He is distracted and does not check the pH at 11am, but remembers to check it at 1:00 p.m. and the pH reads 9.7, now he has to make a decision, what does he log for the 11am reading?

The dilemma becomes "what does he put down for the missed reading at 11:00? Does he leave the 11am reading blank? He will not leave it blank if he believes he may get in trouble. Does he duplicate the 9am or 1pm reading or does he average the two and record a pH of 9.5?

The operator impact on the accuracy of the information can be influenced if he is worried that he will get in trouble or even get fired. Under these circumstances the operator may falsify or fabricate the readings. Looking at graph 1 you see that many things can change in 4 hours, and some events may not get recorded. Another example regarding the accuracy of information is as follows:

The operator forgets to fill the chemical feed tank feeding the chrome reduction or the cyanide destruction process, and the chemical tank goes dry. Several hours pass and contaminated water is allowed to be discharged to the city. The operator comes back and realizes what has happened and refills the chemical tank.

Now the dilemma - does he leave a note in the log? Does he admit that he made a serious mistake? More than likely he assumes that the tank was only empty for a few minutes and does not alert his supervisor or leave a note in the log book.

The only way this release of cyanide or chrome would be detected is if the city happens to be monitoring discharge water that day. Even if the city is monitoring your water, they usually would not indicate the time of day you violated your discharge permit.

The chances are also good that your notice of violation would come several weeks after the event, and the operator would have no recollection of the event or would deny any knowledge of the problem.

Fortunately most waste treatment systems have both audible and visual alarms that alert the operator that a problem existed. I have visited shops where alarms have been disconnected or covered with foam to deaden the sound. Other times I have seen the red light alarm beacon ignored because the operator said it goes off all the time, or the beacon light not working at all because the bulb is burnt out.

Finally, other less obvious problems in manually collecting data include the inability to spot trends or problems before they occur. In most cases information recorded in logbooks is difficult to review. A supervisor or manager may not have time to sift through pages of logs to detect the beginning of a problem or spot trends.

Other times, trends may not be obvious and may require detailed review by engineers or managers with the experience, and normally these people may also be very busy. In most cases even the most experienced manager may have difficulties unless the information is transcribed into a computer spreadsheet and graphed.

Graph 2 shows three heaters monitored in a plating application. The casual observer can see that once the target temperature is reached the desired setting, the heaters do a good job of maintaining the bath temperature.

Under closer inspection you will notice a dip in temperature that is repeated. This dip occurred at almost the same time every day. This dip in temperature resulted from adding water back into the bath to make up for water lost to evaporation. If this dip had been more pronounced the plating supervisor might have decided to add water at more frequent intervals to prevent changes in the bath temperature.

Other information that can be obtained from this graph includes the length of time required to raise the temperature from 130 degrees up to the operating range of 185 degrees. Is six hours too long to heat this tank? If this is Monday and you expected the bath to be at working temperature in a couple of hours, then this graph might alert you that you have may have a bad heater or some other problem electrical problem. If you don't have an electrical problem this information would alert you that maybe you need to start raising the temperature earlier in the morning.

Graphic information will help the manager detect subtle changes or alert him (or her) to long term trends.

On Wednesday, Mr. Farnsworth's suggestions for lowering costs, increasing productivity and running a more efficient plating shop through automated monitoring, will be featured.