To whom it may concern

W‘d like to know about the criteria for choosing between using OP (Operator Panel ) or IPC ( Industrial PC ) for the control system of a plant. W‘d be thankful of you if you would read the following facts & reply your suggestions to us.
We have a dry milk plant to be automated. The plant is around 1500 sq.m. and consists of 4 parts.
1- CIP ( Cleaning In Place ) : to clean pipes & tanks.
2- Homogenizer.
3- Process : to turn milk into dry(powder) milk.
4- Packing : to pack the dry(powder) milk in 2 kinds of packages.
But at the moment we only want to automate the control system of CIP part consisting of 3 tanks ( water,LYE,acid )& having 100 I/Os.
As I said above, we can have a local OP to control the CIP or we can have a remote control room equipped with PCs & printers to do this( & some day we may cover the control of the other 3 parts in this room ,too.).
I want to know which solution is better & considering the higher expense of the second solution (control room) ,
Does it worth having a control room? .
Some important parameters for a logical reply may be as follows:
1- Cost
2- Future expansion possibility
3- Maintenance
4- Work force(operators, technicians, engineers)
5- Conformability
6- Reliability
7- Accuracy
8- Connection to MES(Manufacturing Execution System) ability in future.
9- Reporting facilities(historical & real time)
10-Comparison from HMI based on OP versus HMI based on computer point of view.

Thanks for your cooperation.

Yours truly
Masoumi & Nasehi

 

By OP I understand proprietary operator interfaces. These are some of my thoughts about this topic:

1. What kind of control system do you have already installed to interface with the HMI? Is it a DCS? A PLC? a PC-based control system? The reason for this question is that you need to know the communication capabilities of your existing equipment that will be interfacing the HMI. Will you be using OPC communications? Or will you need a special comm interface? IPC are more flexible and provide more options in terms of connectivity. PC cards for different comm protocols are available (Ethernet, DH+, Controlnet, etc.)

2. What do you want the operators to do on the HMI? Will the operator be just pressing a button to start a process or will the operator be monitoring the whole operation of a process area? IPC are more feasible for graphic intensive applications. OP come in smaller sizes feasible for situations where real estate is an issue.

3. Is the process area dirty? temperature of the area? Washdown area? Vibration? shock? IPC cannot stand high temperatures. I would not recommend an IPC close to a kiln. IPC are not good standing vibration nor shock. IPC hard drive cannot stand vibration or heavy shocks. OP are better in these environments. Will the operator be wearing gloves while working on the HMI? Be carefull because not all touch screens are able to respond to operators wearing gloves. Same with dirty hands. OP tend to be better in those situations. OP are rugged for tough conditions. In washdown situations, you will have to invest in a watertight enclosure for either OP or IPC.

4. What is the local support for your OP or IPC? How fast can you get spare parts? YOur local support will probably dictate what you can implement in your application.

5. Is your technical department knowledgeable in the HMI development package you are considering? You have to consider that if you introduce a new product to your technical and maintenance department, there will be additional cost in training and they will have to go thru a learning curve.

6. will the operator interface be used for other things other than process area control? will you need to run excel? or connect to the web? or reach a database? IPC have max flexibility. You can do everything I mentioned. Of course, you run the risk of viruses and operators playing games or surfing the net rather than doing real work. OP only run one application, the HMI application.

Now to address your other parameters:

1- Cost - As long as you purchase your product from a reputable manufacturer, you pay for what you get. Cost is driven my many factors. It is hard to justify one technology over the other solely based on price.

2- Future expansion possibility - Good point. If you implement IPC you have to consider upgrades of the operating system. Maybe you have an IT group in your facility. If so, you will need to get them in the loop if you implement IPC especially in an ethernet network with access to business applications. IPC you can increase the memory. OP come with a predetermined amount ofmemory and expansion is limited or not possible. With IPC you can upgrade your HMI development program. You cannot do that in an OP unless they allow firmware upgrades.

3- Maintenance - IPC manufacturers claim that IPC equipment has reached the same reliability as OP's. You will have to evaluate the kind of maintenance department you have in your factory. Maybe they are more knowledgeable working with PC's because of the amount of PCs they have in the factory. While an OP could be a one of a kind that they just dont know how to troubleshoot it and the easy fix is to replace it. Maybe the reversed situation is true, that maintenance personnel feel better troubleshooting an OP than a PC. Again, OPs do not suffer viruses. This is an advantage of OPs. Maintenance do not have to learn how to configure Windows.

4- Work force(operators, technicians, engineers) - Usually it does not make a difference. My only concern would be if users tend to fiddle with the equipment. If they are "curious" enough to reach the operating system and mess it up. If they are so curious, I would prefer to implement an OP.

5- Conformability - for conformability, you will have to consider the your existing installation base and where you want to take your factory.

6- Reliability - IPC manufacturers claim that IPC have reached the same level of reliability as OPs. I kind of agree with this as long as the area is a clean area with no vibration and shock.

7- Accuracy - Should be equal. My only concern would be the communication network you use to connect your HMI to your data server. A Well segregated ethernet network should give you the same data response as an OP in a proprietary network.

8- Connection to MES(Manufacturing Execution System) ability in future. - My experience has been that IPC are better suited to communicate with MES. They are based on open standards and OPC should give you the ability to transport your data across the enterprise.

9- Reporting facilities(historical & real time) - Again IPC wins. Many HMI programming packages come with preconfigured reports or Crystal reports that you can use in your application. OPs can only print alarm summaries. But I havent implemented an OP in 3 years. Maybe this is different now.

10- Comparison from HMI based on OP versus HMI based on computer point of view. - All depends in the quality of your OP or IPC. The look and feel of a high quality OP is the same as one in a IPC. However, I have never seen a 21" OP monitor. This will be dictated by the quality of your equipment.

I have developed Panelviews, VB, RSViews and InTouch applications. I cannot say that one is better than the other. It all depends on the application and the quality of the hardware.

Good luck in your application,
Marco A. Rodriguez, P.E.

 

Why not use a PLC with an OIP? You can then add PLCs to other areas later and connect to a SCADA system.

 

It seems you are planning to use it for the
first time & when go in phasewise manner it becomes difficult to select upon the system.

The Royal way of doing instrumentation is use
STABLE system & dispose during entire automation.
Develope or Freeze the P&I diagramm correctly
Use PLC/MMI integrated package which is STABLE &
SIMPLE.
I have gone through this phase no of times, simplicity helps.
Jari
[email protected]