Specifying performance instead of parts
Many plants and facilities purchase machines and process skids from OEM suppliers. The temptation often is to specify parts and vendors down to a very detailed level, but this can result in higher costs, longer lead times and no performance guarantees from the OEM.
A better approach in many instances is to specify performance, while giving the OEM as much leeway as possible in terms of parts and vendors. This is particularly true for plants and facilities with limited onsite staff, and a corresponding heavy reliance on OEM suppliers, often including support contracts.
Issues with specifying vendors
Specifying preferred parts and vendors can make it difficult to create a bid specification because excessive detail is required, very little of which directly influences the most important attribute: performance of the machine or process skid (see Figure 1). It may stop OEMs in their tracks, resulting in fewer bidders, or sometimes only one.
Boxing in the brands that can be used will often push an OEM out of its comfort zone (see Figure 2). For example, if the OEM can’t use its preferred controller or human-machine interface (HMI), the design and schematics will need to be changed, which will cause higher costs and delays in other areas. The learning curve will remain in effect throughout the project, adding even more delays, along with longer lead times for parts.
Focusing on parts and vendors instead of performance in the bid spec may require a new programmable logic controller (PLC) program to be written, one never tested in use before. This required software development time may or may not extend the project schedule, but either way someone must be paid to write it. The OEM often must outsource programming for unfamiliar controllers, adding another layer of risk and complexity. Regardless of who writes the software, it likely will need extensive debugging as it hasn’t been proven in use, which will extend the time needed for startup and commissioning.
Limiting vendor and OEM options is like requiring the wheel to be reinvented. What the OEM knows and has proven in use for years turns into a custom control system, which may result in less reliable operation. All the tuning, tweaks and optimization performed on the OEM’s preferred control system must now be repeated. Some of this can be done during design, test and startup—but other issues will inevitably crop up later.
Combining detailed part and vendor specifications with the changes needed to an OEM’s control system also may lead to delays in support, and/or a much more expensive support contract. Most of the OEM’s technical personnel will not be able to support the unfamiliar control system, in the worst case leading to reliance on a single person within the OEM’s organization, or within one of its subcontractors.
It’s much simpler to specify performance instead of parts and vendors, for instance a certain number of parts produced per hour with 98% uptime. While specifying parts and vendors doesn’t guarantee performance, specifying performance can. Most OEMs will be quite reluctant to guarantee performance if they can’t use their preferred vendors. Allowing them to do so will make performance guarantees much more likely, and also can result in improved assurances. In the preceding example, the OEM might be able to guarantee 99% uptime if it uses its preferred vendors, which could result in substantial savings.
But just how does a company go about specifying performance, while assuring the machine or process skid can fit into its general plant operating parameters? The following list gives an example of some of the most important electrical performance requirements to include in a control design specification, which should be included along with required performance in terms of the machine or process skids output, uptime, maintenance costs, etc.:
- A single-point plant connection shall be provided for a 3-phase, 480 V ac, 60 Hz supply.
- A main disconnect with electrical lockout feature shall be provided.
- Control wiring shall be 24 V dc or less.
- Programmable logic controller shall have a minimum expansion of 128 input/output (I/O) points.
- Supplier must provide programming software for all programmed devices.
- Discrete inputs shall be 24 V dc, sinking, 16-point modules.
- Discrete outputs shall source 24 V dc to a sinking output device, 16-point modules.
- Sensors shall be PNP type with indicator lights and micro (M12) quick-disconnect cables.
- Control enclosure shall maintain a minimum of NEMA 12 environmental protection.
- All wiring and hoses shall have labels that match the electrical schematic.
- Operating temperature shall be 32 F to 140 F or better.
- The operator interface shall be a color touchscreen with a minimum 6-inch diagonal display.
The electrical performance requirements in the preceding list should be self-explanatory, with each requirement simple to verify. These electrical requirements, along with other performance specifications, are usable throughout an automation project from the bid stage to site acceptance testing, where each requirement and specification must be checked to assure it is met.
Beyond cycle time, parts per hour, productivity availability and quality requirements, additional system or machine performance might include critical process performance such as crimping a cap in a housing or other item required to make a good part. This would include, for example, press-to-depth crimp performance of 3-5 tons of force with +/-0.002-inch press stroke depth repeatability. Other performance requirements might be a production rate of 200 parts per hour with 98% uptime.
HMI specifications also can be performance-based using operational parameters. For example, requiring an overview screen with mode, cycle, product and fault information. Product selection via recipes, teach robot points and help and fault message screens are other examples of operational performance requirements for an HMI (see Figure 3).
Basic requirements for data collection are another example of a performance-based specification. This might include storage of fault message data, display of the number of good and reject parts by part number, current cycle time, last 10 cycle times data, etc.
These performance requirements lead the way to a quicker installation and startup. The end goal is a reliable and efficient machine or process skid that fits into ongoing operations.
Supporting the system
Many OEMS are willing and able to maintain their machines and process skids remotely for a low monthly cost after the warranty expires, but often only if they can use their preferred vendors. This approach also fits well with many end users due to a shortage of technical staff.
The need for after-warranty support should be well-defined in the performance-based specification at the start of the project, with costs specified. The provision of remote and onsite support services should be defined. Using these support options in performance-based specifications helps ensure machines and process skids will be supported at the level required and lets the OEM use their standard design.
With the OEM equipment tested, accepted and paid for, quick resolution of any operational problems is a must. To speed this process, remote access is critical. Whether it’s during the first-year warranty period, for example, or after the warranty expires, remote access keeps support costs low for both the end user and the OEM. Troubleshooting via remote access should therefore be a performance requirement. That means that remote access is not an add-on feature, but instead a requirement designed into the control system from the start.
OEMs and their customers look to the future
At least some OEMs are now supplying machines and process skids through lease arrangements instead of requiring a purchase. These lease arrangements often are very performance-oriented, with the OEM not being paid if performance guarantees are not met.
Another wrinkle is for the OEM to be paid based on production of the machine or process skid, for example, a certain amount per pound of product produced, with any set monthly payment. This type of arrangement most closely aligns the purchaser’s needs for maximum production with the OEMs financial goals, and is therefore gaining favor.
Both of these types of agreements, leasing and paying only for production, strongly favor specifying performance instead of parts and vendors, and are a requirement of many of these types of contracts. Even if the OEM consents to enter into one of these types of agreements using parts and vendors specified by the purchaser, costs are sure to be higher.
Therefore, current and future trends may favor specifying performance instead of parts and vendors in many instances, and often may lead to more favorable outcomes for both parties.
Bill Dehner is a technical marketing engineer at AutomationDirect. He has spent the majority of his 14-year engineering career designing and installing industrial control systems for the oil & gas, power and package handling industries.
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