Scaling-up PV fabs? Make tagging your friend

Solar cell manufacturing technologies are advancing and proliferating. To avoid confusion and potential hazards when your fab goes from a handful of people to hundreds, implement an equipment tagging system, says blogger Steve Blaine, CH2M HILL.

Solar cell manufacturing technologies are advancing and proliferating. To avoid confusion and potential hazards when your fab goes from a handful of people to hundreds, implement an equipment tagging system, says blogger Steve Blaine, CH2M HILL.

June 8, 2011 — The solar cell manufacturing industry is in a fascinating phase of evolution, with myriad new solar processing technologies being conceived and tested. This is also a time when, in their eagerness to fast-track scale-up of promising new processes, solar photovoltaics manufacturers are vulnerable to allowing inefficiencies to be institutionalized into their new factory’s operations. Consider the relatively simple procedure of tagging a plant’s equipment and devices at the beginning of the job.

Some operators don’t bother to tag equipment because they’re accustomed to relying on plant operators to remember which pieces of equipment are where in a smaller plant. This seat-of-the-pants approach can break down quickly in a ramped-up environment, where documentation becomes imperative.

When a factory is small and there are just a few employees, it’s easy to talk about “the cooling pump” and everyone knows what you mean. When there are primary cooling, secondary cooling, tertiary cooling, process cooling and even process chilling systems, each with more than one pump, there is plenty of room for confusion.

Every plant can benefit from a straightforward system that identifies the function and location of every piece of equipment, and correlates that information to the plant’s working drawings. This is a sound practice not just for streamlining maintenance, but also for simplifying and speeding the pace of future upgrades to a plant’s tools and systems.

First, decide on a scheme for naming and tagging all equipment and devices at the beginning of the job. Make sure everyone applies this scheme on drawings, programs, and labels in the field. Stick with the plan, even for vendor tools and skids. This will facilitate design, installation, commissioning, maintenance and even doing your taxes (really!).

The scheme should include a comprehensive list of unit processes, organized by types and with room for expansion. Some naming conventions are included below:

MECHANICAL DRY:

101 MAKE-UP AIR  MAU
102 RECIRCULATION AIR RAH
103 MAKE-UP AIR (NON-FACTORY) MAU
104 GENERAL AIR (NON-FACTORY) AHU
105 FAN COOLING UNITS FCU

MECHANICAL WET:

121 PRIMARY CHILLED WATER – HVAC CHW
122 SECONDARY CHILLED WATER – HVAC SCW
123 TERTIARY CHILLED WATER- HVAC TCW
124 CONDENSER/COOLING TOWER WATER – HVAC CNW

EXHAUST:

140 GENERAL EXHAUST GEX
141 SCRUBBED ACID EXHAUST SAX
142 SCRUBBED BASE EXHAUST SBX

If the facility is large, perhaps with multiple buildings, a scheme that includes a location code is useful. When tagging equipment, use F#-CCC-DDD-EEE when F# = fab number, CCC = equipment type, DDD= unit process number and EEE = equipment number. For example, F2-MAU-101-001 references make up air units in fab Click to Enlargebuilding 2.

The plan should encompass not just equipment but the devices associated with the equipment.


In the illustration, xxx = device function designator, CCC = device type, DDD = unit process number, EEE = equipment number, and FF = instrument identifier (device number per loop).

A naming scheme should apply to both facility and production equipment. When there are gas and chemical systems identified by formula names, it can be very easy to mislabel something (was that the “sulfite” or “sulfate” valve?) Formula names should be labeled consistently too.

Production tools deserve a name that fits with the other equipment. What do you call the leak switch that is attached to the Valve Manifold Box feeding the deposition tool? How do you label these sensors when you’re installing several hundred of them? Where do you tell the hazmat team to go when sensor #122 goes into alarm? Take care of these questions ahead of time with a consistent tagging scheme.

If you’re really thinking ahead, this scheme could make sure that all equipment and device tags use the same number of characters. This really makes life simple when you are looking through spreadsheets and trying to organize a list.

Luckily, this problem has already been addressed many times, so you don’t have to create something from scratch. The ISA has a tagging standard that works in even the largest of facilities (ANSI/ISA-5.1-2009 Instrumentation Symbols and Identification).

Most design firms have experience picking a standard and enforcing it throughout a job. In our experience, even a bad standard is better than no standard.

Steve Blaine is an instrumentation and controls specialist with CH2M HILL. He has more than 25 years of experience designing control systems for advanced technology manufacturing industries including semiconductor, solar, and flat panel, as well as high-density data centers. He has designed controls for machines, facilities and innovative energy optimization systems using PLCs, PCs, operator interfaces, and SCADA systems. He is a registered professional engineer in the US states of Oregon, New Mexico, Arizona, Florida, Texas and Utah.

Read Blaine’s colleague Ralph Williams’ blog on water use in solar cell manufacturing facilities: Solar cell makers should consider another (potentially) renewable resource: Water use

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