| My company couldn't see all the fuss. We had been | | | | vaporized titanium tetrachloride. A world-renowned |
| hired by Bechtel as a subcontractor for the ill-fated | | | | valve material expert claimed that zirconium oxide |
| Goro project to refine nickel ore in New Caledonia. | | | | would survive our process. Being prudent, I |
| Bechtel wanted us to match its pipe specifications. | | | | suggested coupons but was overruled because of |
| To us, this was just another symptom of a bloated | | | | time constraints. The expert was dead-wrong! What |
| project. We used to joke that Bechtel had two | | | | we saw was quickly dubbed "the jawbreaker effect" |
| engineers for toilets: one for the men's room and one | | | | by our operators. Over about six weeks, the balls in |
| for the women's room. Looking back, Bechtel's | | | | our ball valves shrunk, flaking away from thermal |
| approach made sense: get the Stainless steel pipe | | | | shock. Coupons would have saved us more than $1 |
| specifications right or live with a project fraught with | | | | million a/year in downtime during the next few years |
| headaches — never mind other minor issues, i.e., | | | | and justified a ball made of a more expensive |
| safety, reliability and profitability. | | | | ceramic. |
| The first decision in establishing a pipe standard is | | | | With all basic facts now in hand, it's time to schedule |
| choosing whether it will be based on function or | | | | follow-up meetings to review the draft pipe |
| condition. A function-based specification would be | | | | specifications. The best format for these |
| something such as a sewer pipe or vent duct. A | | | | specifications consists of a single page summary |
| condition-based specification would discriminate | | | | followed by details, exceptions and references. The |
| between sewer pipe for corrosive versus sanitary | | | | details should include gaskets, valves, fasteners (e.g., |
| service. Usually, a condition-based specification is best. | | | | bolts), special fittings, construction aspects such as |
| Collecting information is the next step. Pipe | | | | weld inspection and paint preparation, etc. If possible, |
| specifications often are presented in tables kept in | | | | review the specifications with your mechanics. They |
| massive volumes. What's missing is supporting | | | | may want to pass on their wisdom on construction |
| information explaining the basis for decisions like the | | | | details. |
| choice of type 316 stainless steel over type 304L, or | | | | Exceptions may exist, and where they do, they must |
| selection of Inconel 601 instead of Inconel 600. This | | | | be clarified and documented. Sometimes exceptions |
| omission in company records almost justifies the | | | | arise because a vendor can't change a valve |
| reluctance I've witnessed to challenge pipe | | | | specification and an acceptable alternative hasn't been |
| specifications. | | | | found yet. In one company, we ordered a PTFE-lined |
| Once information is collected, you should budget time | | | | plug valve and modified it to fit an actuator. |
| for careful analysis by a consultant. The idea is to | | | | Keep the summary table relatively simple. It should |
| look for discrepancies between the pipe specifications | | | | include pressure rating; application, i.e., for which |
| and for areas of improvement. For example, Trevor | | | | chemicals; connections, e.g., threaded or |
| Kletz, in his book "Process Plants: A Handbook for | | | | socket-welded; and material of construction. It's best |
| Inherently Safer Design," suggests eplacing fiber | | | | to isolate the summary table so that it's compact and |
| gaskets with spiral-wound gaskets because their leak | | | | usable by those in the field. |
| rate is lower. | | | | References should include the ANSI number and the |
| With the analysis complete, it's time for a meeting. | | | | old pipe specification number it replaced if there is |
| Bring together maintenance staff, project engineers, | | | | one. Clearly state temperature limits; separately cite |
| vendors and contractors to pencil in the details of the | | | | test pressures for ambient pressure tests. If you |
| new pipe specifications. Leave detailed discussion of | | | | must note vendor information, also try to include |
| any contentious points to follow-up meetings. Rely on | | | | acceptable alternatives. Keep your options open with |
| empirical data! | | | | vendors. Saving a little money now on a sole-source |
| Sadly, plants seldom use one important source of | | | | contract often isn't worth the headache later of |
| empirical data — the corrosion coupon, which is a | | | | finding a replacement when a part fails to meet |
| welded strip of metal designed to be inserted into a | | | | quality standards. |
| process. Instead, they allow analysis of the effects | | | | An often-overlooked item is the cross-comparison |
| of corrosion on parent metal and welds. Coupons, | | | | table, which matches the new specifications against |
| which also can be used for gasket materials in some | | | | the old ones. This table is crucial for working with old |
| applications, provide real data well beyond those | | | | vendors and old inventories. |
| found in textbooks and from laboratory analysis, | | | | Stainless steel seamless pipe specifications are one of |
| which seems artificial by comparison. The downside is | | | | the keys to safe plant operation. By not keeping |
| exposure time; material evaluation takes months. But, | | | | them current or allowing them to become confusing |
| believe me, it's worth it. | | | | or hard to use, you may encourage deviation from |
| Consider what happened on another project. We had | | | | good engineering practices. Make specifications simple |
| to handle a feed stream of aluminum chloride added | | | | and easy to follow. |
| to a stream containing wet chlorine gas and | | | | |