Rely on empirical data! Sadly, plants seldom use one important source of empirical data — the corrosion coupon, which is a welded strip of metal designed to be inserted into a process. But, believe me, it;s worth it.. If possible, review the specifications with your mechanics. Exceptions may exist, and where they do, they must be clarified and documented. With the analysis complete, it;s time for a meeting. This table is crucial for working with old vendors and old inventories.My company couldn;t see all the fuss. The expert was dead-wrong! What we saw was quickly dubbed "the jawbreaker effect" by our operators. Clearly state temperature limits; separately cite test pressures for ambient pressure tests. This omission in company records almost justifies the reluctance I;ve witnessed to challenge pipe specifications. Leave detailed discussion of any contentious points to follow-up meetings. The best format for these specifications consists of a single page summary followed by details, exceptions and referencesg. Usually, a condition-based specification is best.

Once information is collected, you should budget time for careful analysis by a consultant. References should include the ANSI number and the old pipe specification number it replaced if there is one. We had to handle a feed stream of aluminum chloride added to a stream containing wet chlorine gas and vaporized titanium tetrachloride. Saving a little money now on a sole-source contract often isn;t worth the headache later of finding a replacement when a part fails to meet quality standards. A world-renowned valve material expert claimed that zirconium oxide would survive our process. Sometimes exceptions arise because a vendor can;t change a valve specification and an acceptable alternative hasn;t been found yet. The details should include gaskets, valves, fasteners.We had been hired by Bechtel as a subcontractor for the ill-fated Goro project to refine nickel ore in New Caledonia.With all basic facts now in hand, it;s time to schedule follow-up meetings to review the draft pipe specifications. What;s missing is supporting information explaining the basis for decisions like the choice of type 316 stainless steel over type 304L, or selection of Inconel 601 instead of Inconel 600.It;s best to isolate the summary table so that it;s compact and usable by those in the field. The first decision in establishing a pipe standard is choosing whether it will be based Nickel-Based Alloys Welded Tubes on function or condition.

Bechtel wanted us to match its pipe specifications. An often-overlooked item is the cross-comparison table, which matches the new specifications against the old ones. Coupons, which also can be used for gasket materials in some applications, provide real data well beyond those found in textbooks and from laboratory analysis, which seems artificial by comparison. Keep your options open with vendors.g. Stainless steel seamless pipe specifications are one of the keys to safe plant operation. The downside is exposure time; material evaluation takes months. Bring together maintenance staff, project engineers, vendors and contractors to pencil in the details of the new pipe specifications. Keep the summary table relatively simple.e. Over about six weeks, the balls in our ball valves shrunk, flaking away from thermal shock., for which chemicals; connections, e. Being prudent, I suggested coupons but was overruled because of time constraints. Instead, they allow analysis of the effects of corrosion on parent metal and welds. A function-based specification would be something such as a sewer pipe or vent duct. The idea is to look for discrepancies between the pipe specifications and for areas of improvement. If you must note vendor information, also try to include acceptable alternatives. A condition-based specification would discriminate between sewer pipe for corrosive versus sanitary service. It should include pressure rating; application, i. In one company, we ordered a PTFE-lined plug valve and modified it to fit an actuator.

Looking back, Bechtel;s approach made sense: get the Stainless steel pipe specifications right or live with a project fraught with headaches — never mind other minor issues, i. For example, Trevor Kletz, in his book "Process Plants: A Handbook for Inherently Safer Design," suggests eplacing fiber gaskets with spiral-wound gaskets because their leak rate is lower. Collecting information is the next step. Consider what happened on another project. They may want to pass on their wisdom on construction details. Make specifications simple and easy to follow. By not keeping them current or allowing them to become confusing or hard to use, you may encourage deviation from good engineering practices. To us, this was just another symptom of a bloated project. We used to joke that Bechtel had two engineers for toilets: one for the men;s room and one for the women;s room.e. Pipe specifications often are presented in tables kept in massive volumes., bolts), special fittings, construction aspects such as weld inspection and paint preparation, etc. Coupons would have saved us more than $1 million a/year in downtime during the next few years and justified a ball made of a more expensive ceramic., safety, reliability and profitability., threaded or socket-welded; and material of construction

Posted by: incoloytube at 01:39 AM | No Comments | Add Comment
Post contains 840 words, total size 6 kb.