Manway

Figure 7 shows nozzle locations and support arrangements for a typical horizontal vessel (7). The saddles used for support are sustained by concrete pedestals or steel stmctures. Sufficient clearance between the bottom nozzles and the support saddles needs to be provided for access to the nozzle flange bolts. The manway can be located on the end head of the vessel, the topside of the vessel, or the side of the vessel. The preference is for an end manway wherever possible for accessibiHty, except when it is limited by the level gauges and controls that are commonly mounted off the heads. 

A thorough sampling plan should describe when the sample is to be taken and how many samples are required. It also specifies from what location within the equipment, such as the manway or discharge valve, to take the sample. The plan should also indicate what sampling equipment and sample container should be used, as well as the type of tests to be performed and the acceptance criteria. 

Two men were inspecting a large tank in which other equipment was installed. The tank had two large manways attached to it, one near the bottom and one near the top. Ventilation was provided by air entering the bottom manway and leaving the top manway. A sheet of plastic had temporarily been placed over the top manway, which decreased the amount of air circiilation. One of the inspectors chmbed a ladder in the tank, became dizzy, and fell to the tank floor below. He died from the injuries received in the fall. It was found that... 

Open manway/ addition port results in release of flammable, toxic, or environmentally detrimental vapors. 

Use localized ventilation (flexible ventilation pick-up close enough to manway/addition port to effectively capture emissions)... 

Tramp materials introduced into manway, leading to impact or frictional spark, igniting vapors. 

Runaway reaction Interlock manway with vessel pressure with manway, Design system for closed manual operation open—foam out (can be acid based), operator contacted by process materials. CCPS G-22 CCPS G-23 CCPS G-29 Fisher 1990 ISAS84.01... 

The exhaust casing shall be provided with at least one manway opening with gasketed cover for internal casing access by personnel. 

Without a manway in the section the height allowance will run 3 ft (2-ft space plus a 1-ft thick redistributor). With a manway the allowance will be 4ft. ... 

For large vessels, a manway and internally dismantled cone may be used where more economical. 

Manways left off trays. Poor separation. Everything looked good. Scan interpretation did not identify problem until after the tower was opened. In fact, the trays with properly installed manways were thought to be entraining. Installation error. 

If the absorber has aceess manways, blank off a portion of the bubble eaps or valve trays. 

General measures for controlling flammable atmospheres inside equipment are described in NFPA 69 Explosion Prevention Systems. These measures do not necessarily prevent flammable atmospheres in some practical cases, such as when powders are added to an inerted vessel via an open manway. Where possible such cases are identified in the relevant sections of Chapters 5 and 6. 

Figure Figure 12-10. Example of horizontal manway cover davit and sleeve detail.

Old vessels may not be as cheap as they seem at first sight. Nozzles and manways are often in the wrong plaee, and the eost of modifying them may make the vessel more expensive than a new one. A designer who was persuaded to use an old cylindrical pressure vessel ended up using the two dished ends and nothing more ... 

Area between downcomer and inlet weir for up-flow of inlet liquid. All trays included access manway. 

Alignment of Manway Fiange Face shall be within 1° in Both Vertical 8 Circumferential Planes... 

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