Pipe strain

Open impeller has slight rub on casing. Most often occurs in operations from 250 to 400 F due to piping strain and differential growth in the pump. 

Elastic Behavior The assumption that displacement strains will produce proportional stress over a sufficiently wide range to justify an elastic-stress analysis often is not valid for nonmetals. In brittle nonmetallic piping, strains initially will produce relatively large elastic stresses. The total displacement strain must be kept small, however, since overstrain results in failure rather than plastic deformation. In plastic and resin nonmetallic piping strains generally will produce stresses of the overstrained (plasfic) type even at relatively low values of total displacement strain. 

Prior to anv machineiy alignment procedure, it is imperative to check for machine pipe strain. This is accomplished by the placement of dial indicators on the shaft and then loosening the hold-down bolts. Movements of greater than 1 mil are considered indication of a pipe strain condition. 

This minimizes pipe strain and thermal expansion and distortion. Utilizes a elosed impeller with balanee holes. 

Alleviate any possible pipe strain, a force imposed by the piping that... 

Pipe strain is normally caused by misalignment between the piping and the pump nozzles, improper pipe supports, or thermal expansion in the system. 

To verify pipe strain, plaee dial indieators on the shaft and watch for horizontal and vertieal movement. Unite the flanges one at a time eontinually observing the indieator readings. In general the indieator readings should not exeeed 0.002 inehes (Figure 10-12). 

Mechanical problems. Pipe strain distorting the pump casing. 

Forces transmitted to casing and foundations. These forees ean be due to foundation instability, other nearby unbalaneed maehinery, piping strains, rotation in gravitational or magnetie fields, or exeitation of easing or... 

Piping strain is by far the greatest probiem causer, and so piping siiouid be carefuiiy reviewed to ensure that it is properiy done according to code. Piping strains as high as 0.22 inches (0.5588 cm) have been observed. 

A typical cause of piping strain occurs when two flanges do not meet and pipefitters force them together. Pipe hangers that are poorly placed or tensioned can also cause significant piping stress problems. 

PRESSURE 2. Low level in oil reservoir. Vibration may be trans- 3. Piping strain. 

SHAFT MISALIGNMENT 1. Piping strain. 14. Operating in surge region. 

Instruments and controls checked Refractory dried out Piping Strains on Equipment Electric Motors Rotation Drying out No-load tests Steam-Turbine Drivers... 

Piping is required to bring the gas to the compressor and take it away. If it were not for this somewhat basic need, compressors would do well without it. Piping brings with it pipe strain. If one were to ask the maintenance department why pipes are used, the answer would undoubtedly be that piping was installed to the compressor to destroy the fine alignment just completed by the millwright. 

There are many design features and styles of safety relief valves, such as flanged ends, screwed ends, valves fitted internally for corrosive service, high temperature service, cryogenic service/low temperatures, with bonnet or without, nozzle entrance or orifice entrance, and resistance to discharge piping strains on body. Yet most of these variations have little, if anything to do with the actual performance to relieve overpressure in a system/vessel. 

If pressure relief valve is connected to a closed system, care should be taken to keep piping strains away from the valve under all conditions of process operation... 

More pumps fail as a direct result of improper installation than any other single factor. The predominant reasons for these failures include starvation, caused by inadequate or inconsistent suction conditions distortion, caused by pipe strain or improper foundation and turbulent that results from piping or entrained gas problems. Centrifugal pump installation must follow Hydraulic Institute Standards, which provide specific guidelines to prevent these installation and performance problems. This chapter will address the fundamental requirements for proper installation. 

The pre-installation equipment inspection should include the following stuffing box space, lateral or axial shaft movement (end play), radial shaft movement (whip or deflection), shaft runout (bent shaft), stuffing box face squareness, stuffing box bore concentricity, driver alignment, and pipe strain. 

Driver alignment is extremely important and periodic checks should be performed. Pipe strain can also damage pumps, bearings, and seals. 

Steel pipe used for service lines shall be installed in such a manner that the piping strain or external loading shall not be excessive. 

Built-in features to the surveillance module include the ability to scroll up and down through the list of equipment sets and the ability for the technician to provide useful comments. The technician can select comments from a preprogrammed list such as needs alignment, base requires anchoring, or piping strain. The technician can also enter any descriptive short phrase. 

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