The information that follows pertain to parts Campbell manufactures and controls.
The following three factors are taken into account when designing attachments:
- Pressure retaining parts are designed to meet the piping code, which defines minimum walls and materials necessary to meet our working pressure ratings. The most used code is ASME B31.3 for chemical plant and petroleum refinery piping, with ASME B31.1 for power piping also referenced. The piping codes use design pressure which by definition is the same as working pressure is in the hose industry. The piping code designs have a safety factor built into them by virtue of the allowable stress in comparison to the yield or tensile strengths of the material. It also includes a quality factor for the method of material manufacturing and a temperature chart to take all these variables into account. Although designing our fittings to meet the code would be adequate to meet the working pressure we publish, we actually surpass the minimums by a marginal amount for added safety for when the hose assembly may be subjected to higher pressures during proof or burst testing. All allowable materials per the piping codes meet various ASTM standards.
- Non pressure retaining parts or mechanical parts are designed using standard engineering practices and may include portions of the piping code even though the parts are not retaining pressure but only the force developed by the pressure. Materials used for mechanical parts meet various ASTM standards for their manufacture.
- Hose retention of an attachment is ascertained by burst testing to ASTM D380 at 70°F. The working pressure ratings published are based on these tests with a four to one safety factor. Actual hose bursts below the required 4 to 1 are not counted since the hose could not seriously test the attachment. However, hose bursts above the required 4 to 1 are counted as well as other failures of the attachment. Obviously not every hose or every size has been tested but with nearly a thousand tests, there is substantial data to extrapolate for odd sizes and most hoses. Similarly, our temperature-derating chart was established and verified from data developed from elevated temperature testing. Testing is constantly ongoing caused by new product development, customer requests, new available hoses and the want for more substantiating information.
There is no standard for the barbs or shanks of fittings though there is a general recommendation per the RMA IP-2 hose book that fitting shank outside diameter should be 1/32″ larger than the nominal hose diameter. Our proprietary shank designs meet these general requirements except in those instances where another standard dictates otherwise. For example, our chem-joint shanks conform to the shank diameters called by the old military standard for cam and groove fittings MIL-C-27487 and by the current CID (federal commercial item description) A-A-59326.
Wherever standards exist for the mechanical aspects of a fitting, they are employed and adhered to. These may include:
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