How Calculate PCD (Pitch Circle Diameter) of a Flange?

1. As accurately as you can, measure two adjacent holes using a varniar scale and calculate the PCD; then calculate for-
2. 4 holes: multiply by 1.414.
3. 8 holes: multiply by 2.613.
4. 12 holes: multiply by 3.864.
5. 16 holes: multiply by 5.126.

The PCD of a flange is one of the critical dimensions. PCD (Pitch Circle Diameter) is the diameter of a circle that goes through each of the bolt holes.

To calculate the pitch diameter, one must imagine a cylinder whose diameter exists at the point where the thread groove width and the thread crest width are both equal to one another and equal to half the nominal pitch of the thread. The diameter of this imagined cylinder is the pitch diameter.

Using a ruler or measuring tape measure the diameter of your nipple at base (across middle) in millimeters (mm). Do not include areola. Based on your measurement, determine your Medela breast shield size. Example: If your nipple size measures 16 mm in diameter, the recom- mended Medela breast shield size is 21 mm.

Nominal diameter is that size by which the pipe or tube is identified, for example 1 inch or 25mm.

The blind flange is attached by bolts causing an edge moment (Fig. UG- 34. /sketch j) in which the thickness can be calculated by : t = d *(CP/SE+1.9W hg/SE*d^3) ½ ………………. Formula (2) (From ASME UG-34)

Flanges can withstand different pressures at different temperatures. For example, a Class 150 flange is rated to approximately 270 PSIG at ambient conditions, 180 PSIG at approximately 400°F, 150 PSIG at approximately 600°F, and 75 PSIG at approximately 800°F.

Convert Actual Diameter to Nominal Diameter

1. Wrap a string around the pipe.
2. Mark the point where the string touches together.
3. Use a ruler or measuring tape to find the length between the tip of the string and the mark you made (circumference)
4. Divide the circumference by 3.14159.

OD and Nominal Pipe Size Tubing is measured by the OUTSIDE DIAMETER (O.D.), specified in inches (e.g., 1.250) or fraction of an inch (eg. 1-1/4″). Pipe is usually measured by NOMINAL PIPE SIZE (NPS). Although it is related to the outside diameter, it is significantly different.

Measurement. In manufacturing, a nominal size or trade size is a size “in name only” used for identification. The nominal size may not match any dimension of the product, but within the domain of that product the nominal size may correspond to a large number of highly standardized dimensions and tolerances.

When measuring a female pipe thread (FPT), measure the OD of the pipe itself and subtract ¼ inch to find the correct pipe thread size. Perhaps even easier than this is to purchase a measuring tool called a caliper that will measure OD and inside diameter (ID).

NPT and NPTF pipe threads – dimensions according ANSI/ASME B1. 20.1/3

As a general “rule of thumb” an NPT thread is approximately 1/4″ (0.25”) larger than its “name.” For a 1/4″ NPT fitting the “nominal” OD is 0.533”. NPT fittings are slightly tapered so the “nominal” diameter is the diameter in the middle of the threaded portion, as measured by the top (crest) of the threads.

14 threads per inch

Commonly used sizes are 1⁄8, 1⁄4, 3⁄8, 1⁄2, 3⁄4, 1, 11⁄4, 11⁄2, 2, 21⁄2, 3, 4, 5, and 6 inch, as pipe and fittings by most U.S. suppliers. Sizes smaller than 1⁄8 inch are occasionally used for compressed air, while sizes larger than 6 inches are often joined by other methods.

As a general guideline, after hand-tight engagement, tighten 2-3 full turns for sizes up to 1 inches for NPT fittings. You should have between 3.5 and 6 engaged threads. Any number outside of this range may indicate either under or over tightening of the joint or out of tolerance threads.

NPT (or National Pipe Taper) is a U.S. standard for tapered threads widely used on pipes and fittings for over 100 years. NPT connections rely on thread deformation- a metal to metal sealing design where the threads of the connectors themselves form together.

National Pipe Thread

NPT – National Pipe Thread – the US standard for tapered threads. This standard allows NPT threaded fittings to fit together in a water-tight seal. A common measurement in PVC and CPVC piping.

Both NPT and BSP are pipe thread standards for screw threads used on pipes and pipe fittings to seal pipes. With NPT, the peaks and valleys of the threads are flat. In BSP, they are rounded. Secondly, the NPT angle of the thread is 60 degrees and the BSP angle is 55 degrees.

In most situations that don’t involve high pressure, a male NPT fitting can be threaded into a female BSPP fitting, using Teflon tape to seal. Note that because the male NPT fitting is tapered it will thread a little farther into the straight threaded BSPP female fitting.

BSP

Use a tape rule (or vernier gauge) to measure across the outside of the male thread. Note that a thread that measures 1/2″ is not a 1/2″ BSP thread. Using the table below we can see that a thread measuring 1/2″ is actually a 1/4″ BSP thread. Similarly, a thread that measures 1″ is actually a 3/4″ BSP thread.

British Standard Pipe Thread (BSPT)