Hydraulic Series Coupon Holders

Strip Coupon Holders

Strip coupon holders are designed to suspend a pair of 3" or 6" coupons in a vessel or pipe.

Calculating Strip Coupon Holder Length

After selecting the access fitting body style to be used, determine the pipe or pressure vessel size and select the coupon length and line position where the coupon will be located. Coupon holders can be sized to monitor the top, middle, or bottom of the line. Use the following formulas to calculate the required holder length.

Strip Coupon Holder

With a non-flanged access fitting:

Top-of-the-line Monitoring: L = PW + 2.75"
One half of the coupon extends into the pipe and the process environment. The other half is positioned in the access fitting body cavity and may be used to monitor the formation of gas pockets.

Middle-of-the-line Monitoring: L = (1/2 OD + 2.75") - CL
The coupon is centered so that ½ of the coupon is positioned on either side of the pipe’s centerline.

Bottom-of-the-line Monitoring: L = (OD + 2.5") - (CL + PW)
The coupon is positioned approximately ¼" off the bottom of the line.

With a flanged access fitting:

Top-of-the-line Monitoring: L = (FG + MH + PW) + 2.75"
Middle-of-the-line Monitoring: L = (FG + MH + 1⁄2 OD + 2.75") - 1⁄2 CL
Bottom-of-the-line Monitoring: L = (FG + MH + OD + 2.5") - (PW + CL)

Where:
L = Coupon holder length
PW = Pipe wall thickness
OD = Outside diameter of the pipe
CL = Effective length of the coupon (the portion of the coupon that is actually exposed to the process environment)
For a 3" coupon, CL = 1.625" (4.13 cm)
For a 6" coupon, CL = 4.750" (12.07 cm)

FG = Gap between mating flange faces
MH = Mating flange height from face to top of pipe

Disc Coupon Holders

Disc coupon holders are used with flush disc type coupons for measurement in either flush or non-intrusive configurations. They are available as fixed length or adjustable assemblies. These coupon holders offer the following advantages over strip coupon holders:

1. They can be mounted flush with the pipe wall so that process effects occurring at the pipe wall are closely simulated.
2. Holders properly sized to the flush position prevent coupon interference with pigging operations.
3. Orientation of coupons to process flow is not required.

The fixed length flush disc coupon holder may be sized so that the coupon is positioned flush with the pipe wall, or is extended into the line at the top, center, or bottom position.

Disc holder lengths start at 2.75" and are available in 1/8" increments. The holder's adjustable rod allows for a total travel length of 1.5". Example: A 3.25" holder would be adjustable from 3.25 to 4.75 inches.

Calculating Disc Coupon Holder Length

Select the access fitting body style and determine the pipe or vessel size and line position where the coupon will be located. Then use the appropriate formula below to calculate the required fixed length disc coupon holder.

With a non-flanged access fitting:

Flush Monitoring: L = 2.75" + PW
Middle-of-the-Line Monitoring: L = 2.625" + 1⁄2 OD
Bottom-of-the-Line Monitoring: L = (OD + 2.5") - WT
The coupon is positioned approximately 1⁄4" off the bottom of the line.

With a flanged access fitting:

Flush Monitoring: L = PW + FG + MH + 2.75"
Middle-of-the-Line Monitoring: L = FG + MH + 1⁄2 OD + 2.625"
Bottom-of-the-Line Monitoring: L = (FG + MH + OD) - (PW + 0.25")
The coupon is positioned approximately 1⁄4" off the bottom of the line.

Where:
L = Coupon holder length
PW = Pipe wall thickness
OD = Outside diameter of the pipe
FG = Gap between mating flange faces
MH = Mating flange height from face to top of pipe