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Injection and Sampling systems are fundamental to corrosion control and process control
programs. They are applicable to a large variety of processes in the petroleum, chemical,
and water treatment industries. Injection systems are used to inject a wide range of
chemicals into processes. Such chemicals include biocides, demulsifiers, corrosion
inhibitors, oxygen scavengers, glycol and mono-ethylene glycol, dewaxers, methanol,
odorizers, and product additives.
Injection systems may be as simple as using an open-ended tube that allows for even distribution of the injected chemical or as complex as using a head with a cap and core to obtain precise atomization of the chemical.
Sampling systems are used to take samples of the process fluid or medium. Such samples
are then analyzed in the laboratory for inhibitor concentration levels, the presence of
metal ions, oxygen levels, scale forming compounds, and a wide range of process
The art of chemical injection is a complex technology. Irrespective of the type of
injection or injected fluid, several factors relative to the process system and the
injection system must be considered. Principal factors are:
This is the difference between the injection pump pressure and the process line or
vessel pressure. Ideally the pressure differential should be 100 PSI (6.8 Bar). However,
varied injection rates can be achieved by changing the pressure differential.
Temperature directly affects viscosity. Ideally the temperature of both the injected
chemical and the line product should be about 70° F (21° C).
This is the measure of a fluid's resistance to flow. The more viscous the fluid the
smaller the spray angle.
Spray angle is affected by viscosity, spray distance, and pressure differential.
This is the theoretical coverage area.
The specific gravity of a liquid is the density ratio of the liquid to water. The flow
rate of a liquid is affected by its specific gravity.
This is the amount of chemical to be injected within a specified time and is defined as
Gallons Per Hour (GPH), Liters Per Day (LPD), etc. Injection Systems are available for
injection rates varying from 0.1 GPH (0.38 liters/hr) to 65.7 GPH (250 liters/hr).
The maximum fluid velocity is usually at the center of the line. Therefore, the most
effective position for injection is generally at the center of the pipe in the direction
of the product flow. If the line is to be pigged, the injection point may be flush with
the pipe wall. This eliminates the need to remove the injection probe before pigging
operations begin. On pipelines this means that injection is perpendicular to the product
flow. Top of the line may be used if the injection is required to be oblique or horizontal
to the product flow.
A typical Injection Assembly for use with High Pressure Access Systems is shown in Figure
1. A Sampling system uses the same components. The various components of the
a. Quill is an open-ended tube cut at a 45° angle with a slot. It utilizes the turbulence created by its unique design to achieve distribution of the injected chemical into the product flow. Injection Tube Quills are clog proof and give extremely good dispersion of the inhibitor if the product flow is 15 ft. per second or greater. As with the Open Tube, injection rate must be controlled at the injection pump or shut-off valve.
b. Open is an open tube. The natural turbulence within the pipeline is used to insure even distribution. There is essentially no pressure differential experienced at the orifice, so it is necessary to control the injection rate at the injection pump or the shut-off valve.
c. NPT is similar to the Open Tube but is threaded at the dispersion end, thus allowing attachment of female nozzle assemblies. Injection may be perpendicular to the flow with the use of a straight nozzle or parallel to the flow with the use of a right angle nozzle.
d. Head with Caps, Cores, and Strainers are the various devices that, when attached to the dispersion end of the Injection Tube, permit atomization of the fluid as it is injected into the product line or vessel. The assemblies can be provided in complete units that contain caps, cores, and strainers. The head has female threads to match threads on the caps, cores, and strainers, so that these attachments can easily be replaced.
Materials of Construction
All components are manufactured from 316 SS as standard with the exception of seals and
packing. These materials comply with the requirements of NACE Standard MR 01-75
Recommended Materials for sulfide stress cracking environments.
Center of Line Non-Flange Fitting
Open/Quill: (FH + PD/2) - (2.04 + N) = L
Head: (FH + PD/2) - (2.04 + N) = L
*NPT: (FH + PD/2) - (3.353 + N) = L
Center of Line Flange Fitting
Open/Quill: (FH + PD/2 + MF) - (2.04 + N) = L
Head: (FH + PD/2 + MF) - (2.04 + N) = L
*NPT: (FH + PD/2 + MF) - (3.353 + N) = L
Flush Non-Flange Access Fitting
Open/Quill: (FH + PW) - (2.04 + N) = L
Head: (FH + PW) - (2.04 + N) = L
*NPT: (FH + PW) - (3.353 + N) = L
Flush Flange Access Fitting
Open/Quill: (FH + PW + MF) - (2.04 + N) = L
Head: (FH + PW + MF) - (2.04 + N) = L
*NPT: (FH + PW + MF) - (3.353 + N) = L
FH = Access Fitting Height
PW = Pipe Wall Thickness
N = Injection Nut Length
L = Injection Tube Length
MF = Mating Flange Height
PD = Pipe Outer Diameter
IL = Insertion Length into Pipe or Vessel
*Length of tube is based on nozzle length of 1.313".
Nozzle is sold separately.
A) Access Fitting Body height & Tee Size may be determined from the Access Fitting
B) The Injection Nut size may be determined from Table 1.
|Model||Length (Fitting Type / Height)||Probe End Thread||Seal Material||Alloy Code|
|1 - 1.75" (HP / 5.25")
2 - 2.75" (HP / 6.25")
3 - 3.75" (HP / 7.25")
4 - 4.75"
5 - 5.50" (HP / 8.25")
6 - 3.50" (MH / all heights)
|0 - N/A
1 - 1/8" - 27 NPT
2 - 1/4" - 18 NPT
3 - 3/8" - 18 NPT
4 - 1/2" - 14 NPT
5 - 3/4" - 14 NPT
6 - 3/8" - 24 UNF - 2B
7 - 7/16" - 20 UNF - 2B
8 - 1/2" - 24 UNF - 2B
9 - 9/16" - 18 UNF - 2B
A - 5/8" - 18 UNF - 2B
|0 - N/A
1 - Viton® o-ring / Teflon® backing ring
2 - Ethylene propylene / Teflon® backing ring
3 - Kalrez® o-ring / Teflon® backing ring
4 - Hydrin o-ring / Teflon® backing ring
5 - Nitrile o-ring / Teflon® backing ring
6 - Teflon® o-ring / Teflon® backing ring
|158 - 316 SS
A12 - C276
C) Determine the Injection Tube Thread Size required. Determine the Type.
Calculate the Injection Tube Length using the sizing formulas. Use this information to
determine the Part # from Table 2.
|Model||Thread Size||Type||Alloy||Length Designation|
|IQ -----||--- X ---||--- XX ---||---XXX ---||
1 - 1/8" NPT
|01 - Quill
02 - Open
03 - NPT for a Nozzle
04 - Head w/ Cap & Core
|158 - 316 SS
A12 - C276
|Length in inches, stated in 2 decimal place format
(Ex: 6 1/4" = 0625)
D) A Nipple & Shut-Off Valve to match the Tee of the Access Fitting
Body may be selected from Table 3.
Nipple, 4 in (100 mm)
316 SS Sch. 80
|Part No.||Part No.|
E) If applicable, select a suitable Nozzle Type or Cap & Core Assembly from Table
|Nozzle Type / Part Number||
Expected Flow Rate in
GPH @ 100 PSI
|1/4" FNPT Noz.||1/4" MNPT Noz.||Cap & Core Assem. (9/16")|
Teflon® is a registered trademark of DuPont.
Contact Metal Samples Corrosion Monitoring Systems sales department for pricing and availability.
Phone: (256) 358-4202
Fax: (256) 358-4515
Phone: (832) 451-6825
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