Page 81 - JB Product Catalog 50

CAPILLARY TUBING
CAP TUBE LENGTH CONVERSION CHART TO USE CHART
1. Locate recommended cap tube ID in left column
2. Read across and find conversion factor under copper cap tube size
3. Multiply the given length of the cap tube by the conversion factor
4. The resultant length of the cap tube will give you the same flow characteristics as the original recommended cap tube
EXAMPLE: Locate 0.040 in left hand column and reading across gives the following conversion factor:
No. TC-36 cap tube (0.036 ID) -0.62 and No. TC-42 cap tube (0.042 ID) -1.25. Multiply the recommended cap tube length of 9’ by the conversion factor gives the following results: 5.5’ - 0.036 ID and 11.25 - 0.042 ID. Either of these two cap tubes will give the same results as the original cap tube of 9’ -0.40 ID.
Every precaution should be taken to prevent chips, dirt, flux, moisture, etc., from entering the system when changing the cap tube. Most cap tube has very small holes that do not require much debris to plug flow.
The size of the cap tube is critical to its application. While some variation from the ideal can be tolerated, it is important to understand those factors which the service engineer can control. Unlike orifices such as expansion valve seats, capillary tubing depends on its length as well as its diameter to determine the total restriction. A change in diameter on a percentage basis can change the flow more than an equal change in length. For example, changing the diameter by 0.005" as between 0.026" ID and 0.031" ID can double the flow.
The length of the cap tube is the one factor over which the service engineer has the easiest and most immediate control. The best known method of changing the restriction of a cap tube is to change its length. Cut off a piece and its restriction is reduced. Substitute a longer tube and increase the restriction. However, there are factors that are not generally understood that limit the amount of lengthening or shortening.
As a general rule, keep the cap tube no shorter than 5 feet and no longer than 16 feet to eliminate many problems. Only plug drawn capillary tubing should be used in refrigeration and air conditioning applications. JB capillary tubing is drawn to a plus or minus 0.001" on the ID, the finest attainable. Therefore, we recommend using JB cap tubing and the application charts included in the packaging.
The “Capillary Tubing Length Conversion Chart” was developed to enable users of capillary tubing to use standard tubing sizes which are widely available. While many OEMs recommend specific lengths and diameters of cap tube for their units, these tube sizes are not always readily available and may have to be special ordered.
This conversion chart enables the user to translate the recommended length into that of a tube diameter that can be quickly obtained. In using the chart, it is recommended that conversions be made using factors within the shaded area. In addition, it is highly recommended that the minimum length of capillary tubing used is five feet.
JB INDUSTRIES •
PRODUCT CATALOG 50 • 800.323.0811 • sales@jbind.com
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