25.03A and 25.03C
When you manufacture a rubber lined pipe and create your own groove there is basically 2 types of grooves specification you can choose. Victaulic Spec 25.03 which has two sub categories.
25.03A The A stands for cut groove for abrasion only. If you refer to the diagram above you will see that the Victaulic coupling system has gaps when assembled and they vary based on diameter and coupling styles. A list of the gap sizes are listed below. The gaps are there to accommodate a certain amount of pipe line flex approx 1 deg depending on size. The more important fact is in a slurry application the gap exist and will fill with the slurry. In a slurry application with no corrosive material this is not a problem and will pack with fines. But is corrosive application such as Phosphates or Acid the steel in the gasket area is exposed and will deteriorate before the liner will. 25.03A is good for abrasion service but not corrosive service.
|COMMON VICTAULIC END TO END COUPLING GAPS|
|PIPE SIZE (NPS)||CLAMP STYLE||END TO END GAP inches (mm)|
|2 ½ – 3||Style 07, Zero-Flex Rigid Coupling||0.067 (1.7)|
|4 – 6||Style 07, Zero-Flex Rigid Coupling||0.161 (4.1)|
|8||Style 07, Zero-Flex Rigid Coupling||0.189 (4.8)|
|10 – 12||Style 07, Zero-Flex Rigid Coupling||0.130 (3.3)|
|2 ½ – 3 ½||Style 77, Standard Flexible Coupling||0.063 (1.6)|
|4 – 12||Style 77, Standard Flexible Coupling||0.189 (4.8)|
|14 – 24||Style 77, Standard Flexible Coupling||0.189 (4.8)|
|26 – 44||Style 44, Ring Coupling with “D” Type Adapter||0.500 (12.7)|
25.03C The C in this specification means cut groove for corrosion application. In other words if you have any transport material which has corrosive materials, this is the spec you require as rubber is returned into the groove or below the gaskert this can be seen in the diagram at the top. The exposed steel will be covered by a layer of rubber eliminating the opportunity for corrosion in this area. Only use for corrosive service as the additional cut in the steel ads costs to the pipe.
More Advanced 25.03?
25.03 is a good spec but was designed to accommodate a problem in the Vic system when used with rubber lining. When rubber lining a cast Vitc fitting, the recommendation is that you utilizes the specification VS-222 which we will call for this example 25.01B. “B” standing for Bad. This specification states that you add 1/8″ of rubber to the face of the fitting. That this does impede on the gap required in a Vic coupling system. So 25.03 is designed to add more space to the coupling groove, in the instance that a rubber lined cast fitting mates up to a pipe. The additional space is then maintained and the original gap is perfect. The challenge comes when you mate a cast fitting to a cast fitting 25.01B – 25.01B. This adds 1/8″ of rubber per gasket face and on a fitting that is 3″ in Dia. with a gap of 1/16″ and you put 1/4″ of rubber, it doesn’t work.
If this sounds complicated, we’ll, it is. Below is a diagram explaining what happens to the gap in different situations. There is a spec below which is called 25.01A which we will discuss after this diagram but it maintains the designed gap regardless of cast fittings or pipe assembly.
The correct groove to use is 25.01A and 25.01C. These are the dimensions of 25.01 but with 1/8″removed on the face to be replaced with rubber. So the final finished dimension will be the same as 25.01 in all situations. The down side to this is that all cast fittings needed to be rubber lined will be required to be machined back 1/8″ for the addition of the rubber face gasket. No matter what you do this is the correct way to maintain the designed gap in cast fittings as well as the pipe.