What is a slip on flange?
Slip On flange or SO flange is designed to slip over the outside of pipe, long-tangent elbow, reducer, and swage. The flange has poor resistance to shock and vibration. It is easier to align than a weld neck flange. This flange is ideal for low pressure applications since the strength when under internal pressure is about one third that of a weld neck flange. This flange has a raised face. Slip On flanges or SO flanges are commonly lower in price than weld-neck flanges, and to this effect are a popular choice for our customers. However, customers should bear in mind that this initial cost saving may be diminished by the additional cost of the two fillet welds required for proper installation. Moreover, weld-neck flanges have a higher life expentancy than slip-on flanges under duress.
The slip on flange is positioned so the inserted end of the pipe or pipefitting is set short of the flange face by the thickness of the pipe wall plus 1/8 of an inch, which thus allows for a fillet weld inside the SO flange equal without doing any damage to the flange face. The back or outside of the slip-on flange or SO flange is also welded with a fillet weld.
It is welded both inside and out to provide suffcient strength and prevent leakage.
Slip-On Pipe Flanges. As made obvious by their name, these pipe flanges slip over the pipe. They’re manufactured with an inside diameter that is slightly bigger than the pipe’s outside diameter. These attachments are connected to the pipe via fillet weld at the top and bottom of the flange.
However, customers should bear in mind that this initial cost saving may be diminished by the additional cost of the two fillet welds required for proper installation. Moreover, weld-neck flanges have a higher life expentancy than slip-on flanges under duress.
Slip-on flanges are all bored slightly larger than the O.D. of the pipe. They are preferred over welding neck flanges bu many users due to their lower intial cost, but final intallation cost is probably not much less than that of the welding neck flange because of the additional welding involved.
Weldneck and Slip-On Orifice Runs
Slip-on flange is slipped over the pipe and then fillet welded. Slip-on flanges are easy to use in fabricated applications.
- ASME/ANSI B16.5 Class 150 SO
- ASME/ANSI B16.5 Class 300 SO
- ASME/ANSI B16.5 Class 600 SO
- ASME/ANSI B16.5 Class 900 SO
- BS 3293 Class 150 SO
- BS 3293 Class 300 SO
- BS 3293 Class 600 SO
- DIN 86029 PN 10
1. Slip On flange 2. Filled weld outside 3. Filled weld inside 4. Pipe
- Size: 1/2” to 60”, DN 12mm to DN 1500mm .
- Pressure class: Class 150 to Class 2,500, PN 2.5 to PN 250
- Facing: RF / RTJ
- Carbon steel: ASTM A105,ASTM A105N,GB 20,C22.8.
- Alloy steel: ASTM/ASME A182 F1-F12-F11-F22- F5-F9- F91
- Stainless steel: ASTM/ASME A182 F304-304L-304H-304LN-304N
- ASTM/ASME A182 F316-316L-316H-316LN-316N-316Ti
- ASTM/ASME A182 F321-321H, F347-347H
- Low temperature steel: ASTM/ASME A350 LF2.
- High performance steel: ASTM/ASME A694 F42 , F52, F56, F60, F65, F70
- ASME/ANSI B16.5,
- MSS SP 44
- CSA Z245.12
- BS1560,BS 4504,BS 10.
- AFNOR NF E29-200-1
- JIS B2220
- UNI 2276. UNI 2277.UNI 2278 .UNI 6089 .UNI 6090
Factors to consider before buying slip-on flanges are as follows:
Why slip on flanges are preferred to welding neck flanges?
For many users, slip on flanges continue to be preferred to welding neck flanges because of the following reasons:
- On account of their initially lower cost.
- The reduced accuracy needed in cutting the pipe to length.
- The greater ease of alignment of the assembly.
- The calculated strength of slip-on flanges under internal pressure is approximately two-thirds that of welding neck flanges.
Take the measurements of:
- OD: Outside Diameter
- ID: Inside Diameter
- BC: Bolt Circle
- HD: Hole diameter
Some important features are as follows:
- One size fits all pipe schedules.
- Fabricators can more easily cut pipe to length for slip-on flanges.
- The smaller thickness of this flange allows for easier alignment of bolting holes.
- They are generally not preferred for high pressure temperature environments.
Slip-on flanges have certain technical requirements and parameters in production and use, and are produced and processed according to the following methods: The slip-on flange shall be cut into strips along the rolling direction of the steel, and be brazed and welded into a ring shape, and the surface of the steel shall form a cylindrical surface. When producing slip-on flanges, steel plates shall not be directly machined into neck flanges, and they shall be fabricated and processed by certain processes. Steel plates for slip-on flanges shall be ultrasonically inspected without delamination defects to ensure good quality and prevent performance problems that may occur during use. Production and inspection shall be carried out in accordance with certain quality requirements to make sure that there are no quality problems in the steel plates.
Compared with other kinds of flanges, a slip-on flange saves space during use, has lower weight, and most importantly, it has very good sealing performance which ensures no leakage on the head part. The reason why the size of the slip-on flange is reduced is that the diameter of the seal is decreased, which will lessen the cross section of the sealing surface.
In addition, the flange gasket has been replaced by a sealed ring to ensure that the sealing faces are matching, so that only a small pressure is required to press the cover tightly. Snd the size of the bolt is cut down as the required pressure is reduced, and the number of bolts required is correspondingly reduced, a new product with a relatively small volume and light weight is finally designed. The high-pressure flange is mainly used in the installation of pipelines, whose connection is an important connection method for connecting pipes in pipeline construction. High-pressure flange connection is to fix two pipes or equipment on a flange respectively, then add a flange gasket between the two flanges, and fasten them together with bolts.
Some pipe fittings and equipment have their own flange gaskets attached, which can be also considered as a kind of flange connection. The performance of high-pressure flange products has wear resistance – The content of Al2O3 in the ceramic layer of ceramic composite steel pipe is more than 95%, Microhardness HV 1000-1500, so this kind of steel pipe has extremely high wear resistance, which is about ten times higher than that of medium carbon steel after being quenched, and better than tungsten-cobalt cemented carbide.
Applications of a slip on flange:
A slip on flange which is attached by two fillet welds, inside as well as outside the flange. The calculated strength from a Slip On flange under internal pressure is of the order of two-thirds that of Welding Neck flanges, and their life under fatigue is about one-third that of the latter. Normally, these flanges are of forged construction and are provided with hub. Sometimes, these flanges are fabricated from plates and are not provided with the hub.The disadvantage of the flange is that a combination of flange and elbow or flange and tee is not possible because named fittings have not a straight end that complete slid in the Slip On flange.
Advantages of slip on flanges:
- Low cost installation
- Less time needed to spent on ensuring the accuracy of the cut pipe
- They are somewhat easier to align
- The slip-on flanges have low hub because the pipe slips into the flange before welding
- The flange is welded both inside and outside to provide sufficient strength
- They prevent leakage
When to use slip on flanges?
Slip-On Flanges are preferred by some contractors, over the Weld-neck, because of the lower initial cost. However, this may be offset by the added cost of the two fillet welds required for proper installation. The strength of the slip-on flange is ample for it’s rating, but its life under fatigue conditions is considered to be only one-third that of the weld-neck flange.
The slip-on flange may be attached to the end of a piece of pipe or to one or more ends of a pipe fitting. The slip-on flange is positioned so the inserted end of the pipe or fitting is set back or short of the flange face by the thickness of the pipe wall plus 1/8 of an inch. This allows for a fillet weld inside the SO flange equal to the thickness of the pipe wall without doing any damage to the flange face. The back or outside of the flange is also welded with a fillet weld.
A variation of the Slip-On flange also exists. This is the Slip-On Reducing Flange. This is simply a larger (say a 14″) Slip-On flange blank that, instead of the Center (pipe) hole being cut out (or drilled out) for 14″ pipe it is cut out for a 6″ (or some other size) pipe. The SO Reducing flange is basically used for reducing the line size where space limitations will not allow the length of a weld neck flange and reducer combination. The use of the Slip-On Reducing Flange should only be used where the flow direction is from the smaller size into the larger size.
Source: China Slip on Flange Manufacturer – Yaang Pipe Industry (www.steeljrv.com)
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