Everything You Need to Know About Dished Ends

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Dished Ends International is a world-class supplier of top-quality Dished Ends, Pipe Caps and Pressure Vessel Heads. Dished Ends International uses market-leading Hot Press and Cold Press approaches to shaping steel which leads to high quality, strong and reliable end products.

We supply dished ends from 89mm to 10 metres in diameter, with material thicknesses ranging from 2mm to 300mm, used in the fabrication of pressure vessels, storage tanks, and process vessels. Materials include duplex steel, carbon steel, stainless steel, aluminium, and titanium. Surface treatments include sandblasting and pickling.

This is an informative guide to help buyers of dished ends ensure they ask the right questions before deciding what dished ends manufacturer to select.

How Do I Order a Dished End?

It is important to know the following specifications when ordering your dished ends:

  1. Quantity
  2. Material type or grade
  3. The manufacturer code
  4. Shape
  5. Inside and outside diameter
  6. For Torispherical we need to know the Inside crown radius (ICR) and inside knuckle radius (IKR)
  7. The straight flange
  8. The minimum thickness after forming
  9. If it’s a Torisperical shape the ITH (Inside tangential Height)

Industry Jargon

The common terms and industry abbreviations are as follows:

  • Internal Diameter (ID)
  • Outside Diameter (OD)
  • Inside Crown Radius (ICR) – The radius that dictates the shape and depth of the dished end
  • Inside Knuckle Radius (IKR) – the corner radius where the crown radius blends into the Straight Flange
  • Straight Flange (SF)
  • Thickness (T) – minimum thickness after forming and there is a plate thickness prior to forming. So for example if we start off with a 10mm plate, we allow 10% for thinning so we can guarantee that after forming that plate will be a minimum of 9.0mm thickness.

What is the difference between hot pressed and cold forming?  

Hot pressed dished ends are formed within the dished ends normalising range. This results in no inherent stresses built into the finished product. A cold pressed or formed dished end has stresses formed into it and, depending on the material, it may need to be stress relieved once finished. This is a form of heat treatment. These stresses occur when cold forming dished ends or pipe caps exceeds 5% fibre strain.

What are the common causes of Dished End failures?

  1. Microscopic cracks –  a common issue in cold formed dished ends where it could suffer excessive thinning in the process (cold forming).
  2. Incorrect welding procedure.
  3. Manufacturing and Design errors.

How important Is the appearance of a Dished End or Pipe Cap?

The appearance does not determine the quality of the dished ends. A hot pressed dished end usually produces a rougher finish. The more common cold pressed dish ends generally appear shinier because of its finish. Hot pressed types can be shined up with shot blasting and prime coat painting.

How would you know the quality of the Dished End by looking at it?  

When performing a visual inspection, it is important to look for the following signs to make sure that you are getting a product of superior quality:

  1. Crown radius – make sure the dished end is deep enough.  
  2. Check the corner radius or the knuckle radius, and make sure that the radius is not too small.  It would have to be at least 10 or 15%, if it’s a Torispherical or Semi Ellipsoidal.
  3. If it’s cold-formed, check to see if it has a weld seam. If it does, it should be radiographed or ultrasonically examined to check for cracks in the weld or the weld-affected zone.  
  4. Irregularities in shape
  5. Irregularities in size
  6. Making sure it adheres to code requirements

What are the consequences of buying a poor-quality Dished End?

  1. Poor quality dished ends may not fit the barrel that has been rolled for that particular job
  2. It may have minute cracks that will become obvious only after the vessel is in service.
  3. Explosion from dished end failure, which could result in injury or, worse, death.

What are the various shapes of Dished Ends?  

  1. Torispherical (Tori): The shallowest of the three main dished ends – this type has less dishing and is cheaper to produce
  2. Semi Ellipsoidal (also called Semi Elliptical or Semi): Has a bit deeper dishing, there’s more drawing time, and the blank size is bigger, resulting in a higher material cost and a higher forming cost. It can withstand a higher pressure than the Torispherical for the same diameter and thickness.
  3. Hemispherical (Hemi): Can withstand a higher pressure.  It is deeper, and the blank is bigger. This the the most efficient among the three types, but more expensive to make.

What criteria would you use to find the best supplier of Dished Ends?

One should look for a supplier with an excellent track record. Dished Ends International has extensive experience supplying top-quality dished ends to the Australian market.

What makes a great Dished End?

A great dished end is formed strictly following specific codes, and all Dished Ends International products strictly conform to these requirements. Customers are assured they get the right size and shape for their requirements. All our products are of the highest quality, and we are able to provide our customers with complete peace of mind. Testing methods include UT, RT, MT, PT and TOFD. Adhering to Applicable Standards: ASME, PED and GB and Certificates: ISO9001, ISO45001 and OHSAS18001.

This ensures that the dished end is produced and pressed or formed to the right size, with the right material.

How to choose what material to use in making your Dished End.  

There are different types of products that are used to create dished ends. Materials include duplex steel, carbon steel, stainless steel, aluminium and titanium. Surface treatments include sandblasting and pickling.

Dished Ends International For Your Dished Ends Needs

Please contact us for inquiries or quotes to explore how our dished end services can meet your specific requirements and exceed your expectations.