Materials

Selection of materials for a clamp is typically determined by matching the material used for the existing hardware being repaired. It may also be specified by the end user personnel to meet their particular requirements. In cases where several different materials might work for a given service there are other factors to consider such as cost, availability, difficulty of machining, welding requirements, and temperature dependent strength.

Page Contents

Carbon Steel

Chrome

Stainless Steel

Aluminum

PVC

Others

Carbon Steel

Carbon steel is used for the majority of clamps. Generally, it is readily available and least expensive of the steels used. Post-weld heat treating is sometimes required based on size of the components used or end user requirements. SA 516 Grade 70N plate and SA 675 Grade 70N bar are not always readily available in certain geographic locations. In these cases, SA 285 Grade C is used in its place. It is slightly weaker which can impact the final dimensions of clamps. It is important to note that all carbon steels experience a significant reduction in strength above 650-750℉ and can’t be used above 1000℉.
To learn more, we recommend reading this article.

  • SA 516 GRADE 70N - Plate
  • SA 675 GRADE 70N - Bar
  • SA 285 GRADE C - Plate and Bar
  • SA 106 GRADE B - Pipe
  • SA 193 B7 (Bolting) and SA 194 GRADE 2H (Nuts)

    • - Standardly used for all carbon steel designs, except by end user specification.

  • SA 193 B7M (Bolting) and SA 194 GRADE 2HM (Nuts)

    • - Used for many different corrosive services, especially in Alky Units. The service most commonly requiring their use is Hydrofluoric Acid (HF Acid).

Chrome

There are many Chrome Molybdenum Steel alloys. The most commonly used for clamps is 1-1/4 Chrome 1/2 Moly alloy. This alloy is typically stocked by fabrication shops in common sizes of plates, bar, and pipe. Alternatively, 9-Chrome and 5-Chrome are sometimes used, but they are not as readily available by fabrication shops.

Chrome Moly maintains good mechanical strength up to 850-900℉ and can’t be used above 1200℉. Welded clamps made of Chrome Moly always require stress relieving. Material cost is usually between that of Carbon Steel and Stainless Steel.
To learn more, we recommend reading this article.

  • SA 387 GRADE 11 CLASS 2 - Plate and Bar
  • SA 335 GRADE P11 - Pipe
  • SA 193 B16 (Bolts) and SA 194 GRADE 4 (Nuts)

    • - Standardly used for all chrome designs, except by end user specification.

Stainless Steel

The two most common types of Stain Steel are 304 and 316. Both offer good strength at temperatures over 1000℉, and can be used up to 1500℉ for clamp design. The biggest difference has to do with corrosion resistance. 316 Stainless Steel has superior corrosion resistance to 304, but is more expensive. As opposed to Carbon Steel and Chrome Moly, It typically does not require post weld heat treatment.
To learn more, we recommend reading this article.

  • SA 240 GR 304 - Plate and Bar
  • SA 312 TP 304 - Pipe
  • SA 193 B8 CLASS 1 (Bolting) and SA 194 GRADE 8 (Nuts)

    • - Standardly used for 304 Stainless Steel clamps, except by end user specification.

  • SA 240 GR 316 - Plate and Bar
  • SA 312 TP 316 - Pipe
  • SA 193 B8M CLASS 1 (Bolts) and SA 194 GRADE 8M (Nuts)

    • - Standardly used for 316 Stainless Steel clamps, except by end user specification.

Aluminum

Aluminum is primarily used for clamps in the electrical distribution industry where internal pressures are usually 15 psi or less and the only service is transformer oil. Compared to the steels above, it is far less expensive, much lighter in weight, and much quicker to machine. In general, aluminum clamps are manually or CNC machined from plate material but may also be made using castings and occasionally via welded fabrication techniques.
To learn more, we recommend reading this article.

  • SB 209 Alclad 6061 CLASS T651 P23 - Plate and Bar
  • SB 241 A96061 CLASS T6 P23 - Pipe
  • SA 193 B7 (Bolts) and SA 194 GRADE 2H (Nuts)

    • - Standardly used for all aluminum designs, except by end user specification.
    - Note that composite materials can also be used for bolting with aluminum clamps.

PVC

Like Aluminum, PVC is used primarily in the electrical distribution industry, especially when conduction and arcing is a concern. It is very inexpensive and easy to machine. It can be glued, as opposed to welding on metal clamps. It is only suitable for very low pressures. Bolting material is typically 193 B7 or composite. To learn more, we recommend reading this article.

Others

There are several other materials used, but they are special cases. In general, these materials are much harder to find and work with than the materials listed above. They are only used if specifically requested by end user personnel. These include Hastelloy, Monel, Inconel, and the 5 and 9 Chromes mentioned previously.
To learn more, we recommend reading these articles:
Monel - Alloy 400
Hastelloy
5 Chrome
9 Chrome
Inconel