Fitting Material Specifications
Commonly fabricated materials and specifications for industrial fittings are:

Stainless Steel - ASTM A-403 et ASME SA-403, 304, 304L, 304H, 304N, 304LN, 316, 316L, 316H, 316N, 316LN, 309, 310, 317, 317L, 321, 321H, 347 et 347H UNS 31254 (254SMo)

Nickel and Nickel Alloys - ASTM B-366 & ASME SB-366, Nickel 200 & 201 (WPN & WPNL), Monel 400 (WPNC), Inconel 600 (WPNCI), Incoloy 800 (WPNIC), Incoloy 825 (WPNICMC), Alloy 20 (WP 20 CB), Hastelloy, C-276, C-4, C-22

Chrome-molybdenum - ASTM A-234 & ASME SA-234,WP-5, WP-11, WP-22, WP-9, WP-91

Aluminium - ASTM B-361, 66061, 5083, 5086

Titanium - ASTM B-363 & ASME SB-363, WPT2, WPT7, WPT12

Other Materials:

Size Specifications
Size is one of the single most crucial criteria that determine the usage of an industrial fiitting. Here, Inside Diameter and Outside Diameter are the considerations.

Inside Diameter - In this, the ftting size is specified to match inside diameter of connecting line.
Outside Diameter - Here the fitting size is specified to match outside diameter of connecting line.

Apart from the above classification, sizes are also described as

Cleaning of Industrial Fittings
Contamination is the leading cause of problems in most of the fitting systems. This demands for careful installation and regular maintenance to prevent any blockages or system breakdown. Depending on the type of the industrial fitting, the cleaning methods differ.

For instance, one of the tips for cleaning hose / tube assembly is that the hose and tube assemblies should be blown out with filtered shop air or flushed and blown out with a solvent which is chemically compatible with the hose material. The ends of the hose and tube assembly should be capped and/or plugged until the assembly is installed.

Temperature and Pressure Ratings
These are the two important determinants for the safe and effective working of any industrial fitting. The range of temprature and presuure is vas and epends on the final application, the material being used etc. There are various standards that are laid down regarding the temprature and pressure parameters.

Some of them are :
STP - Standard Temperature and Pressure is commonly used to define standard conditions for temperature and pressure which is important for the measurements and documentation of chemical and physical processes:
STP is defined as air at 0oC (273.15 K, 32oF) and 1 atm (101.325 kN/m2, 101.325 kPa, 14.7 psia, 0 psig, 29.92 in Hg, 760 torr, 33.95 Ft.H2O, 407.2 In.W.G, 2116.8 Lbs./Sq.Ft.).

NTP - Normal Temperature and Pressure is defined as air at 20oC (293.15 K, 68oF) and 1 atm ( 101.325 kN/m2, 101.325 kPa, 14.7 psia, 0 psig, 29.92 in Hg, 760 torr). Density 1.204 kg/m3 (0.075 pounds per cubic foot).

SATP - Standard Ambient Temperature and Pressure is a reference with temperature of 25 degC (298.15 K) and pressure of 101 kPa.

ISA - International Standard Atmosphere is used as a reference to aircraft performance.
Here, defined to 101.325 kPa, 15 degC and 0% humidity.

A hose's published working pressure is the maximum pressure the hose should see while in service. This includes any spikes that may occur during operation, a hose's published burst pressure is the value at which a brand new piece of hose will fail at during a one time pressure test.