Compressor casing in Spheroidal graphite cast iron and impact testing

[hirschaplin]

Hello,

Working on the design of a compressor casing in material grade EN-GJS-400-18-LT as per EN 1563:2018. Ultimately I want the compressor casing to fulfill PED, ASME code and API 619 requirements.

The material selection origins from API 619 that suggest that this material may be selected for the compressor casing, see below highlight.

Casing

Material	Specification			Oil-Flooded, Dry-Screw	Form		°C Min.		°C Max.		°F Min.		°F Max.
Gray iron	ASTM A278 class 40		OF			Cast		– 29		260		– 20		500	
Gray iron	EN 1561 GJL-250			OF & DS			Cast		– 10		250		14		482	
Gray iron	JIS G 5501 FC250		OF			Cast		– 29		232		– 20		450	
Gray iron	JIS G 5501 FC300		OF & DS			Cast		– 29		232		– 20		450	
Gray iron	JIS G 5501 FC350		OF			Cast		– 29		232		– 20		450	
Ductile iron	ASTM A395, grade 60		OF			Cast		[highlight #FCE94F]– 29[/highlight]		260		– 20		500	
Ductile iron	EN 1563 GGG 40.3		DS			Cast		– 20		300		– 4		572	
Ductile iron	EN 1563 GJS-400-15		OF & DS			Cast		– 10		250		14		482	
[highlight #FCE94F]Ductile iron	EN 1563 GJS-400-18-LT		OF & DS			Cast		– 20		300		– 4		572[/highlight]	
Steel		ASTM A216 grade WCB		DS & DS			Cast		– 29		400		– 20		750	
Steel		EN 10213 (all parts) GP240 GH	OF & DS			Cast		– 10		300		14		572	
Steel		EN 10213 (all parts) GS-21Mn5	OF			Cast		– 46		343		– 51		649	
Steel		JIS G 5152 SCPL1		OF			Cast		– 45		350		– 49		662	
Steel		JIS G 5152 SCPL11		OF & DS			Cast		– 60		350		– 76		662	
Steel		JIS G 5152 SCPL21		OF			Cast		– 75		200		– 103		392	
Steel		JIS G 5152 SCPL31		OF			Cast		– 100		200		– 148		392	
Steel		JIS G 5202 SCW480		OF & DS			Cast		– 29		399		– 20		750	
Steel		JIS G 5121 SCS13		DS			Cast		– 196		350		– 321		662	
SS		ASTM A351 CF3, CF3M, CF8, CF8M	DS			Cast		– 196		343		– 320		650	
SS		ASTM A351 grade CF3, CF3M	DS			Cast		– 195		345		– 319		653	
SS		ASTM A743 grade CA6 - NM	DS			Cast		– 195		345		– 319		653	
SS		EN 10213 GX3 CrNiMo13-4		DS			Cast		– 105		300		– 157		572	
SS		EN 10213 GX5CrNiMoNb19-11- 2	DS			Cast		– 200		300		– 328		572	
SS		JIS G 5121 SCS14		DS			Cast		– 196		350		– 321		662	
SS		JIS G 5121 SCS5/13Cr-4Ni	DS			Cast		– 196		350		– 321		662

The minimum recommended temperature is -20 deg C which is inline with the impact values specified in EN 1563:

My questions are the following:
[ol 1]
[li]EN 1563:2018 is suppose to be harmonized with PED 2014/68/EU with conformity since 30/09/2019. And PED is stating the following:

7.5. Material characteristics
Unless other values are required in accordance with other criteria that shall be taken into account, a steel is considered as sufficiently ductile to satisfy point 4.1(a) if, in a tensile test carried out by a standard procedure, its elongation after rupture is no less than 14 % and its bending rupture energy measured on an ISO V test-piece is no less than 27 J, at a temperature not greater than 20 °C but not higher than the lowest scheduled operating temperature.

How is this working with the above highlighted minimum impact energy values that are at 10-12 depending on the thickness and therefore less than the required 27 J to my understanding? I know that some pressure codes provide a method to re-calculate impact values based on material thickness, is that relevant here or can someone please explain why values below 27 J are deemed acceptable (through its harmonization) to satisfy PED requirements?

[/li]

[li]In addition to PED and ASME code requirements, there are some specific API 619 requirements for ductile iron castings that need to be fulfilled:

A minimum of one set (three samples) of Charpy V-notch impact specimens at one-third the thickness
of the test block shall be made from the material adjacent to the tensile specimen on each keel or Y-block. All
three specimens shall have an impact value not less than 11 J (8,1 ft-lbf) and the mean of the three specimens
shall not be less than 14 J (10 ft-lbf) at room temperature.

These requirements seems more stringent than the minimum requirements specified in EN 1563 showed above. Is it realistic to think that the material would pass on these API 619 requirements?

[/li]

[li]I would like to use design temperature -29 deg C for the compressor casing. How is that working with the above limitations of -20 deg C? What if the impact test is performed at -29 or -30 deg C instead of -20 deg C? Which are the values to pass? Will the specified material pass at a lower temperature than -20 deg C?

[/li]
[li]My next thinking here was to double certify the material, meaning that the foundry issue a material certificate that states compliance to:
- EN 1563:2018 grade EN-GJS-400-18-LT
- ASTM A395 Grade 60-40-18

Since ASTM A395 Grade 60-40-18 is allowed for -29 deg C as per above yellow highlight in API 619 code.

Then I realize that ASME code and PED has different impact requirements where I understand PED to be the more stringent of the two with higher impact values. Hence perhaps A395 Grade 60-40-18 would pass ASME code and not PED?

Is it possible to dual certify the material to these two different grades and standards as well as fulfilling impact requirements of API 619, PED and ASME code?

[/li]

[li]Which parameters must be fulfilled to claim compliance with NACE MR0103 and NACE MR0175?[/li]
[/ol]

 

[Dhurjati Sen]

The PED talks about steel and you are inclined to substitute caste iron with it.
This is not possible.

DHURJATI SEN
Kolkata, India

 

[EdStainless]

What did your foundry say?
DS is correct, Your talk about 7.5 from EN1563 doesn't apply.
You would have to combine Table 2 and the info from API 619 to come up with the most restrictive limits.
To me that look like the API spec.

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P.E. Metallurgy, consulting work welcomed