ASTM A320-L7 is a specification covering bolts, studs, and screws intended for low temperature service. Portland Bolt regularly supplies both plain finish and hot-dip galvanized A320-L7 fasteners to numerous customers in Canada and Alaska. Recently in our Portland Bolt Live Chat, an engineer asked this question as he needed to know what grade of nuts and washers to specify on his project plans.
- Nuts: The compatible nuts for use with A320-L7 are either ASTM A194 Grade 4 or A194 Grade 7 heavy hex nuts. Grade 7 nuts are more readily available and are most frequently used with A320-L7 bolts, but Grade 4 nuts may be used in cases where Grade 7 is not readily available. Since the assumption is that in most cases the A320-L7 bolts will be used in a cold temperature environment, Supplement 3 of the ASTM A194 specification should be specified which requires the nuts to undergo Charpy impact testing which confirms their ability to perform in low temperatures. An “L” is added to the grade marking of these nuts.
- Washers: The compatible washer for use with A320-L7 bolts is ASTM F436. Made from heat treated, hardened steel, F436 washers are capable of withstanding a broad range of environments including low temperature service.
Note: A194 Grade 4 and Grade 7 nuts are typically only available in plain finish. Galvanized Grade 4 or Grade 7 nuts will normally have to be specially made on a per order basis, as plain nuts cannot be used with galvanized bolts.
Are A194 Gr.7 nuts ‘interchangeable’ with A194 2H type? I see in ASME B31.3 Table A-2 that both Gr.7 and 2H have a min. temperature of -55degF.
Asking the question in a different way, is there a reason why you wouldn’t (or shouldn’t) use A194 Gr. 2H nuts with A320 Gr. L7 studs?
@Kevin- ASTM itself does not require any one specific grade of A194 nut with any specific grade of A193 or A320 bolt. Typically however, the A194 gr.7 nuts are used with A320 L7 in low temperatures because the A194 gr.7 nuts are able to be charpy tested, and sometimes come with said charpy test (gr.7L). A194 gr.2H nuts are not charpy tested and wouldn’t pass regardless. That isn’t to say that 2H nuts cannot be used in some colder applications if ASME allows it, but the industry has chosen to typically mate A320L7 bolts with A194 gr.7 nuts.
Good day,
I’m George Landry, I would like to order some Bolts, below is the specification of my inquiry:
Bolts Details:
Type: Cap Screw
Diameter: 5/8″
Lengh:2″
Head style: Hex
Drive Type:15/16 wrench
Thread type 11 threads per inch
Thread Size: Coarse
Hardness:8
Material: steel
Finish: Yellow Zinc
Quantity: 7000 pieces.
Please email me the sub_total price for the 7000 Bolts plus tax only. If you do not have this type of Bolt available please let me know what you deal in. What do you accept as payment.
Thanks,
George.
@George- One of our salespeople will contact you shortly.