What grade of nuts and washers are compatible with ASTM A320 Grade L7 bolts and rods?
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.