Q: Are these installed with the hatch open or closed?, as the hold open mechanism is bent and not in the full open position.
A: Generally you will perform an installation of replacement lifting mechanisms when the unit is about 35% of the way open.
Q: Do you measure the replacements with the hatch open or closed?
A: The Dur-Red 15 PI Pressure Intensifier for Normal Stair Hatch (NSH) - Galvanized Steel 36" x 72" is a 15” lifting mechanism in the 15-inch literally refers to the length of one of the two telescoping tubes - if you have a tube that measures 15” this would be your replacement.
Q: When one of the Dur-Red 15 PI are purchased, are two telescoping tubes provided? What does the 36" x 72" G.I. bullet note indicate? Might these possibly work for my 4'x8' unit if the tube measures 15"?
A: these pressure intensifiers can be purchased as single units which each single unit is comprised of two telescoping tubes, or they can be purchased in pairs word simply the same as the single unit * 2.
Regarding your note of the 36" x 72", please clarify the question that you're asking is I do not understand.
I would encourage you to not conclude that these would work on a larger unit and the only way to know safely what lifting mechanisms were pressure intensifiers you require would be the four of us photographs to our sales department as seen here:
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of your unit along with the width and the depth of the unit itself and then tell us the composition of the lid meaning is it steel or aluminum.
Without knowing this information we would be not positioned to give you a definitive direction in terms of what units to use