If you're asking how long a limb can survive without blood flow, the only accurate answer is that it varies from person to person.
I remember learning about tourniquets on a first aid course, and they advised us not to use a tourniquet unless absolutely necessary, and that it should be removed every half hour.
However, I found this interesting contribution on Reddit which suggests slightly longer is possible without causing significant tissue damage:
“there is no simple answer….The ischaemia (ie lack of blood/oxygen) tolerance of tissues varies from patient to patient”.
"animal experiments suggest that 2-3 hours or more of ischemia is necessary before significant changes in tissue start to occur. A human study found small histological changes to muscle started to occur after about 30-45 minutes, but it wasn’t until the 2 hour mark that the changes were significant. Even then none of the patients suffered irreversible muscle damage. I think current clinical practice is to limit ischaemia times on limbs to 45 mins, probably based on the above study."
