Replacing expansion tank

I have recently discovered a small crack in the expansion tank...... I have bought a new one but is it possible to change it without having to bleed the system if I clamp the pipes soon as I take them off? 
Thanks 

Well that is exactly what I am going to do tomorrow when I remove mine to clean it out and fit a low water coolant alarm.
The expansion relief hose is the highest point and the bottom hose is higher than the engine block and will vent in to the tank.
You will be fine.

Probably it would depend on how successfully you clamp them off, preferably without damaging them. But sooner or later you are going to have to bleed the system anyway so why not learn to do it now before you start this job. In case you accidently get some air in, it's quite easy to do, look up the how tos  here on the forum.

So it is pretty much safe to remove the pipes from tank and clamp them one by one so to speak as long as I clamp them quickly?

If you draw water down, possibly using a syringe, so the coolant drops below the tank level, it’s a one out, one in. It’s probably a good idea to pop a clamp on the return JIC.
M

I've seen the how to but I don't have ramp or axel stands to get to the bleed point on the underside that's why was asking if could do it without bleeding if clamped well 

Thank you, much appreciated 

Since you are going to this trouble, you are of course fitting a low coolant alarm if not already fitted, and if fitted are fitting a tank suitable with the low coolant alarm.
NO iif's or buts.....or sooking about cost! A low coolant alarm is essential for our cars, It is utter madness to try and run our cars without on fitted, the cost is nothing compared the the cost of not having one! you have been told........stay told!
There are several available, one of our members offers one that is highly regarded, I myself have run the excellent Browns & Gammons Low coolant alarm for over 10 yrs without any trouble.
Failure to head this advice WILL result in a dismissive I told you so! Do not set yourself up to be a victim!

Why do you need to get under the car to bleed the system?
The 6mm bleed on the water rail is accessible after removing the engine bay cover.
The rad and heater bleed points are from the front bonnet.
If you are not disturbing the hose on the engine other than at the tank why do you need to get underneath?

Are you confusing the bleed points with the drain plug?  The bleed points are all accessible from above, as I said check the procedure in the how tos, or the workshop manual also downloadable from this site in the libary section