In the process of cementing a casing string   of an oil or gas well, it may be desirable ornecessary to pump the cement in two stages.  

In order to do this, a mechanical or hydraulic stage collar is necessary to allow   access to the casing annulus at some point in the middle section of the casing string.

The Davis type 778-MC stage Collar allows   access to the annulus by dropping or pumping down an opening device. This device seats in   the opening sleeve and with application of pressure,

the sleeve shifts downward  exposing the ports to allow cement circulation.

Cement can then be displaced out the ports   with a closing plug, which will land on a seat in the closing sleeve. With application   of pressure, this sleeve shifts downward, sealing off the cementing ports.

The tool now   has pressure integrity.

PYZS manufacturing similar type of stage tools which also having good performance. Contact us for the details.