Membrane and Desalination Technologies - TCE Moodle Website

374 N.K. Shammas and L.K. Wang
Fig. 8.5. Double block and bleed valving arrangement.
arrangement is utilized to prevent the cleaning chemicals from contaminating the filtrate
manifold as they are recirculated, which gives rise to the term “double” block and bleed. If the
cleaning process starts automatically, valves V-1A and V-2A (i.e., the block and bleed
valves) must be actuated automatically.
As an alternative to the double block and bleed valving arrangement, a removable spool
(i.e., a short section of pipe) can be placed between valves V-1A and V-3A in lieu of
utilizing valve V-2A. The spool is then removed during the chemical cleaning. A removal