INTRODUCTION:
The MDM-3 is a 3-way shut-off valve suitable for the SH series safety valves. In accordance with ANSI/ASHRAE 15-2014 Safety Code for Mechanical Refrigeration, pressure vessels having 10 cubic feet or more of internal gross volume, shall be fitted with dual pressure-relief valves. This is typically accomplished using a pair of pressure-relief valves interconnected via a three-way dual shut-off valve. Even on smaller vessels this arrangement is often preferred because one valve remains operational, while the other is being replaced; thereby eliminating the need to remove refrigerant from the vessel. Manik Engineers can provide any or all the necessary components, in addition to the actual relief valves, as follows:
THREE-WAY DUAL SHUT-OFF VALVES
These rugged, forged steel bodied valves facilitate the parallel installation of pressure-relief valves. Because three-way valves will not isolate both pressure-relief valves simultaneously, they are considered the only acceptable type of shut-off valve for use with refrigerant relief piping. Their durable metal-to-metal seating and patented non-leak packing plus o-ring stem seal design combine for long, trouble-free service. Inlet and outlet connections are threaded female NPT all the same size. Shown below is a three-way dual shut-off valve in the stem out position (back-seated). The valve stem should be positioned so that only one pressure-relief valve is activated. While the valve can be either front-seated (front port is closed) or back-seated (back port is closed), the back-seated position (shown) is recommended for normal use because it takes pressure off the packing and reduces the possibility of packing leaks.
NOTE:- Dual Manifold MDM Series are upgraded design version of old Dual Manifold DVS series. The dimensions and fitting connections for both valves are same. The MDM Series can be used as drop in replacement for DVS series. The pressure rating of MDM Series is 55 bar where as old DVS series was 28 bar.
