A manifold valve is an essential component of pressure and differential pressure transducers. The main function of a manifold valve is to block or isolate the fluid flow to isolate process media from pressure instrumentation. The inclusion of a valve manifold in a tool helps it to be replaced or calibrated without requiring a shutdown. In this article, we will learn about different types of manifold valves.

What is a Manifold Valve?
A valve manifold is a hydraulic system component that consists of one or more block or isolation valves. Common valves that form a valve manifold are ball, needle, bleed, and vent valves. A block and bleed system in the form of a manifold valve keeps the upstream fluid from coming into touch with the downstream components by separating the fluid flow in the system.
Types of Manifold Valves
Depending on the design configuration and the number of valves, manifold valves are classified as follows:
2-way manifold valve 
2-valve manifold is designed in a single block with a combination of an isolation valve and calibration/vent (bleed) valve. They have a male or female screwed inlet and outlet ports. The block valve is designated with a blue handle, whereas the bleed valve is designated with a red handle.
They are usually produced in 316 stainless steel with standard PTFE valve packing. 2-way valves are available as in-line type, L-shaped, or Y-shaped configurations.
3-Way Manifold Valve
3-way valve manifold consists of two block valves and one equalizing valve. Differential pressure transmitters are typical examples that use 3-way manifold valves. The block valves are identified with blue handles whereas the equalization valve is usually provided with a green handle. During normal operation, the block valves are open and the equalizing valve is closed.
The block valves in a 3-way manifold valve provide instrument isolation. The equalizing valve is positioned between the high and low process connections of the pressure instrument and it provides equal pressures on both sides.
The 3-valve manifold is rarely utilized in the oil and gas industry due to the lack of a test connection. Some 3-valve manifolds are provided with a blocked test connection.
5-Way Manifold Valve
5-valve manifold has two block valves, one equalizing valve, and two vent or test valves. The block valves on the high and low-pressure sides are designated with blue handles, the equalization valve in a green handle and the bleed valves are designated with red handles.

During normal operation, the block valves remain open but the bleed and equalizing valves are kept closed. A typical example of the use of a 5-way manifold valve is a differential pressure transmitter. To test the transmitter’s zero, the block valve is closed and the equalizing valve is opened. To calibrate the transmitter for 3 or 5-point calibration, the test valve is connected to a pressure generator once the pressure has been equalized.