VARIATIONS

Soft Seat Arrangement

In order to avoid seat leakage on light gas services, the main valve/seat and pilot valve/seat are provided with elastomer seat seal. The elastomer material are selected to suit the duty conditions. Another important application for this type of valve, is an explosive nature of gases e.g. Hydrogen. When the gas passes through the valve at high velocity, static charges are created leading to the possibility of spark, this can be disastrous in explosive gas atmosphere. Under these circumstances, the soft seated
valve is always recommended.

Cage Guided Trim

In order to obtain high pressure drop, normally two or more valves are installed, which is expensive and often disappointing, when the leakage of the upstream valve throws all the /\ P on the downstream valve. In such cases, a PRV with multijet caging is recommended. The three stage pressure reduction (number of stages are decided based on critical /\ P ratio) is achieved with the help of multistage perforated cage. The design offers the following advantages :

 

Flow distribution leads to the noise attenuation.
Pressure drop is distributed across different stages and not at the throttling point between main valve and seat, thus reducing the trim wear.
Low cost installation and maintenance of only one valve.
Increased overall system performance.

Reduced Capacity Trim

In cases where it is more convenient, on account of the pipe connection, to have a valve larger than is necessary to deal with the quantity of steam, we can fit smaller seats so that regulation will be satisfactory.

To avoid replacing the valve body with another of a different size when a future increase in the flow is expected in relation to that at the start of operation.

When the pressure drop across the valve is considerable, it is better to use a larger body for the advantage of rigidity.

Low Pressure Pilot :

When set pressure are in the range of 50mm WC to 2000 mm WC, the regular pilot assembly cannot provide enough of controlling thrust. In order to achieve this, Mazda offers Pressure Reducing Valve with a special low pressure top assembly. The assembly is supplied as a complete conversion unit for fitting to the regular pilot assembly. It incorporates a larger diaphragm, thus providing a greater effective area and improved sensitivity to very low outlet pressure conditions.

Auxiliary Valve

The limitation on regulator sizing is rangeability (10:1 in conventional valves). Very low rangeability is observed in case of the steam regulator, because of its limitation to operate the main valve close to its seat (because of wire drawing). There are several ways of increasing rangeability, mainly by design/selection of proper trim characteristics.

The best way to control the Cv minimum is to provide the auxiliary plug. It regulates in the range of minimum flowrate to the minimum controllable flow rate. Once the minimum flow is achieved, the main valve takes over and operates till the maximum flow is obtained.
Thus the twin plug arrangement offers multiple rangeability from 20:1 to several hundred.

 

* On Request Product Catalogue Available