::: JVS ENGINEERS :::

The model NS choke body is available in 3 configurations; Positive (fixed bean), Adjustable needle and seat trim and Control choke utilizing an External Sleeve cage type trim.

	The NS Positive choke has replaceable flow control elements (flow beans), these beans are available in different sizes to give different flow rates and pressure drops.
	The NS Adjustable Needle and Seat choke uses a needle moving into or out of a seat to adjust the area open to flow and thereby controls pressure drop in the valve and flow rate.
	The NS body can be fitted with the In-Line Valve 4x4 External Sleeve type control choke trim. The 4 x 4 ES trim provides a modified equal percent flow characteristic for fine flow control, an ANSI class V shut off and a flow pattern which prevents high velocity flow being directed at the outlet thereby preventing erosion and providing longer life to both trim and body.

Adjustable chokes are fitted with a Handwheel which when rotated will move the flow control element and thereby adjust flow.

The indicator mounted under the Handwheel provides an indication of the equivalent ‘Bean Size’ of the trim (Bean size is the diameter – in /64” of the total trim area open to flow).

Chokes are by definition devices to restrict and regulate the flow of well fluids and are not intended as shut off valves.

It is not necessary for adjustable chokes to provide a positive fluid tight shut off.
In chokes with hardened trim (Tungsten Carbide, Ceramic etc.) it is important that the needle is NOT forced into the seat (doing so may damage the trim).

In order to minimize the erosive effects of the well fluids, the choke should be installed such that the side entry is the inlet and the flow is away from the blanking plug or bonnet.

For the best performance of the choke, it should be sized according to its application, chokes that are too large give poor control and higher wear, chokes which are too small do not provide sufficient flow capacity and have high pressure drop.