Needle Valve in Steam Line

A ball valve gives a positive indication and is quicker to operate.

Ball valve is the most common.

It can be done quickly and be easily locked out.

I like Energygod's answer, (but maybe I'm swayed by his looks). If you had a manifold, you'd be using needle valves, but the manifold is not really purposed for line isolation of the instrument. Normal line isolation would be ball or gate valve.

At your stated operating press and temp you need to to choose well ! I haven't had to do so for some time now, but I remember 'Whitey' being a brand name of choice at one time, with which I had good service and no complaints/failures in the 1/2" and 1/4" sizes.

There should be a datasheet for valves that may be used at that particular tag number on the Utilities Line Diagram [ULD]. That document needs to be followed.

here should be a mechanical hook-up drawing for that type of instrument at that particular tag number on the ULD. That document needs to be followed.

I hope you are using something like this.

it can be made of steel, cooper or inox, then connect the valve, this way you protect your instrument

pig tails for gauges yes..... but at 220 bar, I would not go with copper.

I have sort of forgotten the reason for the tubing loops on gauges...does this reduce hammering of the gauge during opening, or does it limit the impact of particles in the fluid? Certainly not copper at 220 bar, that needs to be a good quality steel tubing, possibly high temperature stainless steel, with a pressure rating that is appropriate, it may have to be a higher wall thickness than standard tubings.

reduces hammer

The loop creates a pocket for condensate to form- protecting the gauge from exposure to the steam (and its heat) while also providing a cushion for any sudden pressure changes.

Understood. Obviously, this really depends on a proper sealing of the pressure gauge to the pigtail loop, and also the loop to the sampling valves. It makes one have an even greater appreciation of all that is required even on low to medium pressure plants, much more so on the high pressure ones.