‘Senior orifice’ lazim juga disebut ‘dual chamber orifice’, sedangkan ‘junior orifice’ lazim disebut ‘single chamber’. Karena memiliki chamber dobel, penggantian orifice plate pada senior orifice dapat dilakukan tanpa mematikan aliran gas dalam pipa. Pada junior orifice tidak mungkin dilakukan penggantian plate tanpa mematikan aliran gas, karena ketika dilakukan penggantian plate, chamber yang Cuma satu2 nya harus dibuka, dan menyebabkan gas yang mengalir di dalam chamber akan keluar ke atmosfer.

Tanya – Wahyu

Dear All,

Saya mau tanya,
Apa yang dimaksud dengan term ‘senior’ pada orifice flow element?
Kapankah senior orifice harus dipakai? Apakah ada bedanya dengan orifice biasa?

Tanggapan 1 – Administrator Migas

Istilah senior pada orifice plate itu menunjuk pada dual chamber yang dimilikinya.
Kalau junior kan single chamber, sedangkan orifice flange, tanpa menggunakan chamber.
Karena dual chamber, maka kita bisa mengganti orifice plate secara online meskipun ada fluida yang mengalir didalam pipa.
Keuntungan yang utama dari tipe senior yaitu plant tidak perlu shutdown bila kita menginginkan mengganti orifice plate didalamnya.

Untuk lebih jelasnya, saya cuplikan keterangan dari salah satu manufacture orifice plate yaitu Daniel.
FYI, Daniel penggantian memang ke arah atas, sedangkan untuk Peco, ke arah samping.

Orifice Flange
The most elementary device used to hold an orifice plate in place is the orifice flange union. Orifice flanges have been used for a great many years but gained in importance during the 1920’s, when the petroleum industry began making extensive use of orifice measurement. It did not take many years to discover that the orifice flange, in spite of simplicity, had many shortcomings in certain applications. It was apparent that it could not be conveniently used for wide variations of flow, dirty fluids requiring frequent plate cleanings, or in services where flow interruptions are expensive. Therefore, it was often necessary to bypass the flow so that the orifice plate could be inspected or changed as conditions warranted.

The Senior ® Orifice Fitting
Changing plates in orifice flanges is time consuming and expensive. It is evident that operating personnel are in need of some device which would make the operation of plate changing or inspection less tedious. Therefore, the first significant type of orifice fitting is known as the Senior type, having a design permitting the change or the removal of a plate under flowing conditions. The Senior® Orifice Fitting is a dual chambered fitting allowing the removal of an orifice plate under flow conditions. The lower chamber, which holds the orifice plate in the fluid flow, is bolted to an upper chamber. Separating the two chambers is a slide valve that opens/closes with a gear shaft. Opening the slide valve allows elevation of the plate carrier and orifice plate into the top chamber. Once the slide valve is closed again and pressure bled from the top chamber, the plate carrier/plate can be removed to the atmosphere.

The Junior Orifice Fitting
Some time after the development of the Senior Orifice Fitting, attention was given to the problem of changing orifice plates when a bypass was in existence, or where two or more meter tubes were joined by common headers. Since orifice flanges are not convenient and require a considerable amount of time when used, thought was turned to developing a simple fitting for speedy operating. The result was the Junior type fitting. The Junior Fitting is much like the Senior, except the Junior does not have a slide valve and a top chamber. The Junior fitting requires only the following steps to remove an orifice plate from the line :
1. Shut in meter tube.
2. Depressure tube.
3. Loosen set screws, remove top clamping bar, sealing bar, and gasket.
4. Turn shaft, elevating orifice plate out of the fitting.

The procedure is reversed to install an orifice plate.
The Junior Fitting is currently available in line sizes 10′ through 34′ and for special applications, has been manufactured in larger sizes up to 48′.

The Simplex® Orifice Plate Holder
The Simplex Orifice Plate Holder is the third basic type of orifice fitting, and was developed specifically to provide an economical, accurate replacement for conventional orifice flanges where plate changings are infrequent and orifice flange unions are too cumbersome. The Simplex is basically the same as the Junior except you do not elevate the orifice plate with a shaft and pinion gear. Since the Simplex is made in sizes 1½ “ thru 8′ only, the plate and plate carrier can easily be removed by hand.

Tanggapan selengkapnya dari rekan-rekan Mailing List Migas Indonesia pembahasan bulan Juni 2007 dapat dilihat dalam file berikut: