ساختمان اين شير طوري طراحي شده که مايع از نقطه ورود به شير تا خروج از آن 180 درجه تغيير جهت ميدهد. ساختمان مجرابند و نشيمنگاه آن طوري است که به محض برقرار شدن جريان، تماس آنها با هم قطع ميشود همچنين باز نبودن کامل شير موجب فرسودگي آن نميشود و لذا از آن ميتوان براي تنظيم و کنترل جريان استفاده کرد. متناسب بودن تعداد دور دسته شير با حجم مجراي خروجي جريان کار تنظيم مقدار جريان را با دست آسان ميسازد. اکثر شيرهاي بشقابي داراي ساقه و فلکه متحرک هستند.

در هنگام مقايسه بين يک Valve Globe و Gate Valve معمولاً نشتي از نشيمنگاه شير بشقابي کمتر از دروازه اي است. اين بدين دليل است که وضعيت تماسي مجرابند با نشيمنگاه در بيشتر وضعيت ها با زاويه قائمه است و اين باعث بوجود آمدن نيروي بيشتري براي بسته شدن و سفت شدن مجرابند و نشيمنگاه آن ميگردد

HANDWHEEL The spoked handwheel is fabricated from steel pipe. The hub has a square hole for coupling with the stem, and for large sizes the hube is coupled with the yoke sleeve by means of a tongue (like gate valves)

YOKE SLEEVE The yoke sleeve is made of cast aluminium bronze having high resistance to wear and a high melting point. It is screwed into the bonnet and properly sized to withstand the stresses which develop when opening and closing the valve. For large sizes the yoke sleeve is designed like for gate valves

GLAND AND FLANGE They are in forged steel and are normally supplied in two pieces, self aligning design to permit the gland to descend parallel to the stem even if the eyebolts are unevenly tightened.

GLAND BOLTS AND NUTS The forged steel gland bolts are of the eyebolt type which can be swung outward for ease of gland repacking. They are fixed to the bonnet by hinge pins.

BONNET BOLTING Bonnet studs and nuts are manufactured from alloy steel to the relevant ASTM standard.

BODY The body is in cast steel. The basic dimension, i.e. wall thickness, face to face and flanges comply with the relevant API and ANSI standards. The body-to-bonnet flange is circular, and the sealing surfaces for connection to the bonnet are recessed in the 150 and 300 lb Series and ring joint in the higher class. The body is threaded for a renewable seat. The bodies from 8" onward are provided with three guides at 120°, to guide the disc. Bosses are provided for drain taps or by.pass piping.

BONNET The bonnet is in cast steel. It is machined to accept yoke sleeve and incorporates a stuffing box dimensioned in accordance with the API standard.

BONNET BUSHING The bonnet bushing or backseats is in forged stainless still and forms part of the trim. Special attention is given to its machining.

STEM The stem is in forged stainless steel and is part of the trim. A ground backseat is provided to ensure a perfectly tight seal to the stuffing box when the valve is fully open. The stem is attached to the disc by means of a threaded ring which allows the disc to rotate, The stem is ground to minimize friction and prevent damage to gland packing. The threading is trapezoidal ACME type.

DISC The disc is part of the trim and is in forged stainless steel in diameters up to 8" and in cast steel for larger valves. It is normally supplied of the flat, tapered or plug type or, on request, of the regulating type. always free to rotate on the stem. Special attention is given to the seating face which is ground and lapped.
SEAT RING The ring is in forged stainless and are part of the trim. Its outer diameter is threaded and its bore is notched to ease installation and dismantling. Special attention is given to the seating face which is ground and lapped, for a perfectly tight seal. Welded-in-seat ring may be supplied upon request.