HIGHER-DENSITY TREE

GATE S. R .

CASTINGS

VALVE Mamedov

FOR

CHRISTMAS

BODIES and I.

M. M a m e d o v

UDC [621.74:669.14]:531.42

The effect of various types of casting feeder heads on the density of castings made for the bodies of gate valves to be used in oil-field wellhead c h r i s t m a s t r e e s was investigated at the Lieutenant Shmidt m a chinery f a c t o r y . Conventional blind r i s e r s and what we t e r m side r i s e r s , c u r r e n t l y in use in casting of valve bodies, blind side r i s e r s with an additional feeder head on the spherical s u r f a c e of the gate valve body casting, g a s - l o a d e d feeder heads, and feeder heads at a t m o s p h e r i c p r e s s u r e , were c o m p a r e d in the investigation. The side r i s e r s : on four valve bodies in the mold box were placed two round r i s e r s 160 m m in d i a m eter and 230 m m in height, and two r e c t a n g u l a r r i s e r s 130 • 200 m m a c r o s s and 230 m m in height. Conventional r i s e r s with an additional feeder head: on the spherical s u r f a c e of each gate valve body in the mold box was placed an additional r i s e r of dimensions 100 • 130 • 80 m m . R i s e r s under gas p r e s s u r e : g a s - g e n e r a t i n g c h a r g e s of chalk w e r e placed in the side r i s e r s 160 m m above the parting joint. R i s e r s at a t m o s p h e r i c p r e s s u r e : a r o d 26 m m in d i a m e t e r and 40 m m in height, with two or three gas drainage channels 3 m m in d i a m e t e r , and dried at 250-300~ was placed in each r i s e r during the m o l d ing p r o c e s s . Five gate valve bodies made f r o m g r a d e 25KhGSL steel were made in 5 ton and 3 ton basic a r c f u r naces, tapped at t e m p e r a t u r e s of 1570-1590~ and were cast in each of those v a r i a n t s . The cast bodies were then cut in half and the density, the mechanical p r o p e r t i e s , and the m a c r o s t r u c t u r e and m i c r o s t r u c ture of the steel were investigated. The density of the metal was determined by examining coupons of dimensions 10 • 10 • 25 m m and cut f r o m specimens tested for impact ductility. Investigations of m i c r o s e c t i o n s r e v e a l e d that the p u r e s t metal free of p o r o s i t y is obtained when the valve bodies are east in the v a r i a n t with the additional feeder head. Best density data were obtained for the metal of valve bodies cast with an additional feeder head on a spherical s u r f a c e , which is accounted for by the efficient way the pipe outlets and the s p h e r i c a l dome of the gate valve body were supplied with additional f e e d e r . Sufficiently high density data w e r e obtained in the case of the steel castings with g a s - l o a d e d feeder heads, which w e r e however m o r e often s c r a p p e d b e c a u s e of large shrinkage cavities f o r m i n g the body of the castings under the feeder heads, and at sites with lap type defects (seven out of 20 such bodies had to be scrapped). The data resulting f r o m this investigation prompted a change in the fabrication technology of the gate valve bodies, with an additional feeder head on the spherical surface of the valve body being p r e s c r i b e d in specifications.

T r a n s l a t e d f r o m Khimicheskoe i Neftyanoe Mashinostroenie, No. 10, p . 2 5 , October, 1972. 9 1973 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011. All rights reserved. This article cannot be reproduced [or any purpose whatsoever without permission of the publisher. A copy of this article is available from the publisher for $15.00.

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