http://www.idpump.com/products-services/specs/wxh.html :
Optional Balance Drum Design: Hydraulic balancing devices are available in either a flanged or straight drum design and are selected according to application requirements. Special materials eliminate erosion and provide extended operating life. Running surfaces on the drum are serrated to reduce leakage and optimize efficiency. (ЮЕТФЕЦЙ РТЙМБЗБАФУС)...
юХФШ ТБОШЫЕ ОБ ЬФПК ЦЕ УФТБОЙЮЛЕ:
Hydraulic Balancing Device maintains axial balance through the entire operating range. A straight drum or flanged disk is available depending on the application. Either may be renewed in the field without disturbing the piping, tie rods or main pump bundle.

фБЛЙН ПВТБЪПН, РПМХЮБЕН, ЮФП "balance drum" - ЬФП "Hydraulic Balancing Device".
hydraulic balance - ЗЙДТБЧМЙЮЕУЛБС ЛПНРЕОУБГЙС (Lyngvo 7.0),
Ф.Е. Hydraulic Balancing Device - ЗЙДТБЧМЙЮЕУЛЙК ЛПНРЕОУБФПТ.

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Note added at 2002-03-28 20:07:41 (GMT)
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Сорри за кодировку. Еще раз то же самое:
гидрокомпенсатор

http://www.idpump.com/products-services/specs/wxh.html :
Optional Balance Drum Design: Hydraulic balancing devices are available in either a flanged or straight drum design and are selected according to application requirements. Special materials eliminate erosion and provide extended operating life. Running surfaces on the drum are serrated to reduce leakage and optimize efficiency. (чертежи прилагаются)...
Чуть раньше на этой же страничке:
Hydraulic Balancing Device maintains axial balance through the entire operating range. A straight drum or flanged disk is available depending on the application. Either may be renewed in the field without disturbing the piping, tie rods or main pump bundle.

Таким образом, получаем, что \"balance drum\" - это \"Hydraulic Balancing Device\".
hydraulic balance - гидравлическая компенсация (Lyngvo 7.0),
т.е. Hydraulic Balancing Device - гидравлический компенсатор.

References:

www.idpump.com/products-services/specs/wxh.html