1 管道组成件 Piping component
1.1 管子 Pipe
管子(按照配管标准规格制造的) pipe 管子(不按配管标准规格制造的其他用管)tube 钢管 steel pipe 铸铁管 cast iron pipe

衬里管 lined pipe 复合管 clad pipe
碳钢管 carbon steel pipe 合金钢管 alloy steel pipe
不锈钢 stainless steel pipe 奥氏体不锈钢管 austenitic stainless steel pipe
铁合金钢管 ferritic alloy steel pipe 轧制钢管 wrought-steel pipe
锻铁管 wrought-iron pipe 无缝钢管 seamless (SMLS) steel pipe
焊接钢管 welded steel pipe 电阻焊钢管 electric-resistance welded steel pipe
电熔（弧）焊钢板卷管 electric-fusion (arc)-welded steel-plate pipe
螺旋焊接钢管 spiral welded steel pipe 镀锌钢管 galvanized steel pipe
热轧无缝钢管 hot-rolling seamless pipe冷拔无缝钢管 cold-drawing seamless pipe
水煤气钢管 water-gas steel pipe 塑料管 plastic pipe
玻璃管 glass tube 橡胶管 rubber tube
直管 run pipe; straight pipe
1.2 管件 Fitting
弯头 elbow 异径弯头 reducing elbow
带支座弯头 base elbow k半径弯头 long radius elbow
短半径弯头 short radius elbow 长半径180°弯头 long radius return
短半径180°弯头 short radius return 带支座三通 base tee
带侧向口的弯头（右向或左向） side outlet elbow (right hand or left hand)
双支管弯头（ 形） double branch elbow 三通 tee
异径三通 reducing tee 等径三通 straight tee
带侧向口的三通（右向或左向） side outlet tee (right hand or 1eft hand)
异径三通（分支口为异径） reducing tee (reducing on outlet)
异径三通（一个直通口为异径）reducing tee (reducing on one run)

异径三通（一个直通口及分支口为异径） reducing tee (reducing on one run and outlet)
异径三通（两个直通口为异径，双头式）reducing tee (reducing on both runs, bull head)
45°斜三通 45°lateral 45°斜三通（支管为异径）45°lateral (reducing on branch)
45°斜三通(一个直通口为异径) 45° lateral (reducing on one run)
45°斜三通(一个直通口及支管为异径) 45° lateral (reducing on one run and branch)
Y型三通（俗称裤衩） true “Y” 四通 cross
等径四通 straight cross 异径四通 reducing cross
异径四通（一个分支口为异径）reducing cross (reducing on one outlet)
异径四通（一个直通口及分支口为异径） reducing cross (reducing on one run and outlet)
异径四通（两个分支口为异径） reducing cross (reducing on both outlet)
异径四通（一个直通口及两个分支口为异径） reducing cross (reducing on one run and both outlet) 异径管 reducer
同心异径管 concentric reducer 偏心异径管 eccentric reducer
锻制异径管 reducing swage 螺纹支管台 threadolet
焊接支管台 weldolet 承插支管台 sockolet
弯头支管台 elbolet 斜接支管台 latrolet
镶入式支管嘴 sweepolet 短管支管台 nipolet
支管台，插入式支管台 boss 管接头 coupling, full coupling
半管接头 half coupling 异径管接头 reducing coupling
活接头 union 内外螺纹缩接（俗称补芯） bushing
管帽 cap (C) 堵头 plug
短节 nipple 异径短节 reducing nipple; swage nipple
1.3 弯管 Bend
预制弯管 fabricated pipe bend 跨越弯管（^ 形） cross-over bend
偏置弯管（~ 形） offset bend 90°弯管 quarter bend
环形弯管 cirele bend 单侧偏置90°弯管（? 形） single offset quarter bend
S形弯管 “S” bend 单侧偏置U形膨胀弯管（| ?形） single offset “U” bend
U形弯管 “U” bend 双偏置U膨胀弯管 double offset expansion “U” bend
斜接弯管 mitre bend 三节斜接弯管 3-piece mitre bend
折皱弯管 corrugated bend 圆度 roundness
1.4 法兰 Flange (FLG）
整体管法兰 integral pipe flange 钢管法兰 steel pipe flange
螺纹法兰 threaded flange 承插焊法兰 socket welding flange
滑套法兰（包括平焊法兰） slip-on flange (SO); slip-on welding flange
松套法兰 lap joint flange (LJF) 对焊法兰 welding neckflange (WNF)
法兰盖 blind flange, blind 孔板法兰 orifice flange
异径法兰 reducing flange 盘座式法兰 pad type flange
松套带颈法兰 loose hubbed flange 焊接板式法兰 welding plate flange
对焊环 welding neck collar （与stub end相似） 平焊环 welding-on collar
突缘短节 stub end, lap 翻边端 lapped pipe end
松套板式法兰 loose plate flange 压力级 pressure rating, pressure rating class
压力—温度等级 pressure-temperature rating 法兰密封面，法兰面 flange facing
突面 raised face (RF) 凸面 male face (MF)
凹面 female face (FMF) 环连接面 ring joint face
榫面 tongue face 槽面 groove face

全平面；满平面 flat face; full face (FF) 光滑突面 smooth raised face (SRF)
法兰面加工 facing finish 粗糙度 roughness
光滑的 smooth 齿形 serrated
均方根 root mean square (RMS) 配对法兰 companion-flange
算术平均粗糙高度 arithmetical average roughness height (AARH)
螺栓圆 bolt circle (B.C.)
1.5 垫片 Gasket (GSKT)
垫片的型式 type of gasket 平垫片 flat gasket
环形平垫片 flat ring gasket 平金属垫片 flat metal gasket
夹棉织物的橡胶 elastomer with cotton fabric insertion
夹石棉织物的橡胶 elastomer with asbestos fabric insertion
夹石棉织物及金属丝加强的橡胶 elastomer with asbestos fabric insertion and with wire reinforcement
无石墨压缩白石棉垫片 non graphited compressed white asbestos gasket
天然白橡胶垫片 natural white rubber gasket
压缩石棉垫片 compressed asbestos class gasket
浸聚四氟乙烯的石棉垫片 PTFE impregnated asbestos gasket
夹石棉的缠绕金属垫片 spiral-wound metal gasket with asbestos filler
内环 inner ring 外环，外定位环 outer ring
波纹金属垫片 corrugated metal gasket
波纹金属包嵌石棉垫片 corrugated metal gasket with asbestos inserted
双夹套波纹金属包石棉垫片corrugated metal double jacketed asbestos filled gasket
双夹套垫片 double jacketed gasket

金属包石棉平垫片 flat metal jacketed asbestos filled gasket
整体金属齿形垫片 solid metal serrated gasket槽形金属垫片 grooved metal gasket
环形连接金属垫片 ring joint metal gasket 八角环形垫片 octagonal ring gasket
椭圆环形垫片 oval ring gasket 透镜式垫片 lens gasket
非金属垫片 non-metallic gasket
1.6 阀门 Valve
1.6.1 阀门结构、零件
阀轭 yoke 外螺纹阀杆及阀轭 outside screw and yoke (OS & Y)
阀杆 stem 内螺纹 inside screw (IS)
阀轭套 yoke sleeve 阀杆环 stem ring
阀座 valve seat (body seat) 阀座环、密封圈 seat ring
整体（阀）座 integral seat 堆焊（阀）座 deposited seat
阀芯（包括密封圈、杆等内件） trim 阀盘 disc
阀盘密封圈 disc seat 阀体 body
阀盖 bonnet 阀盖衬套 bonnet bush
螺纹阀帽 screw cap 螺纹阀盖 screw bonnet
螺栓连接的阀盖 bolted bonnet (BB) 活接阀盖（帽） union bonnet (cap)
螺栓连接的阀帽 bolted cap (BC) 焊接阀盖 welded bonnet (WB)
本体阀杆密封 body stem seal 石棉安全密封 asbestos emenen seal
倒密封 back seal 压力密封的阀盖 pressure-tight bonnet
动力操纵器 powered operator 电动操纵器 electric motor operator
气动操纵器 pneumatic operator 液压操纵器 hydraulic operator
快速操纵器 quick-acting operator 滑动阀杆 sliding stem
正齿轮传动 spur gear operated 伞齿轮传动 bevel gear operated
扳手操作 wrench operated 链轮 chain wheel
手轮 hand wheel 手柄 hand lever (handle)
气缸（或液压缸）操纵的 cylinder operated 链条操纵的 chain operated
等径孔道 full bore; full port 异径孔道 reducing bore, reduced port,venturi port
短型 short pattern 紧凑型（小型） compact type
笼式环 lantern ring 压盖 gland
阀杆填料 stem packing 阀盖垫片 bonnet gasket
升杆式（明杆） rising stem (RS) 非升杆式（暗杆） non-rising stem (NRS)
指示器/限位器 indicator/stopper 注油器 grease injector
可更换的阀座环 renewable seat ring
1.6.2 常用阀
(1）闸阀 gate valve
平行双闸板 double disc parallel seat 开口楔形闸板 split wedge
挠性整体楔形闸扳 flexible solid wedge 整体楔形闸板 solid wedge
塞型闸阀 plug gate valve 直通型闸阀 through conduit gate valve
(2) 截止阀 globe valve
球心型阀盘 globe type disc 塞型阀盘 plug type disc
可转动的阀盘 swivel disc
(3) 节流闪阀 throttle valve
针阀 needle valve
(4) 角阀 angle valve
(5) Y型阀（Y 型阀体截止阀） Y-valve (Y-body globe valve)
(6) 球阀 ball valve
三通球阀 3-way ball valve 装有底轴的 trunnion mounted
耐火型 fire safe type 浮动球型 floating ball type
防脱出阀杆 blowout proof stem
(7) 蝶阀 butterfly valve
对夹式（薄片型） wafer type 凸耳式 lug type
偏心阀板蝶阀 offset disc burerfly valve; eccentric butterfly valve
斜阀盘蝶阀 canted disc butterfly valve 连杆式蝶阀 link butterfly valve
(8) 柱塞阀 piston type valve
(9) 旋塞阀 plug valve
三通旋塞阀 three-way plug valve 四通旋塞阀 four-way plug valve
旋塞 cock 衬套旋塞 sleeve cock
(10) 隔膜阀 diaphragm valve
橡胶衬里隔膜阀 rubber lined diaphragm valve
直通式隔膜阀 straight way diaphragm valve 堰式隔膜阀 weir diaphragm valve
(11) 夹紧式胶管阀 pinch valve（用于泥浆、粉尘等）
(12) 止回阀 check valve
升降式止回阀 lift check valve 旋启式止回阀 swing check valve, flap check valve
落球式止回阀 ball check valve 弹簧球式止回阀 spring ball check valve
双板对夹式止回阀 dual plate wafer type check valve 底阀 foot valve
无撞击声止回阀 non-slam cheek valve

切断式止回阀 stop check valve; non-return valve 活塞式止回阀 piston check valve
斜翻盘止回阀 tilting disc check valve 蝶式止回阀 butterfly check valve
1.6.3 其它用途的阀
安全泄气阀 safety valve (SV) 安全泄液阀 relief valve (RV)
安全泄压阀 safety relief valve 杠杆重锤式 lever and weight type
引导阀操纵的安全泄气阀 pilot operated safety valve 蒸汽疏水阀 steam trap
复式安全泄气阀 twin type safety valve 罐底排污阀flush-bottom tank valve
电磁阀 solenoid valve, solenoid operated valve 气动阀pneumatic operated valve
电动阀 electrically operated valve, electric-motor operated valve
低温用阀 cryogenic service valve机械式疏水阎 mechanical trap
浮桶式疏水阀 open bucket trap, open top bucket trap 浮球式疏水阀 float trap
倒吊桶式疏水阀 inverted bucket trap 自由浮球式疏水阀 loose float trap
恒温式疏水阀 thermostatic trap 金属膨胀式蒸汽疏水阀metal expansion steam trap
液体膨胀式蒸汽疏水阀 liquid expansion steam trap
双金属膨胀式蒸汽疏水阀 bimetallic expansion steam trap
压力平衡式恒温疏水阀 balanced pressure thermostatic trap
热动力式疏水阀 thermodynamic trap 脉冲式蒸汽疏水阀 impulse steam trap
放气阀（自动放气阀） air vent valve (automatic air vent valve) （疏水阀用）
平板式滑动闸阀 slab type sliding gate valve 盖阀 flat valve
换向阀 diverting valve, reversing valve 热膨胀阀 thermo expansion valve
自动关闭阀 self-closing gate valve 自动排液阀 self-draining valve
管道盲板阀 line-blind valve 挤压阀 squeeze valve（用于泥浆及粉尘等）
呼吸阀 breather valve 风门、挡板 damper
减压阀 pressure reducing valve, reducing valve 控制阀 control valve
膜式控制阀 diaphragm operated control valve 执行机构 actuator
背压调节阀 back pressure regulating valve
差压调节阀 differential pressure regulating valve
压力比例调节阀 pressure ratio regulating valve
1.6.4 未指明结构（或阀型）的阀
切断阀 block valve; shut-off valve; stop valve 调节阀 regulating valve
快开阀 quick opening valve 快闭阀 quick closing valve
隔断阀 isolating valve 三通阀 three way valve
夹套阔 jacketed valve 非旋转式阀 non-rotary valve
排污阀 blowdown valve 集液排放阀 drip valve
排液阀 drain valve 放空阀 vent valve
卸载阀 unloading valve 排出阀 discharge valve
吸入阀 suction valve 多通路阀 multiport valve
取样阀 sampling valve 手动阀 hand-operated valve; manually operated valve
锻造阀 forged valve 铸造阀 cast valve
（水）龙头 bibb; bib; faucet 抽出液阀（小阀） bleed valve
旁路阀 by-pass valve 软管阀 hose valve
混合阀 mixing valve 破真空阀 vacuum breaker
冲洗阀 flush valve 第一道阀；根部阀 primary valve
根部阀 root valve 总管阀 header valve
事故切断阀 emergency valve
1.7 管道特殊件 Piping Specialty
1.7.1 管道特殊件（组件）
粗滤器 strainer 过滤器 filter
临时粗滤器（锥型） temporary strainer (cone type) y 型粗滤器 y-type strainer
T型粗滤器 T-type strainer 永久过滤器 permanent filter
丝网粗滤器 gauze strainer 洗眼器及淋浴器 eye washer and shower
视镜 sight glass 阻火器 flame arrester
喷嘴；喷头 spray nozzle 取样冷却器 sample cooler
消声器 silencer 膨胀节 expansion joint
波纹膨胀节 bellow expansion joint 单波 single bellow
双波 double bellow 多波 multiple bellow
压力平衡式膨胀节 pressure balanced expansion带铰链膨胀节hinged expansion joint
轴向位移型膨胀节 axial movement type expansion joint
自均衡膨胀节（外加强环）self-equalizing expansion joint
带接杆膨胀节 tied expansion joint 万向型膨胀节 universal type expansion joint
球形补偿器 ball type expansion joint
填函式补偿器 slip type (packed type) expansion joint
单向滑动填料函补偿器 single actionpacked slip joint
1.7.2 管道特殊元件Piping Special Element
软管接头 hose connection (HC) 快速接头 quick coupling
金属软管 metal hose 橡胶管 rubber hose
挠性管 flexible tube 鞍形补强板 reinforcing saddles
补强板 reinforcement pad 特殊法兰 special flange
漏斗 funnel 排液环 drip ring
排液漏斗 drain funnel 插板 blank
垫环 spacer 8字盲板 spectacle blind; figure 8 blind
限流孔板 restriction orifice 爆破片 rupture disk
法兰盖贴面 protective disc 费托立克接头 victaulic coupling
1.8 端部连接 End Connection
法兰端 flanged end 坡口端 beveled end (BE)
对焊端 butt welded end 平端 plain end (PE)
承插焊端 socket welding end 螺纹端 threaded end (TE)
承口 bell end 焊接端 welding end
法兰连接（接头） flanged joint 对焊连接（接头） butt welded joint
螺纹连接，管螺纹连接 threaded joint, pipe threaded joint
锥管螺纹密封焊连接 seal-welded taper pipe threaded joint
承插焊连接（接头） socket welded joint 承插连接（接头） bell and spigot joint
环垫接头 ring joint (RJ) 万向接头 universal joint
软钎焊连接（接头） soldered joint 搭接接头，松套连接 lapped joint
外侧厚度切斜角 bevel for outside thickncss
内侧厚度切斜角 bevel for inside thickness
内外侧厚度切斜角 bevel for combined thickness
法兰式的 flanged (FLGD) 对焊的 butt welded (BW)
螺纹的 threaded (THD) 承插焊的 socket welded (SW)
小端为平的 small end plain (SEP) 大端为平的 large end plain (LEP)
两端平 both ends plain (BEP) 小端带螺纹 small end thread (SET)
大端带螺纹 large end thread (LET) 两端带螺纹 both end thread (BET)
一端带螺纹 one end thread (OET) 支管连接 branch connection
焊接支管 branch pipe welded directly to the run pipe

2 管道用紧固件及螺纹
2.1 紧固件
螺栓 bolt 六角头螺栓 hexagonal head bolt
方头螺栓 square head bolt 螺柱，双头螺栓 stud bolt
环头螺检 eye bolt 沉头螺栓 countersunk (head) screw
地脚螺栓 anchor bolt; foundation bolt 松紧螺旋扣（花篮螺丝） turnbuckle
U形螺栓 U-bolt T形螺栓 T-bolt
圆头螺钉 round head bolt 机螺栓，机螺钉 maehine bolt
顶开螺栓，顶起螺栓 Jack screw 自攻螺钉 self tapping screw
膨胀螺栓 expansion bolt 粗制的 coarse
精制的 finished, fine 螺母 nut
六角螺母 hexagonal nut 方螺母 square nut
蝶形螺母 wing nut 扁螺母 flat nut
锁紧螺母 lock nut 垫圈 washer
平垫圈 plain washer 球面垫圈 spherical washer
弹簧垫圈 spring washer 方垫圈 square washer
斜垫圈 slant washer 销轴 pinned shan
销 pin 开口销 cotter pin
定位销 dowel pin 带孔销 pin with hole
圆锥销 taper pin 铆钉 rivet
键 key
2.2 螺纹
左螺left hand thread 右螺纹 right hand thread
管螺纹 pipe thread 锥管螺纹 taper pipe thread
直管螺纹straight pipe thread 梯形螺纹 trapezoid thread
螺距pitch of thread 粗牙螺纹coarse thread
细牙螺纹 fine thread 特细牙螺纹extra fine thread
通长螺纹full thread 惠氏螺纹whitworth thread
公制螺纹 metric ibread 螺孔 tap
美国标准锥管螺纹 American standard taper pipe thread (NPT)
3 材料、型钢及填料
3.1 金属材料
3.1.1 黑色金属 Ferrous Metal

碳素钢 carbon steel (CS) 低碳钢 low-carbon steel
中碳钢 medium-carbon steel 高碳钢 high-carbon steel
普通碳素钢 general carbon steel 优质碳素钢 high-quality carbon steel
普通低合金结构钢 general structure low-alloy steel
合金结构钢 structural alloy steel 合金钢 alloy steel
低合金钢 low alloy steel 中合金钢 medium alloy steel
高合金钢 high alloy steel 耐热钢 heat resisting steel
高强度钢 high strength steel 复合钢 clad steel
工具钢 tool steel 弹簧钢 spring steel
钼钢 molybdenum steel 镍钢 nickel steel
铬钢 chromium steel 铬钼钢 chrome-molybdenum steel
铬镍钢 chromium-nickel steel,chrome-nickel steel 不锈钢 stainless steel (S.S.)
奥氏体不锈钢 Austenitic stainless steel马氏体不锈钢 Martensitic stainless steel
司特来合金（钨铬钴台金） Stellite 耐蚀耐热镍基合金 Hastelloy
铬镍铁合金 inconel 耐热铬镍铁合金 incoloy
20合金 20 alloy 平炉钢（马丁钢） Martin steel
镇静钢 killed steel 半镇静钢 semi-killed steel
沸腾钢 rimmed steel; rimming steel; open-steel 锻钢 forged steel
铸钢 cast steel 铸铁 cast iron (C.I.)
灰铸铁 grey cast iron 可锻铸铁 malleable iron (MI)
球墨铸铁 nodular cast iron; nodular graphite iron 生铁 pig iron
熟铁，锻铁 wrought iron 铸件 casting
高硅铸铁 high silicon cast iron
3.1.2 镀层及制造方法
铬钢，镀铬钢 chromized steel 镀铬的 chromium-plated, chrome-plated
镀层 plating 锻造，型钢 swage
锻造的，锻造 forging 轧制 rolling
热轧 hot rolling 冷轧 cold rolling
挤压 extruding 冷加工 cold working
热加工 hot working 拔制 drawing
3.1.3 有色金属Non-ferrous Metal
铝 aluminum 铜，紫铜 copper
黄铜 brass 青铜 bronze
铝青铜 aluminum bronze 磷青铜 phosphor bronze
铝镁合金 aluminum magnesium 锰青铜 manganese bronze
蒙乃尔（注：镍及铜合金） Monel 镍铜台金 nickel copper alloy
非铁合金 nonferrous alloy 钛 titanium
铅 lead 硬铅 hard lead
3.1.4 材料性能
极限强度 ultimate strength 抗拉强度 tensile strength
屈服极限 yield limit 屈服点 yield point
延伸率 percentage elongation 抗压强度 compressive strength
抗弯强度 bending strength 弹性极限 elastic limit
冲击值 impact value 疲劳极限 fatigue limit
蠕变极限 creep limit 持久极限 endurance limit
布氏硬度 Brinell hardness 洛氏硬度 Rockwell hardness
维氏硬度 Vickers diamond hardness, diamond penetrator hardness
蠕变断裂强度 creep rupture strength 断面收缩率 reduction of area
韧性 toughess 脆性 brittleness
延性 ductility 冷脆 cold shortness
冷流 cold flow
3.2 非金属材料 Non-metallic Material
塑料 plastic 丙烯腈—丁二烯—苯乙烯 acrylonitrile-butadiene-styrene (ABS)
聚乙烯 polyethylene (PE) 聚氯乙烯 polyvinyl chloride (PVC)
苯乙烯橡胶 styrene-rubber (SR) 聚丁烯 polybutylene (PB)
聚丙烯 polypropylene (PP) 聚苯乙烯 polystyrene (PS)
氯化聚醚 chlorinated polyether (CPE) 聚酰胺 polyamide (PA)
聚碳酸酯 polycarbonate (PC) 聚甲基丙烯酸甲酯 polymethyl methacrylate (PMMA)
醋酸丁酸纤维素cellulose acetate butyrate (CAB)
氯化聚氯乙烯 chlorinated polyvinyl chloride (CPVC)
聚偏二氟乙烯 polyvinylidene fluoride (PVDF) 缩醛塑料 acetal plastic
尼龙塑料 nylon plastic 聚烯烃 polyolefin (PO)
石墨酚醛塑料graphite phenolic plastics聚四氟乙烯polytetrafluoroethylene (PTFE)
纤维增强热塑性塑料 fiber reinforced thermoplastics 热塑性塑料 thermoplastic
热固性塑料 thermosetting plastics 胶粘剂 adhesive
溶剂胶接剂 solvent cement 树脂 resin
环氧树脂 epoxy, epoxy resin 聚酯树脂 polyester resin
聚酯纤维 polyester fibers 氟塑料 fluoroplastics
聚氨基甲酸酯 polyurethane 丙烯酸树脂 acrylic resin
脲醛树脂 urea resin 呋哺树脂 furan resin
乙烯丙烯二烃单体 ethylene propylene diene monomer (EPDM)
合成橡胶 synthetic rubber 橡胶 rubber
丁腈橡胶 nitrile butadiene rubber 氯丁橡胶 neoprene
天然橡胶 natural rubber 乙丙橡胶 ethylene propylene rubber (EPR)
玻璃 glass 硼硅玻璃 borosilicate glass
耐火砖 fire brick 陶瓷 ceramic
搪瓷 porcelain enamel 木材 wood
3.3 型材
型钢 shaped steel, section steel, swage 角钢 angle steel
槽钢 channel 工字钢 I-beam
宽缘工字钢或H钢 wide flanged beam T型钢 T-bar
方钢 square bar 扁钢 flat bar
角钢 hexagonal steel bar 圆钢 round steel; rod
钢带 strap steel 钢板 plate
网纹钢板 checkered plate 腹板（指型钢的立板） web
翼缘（指型钢的缘） wing
3.4 填料及填料函
填料 packing 石棉绳 asbestos rope, asbestos cord．
O形环 O-ring 自密封 self-sealing
四氟带 Teflon tap 金属填料 metallic stuffing
带铬镍合金丝的石棉绳 asbestos rope with inconel wire, inconel wire asbestos
浸聚四氟乙烯的石棉填料 Teflon impregnated asbestos packing

填料箱，填料函 packing box, stuffing box 填料函压盖 stuffing box gland