在截止阀管件行业中，根据公称压力PN的大小，我们可以把公称压力小于等于1.6MPa的阀门为低压阀门，公称压力为2.5MPa、4.0MPa、6.4MPa的阀门为中压阀门，同时我们也经常会提到1.6MPa压力、2.5MPa压力和多少公斤压力、多少个标准大气压等之类的术语，那么1MPa压力到底有多大压强，1MPa压力等于多少公斤压力呢蒸汽压力为2.5㎏是表示2.5kg/cm2，是表示的单位面积上的压力--压强，通常俗称为2.5kg压力。新的表示方法约为0.25MPa。
换算关系：1kg/cm2=0.098MPa，因此压力2.5kg/cm2=0.245MP，可约等于0.25MPa.ISO标准帕斯卡(1Pa=1N/m2)
1公斤力/平方厘米=98.0665千帕
粗算时常按1公斤力=10N 则:
1公斤力/平方厘米=100千帕=1bar=0.1MPa
10公斤力/平方厘米=1000千帕=1MPa
公斤的单位是质量单位
MPA是压力的单位
质量m=压力/重力加速度
压力p=压力/面积
这是他们之间的关系

1公斤压力指的是1公斤重的物体作用为1cm2面积上所产生的压强，可以想像一下，1公斤重（比两瓶一元钱的康师傅矿泉水重略轻）的物体全部压在一个手指头上所产生的压强。  我们来计算一下， 1MPa=1×106Pa 1Pa=1N/1m2  1MPa=106N/m2=106N/104cm2=100N/cm2  重力加速度g约等于9.8 N/KG，为方便计算，g按整数10。 1KG的物体重力=1KG×10N/KG=10N  1公斤压力是1KG的重力作用于1cm2面积上产生的压强，即 1公斤压力=10N/cm2 1MPa=100N/cm2=10×10N/cm2 即1MPa压力等于10公斤压力。
单位说明：  Pa，压强单位，中文名称为“帕斯卡”，简称“帕”，即牛/平方米，1帕=1牛/平方米  M，数量单位，M即million，数值为一百万  N，物理力学单位，简称牛，是一种衡量力的大小的单位，两个鸡蛋的重力约为1N（0.1千克的物体的重量）  m，长度单位，米 m2，面积单位，平方米 cm2，面积单位，平方厘米 KG，重量单位，千克，公斤

减压阀标准一览表 
标准编号  标准中文名称  标准英文名称  JB/T10367-2002  液压减压阀      GB/T12245-1989  减压阀性能试验方法  Methods of performance test for pressure reducing valves GB/T12246-1989  先导式减压阀  Pilot-operated reducing valves  GB/T12244-1989  减压阀一般要求  General specification for pressure reducing valves GB/T1852-1993  船用法兰铸钢蒸汽减压阀  Marine steel flanged steam pressure reducing valves  GB10868-1989  电站减温减压阀技术条件   Specification of the steam converting valve for fossil power stations JB/T7376-1994(2005复审)   气动空气减压阀 技术条件       JB/T7310-1994(2005复审)   装载机用减压阀式先导阀     JB/T53361-1994  液压减压阀产品质量分等(试行)    JB/T53265-1999  先导式减压阀 产品质量分等     JB/T2205-2000  减压阀结构长度       NF P43-035-2000   建筑阀门.供水减压阀和复合供水减压阀.要求和试验   (Building valves - Water pressure reducing valves and combination water pressure reducing valves - Requirements and tests.)  NF A84-420-1991   气焊设备和有关方法.减压阀入品接头.尺寸   (Equipment for gas welding and allied processes. Pressure regulators inlet connections. Dimensions.)  NF M88-773-1981   商用丁烷容器装置.低压固定调节的家用商品丁烷减压阀   (INSTALLATIONS BURNING COMMERCIAL BUTANE. PRESSURE REGULATOR TRIP,LOW-PRESSURE FIXED FLOW,FOR COMMERCIAL BUTANE FOR DOMESTIC USE.)  NF M88-775-1990   装液态碳氢化合物的钢瓶.可移动部分和半移动部分用高压可调减压阀.功能.标记、试验   (LIQUEFIED HYDROCARBONS SYSTEMS IN CYLINDERS. FIXED  ADJUSTEMENT,HIGH PRESSURE REGULATOR FOR AND SEMI- PREMISES. CONSTRUCTION. OPERATION, MARKING,TESTS.)  NF M88-737-2003   可运输可再填充液化石油气瓶用减压阀   (Pressure relief valves for transportable refillable cylinders for Liquefied Petroleum Gas (LPG).)  NF E48-423-2001   液压传动.减压阀、顺序阀、卸载阀、 节流阀和止回阀.装配面   (Hydraulic fluid power - Pressure-reducing valves, sequence valves, unloading valves, throttle valves and check valves -  Mounting surfaces.)  ANSI/ASSE 1003-1995  家用供水系统用减压阀  (Water Pressure Reducing Valves for Domestic Water Supply Systems)  ANSI/ASSE 1046-1990  热膨胀减压阀  (Thermal Expansion Relief Valve)  ANSI Z 21.22a-1999  减压阀和真空减压阀  (Pressure Relief Valves and Vacuum Relief Valves)  ANSI Z 21.22b-2001  热水供应系统的减压阀  (Relief Valves for Hot Water Supply Systems (same as CSA 4.4b))  ANSI/ASTM F 1508-1997   用于蒸汽、气体和液体设备的角型减压阀规范   (Specification for Angle Style, Pressure Relief Valves for Steam, Gas, and Liquid Services)  ASME A112.4.1-1993  热水器减压阀排水管  (Water heater relief valve drain tubes) ASME PTC 25.3-1988  安全和减压阀   (Safety and relief valves) 

ASTM E 1008-2003  地热和其它高温液体设备用减压阀体的安装、检验及维修用标准实施规范   (Standard Practice for Installation, Inspection, and Maintenance  of Valve-body Pressure-relief Methods for Geothermal and Other  High-Temperature Liquid Applications)  标准编号  标准中文名称  标准英文名称  ASTM F 1795-2000   空气或氮气系统用减压阀标准规范   (Standard Specification for Pressure-Reducing Valves for Air or Nitrogen Systems)  ASTM F 1565-2000  蒸汽设备用减压阀标准规范   (Standard Specification for Pressure-Reducing Valves for Steam Service)  ASTM F 1508-1996   用于蒸汽、气体和液体设备的角型减压阀标准规范   (Standard Specification for Angle Style, Pressure Relief Valves for Steam, Gas and Liquid Services) ASTM F 1370-1992   船上给水系统用减压阀   (Standard Specification for Pressure-Reducing Valves for Water Systems, Shipboard)  BS EN 1567-2000   建筑物阀门.减压阀和组合减压阀.要求和试验   (Building valves - Water pressure reducing valves and combination water reducing valves - Requirements and tests)  BS ISO 5781-2000   液压传动.减压阀、顺序阀、卸荷阀、节流阀和止回阀.安装面   (Hydraulic fluid power - Pressure reducing valves, sequence valves, unloading valves, throttle valves and check valves - Mounting surfaces)  BS ISO 6264-1998  液压传动.减压阀.装配面   (Hydraulic fluid power - Pressure-relief valves - Mounting surfaces)  prEN 14071-2000   液化石油气（LPG）罐的减压阀 辅助设备   Pressure relief valves for LPG tanks - Ancillary equipment  BS 6283-2-1991   热水系统中使用的安全和控制装置.压力范围从1bar到10bar温度减压阀规范   (Safety and control devices for use in hot water systems  - Specifications for temperature relief valves for pressures from 1 bar to 10 bar)  BS 6283-4-1991   热水系统中使用的安全和控制装置.第 4部分:zui大供给压力为12bar,标准尺寸包括DN50的微量绷紧减压阀规范   (Safety and control devices for use in hot water systems - Specification for drop-tight pressure reducing valves of nominal size up to and including DN 50 for supply pressures up to and including 12 ba)  DIN EN 13953-2003   液化石油气(LPG)用可运输的可再充式储气瓶的减压阀   (Pressure relief valves for transportable refillable cylinders for Liquefied Petroleum Gas (LPG); German version EN 13953:2003)  DIN EN 1567-2000   建筑阀门.水减压阀和组合水减压阀.要求和试验   (Building valves - Water pressure reducing valves and combination water pressure reducing valves - Requirements and tests; German version EN 1567:1999) JIS B8652-2002   比例电动液压减压阀及安全阀的试验方法   (Test methods for electro-hydraulic proportional pressure relief valves and electro-hydraulic  proportional pressure reducing and relieving valves)  JIS F0504-1989  船上机械装置用减压阀的应用和压力调节  (Application and setting pressure of relief valves for ships' machinery)  UL 1478-1995  消防泵减压阀   (Fire pumps relief valves )  UL 1468-1995   防火设备用直接控制的减压阀和压力(Direct acting pressure reducing and pressure 
控制阀   restricting valves )  JIS B8666-2001  液压动力.减压阀.安装表面  (Hydraulic fluid power -- Pressure-relief valves -- Mounting surfaces)  JIS B8372-1994   气动装置用减压阀   (PRESSURE REDUCING VALVES FOR PNEUMATIC USE) JIS B8664-2001   液压动力.压力控制阀(不包括减压 阀)、顺序活门、释荷阀、节流阀和止回阀.安装表面   (Hydraulic fluid power -- Pressure-control valves (excluding pressure-relief valves), sequence valves, unloading valves, throttle valves and check valves -- Mounting surfaces)  JIS B8410 AMD 1-2003  水管用减压阀(修改件1)  (Pressure reducing valves for water works (Amendment 1))  JIS B8651-2002  比例电动液压减压阀试验方法  (Test methods for electro-hydraulic proportional pressure relief valves)  JIS B8410-1999   水管用减压阀   (Pressure reducing valves for water works) ISO 15500-12-2001   道路车辆.压缩天然气(CNG)燃料系统元部件.第12部分:减压阀   (Road vehicles - Compressed natural gas (CNG) fuel system components - Part 12: Pressure relief valve (PRV))  ISO 6264-1998  液压传动.减压阀.装配面   (Hydraulic fluid power - Pressure-relief valves - Mounting surfaces)  ISO 5781-2000   液压传动.减压阀、顺序阀、卸荷阀、节流阀和止回阀.装配面  (Hydraulic fluid power - Pressure-reducing valves, sequence valves, unloading valves, throttle valves and check valves - Mounting surfaces) GB/T10868-2005   电站减温减压阀