译文：
在水电站运行中，当水轮发电机组突然甩负荷时，调速器自动控制水轮机快速关闭导叶，压力管道内产生水压和机组转速上升。对于压力引水管道较长的电站，改变导叶关闭时间，有时不能同时使压力和转速上升都控制在允许的范围之内。为时，通常采用设置调压井或调压阀等方法来解决压力和转速上升的矛盾，保证电站安全运行。但设置调压井需要较大的投资和较长的工期，而有些电站限于地形、地质条件，还难于建造调压井，因此对于这一类中小型电站采用调压阀方案具有较明显的优势。 目前生产的全油压控制TFW型调压阀具有和导叶液压联动的特点，安全可靠、投资少、工期短等优势。从上个世纪80年代以来国内已有近百座水电站设计中取消了调压井，采用TFW型全油压控制调压阀，还没有发生一起安全事故。浙江的金坑、宣平溪等水电站已经安全运行了多年，即使是发达国家，如挪威在水电站中也大量使用调压阀来代替调压井(额定水头为158m、单机容量60MW的TJΦRHM水电站就是一个例子)。 现就调压阀的液压原理、特点、过渡过程等作如下阐述。 1、全油压控制调压阀液压原理 全油压控制TFW型调压阀基本动作是：快速开启，缓慢关闭；小负荷变化时，调压阀不动作；甩较大负荷时，调压阀开启，并具有导叶两段关闭的性能；增负荷时，调压阀不起作用。 经过改装的调速器特殊主配压阀和调压阀的液压控制系统见图1，其特点是全部采用压力油直接进行控制和操作，其液压原理如下： (1)机组负荷不变时。主配压阀活塞在“平衡位置”，压力油通过P1腔经过节流阀A后进入调压阀接力器关闭腔TG，调压阀开启腔TK通排油腔O2。由于调压阀关闭腔的压力大于阀盘上的水推力，故调压阀处于关闭位置。如果调压阀本来已经打开，就向关闭侧运动。 (2)机组减少量负荷时(约机组额定出力的15％以内)。由于主配压阀上移量较小，处于“减部分负荷”位置，仅有少量压力油从P1腔经节流阀A后进入导叶接力器关闭腔JG腔而缓慢关闭导叶，调压阀关闭腔压力略微减少，但仍大于阀盘上的水推力，调压阀开启腔TK通排油腔O2，故调压阀保持关闭状态。 (3)当机组瞬时甩较大负荷时(大于机组额定出力的15％以上)。主配压阀活塞上移量较大，处于“甩较大负荷”位置，大量压力油直接经过TK腔进入调压阀接力器开启腔，调压阀快速开启，而调压阀关闭腔TG与导叶接力器关闭腔JG连通，导叶接力器开启腔JK通排油腔O2，导叶快速关闭。所以调压阀快速开启，导叶快速关闭，两者是协联同步的，滞后时间为零。 (4)当机组增负荷时。主配压阀活塞下移，处于“增负荷”位置，压力油P1直接进入导叶接力器开启腔中，调压阀关闭腔压力略微减少，但仍大于阀盘上的水推力，调压阀开启腔TK通排油腔O2，故调压阀保持关闭状态。 (5)导叶两段关闭装置。在调压阀开始快速开启时，受节流阀C的限制，油压迅速升高，油压逆止阀开启，调压阀关闭腔TG的压力油进入导叶接力器关闭腔JG，多余的油量经节流阀D回至调速器回油箱，故调压阀开启速度加快，提前开到限位环所限制的位置，此时导叶接力器未处于全关位置，只能通过少量来自节流阀A的压力油缓慢关闭，从而起到导叶分两段关闭的功能。 (6)如果调压阀失灵，机组只能通过节流阀A的少量压力油慢速关闭，以保证引水管道压力上升不超过允许值。 (7)各节流阀的作用。①节流阀A：整定调压阀失灵时导叶慢关时间，也定了调压阀的关闭时间；②节流阀C：整定油压逆止阀的开启压力，以保证逆止阀迅速开启；③节流阀D：整定导叶两段关闭的拐点位置。 2、调压阀特性 国内现有全油压控制调压阀按直径和水头共分7个品种，主要由四川夹江水工机械厂和重庆水轮机厂生产，主要参数见表1。 (1)结构特点。TFW型调压阀的本体带导叶消能和补气的阀壳、锥型或圆形的阀盘、平衡腔、接力器、引导油腔、活塞行程限制环、进排水管和补气阀等组成。接力器及引导油腔直接与阀壳连成整体，体积小，结构简单，布置紧凑。 (2)流量特性。根据调压阀的阀塞类型和Yx/Dx值查询单位流量Q1x′见表2，由此得到调压阀的相应流量Q＝，从而可以绘制出各种调压阀的开度与流量关系曲线。 (3)操作特性。调压阀{zd1}操作油压的范围一般在1.3～2.0MPa之间，并随着调压阀工作水头的提高而提高，{zg}的操作压力一般为2.5MPa。 (4)布置要点。调压阀的布置应尽可能不增加机组间距和跨度，并与调速器、进水阀等协调布置。对于立式机组，一般布置在蜗壳进口前或蜗壳进口段上，对于卧式机组一般布置在水轮机进水阀后蜗壳进口前的钢管上。调压阀的泄流方式应考虑消能效果，尽管水流通过调压阀后xx了大部分能量，但仍应考虑剩余能量的xx。 3、设置调压阀电站的过渡过程 假定水轮机、调压阀的流量与时间呈线性关系，而且互相匹配很好，因而整个引水系统的流量也呈线性关系变化。设置调压阀后的调节特性和流量与时间的变化见图2所示。图中实线1为导叶快速关闭过程线；虚线2为调压阀拒动时导叶慢关闭过程线；点划线3为调压阀启闭过程线。为了控制水轮机转速的升高，拐点流量Qg一般选择在空载开度附近，因此水轮机没有多余的能量使机组转速继续上升。同时要限制水压的升高，机组流量的减少应控制在一定的范围内。 3.1计算标准 （1）机组突甩负荷后，有关规范蜗壳{zd0}压力升高率按以下情况考虑：①额定水头小于40m时，宜为70％～50％；②额定水头在40～100m时，宜为50％～30％；③额定水头大于100m时，宜小于30％。装设调压阀后，有条件将压力升高控制在更小的升压范围内，结合引水系统的设计和分段关闭装置的现场调整，获得较优的关闭规律。 （2）机组甩负荷时转速升高率按以下情况考虑：①当机组容量占电力系统总容量的比重较大，且担负调频任务时，宜小于45％；②当机组容量占电力系统总容量的比重不大或担负基荷时，宜小于55％。 考虑到目前的允许转速升高有提高的趋势，建议装设调压阀后转速升高率在计算时可按50％控制。 （3）机组突增负荷和甩部分负荷时，压力下降应保证在水库死水位时整个压力管道都有2m以上的正压力余量。 3.2变量说明 除图2中说明的变量之外，计算时仍需涉及到的变量如下： （1）Ts′：不考虑压力升高，控制速率升高的情况下，机组全关闭时间； （2）β：允许的转速升高率； （3）ζ：允许的压力升高率； （4）QTM：允许机组减少的流量； （5）Yg：水轮机空载相对开度； （6）Yk：调压阀全开时水轮机接力器相对开度。 3.3计算方法 (1)根据β求Ts′及调压阀开启时间Txk。计算Ts′与不设调压阀时的方法一样，可以根据《水电站机电设计手册》(水力机械)中的有关公式计算。由此得到Txk＝(1－Yg)×Ts′。当采用导叶一段关闭规律时，Txk＝Ts′。 (2)根据ζ求水轮机慢关闭时间Tsm。计算Ts′与不设调压阀时的方法一样，可根据水锤相的特点，利用阿列维公式反算得到。 (3)计算机组允许的流量减少QTM。按线性关系，调压阀开始关闭前的时间为Txk＋Tp，而机组流量减少的速率允许值为(Txk＋Tp)／Tsm，因此，QTM＝(Txk＋Tp)／Tsm×QT。计算时，由于Tp的不确定性，采用QTM＝Txk／Tsm×QT简化计算是安全的。 (4)计算调压阀的泄放流量Qx及开度Yx。水轮机流量的减少和调压阀泄流的增加导致引水系统的过流量变化，因此应保证QTM≤QT－QX－Qg，由此得到调压阀的泄放流量QTM。根据调压阀的流量特性计算得到所需的开度Yx，并选择调压阀型号及参数。 (5)验算机组增负荷造成的压力下降。此时调压阀不动作，计算时可按1台机组从空载开度突增到全负荷的情况，计算方法与不设调压阀的情况一样，可根据有关设计手册的公式计算压降，从而确定合理的增负荷开机时间。 (6)验算甩部分负荷时调压阀仍全开时造成的压力下降。①计算调压阀全开时水轮机接力器开度：Yk＝(Tsm＋Txk－Ts)／Tsm；②根据机组接力器行程和导叶开度关系曲线查得导叶开度τ０，然后从转轮综合特性曲线查得单位流量Q１′，计算水轮机流量QT＝Q１′×D12×H(1／2)；③根据调压阀限制开度计算调压阀全开流量：QＸ＝；④如果QＸ＞QT，则在起始段出现压力下降：计算引水系统平均流速Ｖ、计算流速变化ΔV＝(QＸ－QT)×V／QT、计算导叶接力器从Yk开度开始关闭的时间Tk＝Yk×Ts′、计算管道特性系数ρ＝a×ΔV／(2×g×H)、σ＝L×ΔV／(g×H×Tk)，根据ρτ０判断{zd0}水锤出现的相序计算压力下降。 (7)根据压力下降计算成果确定是否需要优化压力管道的布置。 4、调压阀的整定 调压阀参数整定前，机组、调速器、油压装置及调压阀设备应全部安装合格，并达到启动试运行的要求后，根据调节保证计算成果进行有关参数的整定。 (1)初调各节流阀至一定位置，模拟动作数次，排除管路中的空气。 (2)切除调压阀，调整节流阀A，整定导叶的慢关闭时间。 (3)投入调压阀，调整节流阀D，整定两段关闭的拐点位置。 (4)调整节流阀C，整定油压逆止阀的启动油压。 (5)导叶快关闭时间和增负荷开机时间仍由特殊主配压阀开口大小来整定。 5、结语 (1)由于全油压控制TFW型调压阀具有动作灵敏、安全可靠、结构简单、调整维护方便、没有滞后时间、投资少等优点，因此自20世纪80年代以来，国内已有近百座水电站在设计中取消了调压井而采用TFW型含油压控制调压阀；即使发达国家的水电站中也大量采用调压阀替代调压井(挪威TJΦRHM水电站就是其中之一，该电站额定水头为158m，单机容量为60MW)。 (2)由于本控制系统的调压阀在负荷小扰动条件下不动作，而此类电站的水流惯性时间常数TW均较大，因此对于装设调压阀的电站，在选择调速器时，其暂态反馈强度bt和缓冲时间常数Td及有关技术参数，要有尽可能大的可调范围。 (3)由于机组流量特性和调压阀流量特性不同，难以xx匹配一致，往往在导叶关闭起始时段和关闭结束时段发生压力下降，因此合理选择调压阀和水轮机导叶的启闭规律，使整个引水系统流量均匀变化，可以减少或避免压力下降。 (4)对于高水头电站的调压阀可采用不锈钢密封环，以提高止水效果和延长密封寿命，从而减少能源浪费。 (5)目前多数中小型调速器的操作油压已经提高到4～16MPa，计算机监控系统也在大多数的水电站投入使用。为适应这种变化，调压阀也需作相应的改进(如增设调压阀行程信号装置，参与到机组的运行控制中，防止调压阀仍处于开启状态时机组增负荷)。

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原文：
In the hydropower station operation, when hydro-generating unit a sudden load rejection, the governor quickly turn off automatic control of turbine guide vanes, the pressure generated within the hydraulic piping and crew speed up. For the pressure of the pipeline a long power plants, to change the guide vane closing time, and sometimes can not be increased while the pressure and speed are controlled within the range allowed. Too, usually set the surge shaft, or the relief valve and other methods to resolve the contradiction between pressure and speed up and ensure the safe operation of power plants. However, a larger set of investment surge shaft and a longer duration, and some power plants limited to the topography, geological conditions, but also more difficult to construct the surge shaft, so for small and medium sized power plant using this type of relief valve has a more obvious advantage of the program . Hydraulic control over the entire current production TFW-type pressure regulating valve and the guide vane hydraulic linkage with the characteristics of safe and reliable, less investment and shorter construction period and other advantages. From the last century has been nearly 80 years of domestic hydropower since the elimination of the surge tank design, using TFW-type full-hydraulic control relief valve, there is no security incidents occurred. Zhejiang Golden pits, such as hydropower stations have been declared safe operation of Pinghsi for many years, even in developed countries such as Norway, are also widely used in the hydropower station to replace the surge shaft, pressure regulating valve (nominal head of 158m, stand-alone capacity of 60MW hydropower station is the TJΦRHM an example). Hydraulic relief valve is now on the principle, characteristics, such as the transition process set out as follows.  1, full-hydraulic relief valve hydraulic control theory Full hydraulic control TFW-type relief valve basic movements are: fast opening, slow closing; small load change, the relief valve does not move; rejection large load, relief valve to open, and has closed the performance of two guide vane ; increasing load, pressure regulating valve does not work. Converted the special master governor pressure valves and pressure regulating valve with the hydraulic control system shown in Figure 1, which is characterized by pressure of the oil used in all the direct control and operation of the hydraulic principles are as follows: (1) The unit load constant. A primary service pressure valve piston in the "equilibrium position", the pressure oil through the P1 and entered the chamber through the throttle valve A pressure regulating valve relay to close cavity TG, pressure regulating valve to open cavity TK-pass oil-drain cavity O2. As the pressure regulating valve closure of the cavity pressure is higher than the water thrust on the valve disc, so pressure regulating valve in the closed position. If the relief valve was already open, on the side of campaigns to shut down. (2) units to reduce the amount of load (about 15% of unit rated output or less). As the primary service pressure valve on the shift was smaller, and in the "reduced part-load" position, only a small amount of pressure oil from the P1 and entered the chamber through the throttle valve A guide blade relay to close cavity JG cavity and slow closure of guide vanes, pressure regulator valve closed cavity pressure slightly reduced, but still larger than the water on the valve disc thrust, pressure regulating valve to open cavity TK-pass row of the oil cavity O2, so pressure regulating valve to keep off. (3) When a larger load rejection transient units (greater than 15% of unit rated output above). A primary service pressure valve piston move up relatively large quantities in the "rejection greater load" position, a large number of oil pressure relief valve directly into the cavity through the TK open relay device cavity, pressure regulating valve to open quickly, while the pressure regulating valve closing cavity TG and guide vanes closed cavity JG relay device connected, open the guide vane servomotor chamber JK Tong Pai oil cavity O2, quickly close the guide vanes. Therefore, fast relief valve to open, quick guide vanes closed, the two are synchronized the Federation, the lag time is zero. (4) When the unit increased load. The main valve piston down with pressure, in the "additional load" position, pressure oil-P1 relay device directly into the guide vane open cavity, close the cavity pressure relief valve slightly reduced, but still larger than the water on the valve disc thrust, voltage regulator TK-pass valve is open row of the oil chamber cavity O2, so pressure regulating valve to keep off. (5) guide vanes two shut-off device. In the pressure regulating valve began to open quickly when the throttle valve C, subject to restrictions, the rapid increase in oil pressure, oil pressure check valve opened, the pressure relief valve closed cavity TG oil into the guide vane servomotor closed cavity JG, redundant D back to the fuel through the throttle governor back to the fuel tank, so pressure regulating valve to open faster, ahead of open-loop constrained to limit the location of guide vane relay devices at this time is not in fully closed position, only by a small amount of A throttle pressure from the oil slowly closed, and thus play a guide vane closure of the function into two sections. (6) If the relief valve failure, unit only through the throttle valve A small amount of pressure on the oil slowly closed, to ensure that the pipeline pressure rise does not exceed the allowable value. (7) of the throttle effect. ① throttle A: Setting pressure regulating valve failure in the slow wicket off time, but also set the relief valve closing time; ② throttle C: tuning of hydraulic check valve opening pressure of check valve in order to ensure speedy Open; ③ throttle D: Tuning guide blade turning point two closed position. 2, pressure regulating valve characteristics Existing domestic control of all hydraulic relief valve according to diameter and the head is divided into seven varieties, mainly in Sichuan and Chongqing Jiajiang Hydraulic Machinery Factory hydraulic turbine plant production, the main parameters in Table 1. (1) structural characteristics. TFW Type Pressure Regulating Valve body with a guide vane, and qi energy dissipation of the valve shell, conical, or circular valve plate, balanced cavity, relay device, and guide the oil chamber, the piston stroke limit ring, into the drain pipes and fill valve so on. Relay device and guide the oil chamber connected directly with the valve housing into a whole, small size, simple structure, compact layout. (2) The flow characteristics. According to Valve Pressure Regulating Valve plug type and Yx / Dx value check unit flow Q1x 'in Table 2, the resultant pressure regulating valve of the corresponding flow rate Q =, so you can draw all kinds of Pressure Regulating Valve opening and the discharge curve . (3) The operation characteristics. The scope of the minimum operating oil pressure relief valve is generally between 1.3 ~ 2.0MPa, and the improvement of working head with the pressure regulating valve and increase the maximum operating pressure is generally 2.5MPa. (4) The layout of the main points. Pressure Regulating Valve arrangement as far as possible not to increase the unit spacing and span and with the governor, inlet valve and other co-ordination arrangements. For the vertical unit, the general layout of the scroll, or scroll import import segment, the general arrangement for the horizontal unit in the turbine inlet valve after the import of steel pipes on the scroll. Pressure Regulating Valve Discharge method should consider the effect of energy dissipation, despite the water flow through the relief valve after the elimination of most of the energy, but the elimination of residual energy should be considered. 3, set the pressure regulating valve power plant transition process Assumed that turbine, pressure regulating valve of the linear relationship between flow and time, and match each other well, and thus the entire water system is also a linear relationship between flow changes. Set Pressure Regulating Valve features and traffic regulation after the change with time as shown in Figure 2. Solid line a fast-closing process for the guide vanes line; dashed line 2 for the relief valve tripping off when the guide vanes slow process line; point crossed three lines for the relief valve open and close the process. In order to control the turbine speed increased, the inflection point flow Qg generally opt for no-load opening in the vicinity, so no extra power turbine speed and the unit continues to rise. At the same time to limit the water pressure increased, the reduction in the flow unit should be controlled in a certain range. 3.1 The calculation of the standard (1) Unit sudden load rejection, the relevant norms of the maximum pressure rise rate volute be considered according to the following: ① rated water head is less than 40m, it is desirable for the 70% ~ 50%; ② head rated at 40 ~ 100m, it is desirable for the 50% ~ 30%; ③ rated head is greater than 100m, it is desirable is less than 30%. The installation of pressure regulating valve, the conditional control of the pressure rise within the framework of a smaller boost, combined with water system design and sub-closing devices on-site adjustments to get on better closure rule. (2) units increase in the rate of speed and load rejection by the following considerations: ① When the power system capacity of the units accounted for a larger proportion of the total capacity, and responsible for FM task, should less than 45%; ② When the capacity of the units accounted for the total power system the proportion of the capacity of little or responsible baseload, it is desirable is less than 55%. Taking into account the current speed increases to allow for increased trend, the proposed increase in the rate of speed after the installation of pressure regulating valve in the calculation of 50% when you can control. (3) The sudden increase in unit load and partial load rejection, the pressure drop dead in the reservoir water level should ensure that their entire pressure pipe has a positive pressure margin of more than 2m. 3.2 Variable Description In addition to the variables described in Figure 2, the calculation still involves the variable is as follows: (1) Ts': do not take into account pressure increases to control the rate of increase in the case of the crew shut down the whole time; (2) β: to allow higher rates of speed; (3) ζ: to allow the pressure rise rate; (4) QTM: allow the unit to reduce the flow; (5) Yg: turbine load relative aperture; (6) Yk: pressure regulating valve fully open when the turbine is relatively opening relay device. 3.3 Calculation Method (1) According to the β seeking Ts' and the relief valve open time Txk. Calculate Ts' and when no relief valve the same way as under the "Hydropower Electrical and Mechanical Design Manual" (hydraulic machinery) in the formula. The resulting Txk = (1-Yg) × Ts'. When using a closure rule when the guide vanes, Txk = Ts'. (2) According to the ζ seeking turbine slow closing time Tsm. Calculate Ts' and when no relief valve the same way as, according to the characteristics of water hammer phase, using the formula A counter-balance to be Levi. (3) Computer Group to allow traffic to reduce the QTM. According to linear relationship between the pressure regulating valve started closing before the time for Txk + Tp, while the crew to reduce the rate of flow to allow the value of (Txk + Tp) / Tsm, therefore, QTM = (Txk + Tp) / Tsm × QT. Calculation, due to the uncertainty of Tp using QTM = Txk / Tsm × QT simplified calculation is safe. (4) Calculate the pressure regulating valve of the discharge flow rate Qx and opening Yx. Turbine flow reduction and the increase of discharge pressure regulating valve leading to over-flow diversion system change, so should ensure that QTM ≤ QT-QX-Qg, the resultant pressure regulating valve of the discharge flow of QTM. Pressure Regulating Valve flow characteristics according to the required calculated opening Yx, and select the pressure regulating valve models and parameters. (5) Checking unit pressure drop caused by load. Relief valve does not move at this time, calculated according to a generating unit from the sudden increase in load opening to full-load conditions, the calculation method and no relief valve in the case, according to the design manual pressure drop formula to determine a reasonable load-boot time. (6) Checking rejection part of the load relief valve remains fully open when the pressure drop caused. ① full-time calculation of pressure regulating valve turbine servomotor opening: Yk = (Tsm + Txk-Ts) / Tsm; ② unit relay device according to schedule and I. Ye Kai-degree curve of Richard I. Ye Kai-degree τ0, and then from a comprehensive runner Richard characteristic flat flow Q1 ', the calculation of turbine flow rate QT = Q1' × D12 × H (1 / 2); ③ limitations under the relief valve opening calculation of full-flow relief valve: QX =; ④ If the QX> QT , then the pressure drop occurs in the initial segment: Calculate the average velocity water diversion system, V, calculate velocity change ΔV = (QX-QT) × V / QT, calculated from the guide vane servomotor Yk opening to begin shutting down the time Tk = Yk × Ts ', the calculation pipeline coefficients ρ = a × ΔV / (2 × g × H), σ = L × ΔV / (g × H × Tk), according to ρτ0 appear to determine the largest water hammer pressure drop calculation of phase sequence. (7) According to the results of pressure drop calculations to determine whether the need to optimize the pressure piping. 4, Pressure Regulating Valve Setting Pressure regulating valve parameter tuning before the unit, governor, oil pressure relief valve installations and equipment should be installed with qualified, and meet the requirements to start trial operation, based on the calculation results of regulation to ensure the relevant parameters tuning. (1) The initial adjustment to a certain position of the throttle to simulate movement several times to remove the air pipe. (2) removal of pressure regulating valve, adjusting the throttle valve A, the slow tuning guide vane closing time. (3) put pressure regulating valve, adjusting the throttle valve D, setting off two knee positions. (4) The adjustment of throttle C, setting the start hydraulic oil pressure check valve. (5) guide vane closing time and increasing load faster boot time, still a special primary service pressure valve opening size setting. 5 Conclusion (1) Since the full-hydraulic control TFW-type relief valve with a motion sensitive, safe and reliable, simple structure, convenient maintenance and adjustment, there is no lag time, the advantages of low investment, it has been since the 20th century, 80 years, the domestic has been nearly Block hydropower stations in the design eliminated the use of TFW-type surge shaft with hydraulic control pressure regulating valve; even in developed countries is also a large number of hydropower stations in the surge tank using pressure regulating valve replacement (Norway TJΦRHM hydropower station is one of them, the station head for the rated 158m, stand-alone capacity of 60MW). (2) Since this control system, pressure regulating valve in the load under the conditions of small perturbations is not action, and such power plant water inertia time constant T  W are large, so the installation of relief valve for power stations, the choice of speed device, its transient bt feedback intensity and buffering time constant Td and related technical parameters, the adjustable range must be as large as possible. (3) The unit flow characteristics and pressure regulating valve flow characteristics of different, difficult to match exactly the same, often starting in the guide vane closing time and closing the end of the pressure drop happened during the period, so rational selection pressure regulating valve and the turbine guide vane open and close the law so that the whole water system, even changes in flow can reduce or avoid pressure drop. (Four) of the relief valve for high-head power plants can use stainless steel seal ring to improve sealing performance and to extend the seal life, thus reducing energy waste. (5) At present, the operation of the majority of small and medium sized hydraulic governor has been increased to 4 ~ 16MPa, a computer monitoring system was also put to use most of the hydropower station. To adapt to this change, pressure regulating valve also need to make corresponding improvements (such as an additional relief valve stroke signal devices, to participate in the operation control unit to prevent the relief valve when the unit is still turned on by load).

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