A digital valve positioner for use with an actuator. The digital valve positioner includes a housing, at least one exhaust port opening formed in the housing, and a vent assembly operatively coupled to the at least one exhaust port opening. The vent assembly includes a body having a bore, a valve seat surrounding the bore, and a check valve disposed within the bore. The check valve is arranged to shift from a closed position seated against the valve seat to an open position disposed away from the valve seat. A plurality of barriers is disposed around and positioned to enclose the check valve. The plurality of barriers is arranged to prevent an external medium from entering the check valve and to provide a tortuous flow path for the exhaust medium reducing sound through the vent assembly.

A liquid tank system comprises a main liquid tank, an outlet communicating between a fluid circuit and the main liquid tank, an inlet communicating between the fluid circuit and the main liquid tank, and an auxiliary cavity. First vent passage and second vent passage(s) communicate between the main liquid tank and the auxiliary cavity and allows liquid and gas to flow from the main liquid tank to the auxiliary cavity. The second vent passage has a flow control device regulating flow through the second vent passage and having a set point at which it allows liquid and gas to flow from the main liquid tank to the auxiliary cavity only when a pressure in the main liquid tank is beyond a threshold. The liquid tank system has an attitude envelope in which the liquid tank system is configured such that, in use, the flow control device blocks flow through the second vent passage when an end of the first vent passage in the main liquid tank is above a liquid level, and the flow control device allows gas and/or fluid flow through the second vent passage when main fluid tank pressure is above the threshold and the end of the first vent passage in the main liquid tank is below the liquid level.

A digital valve positioner for use with an actuator. The digital valve positioner includes a housing, at least one exhaust port opening formed in the housing, and a vent assembly operatively coupled to the at least one exhaust port opening. The vent assembly includes a body having a bore, a valve seat surrounding the bore, and a check valve disposed within the bore. The check valve is arranged to shift from a closed position seated against the valve seat to an open position disposed away from the valve seat. A plurality of barriers is disposed around and positioned to enclose the check valve. The plurality of barriers is arranged to prevent an external medium from entering the check valve and to provide a tortuous flow path for the exhaust medium reducing sound through the vent assembly.

A tanker vehicle for distributing liquid on a surface includes a chassis that supports a tank for holding the liquid. A fluid pump discharges the liquid from the tank and is driven by a hydraulic motor. A hydraulic system delivers hydraulic fluid to the motor through a supply line and returns the fluid to a tank through a return line. A bypass circuit is disposed between the supply line and the return line, bypassing the motor. The bypass circuit includes a system for providing a combination soft start and soft stop of the hydraulic motor that is configured to enable hydraulic fluid to flow from the supply line through the bypass circuit to the return line at a start of the hydraulic system and to flow from the return line through the bypass circuit to the supply line at a shutdown of the hydraulic system.

A digital valve positioner for use with an actuator. The digital valve positioner includes a housing, at least one exhaust port opening formed in the housing, and a vent assembly operatively coupled to the at least one exhaust port opening. The vent assembly includes a body having a bore, a valve seat surrounding the bore, and a check valve disposed within the bore. The check valve is arranged to shift from a closed position seated against the valve seat to an open position disposed away from the valve seat. A plurality of barriers is disposed around and positioned to enclose the check valve. The plurality of barriers is arranged to prevent an external medium from entering the check valve and to provide a tortuous flow path for the exhaust medium reducing sound through the vent assembly.

A liquid tank system comprises a main liquid tank, an outlet communicating between a fluid circuit and the main liquid tank, an inlet communicating between the fluid circuit and the main liquid tank, and an auxiliary cavity. First vent passage and second vent passage(s) communicate between the main liquid tank and the auxiliary cavity and allows liquid and gas to flow from the main liquid tank to the auxiliary cavity. The second vent passage has a flow control device regulating flow through the second vent passage and having a set point at which it allows liquid and gas to flow from the main liquid tank to the auxiliary cavity only when a pressure in the main liquid tank is beyond a threshold. The liquid tank system has an attitude envelope in which the liquid tank system is configured such that, in use, the flow control device blocks flow through the second vent passage when an end of the first vent passage in the main liquid tank is above a liquid level, and the flow control device allows gas and/or fluid flow through the second vent passage when main fluid tank pressure is above the threshold and the end of the first vent passage in the main liquid tank is below the liquid level.

A vent apparatus is described for providing filtered air intake and rollover protection for a fuel tank. The apparatus may include a housing configured to be coupled with the fuel tank, the housing including at least one air intake port and at least one air exhaust port. The apparatus may include an air intake filter disposed within the housing and configured to receive and filter air from the at least one air intake port. The apparatus may include a rollover protection valve disposed adjacent to the housing and configured to be located inside the fuel tank when the housing is coupled with the fuel tank, the rollover protection valve coupled with the at least one air exhaust port. The rollover protection valve may include a chamber and a plug configured to impede the flow of fuel from the fuel tank into the at least one air exhaust port.

A system comprises a non-transitory machine readable storage medium storing instructions and a database identifying a plurality of assets and a state of each asset. The instructions configure a processor for receiving updates to a distributed electronic ledger managed by plural peer processors. Each update includes an event or change affecting one of the assets. The peer processors verify portions of the ledger describing each event or change. At least one of the updates has not yet been recorded in the ledger at a time of the receiving. The processor computes a state of each asset, based on the updates, receives a request for a state of one of the assets; and responds to the request, reflecting each event and change affecting that asset. The response is performed without waiting for the peer processors to verify an update that has not yet been recorded in the ledger.

A liquid tank system comprises a main liquid tank, an outlet communicating between a fluid circuit and the main liquid tank, an inlet communicating between the fluid circuit and the main liquid tank, and an auxiliary cavity. First vent passage and second vent passage(s) communicate between the main liquid tank and the auxiliary cavity and allows liquid and gas to flow from the main liquid tank to the auxiliary cavity. The second vent passage has a flow control device regulating flow through the second vent passage and having a set point at which it allows liquid and gas to flow from the main liquid tank to the auxiliary cavity only when a pressure in the main liquid tank is beyond a threshold. The liquid tank system has an attitude envelope in which the liquid tank system is configured such that, in use, the flow control device blocks flow through the second vent passage when an end of the first vent passage in the main liquid tank is above a liquid level, and the flow control device allows gas and/or fluid flow through the second vent passage when main fluid tank pressure is above the threshold and the end of the first vent passage in the main liquid tank is below the liquid level.

Aspects of a flow balanced frac tank farm are described herein. In one embodiment, the flow balanced frac tank farm includes at least one battery of frac tanks comprising a plurality of frac tank trailers, a header pipe arrangement, and at least one valve between one or more of the frac tank trailers and the header system. The header pipe arrangement may include a header supply pipe to supply water to individual ones of the plurality of frac tank trailers and a header discharge pipe to discharge water from individual ones of the plurality of frac tank trailers. The header pipe arrangement may be relied upon to help balance the flow of heated fluids among the frac tank trailers in frac tank farm.